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GUY WHITE: Hello, Indonesia.

3
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[CHEERING AND APPLAUSE]

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5
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It's so good to see all my friends here.

6
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So many of you come from
such a long way away.

7
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How many of you walked here?

8
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How many walked here?

9
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[LAUGHTER]

10
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How many of you took a plane?

11
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How many were on a plane?

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Oh, my gosh.

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I want to say from the bottom
of our heart here at CS 50.

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We are so thankful for you.

15
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And please, tonight we want you to
contact your family, and we want--

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[LAUGHTER]

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Seriously.

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I'm serious.

19
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I want you to contact
your family, and please,

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extend our thanks to
them for allowing you

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to come here this distance to be
away from your family and to work.

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[CHEERING AND APPLAUSE]

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It takes such a commitment to
have done what you have done.

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But today, is not the
end of your journey.

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This weekend is not the
end of your journey.

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This weekend is just
the start of something.

28
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[CHEERING]

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30
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So I want to see who has
traveled the longest way.

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So the way we're going to
do this is let us stand up.

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All of you stand up, please.

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Thank you.

34
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Stand up, please.

35
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All right, so if you have come less
than five kilometers, please, sit down.

36
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Five kilometers?

37
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10 kilometers or less sit down.

38
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How about 50 kilometers or
less, go ahead and sit down.

39
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Thank you, 50 kilo-- oh, there we go.

40
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Got some movement.

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[SIDE CONVERSATIONS]

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43
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OK, if you had come more--

44
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less, if you've come less than 100
kilometers, go ahead and sit down.

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Sit down.

46
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How about 300, less than
300, please, sit down.

47
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Less than 300?

48
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Oh, it's the longest.

49
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It's--

50
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[SIDE CONVERSATIONS]

51
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I'm going to have to make it higher.

52
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How many of you have come
from less than 1,000?

53
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Go ahead and sit down.

54
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Oh.

55
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56
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How many of you have
come less than 1,500?

57
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Go ahead and sit down.

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OK, all right, now let's look around.

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Let's look around and
look at these people.

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How many people have
come less than 2,500?

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Go ahead and sit down.

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Less than 2,500?

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Oh, one?

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Wait, oh, we have two?

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We have two?

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OK, those people stand back up.

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Stand back up.

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I did it again.

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OK, not a good--

71
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OK, so let's try this again.

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2,200.

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If you have travelled-- if you
traveled more than 2,200, stand up.

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OK, now, let's try here.

75
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If you traveled less
than 2,300, sit down.

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2,300.

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2,300?

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AUDIENCE: Whoa.

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GUY WHITE: Oh, look at--

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OK, so sir, please, where are you from?

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AUDIENCE: [INAUDIBLE].

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GUY WHITE: Wonderful, give
him a round of applause.

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[APPLAUSE]

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Thank you.

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And right here.

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My friend, where are you from?

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AUDIENCE: Oh, oh.

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[SIDE CONVERSATIONS]

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AUDIENCE: I'm Indonesian
but based on [INAUDIBLE]..

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[CHEERING AND APPLAUSE]

93
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GUY WHITE: And how about you?

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AUDIENCE: I'm from London.

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GUY WHITE: Wonderful.

97
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How many kilometers?

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AUDIENCE: [? 234. ?]

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GUY WHITE: Wonderful.

100
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AUDIENCE: [INAUDIBLE].

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GUY WHITE: Wonderful.

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[APPLAUSE]

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And up here.

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AUDIENCE: I'm from [INAUDIBLE].

105
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GUY WHITE: Wonderful.

106
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[CHEERING AND APPLAUSE]

107
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108
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Thank you.

109
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Thank you.

110
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Thank you.

111
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And did I see--

112
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I see a face over here.

113
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Excellent.

114
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I'm going to go this
way and not get injured.

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[LAUGHTER]

116
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And let's pass the mic
up, but I want it back.

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OK.

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AUDIENCE: I come from
the western of Indonesia

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at the end of Sumatra and Aceh province.

121
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[APPLAUSE]

122
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123
00:04:29,520 --> 00:04:30,520
AUDIENCE: Thank you.

124
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I'm from [INAUDIBLE],, around
[? 3,000 ?] kilometers.

125
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AUDIENCE: Wow.

126
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[APPLAUSE]

127
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GUY WHITE: So not only is
your family proud of you,

128
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but your city, you
province is proud of you.

129
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Last night the minister
visited you and the school.

130
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You're part of the reason--

131
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you are the reason
this is all happening.

132
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We are so happy to be
here with you today.

133
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So we're going to play is we're going
to play a game really quick to get

134
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us started called counting to 23.

135
00:05:02,960 --> 00:05:04,280
But we can do it in Bahasa.

136
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So how do you say the
number one in Bahasa?

137
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AUDIENCE: [SPEAKING BAHASA]

138
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GUY WHITE: [SPEAKING BAHASA]

139
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AUDIENCE: Yes.

140
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GUY WHITE: [SPEAKING BAHASA].

141
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[LAUGHTER]

142
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OK, so we're going to count.

143
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In a minute, we're going
to hand of the mic.

144
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We're going to go 1,
2, 3 in [? Bahasa. ?]

145
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AUDIENCE: [SPEAKING BAHASA].

146
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AUDIENCE: [SPEAKING BAHASA].

147
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AUDIENCE: [SPEAKING BAHASA].

148
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AUDIENCE: [SPEAKING BAHASA].

149
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AUDIENCE: [SPEAKING BAHASA].

150
00:05:29,932 --> 00:05:31,800
AUDIENCE: [SPEAKING BAHASA].

151
00:05:31,800 --> 00:05:33,210
AUDIENCE: [SPEAKING BAHASA].

152
00:05:33,210 --> 00:05:34,830
AUDIENCE: [SPEAKING BAHASA].

153
00:05:34,830 --> 00:05:37,850
AUDIENCE: [SPEAKING BAHASA].

154
00:05:37,850 --> 00:05:39,481
AUDIENCE: [SPEAKING BAHASA].

155
00:05:39,481 --> 00:05:40,942
AUDIENCE: [SPEAKING BAHASA].

156
00:05:40,942 --> 00:05:42,890
AUDIENCE: [SPEAKING BAHASA].

157
00:05:42,890 --> 00:05:44,300
AUDIENCE: [SPEAKING BAHASA].

158
00:05:44,300 --> 00:05:46,220
AUDIENCE: [SPEAKING BAHASA].

159
00:05:46,220 --> 00:05:47,813
AUDIENCE: [SPEAKING BAHASA].

160
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AUDIENCE: [SPEAKING BAHASA].

161
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GUY WHITE: And 123.

162
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[LAUGHTER]

163
00:05:50,992 --> 00:05:52,356
AUDIENCE: [SPEAKING BAHASA].

164
00:05:52,356 --> 00:05:53,523
AUDIENCE: [SPEAKING BAHASA].

165
00:05:53,523 --> 00:05:54,690
AUDIENCE: [SPEAKING BAHASA].

166
00:05:54,690 --> 00:05:56,250
AUDIENCE: [SPEAKING BAHASA].

167
00:05:56,250 --> 00:05:58,220
AUDIENCE: [SPEAKING BAHASA].

168
00:05:58,220 --> 00:06:01,823
AUDIENCE: [SPEAKING BAHASA].

169
00:06:01,823 --> 00:06:02,990
AUDIENCE: [SPEAKING BAHASA].

170
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GUY WHITE: 21.

171
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AUDIENCE: Yeah!

172
00:06:04,961 --> 00:06:07,710
AUDIENCE: [SPEAKING BAHASA].

173
00:06:07,710 --> 00:06:08,940
AUDIENCE: [SPEAKING BAHASA].

174
00:06:08,940 --> 00:06:10,764
[CHEERING AND APPLAUSE]

175
00:06:10,764 --> 00:06:13,460


176
00:06:13,460 --> 00:06:15,060
AUDIENCE: [SPEAKING BAHASA].

177
00:06:15,060 --> 00:06:16,980
AUDIENCE: [SPEAKING BAHASA].

178
00:06:16,980 --> 00:06:18,390
AUDIENCE: [SPEAKING BAHASA].

179
00:06:18,390 --> 00:06:20,380
AUDIENCE: [SPEAKING BAHASA].

180
00:06:20,380 --> 00:06:22,020
AUDIENCE: [SPEAKING BAHASA].

181
00:06:22,020 --> 00:06:24,090
AUDIENCE: [SPEAKING BAHASA].

182
00:06:24,090 --> 00:06:25,740
AUDIENCE: [SPEAKING BAHASA].

183
00:06:25,740 --> 00:06:27,621
AUDIENCE: [SPEAKING BAHASA].

184
00:06:27,621 --> 00:06:29,213
AUDIENCE: [SPEAKING BAHASA].

185
00:06:29,213 --> 00:06:30,380
AUDIENCE: [SPEAKING BAHASA].

186
00:06:30,380 --> 00:06:33,250
AUDIENCE: [SPEAKING BAHASA].

187
00:06:33,250 --> 00:06:35,660
AUDIENCE: [SPEAKING BAHASA].

188
00:06:35,660 --> 00:06:37,019
AUDIENCE: [SPEAKING BAHASA].

189
00:06:37,019 --> 00:06:40,931


190
00:06:40,931 --> 00:06:42,398
AUDIENCE: [INAUDIBLE].

191
00:06:42,398 --> 00:06:45,332
[CHEERING AND APPLAUSE]

192
00:06:45,332 --> 00:06:47,780


193
00:06:47,780 --> 00:06:49,043
AUDIENCE: [SPEAKING BAHASA].

194
00:06:49,043 --> 00:06:50,210
AUDIENCE: [SPEAKING BAHASA].

195
00:06:50,210 --> 00:06:51,716
[LAUGHTER]

196
00:06:51,716 --> 00:06:53,410
AUDIENCE: [SPEAKING BAHASA].

197
00:06:53,410 --> 00:06:54,577
AUDIENCE: [SPEAKING BAHASA].

198
00:06:54,577 --> 00:06:56,260
[LAUGHTER]

199
00:06:56,260 --> 00:06:58,190
AUDIENCE: [SPEAKING BAHASA].

200
00:06:58,190 --> 00:06:59,626
AUDIENCE: [SPEAKING BAHASA].

201
00:06:59,626 --> 00:07:01,700
AUDIENCE: [SPEAKING BAHASA].

202
00:07:01,700 --> 00:07:03,530
AUDIENCE: [SPEAKING BAHASA].

203
00:07:03,530 --> 00:07:05,696
AUDIENCE: [SPEAKING BAHASA].

204
00:07:05,696 --> 00:07:07,570
AUDIENCE: [SPEAKING BAHASA].

205
00:07:07,570 --> 00:07:09,624
AUDIENCE: [SPEAKING BAHASA].

206
00:07:09,624 --> 00:07:12,510
AUDIENCE: [SPEAKING BAHASA].

207
00:07:12,510 --> 00:07:13,953
AUDIENCE: [SPEAKING BAHASA].

208
00:07:13,953 --> 00:07:15,877
AUDIENCE: [SPEAKING BAHASA].

209
00:07:15,877 --> 00:07:17,320
AUDIENCE: [SPEAKING BAHASA].

210
00:07:17,320 --> 00:07:18,487
AUDIENCE: [SPEAKING BAHASA].

211
00:07:18,487 --> 00:07:20,090
AUDIENCE: [SPEAKING BAHASA].

212
00:07:20,090 --> 00:07:21,950
AUDIENCE: [SPEAKING BAHASA].

213
00:07:21,950 --> 00:07:23,960
AUDIENCE: [SPEAKING BAHASA].

214
00:07:23,960 --> 00:07:25,400
AUDIENCE: [SPEAKING BAHASA].

215
00:07:25,400 --> 00:07:27,110
AUDIENCE: [SPEAKING BAHASA].

216
00:07:27,110 --> 00:07:29,820
AUDIENCE: [SPEAKING BAHASA].

217
00:07:29,820 --> 00:07:31,661
AUDIENCE: [SPEAKING BAHASA].

218
00:07:31,661 --> 00:07:33,363
AUDIENCE: [SPEAKING BAHASA].

219
00:07:33,363 --> 00:07:34,530
AUDIENCE: [SPEAKING BAHASA].

220
00:07:34,530 --> 00:07:36,030
GUY WHITE: And remember your number.

221
00:07:36,030 --> 00:07:37,065
[LAUGHTER]

222
00:07:37,065 --> 00:07:39,308
AUDIENCE: [SPEAKING BAHASA].

223
00:07:39,308 --> 00:07:41,970
AUDIENCE: [SPEAKING BAHASA].

224
00:07:41,970 --> 00:07:44,140
AUDIENCE: [SPEAKING BAHASA].

225
00:07:44,140 --> 00:07:45,363
AUDIENCE: [SPEAKING BAHASA].

226
00:07:45,363 --> 00:07:47,430
AUDIENCE: [SPEAKING BAHASA].

227
00:07:47,430 --> 00:07:49,680
AUDIENCE: [SPEAKING BAHASA].

228
00:07:49,680 --> 00:07:50,926
AUDIENCE: [SPEAKING BAHASA].

229
00:07:50,926 --> 00:07:53,370
AUDIENCE: [SPEAKING BAHASA].

230
00:07:53,370 --> 00:07:54,753
AUDIENCE: [SPEAKING BAHASA].

231
00:07:54,753 --> 00:07:55,920
AUDIENCE: [SPEAKING BAHASA].

232
00:07:55,920 --> 00:07:59,280
AUDIENCE: [SPEAKING BAHASA].

233
00:07:59,280 --> 00:08:01,290
AUDIENCE: [SPEAKING BAHASA].

234
00:08:01,290 --> 00:08:02,584
AUDIENCE: [SPEAKING BAHASA].

235
00:08:02,584 --> 00:08:04,900
AUDIENCE: [SPEAKING BAHASA].

236
00:08:04,900 --> 00:08:06,640
AUDIENCE: [SPEAKING BAHASA].

237
00:08:06,640 --> 00:08:08,302
AUDIENCE: [SPEAKING BAHASA].

238
00:08:08,302 --> 00:08:10,150
AUDIENCE: [SPEAKING BAHASA].

239
00:08:10,150 --> 00:08:13,770
AUDIENCE: [SPEAKING BAHASA].

240
00:08:13,770 --> 00:08:15,491
AUDIENCE: [SPEAKING BAHASA].

241
00:08:15,491 --> 00:08:16,658
AUDIENCE: [SPEAKING BAHASA].

242
00:08:16,658 --> 00:08:18,570
AUDIENCE: [SPEAKING BAHASA].

243
00:08:18,570 --> 00:08:20,004
AUDIENCE: [SPEAKING BAHASA].

244
00:08:20,004 --> 00:08:26,230


245
00:08:26,230 --> 00:08:27,737
AUDIENCE: [SPEAKING BAHASA].

246
00:08:27,737 --> 00:08:28,445
[SPEAKING BAHASA]

247
00:08:28,445 --> 00:08:30,295
[LAUGHTER]

248
00:08:30,295 --> 00:08:32,020
AUDIENCE: [SPEAKING BAHASA].

249
00:08:32,020 --> 00:08:33,979
AUDIENCE: [SPEAKING BAHASA].

250
00:08:33,979 --> 00:08:35,806
AUDIENCE: [SPEAKING BAHASA].

251
00:08:35,806 --> 00:08:38,105
AUDIENCE: [SPEAKING BAHASA].

252
00:08:38,105 --> 00:08:39,460
AUDIENCE: [SPEAKING BAHASA].

253
00:08:39,460 --> 00:08:42,349
AUDIENCE: [SPEAKING BAHASA].

254
00:08:42,349 --> 00:08:44,770
AUDIENCE: [SPEAKING BAHASA].

255
00:08:44,770 --> 00:08:45,992
AUDIENCE: [SPEAKING BAHASA].

256
00:08:45,992 --> 00:08:47,680
AUDIENCE: [SPEAKING BAHASA].

257
00:08:47,680 --> 00:08:49,030
AUDIENCE: [SPEAKING BAHASA].

258
00:08:49,030 --> 00:08:50,300
AUDIENCE: [SPEAKING BAHASA].

259
00:08:50,300 --> 00:08:51,800
AUDIENCE: [SPEAKING BAHASA].

260
00:08:51,800 --> 00:08:53,800
AUDIENCE: [SPEAKING BAHASA].

261
00:08:53,800 --> 00:08:55,774
AUDIENCE: [SPEAKING BAHASA].

262
00:08:55,774 --> 00:08:57,240
AUDIENCE: [SPEAKING BAHASA].

263
00:08:57,240 --> 00:08:58,980
AUDIENCE: [SPEAKING BAHASA].

264
00:08:58,980 --> 00:09:01,800
AUDIENCE: [SPEAKING BAHASA].

265
00:09:01,800 --> 00:09:03,620
AUDIENCE: [SPEAKING BAHASA].

266
00:09:03,620 --> 00:09:05,460
AUDIENCE: [SPEAKING BAHASA].

267
00:09:05,460 --> 00:09:07,430
AUDIENCE: [SPEAKING BAHASA].

268
00:09:07,430 --> 00:09:09,410
AUDIENCE: [SPEAKING BAHASA].

269
00:09:09,410 --> 00:09:11,084
AUDIENCE: [SPEAKING BAHASA].

270
00:09:11,084 --> 00:09:13,060
AUDIENCE: [SPEAKING BAHASA].

271
00:09:13,060 --> 00:09:14,814
AUDIENCE: [SPEAKING BAHASA].

272
00:09:14,814 --> 00:09:16,630
AUDIENCE: [SPEAKING BAHASA].

273
00:09:16,630 --> 00:09:18,900
AUDIENCE: [SPEAKING BAHASA].

274
00:09:18,900 --> 00:09:20,444
AUDIENCE: [SPEAKING BAHASA].

275
00:09:20,444 --> 00:09:23,500
AUDIENCE: [SPEAKING BAHASA].

276
00:09:23,500 --> 00:09:25,530
AUDIENCE: [SPEAKING BAHASA].

277
00:09:25,530 --> 00:09:27,670
AUDIENCE: [SPEAKING BAHASA].

278
00:09:27,670 --> 00:09:29,400
AUDIENCE: [SPEAKING BAHASA].

279
00:09:29,400 --> 00:09:30,966
AUDIENCE: [SPEAKING BAHASA].

280
00:09:30,966 --> 00:09:32,700
AUDIENCE: [SPEAKING BAHASA].

281
00:09:32,700 --> 00:09:34,240
AUDIENCE: [SPEAKING BAHASA].

282
00:09:34,240 --> 00:09:35,570
AUDIENCE: [SPEAKING BAHASA].

283
00:09:35,570 --> 00:09:38,710


284
00:09:38,710 --> 00:09:41,710
AUDIENCE: [SPEAKING BAHASA].

285
00:09:41,710 --> 00:09:42,980
AUDIENCE: [SPEAKING BAHASA].

286
00:09:42,980 --> 00:09:44,032
AUDIENCE: [SPEAKING BAHASA].

287
00:09:44,032 --> 00:09:44,420
GUY WHITE: Is that it?

288
00:09:44,420 --> 00:09:44,920
Yay!

289
00:09:44,920 --> 00:09:47,475
[APPLAUSE]

290
00:09:47,475 --> 00:09:50,470


291
00:09:50,470 --> 00:09:54,425
And now we will spend the entire weekend
making a better algorithm for that.

292
00:09:54,425 --> 00:09:56,083
[LAUGHTER]

293
00:09:56,083 --> 00:09:57,350
All right.

294
00:09:57,350 --> 00:10:01,070
It is so awesome to be
with you here today.

295
00:10:01,070 --> 00:10:02,500
I'm so honored to be part of this.

296
00:10:02,500 --> 00:10:05,510
We're so happy to be joined by
the Harvard team today to be here

297
00:10:05,510 --> 00:10:07,280
and just to be here with you.

298
00:10:07,280 --> 00:10:09,410
So please, do send our
thanks to your family.

299
00:10:09,410 --> 00:10:13,570
To get us started, we need to make
some noise to bring on Dr. David Malan.

300
00:10:13,570 --> 00:10:16,420
[CHEERING AND APPLAUSE]

301
00:10:16,420 --> 00:10:20,220


302
00:10:20,220 --> 00:10:22,920
DAVID MALAN: Thank you so
much to CS50 [INAUDIBLE]..

303
00:10:22,920 --> 00:10:24,620
This is a very hard act to follow.

304
00:10:24,620 --> 00:10:27,520
And in fact, he was kind enough
to pass the applause off to me.

305
00:10:27,520 --> 00:10:29,340
But I think we should
give it back to him.

306
00:10:29,340 --> 00:10:32,238
[CHEERING AND APPLAUSE]

307
00:10:32,238 --> 00:10:33,690


308
00:10:33,690 --> 00:10:36,330
And allow me to begin
this way, if we may.

309
00:10:36,330 --> 00:10:37,800
This is--

310
00:10:37,800 --> 00:10:40,090
AUDIENCE: CS50!

311
00:10:40,090 --> 00:10:42,950
DAVID MALAN: So nice to have all
of you here with us this weekend.

312
00:10:42,950 --> 00:10:45,500
And welcome to CS50's full community.

313
00:10:45,500 --> 00:10:50,246
We thought we-- before we dive into the
behind the scenes of CS50's pedagogy,

314
00:10:50,246 --> 00:10:53,090
let's do a bit of a pop quiz of sorts.

315
00:10:53,090 --> 00:10:57,470
Could we get eight brave
volunteers to come on down?

316
00:10:57,470 --> 00:10:59,420
We need eight volunteers.

317
00:10:59,420 --> 00:11:03,020
1, 2, 3, 4, 5.

318
00:11:03,020 --> 00:11:04,670
Let me go over here.

319
00:11:04,670 --> 00:11:05,690
No hands over here?

320
00:11:05,690 --> 00:11:08,120
OK, 6, 7, 8.

321
00:11:08,120 --> 00:11:09,620
Come on down.

322
00:11:09,620 --> 00:11:14,080
And if you can form a line
right here in the middle.

323
00:11:14,080 --> 00:11:16,202
Come on down [INAUDIBLE].

324
00:11:16,202 --> 00:11:19,527


325
00:11:19,527 --> 00:11:20,360
AUDIENCE: All right.

326
00:11:20,360 --> 00:11:21,720
DAVID MALAN: Thank you.

327
00:11:21,720 --> 00:11:27,220
All right, here comes number
eight, so 1, 2, 3, 4, 5, 6, 7, 8.

328
00:11:27,220 --> 00:11:30,307
OK, from left to right, do you want
to introduce yourself to the group?

329
00:11:30,307 --> 00:11:31,390
AUDIENCE: I'm [INAUDIBLE].

330
00:11:31,390 --> 00:11:34,518
My name is [INAUDIBLE] from [INAUDIBLE].

331
00:11:34,518 --> 00:11:35,560
AUDIENCE: Hello, welcome.

332
00:11:35,560 --> 00:11:36,790
My name is [? Zach. ?]

333
00:11:36,790 --> 00:11:38,251
[LAUGHTER]

334
00:11:38,251 --> 00:11:42,550
I'm mathematics teachers
from South Sulawesi.

335
00:11:42,550 --> 00:11:46,477
AUDIENCE: Hi, my name is [? Luth ?]
from [INAUDIBLE],, Jordan.

336
00:11:46,477 --> 00:11:47,560
AUDIENCE: Hello, everyone.

337
00:11:47,560 --> 00:11:49,240
My name is [INAUDIBLE].

338
00:11:49,240 --> 00:11:51,280
I'm from West Sumatra.

339
00:11:51,280 --> 00:11:52,550
AUDIENCE: Hello, everyone.

340
00:11:52,550 --> 00:11:56,068
My name is Diana, and I
am from Pocasi, West Java.

341
00:11:56,068 --> 00:11:56,860
AUDIENCE: Hi, guys.

342
00:11:56,860 --> 00:11:58,180
My name's [INAUDIBLE].

343
00:11:58,180 --> 00:11:58,885
I'm [INAUDIBLE].

344
00:11:58,885 --> 00:12:01,807
[LAUGHTER]

345
00:12:01,807 --> 00:12:02,890
AUDIENCE: Hello, everyone.

346
00:12:02,890 --> 00:12:05,310
My name is [INAUDIBLE],, and
I'm an [? MS ?] teacher,

347
00:12:05,310 --> 00:12:08,100
and I'm from [INAUDIBLE].

348
00:12:08,100 --> 00:12:08,983
Thank you.

349
00:12:08,983 --> 00:12:10,080
AUDIENCE: Hello, guys.

350
00:12:10,080 --> 00:12:11,070
My name is [INAUDIBLE].

351
00:12:11,070 --> 00:12:14,120
I come from Aceh.

352
00:12:14,120 --> 00:12:18,838
AUDIENCE: Hello, my name is [INAUDIBLE]
[? Sandy, ?] and [INAUDIBLE]..

353
00:12:18,838 --> 00:12:22,240


354
00:12:22,240 --> 00:12:25,120
DAVID MALAN: Thank you so
much to our nine volunteers.

355
00:12:25,120 --> 00:12:27,532
[APPLAUSE]

356
00:12:27,532 --> 00:12:29,033
So what's your name again?

357
00:12:29,033 --> 00:12:29,950
AUDIENCE: [? Sandy. ?]

358
00:12:29,950 --> 00:12:31,600
DAVID MALAN: [? Sandy. ?]
OK, let's have you step--

359
00:12:31,600 --> 00:12:32,080
step this way.

360
00:12:32,080 --> 00:12:33,913
You're going to help
me with this algorithm.

361
00:12:33,913 --> 00:12:36,886
[CHEERING AND APPLAUSE]

362
00:12:36,886 --> 00:12:41,470
All right, volunteers now could reveal
by turning around their pieces of paper

363
00:12:41,470 --> 00:12:43,360
what number they are.

364
00:12:43,360 --> 00:12:45,640
So show your number to the audience.

365
00:12:45,640 --> 00:12:48,880
You'll see that, unfortunately,
they're unsorted.

366
00:12:48,880 --> 00:12:52,960
And so I think our first
question for the volunteers

367
00:12:52,960 --> 00:12:55,795
here is, please, sort yourselves.

368
00:12:55,795 --> 00:12:58,610
[LAUGHTER]

369
00:12:58,610 --> 00:13:06,330


370
00:13:06,330 --> 00:13:09,210
OK, [? Sandy, ?] what
algorithm was that?

371
00:13:09,210 --> 00:13:11,916
[LAUGHTER]

372
00:13:11,916 --> 00:13:13,720


373
00:13:13,720 --> 00:13:16,060
Unclear, unclear, so let's rewind.

374
00:13:16,060 --> 00:13:21,490
Randomize yourself, different
order, any order is fine.

375
00:13:21,490 --> 00:13:26,378
All right, and now, why don't we
propose to have just our volunteers--

376
00:13:26,378 --> 00:13:28,045
Sandy will give you the third algorithm.

377
00:13:28,045 --> 00:13:28,813
[LAUGHTER]

378
00:13:28,813 --> 00:13:31,730
[INAUDIBLE] volunteers,
could you bubble sort?

379
00:13:31,730 --> 00:13:34,100
[LAUGHTER]

380
00:13:34,100 --> 00:13:37,190
Starting from left to right,
bubble sort yourselves.

381
00:13:37,190 --> 00:13:39,950
[SIDE CONVERSATIONS]

382
00:13:39,950 --> 00:14:00,290


383
00:14:00,290 --> 00:14:02,830
[? Sandy, ?] what algorithm was that?

384
00:14:02,830 --> 00:14:05,830
[LAUGHTER]

385
00:14:05,830 --> 00:14:08,220


386
00:14:08,220 --> 00:14:10,420
Hopefully, that was the bubble sort.

387
00:14:10,420 --> 00:14:10,920
I know.

388
00:14:10,920 --> 00:14:11,840
Sorry.

389
00:14:11,840 --> 00:14:13,356
Let's run the randomizer.

390
00:14:13,356 --> 00:14:16,284
[LAUGHTER]

391
00:14:16,284 --> 00:14:19,212
[SIDE CONVERSATIONS]

392
00:14:19,212 --> 00:14:22,140


393
00:14:22,140 --> 00:14:25,180
[? Sandy ?] and I
[INAUDIBLE] out with this.

394
00:14:25,180 --> 00:14:26,550
So now they're unsorted.

395
00:14:26,550 --> 00:14:29,230
Now, [INAUDIBLE] the bubble
sort has us go left to right,

396
00:14:29,230 --> 00:14:34,226
left to right, left to right, swapping
elements that are out of order.

397
00:14:34,226 --> 00:14:36,955
So accordingly, at the 6 and 7 are OK.

398
00:14:36,955 --> 00:14:40,000
So [? Sandy ?] look over here.

399
00:14:40,000 --> 00:14:41,386
7 and 3 are out of order.

400
00:14:41,386 --> 00:14:42,886
So what should they do, [? Sandy? ?]

401
00:14:42,886 --> 00:14:45,802
[INTERPOSING VOICES]

402
00:14:45,802 --> 00:14:52,120


403
00:14:52,120 --> 00:14:55,036
[CHEERING]

404
00:14:55,036 --> 00:14:57,466
OK, [? Sandy, ?] 7 and 4?

405
00:14:57,466 --> 00:14:58,195
AUDIENCE: Yeah!

406
00:14:58,195 --> 00:14:59,070
DAVID MALAN: 7 and 8?

407
00:14:59,070 --> 00:14:59,896
AUDIENCE: No!

408
00:14:59,896 --> 00:15:00,938
DAVID MALAN: [INAUDIBLE].

409
00:15:00,938 --> 00:15:03,273
AUDIENCE: [INAUDIBLE].

410
00:15:03,273 --> 00:15:05,335
AUDIENCE: [INAUDIBLE].

411
00:15:05,335 --> 00:15:06,460
DAVID MALAN: Yeah, 8 and 1?

412
00:15:06,460 --> 00:15:07,910
AUDIENCE: Yeah!

413
00:15:07,910 --> 00:15:08,820
DAVID MALAN: 8 and 2?

414
00:15:08,820 --> 00:15:10,288
AUDIENCE: Yeah!

415
00:15:10,288 --> 00:15:11,330
DAVID MALAN: Are we done?

416
00:15:11,330 --> 00:15:11,872
AUDIENCE: No!

417
00:15:11,872 --> 00:15:14,202


418
00:15:14,202 --> 00:15:16,660
DAVID MALAN: OK, again,
[? Sandy, ?] you take it from here.

419
00:15:16,660 --> 00:15:17,410
6 and 3?

420
00:15:17,410 --> 00:15:19,880
[INTERPOSING VOICES]

421
00:15:19,880 --> 00:15:31,242


422
00:15:31,242 --> 00:15:34,206
[CHEERING]

423
00:15:34,206 --> 00:15:37,170
[INTERPOSING VOICES]

424
00:15:37,170 --> 00:15:54,155


425
00:15:54,155 --> 00:15:55,280
DAVID MALAN: Are they done?

426
00:15:55,280 --> 00:15:55,822
AUDIENCE: No!

427
00:15:55,822 --> 00:15:58,370


428
00:15:58,370 --> 00:16:00,325
DAVID MALAN: 3 and 4, 4 and 6, 6 and 5.

429
00:16:00,325 --> 00:16:01,336
[INTERPOSING VOICES]

430
00:16:01,336 --> 00:16:02,211
DAVID MALAN: 6 and 1.

431
00:16:02,211 --> 00:16:02,652
AUDIENCE: Yeah!

432
00:16:02,652 --> 00:16:03,534
DAVID MALAN: 6 and 2.

433
00:16:03,534 --> 00:16:03,975
AUDIENCE: Yeah!

434
00:16:03,975 --> 00:16:04,857
DAVID MALAN: 6 and 7?

435
00:16:04,857 --> 00:16:05,742
AUDIENCE: No!

436
00:16:05,742 --> 00:16:06,626
DAVID MALAN: 7 and 8.

437
00:16:06,626 --> 00:16:07,385
AUDIENCE: No!

438
00:16:07,385 --> 00:16:08,510
DAVID MALAN: Are they done?

439
00:16:08,510 --> 00:16:09,510
AUDIENCE: No!

440
00:16:09,510 --> 00:16:12,323
DAVID MALAN: 3 and 4, 4 and 5, 5 and 1.

441
00:16:12,323 --> 00:16:12,948
AUDIENCE: Yeah!

442
00:16:12,948 --> 00:16:13,824
DAVID MALAN: 5 and 2.

443
00:16:13,824 --> 00:16:14,449
AUDIENCE: Yeah!

444
00:16:14,449 --> 00:16:15,514
DAVID MALAN: 5 and 6.

445
00:16:15,514 --> 00:16:16,056
AUDIENCE: No!

446
00:16:16,056 --> 00:16:16,942
DAVID MALAN: 6 and 7.

447
00:16:16,942 --> 00:16:17,484
AUDIENCE: No!

448
00:16:17,484 --> 00:16:17,960
DAVID MALAN: 7 and 8.

449
00:16:17,960 --> 00:16:18,620
Are they done?

450
00:16:18,620 --> 00:16:20,380
AUDIENCE: No!

451
00:16:20,380 --> 00:16:22,268
DAVID MALAN: 3 and 4, for 4 and 1.

452
00:16:22,268 --> 00:16:22,810
AUDIENCE: No!

453
00:16:22,810 --> 00:16:23,685
DAVID MALAN: 4 and 2.

454
00:16:23,685 --> 00:16:24,310
AUDIENCE: Yeah!

455
00:16:24,310 --> 00:16:25,240
DAVID MALAN: 4 and 5.

456
00:16:25,240 --> 00:16:26,052
5 and 6.

457
00:16:26,052 --> 00:16:26,940
6 and 7.

458
00:16:26,940 --> 00:16:27,440
7 and 8.

459
00:16:27,440 --> 00:16:28,018
AUDIENCE: No!

460
00:16:28,018 --> 00:16:29,060
DAVID MALAN: Are we done?

461
00:16:29,060 --> 00:16:30,545
AUDIENCE: No!

462
00:16:30,545 --> 00:16:31,535
DAVID MALAN: 3 and 1.

463
00:16:31,535 --> 00:16:32,525
AUDIENCE: Yes!

464
00:16:32,525 --> 00:16:33,861
DAVID MALAN: 3 and 2.

465
00:16:33,861 --> 00:16:34,444
AUDIENCE: Yes!

466
00:16:34,444 --> 00:16:35,388
DAVID MALAN: 3 and 4.

467
00:16:35,388 --> 00:16:36,304
1 and 5.

468
00:16:36,304 --> 00:16:36,804
[INAUDIBLE]

469
00:16:36,804 --> 00:16:39,443
[CHEERING AND APPLAUSE]

470
00:16:39,443 --> 00:16:40,860
Round of applause for [? Sandy. ?]

471
00:16:40,860 --> 00:16:43,580
[CHEERING AND APPLAUSE]

472
00:16:43,580 --> 00:16:45,590
Thank you so much to our volunteers.

473
00:16:45,590 --> 00:16:47,510
Please, have a seat.

474
00:16:47,510 --> 00:16:51,350
All right, so that you
can keep this [INAUDIBLE]..

475
00:16:51,350 --> 00:16:55,160
So that then was bubble sort.

476
00:16:55,160 --> 00:16:58,640
Well, then the next two days
are meant to be about CS50.

477
00:16:58,640 --> 00:17:02,000
It's meant to be not what is CS50
and what is computer science,

478
00:17:02,000 --> 00:17:03,980
but really why is CS50?

479
00:17:03,980 --> 00:17:06,710
Among our goals for
today and tomorrow are

480
00:17:06,710 --> 00:17:11,480
to look initially at the
pedagogy behind CS50 itself,

481
00:17:11,480 --> 00:17:13,640
looking at why we
teach things the way we

482
00:17:13,640 --> 00:17:17,220
do so that you can decide for
yourselves as a teacher, do you agree?

483
00:17:17,220 --> 00:17:17,970
Do you disagree?

484
00:17:17,970 --> 00:17:21,020
Do you want to adopt the
class for your own students?

485
00:17:21,020 --> 00:17:23,520
Do you want to adapt the
class for your own students?

486
00:17:23,520 --> 00:17:27,170
So there is no one way to teach
certainly computer science and even

487
00:17:27,170 --> 00:17:28,040
CS50.

488
00:17:28,040 --> 00:17:30,200
Both back home and around
the world, teachers

489
00:17:30,200 --> 00:17:33,920
like you really modified it as
they see fit for their students.

490
00:17:33,920 --> 00:17:35,720
And what you'll find
typically is that when

491
00:17:35,720 --> 00:17:39,120
you're teaching computer science
or CS50 for the first time,

492
00:17:39,120 --> 00:17:42,620
you might indeed want to
adopt the class, lean on us.

493
00:17:42,620 --> 00:17:46,100
So have your students watch,
for instance, my videos or some

494
00:17:46,100 --> 00:17:49,430
of our shorts online until
you get comfortable yourselves

495
00:17:49,430 --> 00:17:50,240
with the material.

496
00:17:50,240 --> 00:17:53,540
And then maybe later in the
year or a year or two later

497
00:17:53,540 --> 00:17:57,980
you can adapt the class and make it
your own doing what you agree with,

498
00:17:57,980 --> 00:17:59,660
not doing what you don't disagree with.

499
00:17:59,660 --> 00:18:01,880
And instead of having your
students watch the videos,

500
00:18:01,880 --> 00:18:05,030
maybe just you watch the videos
and then bring the same material

501
00:18:05,030 --> 00:18:07,640
to life yourself in the classroom.

502
00:18:07,640 --> 00:18:11,510
But before we dive into the why, allow
me to thank all of our amazing hosts

503
00:18:11,510 --> 00:18:12,290
here at JIS.

504
00:18:12,290 --> 00:18:14,133
You met some of the Ministry last night.

505
00:18:14,133 --> 00:18:17,383
And a round of applause if we could for
everyone who's made this [INAUDIBLE]..

506
00:18:17,383 --> 00:18:20,694
[APPLAUSE]

507
00:18:20,694 --> 00:18:23,620
Allow me to take a moment
to in that same microphone

508
00:18:23,620 --> 00:18:27,620
to introduce, not just Guy and
myself, but more of CS50's team,

509
00:18:27,620 --> 00:18:31,300
including CS50's own, formerly
JIS's own Bernie Longboy.

510
00:18:31,300 --> 00:18:34,210
[CHEERING AND APPLAUSE]

511
00:18:34,210 --> 00:18:35,135


512
00:18:35,135 --> 00:18:36,635
BERNIE LONGBOY: [NON-ENGLISH SPEECH]

513
00:18:36,635 --> 00:18:38,980
AUDIENCE: [NON-ENGLISH SPEECH]

514
00:18:38,980 --> 00:18:40,480
BERNIE LONGBOY: Is it [NON-ENGLISH].

515
00:18:40,480 --> 00:18:43,878
AUDIENCE: [NON-ENGLISH SPEECH]

516
00:18:43,878 --> 00:18:45,920
BERNIE LONGBOY: I could
never get that one right.

517
00:18:45,920 --> 00:18:48,890
[NON-ENGLISH SPEECH].

518
00:18:48,890 --> 00:18:51,870
Welcome, so happy to have you all here.

519
00:18:51,870 --> 00:18:53,330
We waited for what?

520
00:18:53,330 --> 00:18:57,000
Six months, and super excited
to have you all here today.

521
00:18:57,000 --> 00:19:00,410
So I'm Bernie, and I'm in
charge of-- what do I do?

522
00:19:00,410 --> 00:19:02,000
outreach and partnerships.

523
00:19:02,000 --> 00:19:05,900
So really this big event is
something that we all worked on,

524
00:19:05,900 --> 00:19:07,980
and we're really excited
to kick off today.

525
00:19:07,980 --> 00:19:09,260
So again, welcome.

526
00:19:09,260 --> 00:19:12,860
And if you have any questions or
anything, just look out for any of us,

527
00:19:12,860 --> 00:19:14,180
and we're happy to answer them.

528
00:19:14,180 --> 00:19:17,000
[CHEERING AND APPLAUSE]

529
00:19:17,000 --> 00:19:19,360


530
00:19:19,360 --> 00:19:22,350
DAVID MALAN: And we next
introduce CS50's own Carter Zenke,

531
00:19:22,350 --> 00:19:25,350
who has the distinction of
running CS50 itself back home

532
00:19:25,350 --> 00:19:28,930
at Harvard with our 600, 700
students over the course of the year.

533
00:19:28,930 --> 00:19:29,430
Carter.

534
00:19:29,430 --> 00:19:31,972
[CHEERING AND APPLAUSE]

535
00:19:31,972 --> 00:19:33,222
CARTER ZENKE: Hello, everyone.

536
00:19:33,222 --> 00:19:34,900
It's so good to see you again.

537
00:19:34,900 --> 00:19:35,760
My name is Carter.

538
00:19:35,760 --> 00:19:37,470
And I [? lead ?] the courses lectures.

539
00:19:37,470 --> 00:19:40,740
I lead our sections, our recitations,
our [INAUDIBLE] hands-on [INAUDIBLE]

540
00:19:40,740 --> 00:19:41,545
classes.

541
00:19:41,545 --> 00:19:44,670
I also get to work with our 80 teachers
that we have at Harvard College who

542
00:19:44,670 --> 00:19:46,020
help teach the class.

543
00:19:46,020 --> 00:19:47,220
It's a big group.

544
00:19:47,220 --> 00:19:48,330
We are a big group here.

545
00:19:48,330 --> 00:19:49,810
And I love being part of that community.

546
00:19:49,810 --> 00:19:51,090
So it's exciting being
part of that community.

547
00:19:51,090 --> 00:19:53,290
You all as teachers
can grow in that way.

548
00:19:53,290 --> 00:19:55,207
So thank you [INAUDIBLE]
here in [INAUDIBLE]..

549
00:19:55,207 --> 00:19:57,660
[APPLAUSE]

550
00:19:57,660 --> 00:19:58,205


551
00:19:58,205 --> 00:20:00,330
DAVID MALAN: Allow us to
next introduce all the way

552
00:20:00,330 --> 00:20:04,568
from New York City, Margaret Tanzosh
who teaches her own classes of computer

553
00:20:04,568 --> 00:20:05,610
science for high schools.

554
00:20:05,610 --> 00:20:08,250
And has been wonderfully
working with CS50 for years,

555
00:20:08,250 --> 00:20:11,130
adopting and adapting the
class as she sees fit too.

556
00:20:11,130 --> 00:20:13,330
MARGARET TANZOSH: Hi, so
nice to meet all of you.

557
00:20:13,330 --> 00:20:17,820
I am so excited to share what I've
been doing in my classroom in CS50

558
00:20:17,820 --> 00:20:19,410
for the past eight years.

559
00:20:19,410 --> 00:20:22,493
I was actually one of the first high
school teachers to take on the course

560
00:20:22,493 --> 00:20:25,612
and do a combination of adopting and
adapting and everything in between.

561
00:20:25,612 --> 00:20:27,570
So I'll be talking to
you tomorrow a little bit

562
00:20:27,570 --> 00:20:28,930
about what I do my class like.

563
00:20:28,930 --> 00:20:30,882
And I'm [? asking ?] if
you can now visualize

564
00:20:30,882 --> 00:20:33,465
how you want to run your class
as well [INAUDIBLE] discussion.

565
00:20:33,465 --> 00:20:36,090
[CHEERING AND APPLAUSE]

566
00:20:36,090 --> 00:20:38,430


567
00:20:38,430 --> 00:20:40,780
DAVID MALAN: I daresay he
needs no reintroduction,

568
00:20:40,780 --> 00:20:42,746
but for those of you who [INAUDIBLE]--

569
00:20:42,746 --> 00:20:44,460
[LAUGHTER]

570
00:20:44,460 --> 00:20:46,868
--allow us to ask Guy to
introduce himself [INAUDIBLE]..

571
00:20:46,868 --> 00:20:50,291
[CHEERING AND APPLAUSE]

572
00:20:50,291 --> 00:20:53,230
GUY WHITE: Hello, I'm Guy
White from Portland, Oregon--

573
00:20:53,230 --> 00:20:55,800
[CHEERING AND APPLAUSE]

574
00:20:55,800 --> 00:20:58,110
--where are the weather
is a lot like this today.

575
00:20:58,110 --> 00:21:00,150
It's raining there right now.

576
00:21:00,150 --> 00:21:03,990
I just want to say again, it is my
pleasure to have worked with you.

577
00:21:03,990 --> 00:21:06,180
Truly, please, thank your family.

578
00:21:06,180 --> 00:21:08,245
You've just filled my heart.

579
00:21:08,245 --> 00:21:09,120
This such a blessing.

580
00:21:09,120 --> 00:21:10,560
Thank you so much, everyone.

581
00:21:10,560 --> 00:21:13,143
And I look forward to working
with you over the next two days.

582
00:21:13,143 --> 00:21:15,115
[CHEERING AND APPLAUSE]

583
00:21:15,115 --> 00:21:17,240
DAVID MALAN: And we don't
want to give them the mic

584
00:21:17,240 --> 00:21:19,323
because otherwise we'll
stop recording everything.

585
00:21:19,323 --> 00:21:22,040
But not only are we joined
by JIS's video team here,

586
00:21:22,040 --> 00:21:24,590
we also have Max, and Xochi and Rongxin.

587
00:21:24,590 --> 00:21:27,455
[CHEERING AND APPLAUSE]

588
00:21:27,455 --> 00:21:29,370


589
00:21:29,370 --> 00:21:32,850
So indeed, the videos that
we film this weekend we'll

590
00:21:32,850 --> 00:21:34,290
make available ultimately online.

591
00:21:34,290 --> 00:21:36,540
All of the photos that we've been
taking out in the photo booth,

592
00:21:36,540 --> 00:21:39,510
we'll follow up with the URL so
you can get our versions thereof.

593
00:21:39,510 --> 00:21:43,680
And all of the materials today and
onward will be available on this

594
00:21:43,680 --> 00:21:50,250
website here, CS50.ly/indonesia, which
will give you links to the slides,

595
00:21:50,250 --> 00:21:53,620
any code that we distribute,
the agenda itself.

596
00:21:53,620 --> 00:21:56,940
So this is the URL that you should
keep in your phone today and tomorrow,

597
00:21:56,940 --> 00:21:59,880
but perhaps after the workshop as well.

598
00:21:59,880 --> 00:22:03,390
As we forge ahead today, please,
do interject at any point

599
00:22:03,390 --> 00:22:06,630
if you have questions and also during
the breaks or lunch time tomorrow.

600
00:22:06,630 --> 00:22:09,750
Please, feel free to ask any of
us questions that you might have.

601
00:22:09,750 --> 00:22:12,540
But thought I'd give you an
overview of what we hope to do over

602
00:22:12,540 --> 00:22:14,260
the next couple of days as follows.

603
00:22:14,260 --> 00:22:18,600
So today, we are at that first
white bullet, CS50 explained,

604
00:22:18,600 --> 00:22:19,860
behind the pedagogy.

605
00:22:19,860 --> 00:22:24,030
Between now and 4:00 PM, what
we'll do is focus on that line

606
00:22:24,030 --> 00:22:26,220
of teaching CS50 the way that we do.

607
00:22:26,220 --> 00:22:27,690
We'll then take a 30-minute break.

608
00:22:27,690 --> 00:22:31,140
And at 4:30 PM we'll resume
focusing on what we call back

609
00:22:31,140 --> 00:22:34,170
in Cambridge microteaching,
giving everyone an opportunity

610
00:22:34,170 --> 00:22:39,210
to very comfortably, very safely,
very experimentally teach something

611
00:22:39,210 --> 00:22:41,515
to some of your fellow teachers.

612
00:22:41,515 --> 00:22:43,890
And we'll explain after the
break what that will involve.

613
00:22:43,890 --> 00:22:47,370
No prior preparation is expected.

614
00:22:47,370 --> 00:22:48,443
Maybe we should do this.

615
00:22:48,443 --> 00:22:51,360
Maybe we should teach bubble sort
in all of the individual [INAUDIBLE]

616
00:22:51,360 --> 00:22:52,260
you can do that.

617
00:22:52,260 --> 00:22:54,390
[INAUDIBLE] explain what
that's all about it.

618
00:22:54,390 --> 00:22:57,030
It's meant to really help
you get any of the nerves you

619
00:22:57,030 --> 00:23:00,628
have out now because, especially if
you're teaching CS50 for the first time

620
00:23:00,628 --> 00:23:03,420
or will have been a few months
since you've seen your own students,

621
00:23:03,420 --> 00:23:05,837
it will be a much safer space,
much more comfortable space

622
00:23:05,837 --> 00:23:08,940
to be nervous in among your
colleagues than necessarily

623
00:23:08,940 --> 00:23:12,030
feeling that way in a few weeks
or month's time in your classes.

624
00:23:12,030 --> 00:23:14,270
Tomorrow, meanwhile,
we'll get started early.

625
00:23:14,270 --> 00:23:17,490
And over breakfast, we'll
distribute a packet of puzzles.

626
00:23:17,490 --> 00:23:21,090
Some of you might know online that we
have a tradition of CS50 Puzzle Day.

627
00:23:21,090 --> 00:23:22,120
More on that in a bit.

628
00:23:22,120 --> 00:23:24,450
So upon arrival tomorrow,
you'll be provided

629
00:23:24,450 --> 00:23:26,355
with some food as well as some puzzles.

630
00:23:26,355 --> 00:23:28,900
Now, you don't have to
solve all of the puzzles.

631
00:23:28,900 --> 00:23:31,740
You'll find that they're
somewhat easy or medium or hard.

632
00:23:31,740 --> 00:23:35,160
But the goal is just to enable
you to chat with more teachers

633
00:23:35,160 --> 00:23:37,620
than you came into this workshop
knowing so you hopefully

634
00:23:37,620 --> 00:23:40,320
make a few new connections
and friends and colleagues

635
00:23:40,320 --> 00:23:42,765
while having some fun solving
the very types of problems

636
00:23:42,765 --> 00:23:44,890
that we'll make available
to you in the coming year

637
00:23:44,890 --> 00:23:47,370
if you to run a similar
event for your students.

638
00:23:47,370 --> 00:23:51,930
We'll then focus on teaching CS50
itself and actually experimenting with

639
00:23:51,930 --> 00:23:54,510
and talking about methodologies thereof.

640
00:23:54,510 --> 00:23:57,480
Managing a CS50 classroom,
really a computer science

641
00:23:57,480 --> 00:24:01,320
classroom more generally, focusing
thereafter on comfort levels.

642
00:24:01,320 --> 00:24:04,140
As you might know, within CS50,
certainly back home where we

643
00:24:04,140 --> 00:24:06,270
have a lot of undergraduate
students, we have

644
00:24:06,270 --> 00:24:09,210
problems for those less
comfortable and more comfortable

645
00:24:09,210 --> 00:24:11,040
and somewhere in between too.

646
00:24:11,040 --> 00:24:13,890
And so what we'll discuss
is exactly how you too,

647
00:24:13,890 --> 00:24:16,200
having students who might
have been programming since

648
00:24:16,200 --> 00:24:19,800
they were six years old, and some
students who don't even have access

649
00:24:19,800 --> 00:24:22,560
to computers outside of school,
but you can balance those two

650
00:24:22,560 --> 00:24:24,240
different types of demographics.

651
00:24:24,240 --> 00:24:27,960
We'll take a break and do a working
lunch with some Q&A followed

652
00:24:27,960 --> 00:24:31,950
by a hands-on opportunity to actually--
and this will be much more fun than

653
00:24:31,950 --> 00:24:33,930
being graded by the teaching fellows--

654
00:24:33,930 --> 00:24:38,880
actually grading some sample work so
that you'll get a sense of what is a 5

655
00:24:38,880 --> 00:24:42,630
out of 5 for correctness, at least
as we view it, or design, or style,

656
00:24:42,630 --> 00:24:44,640
and getting you to
think about the teacher

657
00:24:44,640 --> 00:24:48,390
perspective of what you've just
experienced for months as the students

658
00:24:48,390 --> 00:24:49,110
as well.

659
00:24:49,110 --> 00:24:52,290
We'll then have a round two of
microteaching, an opportunity

660
00:24:52,290 --> 00:24:55,140
to improve on however later today goes.

661
00:24:55,140 --> 00:24:57,330
And ultimately, we'll be
giving you an overview

662
00:24:57,330 --> 00:24:59,460
at the end of tomorrow,
all of the resources

663
00:24:59,460 --> 00:25:01,710
that will be available
to you from CS50's team,

664
00:25:01,710 --> 00:25:04,180
both now and in the
coming months and years.

665
00:25:04,180 --> 00:25:07,710
And then we'll conclude with a
presentation of your very own CS50

666
00:25:07,710 --> 00:25:10,936
certificates and congratulate you
and acknowledge you [INAUDIBLE]..

667
00:25:10,936 --> 00:25:13,912
[APPLAUSE]

668
00:25:13,912 --> 00:25:14,910


669
00:25:14,910 --> 00:25:19,730
I do think the right way to think
about CS50 as being OpenCourseWare,

670
00:25:19,730 --> 00:25:24,680
freely available open concept, is that
you can indeed adopt it or adapt it.

671
00:25:24,680 --> 00:25:28,880
And to reiterate, adopt in our
mind means lean on us heavily.

672
00:25:28,880 --> 00:25:32,120
Have your students watch me,
watch Doug in the shorts,

673
00:25:32,120 --> 00:25:37,700
use our problem sets as is, use all
our [? grading ?] as is until such time

674
00:25:37,700 --> 00:25:40,760
as you just feel more comfortable
maybe making some changes

675
00:25:40,760 --> 00:25:44,120
or creating your own problems or
presenting material your own way.

676
00:25:44,120 --> 00:25:47,360
Now, you could certainly do that from
day one if you're already comfortable.

677
00:25:47,360 --> 00:25:50,540
But in general, adapting the
course would be just that.

678
00:25:50,540 --> 00:25:54,560
Like any good teacher, using what
you like or what you don't like

679
00:25:54,560 --> 00:25:57,645
or changing what you don't like
in order to really make the class

680
00:25:57,645 --> 00:25:59,270
and your students' experience your own.

681
00:25:59,270 --> 00:26:01,280
And so that's generally
how we frame the course.

682
00:26:01,280 --> 00:26:02,810
It's not some curriculum.

683
00:26:02,810 --> 00:26:06,200
It's not some textbook that you
have to either use or not use.

684
00:26:06,200 --> 00:26:08,390
So do know that first and foremost.

685
00:26:08,390 --> 00:26:11,300
And those of you who have
never taught CS before,

686
00:26:11,300 --> 00:26:13,820
are maybe coming from another
field, maybe it's math.

687
00:26:13,820 --> 00:26:15,680
Maybe it's something
completely unrelated.

688
00:26:15,680 --> 00:26:18,240
Realize and know that
it is perfectly OK,

689
00:26:18,240 --> 00:26:21,480
and I would encourage you to just
learn along with your students,

690
00:26:21,480 --> 00:26:25,040
especially those kids who are already
a little more comfortable, maybe

691
00:26:25,040 --> 00:26:26,905
have been programming
even longer than you.

692
00:26:26,905 --> 00:26:29,030
They're going to catch on
if you're just pretending

693
00:26:29,030 --> 00:26:30,447
to know what you're talking about.

694
00:26:30,447 --> 00:26:32,220
And so no good will come from that.

695
00:26:32,220 --> 00:26:35,030
So I would encourage
you to be comfortable

696
00:26:35,030 --> 00:26:36,750
feeling uncomfortable at times.

697
00:26:36,750 --> 00:26:39,250
And if you don't know some topic
or some answer, just offer,

698
00:26:39,250 --> 00:26:40,740
well, we'll figure it out together.

699
00:26:40,740 --> 00:26:43,130
And indeed, that plays
into really something

700
00:26:43,130 --> 00:26:46,670
that's a little unusual within
CS50 or at least certain courses

701
00:26:46,670 --> 00:26:50,480
back at Harvard is consider, if
you so can with your schools,

702
00:26:50,480 --> 00:26:54,290
using students as your own teaching
assistants or teaching fellows,

703
00:26:54,290 --> 00:26:55,730
as we call them, or TAs.

704
00:26:55,730 --> 00:26:59,990
And by this I mean, if you already have
that one or a few students who probably

705
00:26:59,990 --> 00:27:01,793
don't really need to
be taking the class,

706
00:27:01,793 --> 00:27:03,960
but maybe it still fills
in gaps in their knowledge,

707
00:27:03,960 --> 00:27:07,245
so it's not pointless for them
to be taking the class formally.

708
00:27:07,245 --> 00:27:10,370
But if you already know that they're
going to be the kid with their hand up

709
00:27:10,370 --> 00:27:13,730
or they're going to be the one getting
100% on the assignments already,

710
00:27:13,730 --> 00:27:17,630
consider, if you can, deputizing
them, so to speak, so as

711
00:27:17,630 --> 00:27:20,540
to be in addition to you
one of the humans walking

712
00:27:20,540 --> 00:27:22,340
around helping their classmates.

713
00:27:22,340 --> 00:27:24,680
For instance, we give some
of our staff little lanyards

714
00:27:24,680 --> 00:27:27,950
that say CS50 that make clear
that they are part of the team.

715
00:27:27,950 --> 00:27:29,840
So little touches like
that, or name tags,

716
00:27:29,840 --> 00:27:32,990
or just knowing that
this person or that is

717
00:27:32,990 --> 00:27:34,650
the teaching assistant for the class.

718
00:27:34,650 --> 00:27:37,130
That's an invaluable
resource, truly, especially

719
00:27:37,130 --> 00:27:39,020
if your class is somewhat larger.

720
00:27:39,020 --> 00:27:43,080
You now had two humans or
three instead of just one.

721
00:27:43,080 --> 00:27:43,940
So here we go.

722
00:27:43,940 --> 00:27:46,573
CS50 explained, behind the pedagogy.

723
00:27:46,573 --> 00:27:47,240
This is the why.

724
00:27:47,240 --> 00:27:49,250
Please, interject at any point.

725
00:27:49,250 --> 00:27:52,400
And of course, we'll make these slides
available for reference thereafter.

726
00:27:52,400 --> 00:27:57,350
Thought we would present to you a
few types of answers to why, namely

727
00:27:57,350 --> 00:28:01,040
on the courses languages,
on the courses lectures,

728
00:28:01,040 --> 00:28:04,070
or really classroom
curriculum, and finally,

729
00:28:04,070 --> 00:28:07,910
focusing too on some of
the courses problem sets.

730
00:28:07,910 --> 00:28:10,070
So this is an image you might recall.

731
00:28:10,070 --> 00:28:12,050
It might still feel this way.

732
00:28:12,050 --> 00:28:16,280
This is a photograph of a [? half ?]
down the road from Harvard and MIT,

733
00:28:16,280 --> 00:28:19,820
where some industrious students
connected a fire hose and fire

734
00:28:19,820 --> 00:28:22,160
hydrant to a water fountain.

735
00:28:22,160 --> 00:28:25,280
And pictured on that sign there,
even though it's very pixelated,

736
00:28:25,280 --> 00:28:29,210
is a the statement along the lines
of, getting an education from MIT

737
00:28:29,210 --> 00:28:32,270
is like drinking from
a fire hose, which is

738
00:28:32,270 --> 00:28:35,150
to say there's no way you're
going to absorb or swallow

739
00:28:35,150 --> 00:28:36,590
all of the information at once.

740
00:28:36,590 --> 00:28:38,150
And it is a little bit forceful.

741
00:28:38,150 --> 00:28:40,760
But the point though,
is that to expect this

742
00:28:40,760 --> 00:28:44,210
from the get go means that you
can indeed be comfortable feeling

743
00:28:44,210 --> 00:28:46,890
uncomfortable throughout the course.

744
00:28:46,890 --> 00:28:49,070
It is not the expectation,
even of our own students

745
00:28:49,070 --> 00:28:51,750
back home, that they'll
master each and every topic,

746
00:28:51,750 --> 00:28:53,320
but that they'll have that exposure.

747
00:28:53,320 --> 00:28:57,560
CS50 is indeed meant to be this
foundation for, this introduction

748
00:28:57,560 --> 00:29:00,560
to computer science, not
necessarily something that's

749
00:29:00,560 --> 00:29:03,950
going to come naturally to all
students the very first time

750
00:29:03,950 --> 00:29:05,610
that they dive into it.

751
00:29:05,610 --> 00:29:09,380
So with that said, why do we
use the languages that we do?

752
00:29:09,380 --> 00:29:12,920
Because CS50, as you might have gleaned,
is already a little different from many

753
00:29:12,920 --> 00:29:15,260
introductory courses,
most introductory courses,

754
00:29:15,260 --> 00:29:19,520
which are typically a Java class or
a Python class or a C++ [INAUDIBLE]..

755
00:29:19,520 --> 00:29:21,470
They are very language centric.

756
00:29:21,470 --> 00:29:25,190
And we're not, because over the course
of 12 or so weeks we, of course,

757
00:29:25,190 --> 00:29:29,720
go from Scratch to C to Python
to SQL to HTML, CSS, Java.

758
00:29:29,720 --> 00:29:32,540
It's very fire hose,
right, on my fingers.

759
00:29:32,540 --> 00:29:33,500
It's a lot.

760
00:29:33,500 --> 00:29:34,400
But what's the point?

761
00:29:34,400 --> 00:29:37,670
Well, very early on when I
actually started teaching CS50,

762
00:29:37,670 --> 00:29:39,592
the course was pretty
much only taught in SQL.

763
00:29:39,592 --> 00:29:42,300
Though there's a little bit of a
language called Ruby at the end.

764
00:29:42,300 --> 00:29:44,133
But students would exit
the class, even when

765
00:29:44,133 --> 00:29:48,860
I took it 20 years ago, with the mindset
that they learned how to program in C.

766
00:29:48,860 --> 00:29:53,180
And so it was rather exclusionary
to them understanding or diving

767
00:29:53,180 --> 00:29:56,513
into other courses or other
languages because they had learned C.

768
00:29:56,513 --> 00:29:58,430
They hadn't learned
computer science, and they

769
00:29:58,430 --> 00:30:00,930
hadn't learned how to program period.

770
00:30:00,930 --> 00:30:04,140
And so among our goals with this
suite of languages is twofold.

771
00:30:04,140 --> 00:30:07,850
One, to make sure that students
do feel that they learned how

772
00:30:07,850 --> 00:30:09,590
to program period.

773
00:30:09,590 --> 00:30:12,800
Or if we want to qualify it, they
learned how to program procedurally.

774
00:30:12,800 --> 00:30:16,420
So not so much object-oriented
stuff, not so much functional stuff,

775
00:30:16,420 --> 00:30:19,458
if you're familiar with these
terms, procedurally programming.

776
00:30:19,458 --> 00:30:22,000
And this is the type of languages
we've generally introduced.

777
00:30:22,000 --> 00:30:24,700
But beyond that, among
our goals in CS50,

778
00:30:24,700 --> 00:30:27,700
is to ensure that it's a
foundation for students taking

779
00:30:27,700 --> 00:30:31,690
computer science for the very first
time before they go on to higher level

780
00:30:31,690 --> 00:30:35,110
classes and more computer science and
programming so they're prepared for it.

781
00:30:35,110 --> 00:30:38,170
But at least back home at
Harvard, half of our students

782
00:30:38,170 --> 00:30:40,850
never take another CS course before.

783
00:30:40,850 --> 00:30:42,250
And we know that going into it.

784
00:30:42,250 --> 00:30:44,980
And for those students we
felt that it's very important

785
00:30:44,980 --> 00:30:49,570
that they not only have the conceptual
mindset of a computer scientist,

786
00:30:49,570 --> 00:30:53,050
they know how to process information
and think about problem solving more

787
00:30:53,050 --> 00:30:56,380
effectively, but they also have some
practical skills that they can bring

788
00:30:56,380 --> 00:30:59,890
back to the arts, humanities,
social sciences, physical sciences,

789
00:30:59,890 --> 00:31:01,300
medical sciences, and the like.

790
00:31:01,300 --> 00:31:03,940
They just have some practical
programming techniques.

791
00:31:03,940 --> 00:31:07,690
And so while we start with
this terminal window using C,

792
00:31:07,690 --> 00:31:11,110
and we end with more of a familiar
paradigm, namely of course,

793
00:31:11,110 --> 00:31:13,770
web programming that's
also increasingly used--

794
00:31:13,770 --> 00:31:17,000
thanks to HTML, CSS, and JavaScript
in the mobile world as well.

795
00:31:17,000 --> 00:31:20,110
So the students are prepared
to never again take a CS class,

796
00:31:20,110 --> 00:31:23,570
but at least to continue to
teach themselves new languages.

797
00:31:23,570 --> 00:31:24,670
So why Scratch?

798
00:31:24,670 --> 00:31:27,670
So back in 2007, one
of the first changes

799
00:31:27,670 --> 00:31:31,600
we made when I took over the class was
changed the class from introducing--

800
00:31:31,600 --> 00:31:36,100
no joke-- assembly language in the first
week of the class to Scratch, which is

801
00:31:36,100 --> 00:31:37,630
dare say the complete opposite.

802
00:31:37,630 --> 00:31:40,120
And even though you might not
know much assembly yourself,

803
00:31:40,120 --> 00:31:43,720
if you think back to week
two, we talked about this.

804
00:31:43,720 --> 00:31:46,690
And we showed the very scary looking
code that wasn't even 0s and 1s.

805
00:31:46,690 --> 00:31:48,790
It was almost scarier and more cryptic.

806
00:31:48,790 --> 00:31:50,590
But that's still with
us today, and that's

807
00:31:50,590 --> 00:31:53,800
a worthy topic for computer
science or engineering students

808
00:31:53,800 --> 00:31:56,120
to learn but maybe not on
the first day of class.

809
00:31:56,120 --> 00:31:59,740
So Scratch, for us, is really meant to
introduce these ideas, these building

810
00:31:59,740 --> 00:32:00,580
blocks to students.

811
00:32:00,580 --> 00:32:02,928
By the way, this is fun,
and better yet, in a way

812
00:32:02,928 --> 00:32:04,720
that they can share it
with their roommates

813
00:32:04,720 --> 00:32:08,320
or send a link back to their parents
back home and delight in what they've

814
00:32:08,320 --> 00:32:12,940
created very visually, very graphically,
without the stupidity of semicolons

815
00:32:12,940 --> 00:32:14,920
and parentheses and
curly braces and stuff

816
00:32:14,920 --> 00:32:17,260
that is just not
intellectually interesting.

817
00:32:17,260 --> 00:32:20,330
Certainly, something you have to
get over eventually, but again,

818
00:32:20,330 --> 00:32:22,238
not on the first day of the class.

819
00:32:22,238 --> 00:32:25,030
And so it's very deliberate, as
you might recall, from our own week

820
00:32:25,030 --> 00:32:28,810
0 and week 1, that when we
introduce this as the first program

821
00:32:28,810 --> 00:32:30,910
that someone could write
in Scratch, we then

822
00:32:30,910 --> 00:32:34,630
tease students with this code, which,
my god, that escalated quickly.

823
00:32:34,630 --> 00:32:38,260
But then if you think about what
you can do with these visuals,

824
00:32:38,260 --> 00:32:39,730
we briefly color code it.

825
00:32:39,730 --> 00:32:43,990
So now, everything that's orange has to
do with the green flag being clicked.

826
00:32:43,990 --> 00:32:46,870
Everything that's purple has
to do with the save block.

827
00:32:46,870 --> 00:32:48,250
And yes, it looks ridiculous.

828
00:32:48,250 --> 00:32:50,920
It's not going to be obvious
what most of those symbols do.

829
00:32:50,920 --> 00:32:53,210
But that's not the point,
certainly on the first day.

830
00:32:53,210 --> 00:32:56,860
This program, of course, still
just prints out, Hello, world.

831
00:32:56,860 --> 00:33:00,100
And then of course, we translate
it to the actual Scratch blocks

832
00:33:00,100 --> 00:33:02,770
so that in the subsequent
week 1, as we call it,

833
00:33:02,770 --> 00:33:04,840
now students hopefully
have a mental model

834
00:33:04,840 --> 00:33:08,620
where they're comfy with the idea
of functions and conditionals

835
00:33:08,620 --> 00:33:11,650
and loops and maybe a few other
ideas like variables and more.

836
00:33:11,650 --> 00:33:15,410
Now we can literally side
by side compare the two

837
00:33:15,410 --> 00:33:17,320
so that if you're comfy
with the program you

838
00:33:17,320 --> 00:33:20,440
wrote just having the task
say, Hello, world, OK, it

839
00:33:20,440 --> 00:33:24,920
looks a little harder to master now on
the right, but it's just the same idea.

840
00:33:24,920 --> 00:33:27,400
So the syntax will come,
but the ideas are the same.

841
00:33:27,400 --> 00:33:28,450
Same thing here.

842
00:33:28,450 --> 00:33:31,900
On the left here, we have an if,
else if, else statement in Scratch.

843
00:33:31,900 --> 00:33:36,850
And of course, it looks much scarier to
a student unfamiliar with textual code,

844
00:33:36,850 --> 00:33:38,300
but it's the same idea.

845
00:33:38,300 --> 00:33:41,680
And so pedagogically the motivation
is to really assure students

846
00:33:41,680 --> 00:33:43,960
that it's fine if you don't
quite get all the syntax

847
00:33:43,960 --> 00:33:45,790
or you make stupid typographical errors.

848
00:33:45,790 --> 00:33:48,500
What's important is that
you understand this,

849
00:33:48,500 --> 00:33:51,612
and you'll get, with practice,
more comfort with this.

850
00:33:51,612 --> 00:33:53,320
And of course, we can
do this with loops,

851
00:33:53,320 --> 00:33:56,380
and we can do this with so many
other different features, including

852
00:33:56,380 --> 00:33:56,990
transitioning.

853
00:33:56,990 --> 00:34:01,720
And this too is delivered mid-semester
in week 6 from C to Python.

854
00:34:01,720 --> 00:34:04,150
You might recall that we
use the same kinds of slides

855
00:34:04,150 --> 00:34:07,120
where I pulled out the exact
same pictures of Scratch blocks

856
00:34:07,120 --> 00:34:11,320
but then showed students how we
would translate it to Python as well.

857
00:34:11,320 --> 00:34:13,810
And this [? isn't ?] very intentional.

858
00:34:13,810 --> 00:34:16,000
Among our goals with
CS50 too in teaching

859
00:34:16,000 --> 00:34:18,219
these different languages
is to show students

860
00:34:18,219 --> 00:34:22,510
that you don't need to take a whole
course on Python to learn Python.

861
00:34:22,510 --> 00:34:24,219
Now, that might
accelerate your learning,

862
00:34:24,219 --> 00:34:26,199
and there is something
to be said for learning

863
00:34:26,199 --> 00:34:29,440
from an expert in the field who might
be able to structure your lessons.

864
00:34:29,440 --> 00:34:32,889
But in reality, they're probably
not going to take courses endlessly

865
00:34:32,889 --> 00:34:33,920
in the future.

866
00:34:33,920 --> 00:34:35,739
And so all the better
if we can give them

867
00:34:35,739 --> 00:34:39,850
some discomfort now looking some
things up online, looking at some

868
00:34:39,850 --> 00:34:42,909
slides, googling for some answer
as to how to do the syntax,

869
00:34:42,909 --> 00:34:47,409
but making clear to them that, even
after three, after six months of CS50,

870
00:34:47,409 --> 00:34:49,600
you've seen most of the ideas out there.

871
00:34:49,600 --> 00:34:54,010
And you just now need to translate
them to some different syntax as well.

872
00:34:54,010 --> 00:34:58,310
We introduce beyond those languages,
of course, SQL for databases.

873
00:34:58,310 --> 00:35:01,990
And here is where I think teachers,
among them Margaret and others,

874
00:35:01,990 --> 00:35:04,780
have made different decisions as
how to structure their classes.

875
00:35:04,780 --> 00:35:09,880
So SQL we introduce so that students
have a real-world database that they

876
00:35:09,880 --> 00:35:10,630
can rely on.

877
00:35:10,630 --> 00:35:14,488
And nowadays, data science and
statistics are increasingly popular.

878
00:35:14,488 --> 00:35:17,280
So this is just a really useful
tool, especially for those students

879
00:35:17,280 --> 00:35:18,780
who never take CS again.

880
00:35:18,780 --> 00:35:22,410
And we use it so that at the end of
the term, especially when we introduce

881
00:35:22,410 --> 00:35:24,480
web programming,
students just don't have

882
00:35:24,480 --> 00:35:27,720
to use a CSV file, which
would work for small websites.

883
00:35:27,720 --> 00:35:29,760
You could read and
write data, but it's not

884
00:35:29,760 --> 00:35:33,190
the right way to do things for
any decent number of users.

885
00:35:33,190 --> 00:35:35,670
So we introduce students to
at least the simplest flavor

886
00:35:35,670 --> 00:35:38,910
of SQL, so not my SQL anymore
or [INAUDIBLE] or, god forbid,

887
00:35:38,910 --> 00:35:41,400
Oracle or the like, but
rather just SQL lite,

888
00:35:41,400 --> 00:35:43,960
which shows all of the
ideas of the language

889
00:35:43,960 --> 00:35:48,820
but also helps students get the job done
on the web or in mobile environments

890
00:35:48,820 --> 00:35:49,320
too.

891
00:35:49,320 --> 00:35:51,030
We introduce HTML, right?

892
00:35:51,030 --> 00:35:52,380
This isn't going anywhere.

893
00:35:52,380 --> 00:35:54,690
Like it or hate it, it's
being used now for the web,

894
00:35:54,690 --> 00:35:57,698
of course, but also for mobile
applications increasingly,

895
00:35:57,698 --> 00:36:00,240
especially since in this room
some of you might have iPhones.

896
00:36:00,240 --> 00:36:02,070
Some of you might have Android devices.

897
00:36:02,070 --> 00:36:06,180
That means twice as much labor for
a company or an individual developer

898
00:36:06,180 --> 00:36:09,123
to make if they want to have
an app that is cross-platform.

899
00:36:09,123 --> 00:36:11,040
So increasingly, you're
seeing, even though we

900
00:36:11,040 --> 00:36:15,330
don't talk about this in CS50 much, but
you're seeing HTML, CSS, and JavaScript

901
00:36:15,330 --> 00:36:15,870
being used.

902
00:36:15,870 --> 00:36:17,910
So you write the code
once, and then you just

903
00:36:17,910 --> 00:36:20,830
put it in a different type of
rectangular window, if you will,

904
00:36:20,830 --> 00:36:25,150
so that it works on both
Android and iOS as well.

905
00:36:25,150 --> 00:36:27,270
So we introduce this
though, again, so that we

906
00:36:27,270 --> 00:36:30,780
could off-board students at the end
of the semester to an environment

907
00:36:30,780 --> 00:36:33,390
that they can actually
build real world tools with.

908
00:36:33,390 --> 00:36:35,820
Of course, we introduce
Flask, which I think

909
00:36:35,820 --> 00:36:38,550
is probably the simplest
of the Python frameworks

910
00:36:38,550 --> 00:36:41,670
that doesn't abstract too much,
doesn't get especially bloated,

911
00:36:41,670 --> 00:36:43,770
like I think Django gets,
especially if we just

912
00:36:43,770 --> 00:36:45,780
have a week or two to introduce it.

913
00:36:45,780 --> 00:36:48,150
And this of course, is how
we introduce students then

914
00:36:48,150 --> 00:36:53,820
to writing code but now interacting
with users via HTTP and the like.

915
00:36:53,820 --> 00:36:57,300
And as for tools, of course, we've
introduced, over the past two

916
00:36:57,300 --> 00:37:00,060
years now, Visual Studio
code, implemented by way

917
00:37:00,060 --> 00:37:02,430
of GitHub code spaces in the cloud.

918
00:37:02,430 --> 00:37:04,830
For us, this too is very deliberate.

919
00:37:04,830 --> 00:37:06,900
Code.org has their own platform.

920
00:37:06,900 --> 00:37:09,990
Many of you might have used
Replit or certain other platforms

921
00:37:09,990 --> 00:37:15,000
out there or even client side IDEs,
like Eclipse or NetBeans or the like.

922
00:37:15,000 --> 00:37:20,070
It's deliberate that we use VS Code
insofar as it's a very general purpose

923
00:37:20,070 --> 00:37:20,640
solution.

924
00:37:20,640 --> 00:37:22,800
It's not one language specific.

925
00:37:22,800 --> 00:37:25,210
It's also free, which is great.

926
00:37:25,210 --> 00:37:27,045
It's also very popular nowadays.

927
00:37:27,045 --> 00:37:30,630
And certainly among US tech companies
and increasingly internationally,

928
00:37:30,630 --> 00:37:34,260
it's just VS code [INAUDIBLE]
development environment of choice

929
00:37:34,260 --> 00:37:37,595
because it's so extensible by having
extensions and plugins and the like.

930
00:37:37,595 --> 00:37:39,720
And so this is deliberate
too that we want students

931
00:37:39,720 --> 00:37:43,337
not using a toy CS50
specific environment such

932
00:37:43,337 --> 00:37:46,170
that when they finish the class
they have no idea how to write code.

933
00:37:46,170 --> 00:37:48,180
But rather, they use this in the cloud.

934
00:37:48,180 --> 00:37:52,830
And then at the end of our term, we try
to off-board as many of our students

935
00:37:52,830 --> 00:37:55,740
as we can by giving them
instructions and videos

936
00:37:55,740 --> 00:37:59,970
for learning how to install Python
and VS Code and anything else

937
00:37:59,970 --> 00:38:01,770
they want on their own Mac or PC.

938
00:38:01,770 --> 00:38:04,500
It's still a headache even
a few months into the class,

939
00:38:04,500 --> 00:38:07,130
but it's not like a barrier
on day one when they just

940
00:38:07,130 --> 00:38:08,880
want to write Hello,
world, but they can't

941
00:38:08,880 --> 00:38:12,630
get Python working in their Windows
path or something like that.

942
00:38:12,630 --> 00:38:18,790
So it's literally start in the cloud but
try to end in the local Macs and PCs.

943
00:38:18,790 --> 00:38:24,130
Any questions now on this whirlwind
tour of our use of languages and tools

944
00:38:24,130 --> 00:38:25,854
and why?

945
00:38:25,854 --> 00:38:28,776
AUDIENCE: Questions [INAUDIBLE].

946
00:38:28,776 --> 00:38:30,724
DAVID MALAN: Yeah.

947
00:38:30,724 --> 00:38:35,107
AUDIENCE: [INAUDIBLE] about [INAUDIBLE]?

948
00:38:35,107 --> 00:38:38,030


949
00:38:38,030 --> 00:38:40,880
DAVID MALAN: Ah, sure try me and
I'll defer it if its two specific.

950
00:38:40,880 --> 00:38:42,824
AUDIENCE: I was thinking
about [INAUDIBLE]..

951
00:38:42,824 --> 00:38:46,950
Is it like [INAUDIBLE]?

952
00:38:46,950 --> 00:38:48,560
Or is it [INAUDIBLE]?

953
00:38:48,560 --> 00:38:57,138


954
00:38:57,138 --> 00:39:01,592
And then [INAUDIBLE]

955
00:39:01,592 --> 00:39:03,300
DAVID MALAN: Sure, a
really good question

956
00:39:03,300 --> 00:39:05,940
about the capacity of a
SQL-like database as it

957
00:39:05,940 --> 00:39:07,800
relates to something like Google Drive.

958
00:39:07,800 --> 00:39:11,370
The capacity of a SQL-like database
completely depends on the device

959
00:39:11,370 --> 00:39:13,140
that your storing the database on.

960
00:39:13,140 --> 00:39:15,090
As you might recall from
the end of the class,

961
00:39:15,090 --> 00:39:18,870
a SQL-like file is usually
[INAUDIBLE] in something like dot dB

962
00:39:18,870 --> 00:39:20,310
or even dot SQL lite.

963
00:39:20,310 --> 00:39:24,330
And that's literally just a file,
a binary file made with 0s and 1s

964
00:39:24,330 --> 00:39:27,098
that might be 0 bytes if
there's nothing in it yet.

965
00:39:27,098 --> 00:39:29,640
That could be a megabyte if
you've got a few tables and rows.

966
00:39:29,640 --> 00:39:32,290
Could be 100 megabytes if
you've got a lot of data.

967
00:39:32,290 --> 00:39:36,360
So the only limiting factor is what's
available on your own Mac or PC

968
00:39:36,360 --> 00:39:38,520
or Android or iOS device.

969
00:39:38,520 --> 00:39:39,770
AUDIENCE: I have a question.

970
00:39:39,770 --> 00:39:41,520
DAVID MALAN: Other
questions on languages.

971
00:39:41,520 --> 00:39:45,170


972
00:39:45,170 --> 00:39:57,850
AUDIENCE: [INAUDIBLE] to make
SQL [? lite ?] by sending some

973
00:39:57,850 --> 00:40:05,140
[? technical ?] [INAUDIBLE] as
easy to write code [INAUDIBLE]..

974
00:40:05,140 --> 00:40:14,280
And can we use [INAUDIBLE]
for our student [INAUDIBLE]??

975
00:40:14,280 --> 00:40:15,600
DAVID MALAN: Yes, absolutely.

976
00:40:15,600 --> 00:40:19,500
So you can, in fact,
use code.CS50.IO, which

977
00:40:19,500 --> 00:40:22,470
will lead you to the same environment
that you've all been using

978
00:40:22,470 --> 00:40:24,180
as students the past several months.

979
00:40:24,180 --> 00:40:26,130
Your own students can use the same.

980
00:40:26,130 --> 00:40:30,840
There are also other ways you can use
code spaces even independent of CS50.

981
00:40:30,840 --> 00:40:33,030
And what we'll do in
the coming weeks is we

982
00:40:33,030 --> 00:40:36,300
hold a Zoom-based tutorial
for those who want to see

983
00:40:36,300 --> 00:40:38,130
other ways of using these same tools.

984
00:40:38,130 --> 00:40:42,750
You can actually use code spaces itself
as a teacher for free because of grants

985
00:40:42,750 --> 00:40:46,500
that Microsoft and GitHub provide
that essentially it gives you more

986
00:40:46,500 --> 00:40:48,390
control over the student's experience.

987
00:40:48,390 --> 00:40:52,180
Whereas, code.CS50.IO automates
a lot of things right now.

988
00:40:52,180 --> 00:40:52,970
So both options.

989
00:40:52,970 --> 00:40:55,312
AUDIENCE: Including all
the [INAUDIBLE] class.

990
00:40:55,312 --> 00:40:56,020
DAVID MALAN: Yes.

991
00:40:56,020 --> 00:40:57,320
AUDIENCE: In C or Python.

992
00:40:57,320 --> 00:41:00,650
DAVID MALAN: There is nothing you have
just experienced in the past six months

993
00:41:00,650 --> 00:41:02,600
that you will not continue
to have access to.

994
00:41:02,600 --> 00:41:05,540
[CHEERING AND APPLAUSE]

995
00:41:05,540 --> 00:41:08,980


996
00:41:08,980 --> 00:41:12,880
So allow me to transition now to
the more curricular side of things.

997
00:41:12,880 --> 00:41:16,740
And as you might know
from the videos, we

998
00:41:16,740 --> 00:41:19,680
tried within CS50 on
that beautiful stage

999
00:41:19,680 --> 00:41:23,980
that in Sanders create as many memorable
moments for students as possible.

1000
00:41:23,980 --> 00:41:27,390
And what this means is just trying
to bring the material to life in ways

1001
00:41:27,390 --> 00:41:31,560
that PowerPoint slides do not belong
or just talking about the material

1002
00:41:31,560 --> 00:41:33,150
or having students read a textbook.

1003
00:41:33,150 --> 00:41:35,790
It doesn't necessarily mean
that these memorable moments

1004
00:41:35,790 --> 00:41:40,440
and these physical demonstrations
are showing or introducing any more

1005
00:41:40,440 --> 00:41:43,440
material that you couldn't introduce
via those other technologies

1006
00:41:43,440 --> 00:41:45,870
and techniques, but that
you're creating, hopefully,

1007
00:41:45,870 --> 00:41:49,650
this visual, like the eight
or nine of you who came up.

1008
00:41:49,650 --> 00:41:52,860
You will never again forget how
not to do bubbles sort perhaps,

1009
00:41:52,860 --> 00:41:55,110
like [? leading ?] that demonstration.

1010
00:41:55,110 --> 00:41:58,628
Until then, we actually did
it with the one final way.

1011
00:41:58,628 --> 00:42:00,420
And so the goal is just
to give that visual

1012
00:42:00,420 --> 00:42:05,220
that persists long after term's end
for many more months, maybe even years.

1013
00:42:05,220 --> 00:42:07,320
And we don't do that for
every topic, of course.

1014
00:42:07,320 --> 00:42:09,265
Otherwise, we'd be here forever.

1015
00:42:09,265 --> 00:42:11,640
But we try to do it for some
of the most difficult topics

1016
00:42:11,640 --> 00:42:15,570
or at least those topics that
lend themselves to theatricality,

1017
00:42:15,570 --> 00:42:16,420
so to speak.

1018
00:42:16,420 --> 00:42:21,180
And so I thought I'd share with you a
few screenshots in a few slides that

1019
00:42:21,180 --> 00:42:24,840
explain why we did things
this past year the way we did.

1020
00:42:24,840 --> 00:42:27,030
So with that said, the
first and foremost,

1021
00:42:27,030 --> 00:42:29,160
maybe most memorable for
students, tends to be

1022
00:42:29,160 --> 00:42:32,620
our implementation of binary search
at the very beginning of the class.

1023
00:42:32,620 --> 00:42:37,200
So here is me in a very awkward
screenshot, tearing that phone

1024
00:42:37,200 --> 00:42:39,420
book, which admittedly
are getting very hard

1025
00:42:39,420 --> 00:42:43,056
to find, so much so we tried to find
one here in Indonesia, and we could not.

1026
00:42:43,056 --> 00:42:44,010
[LAUGHTER]

1027
00:42:44,010 --> 00:42:46,050
But they're even hard
to find back home too.

1028
00:42:46,050 --> 00:42:49,630
But this is an example that,
honestly, after 16 years of teaching

1029
00:42:49,630 --> 00:42:52,830
CS50, some students,
alumni still come up to me

1030
00:42:52,830 --> 00:42:55,986
and mention, oh, I still remember
when you tore that phone book.

1031
00:42:55,986 --> 00:42:56,780
[LAUGHTER]

1032
00:42:56,780 --> 00:42:59,280
There's something to be said
for certainly the memories that

1033
00:42:59,280 --> 00:43:01,140
instills but also just the idea.

1034
00:43:01,140 --> 00:43:05,670
Those students, hopefully, will never
forget the essence of binary search.

1035
00:43:05,670 --> 00:43:08,790
They forget the term, the essence
of dividing and conquering

1036
00:43:08,790 --> 00:43:11,820
a problem by dividing and
dividing and dividing again.

1037
00:43:11,820 --> 00:43:16,260
And so when you have access to
props like this or anything,

1038
00:43:16,260 --> 00:43:18,600
any collection of paper
that you can tear this way,

1039
00:43:18,600 --> 00:43:20,940
consider doing it to bring
that material to life.

1040
00:43:20,940 --> 00:43:21,820
Vary it up.

1041
00:43:21,820 --> 00:43:24,000
Sometimes I have students
come up onto the stage,

1042
00:43:24,000 --> 00:43:25,620
and I have to whisper into
their ear that you have

1043
00:43:25,620 --> 00:43:27,360
to want them to tear the phone book.

1044
00:43:27,360 --> 00:43:29,610
But for now, that just
allows you to create

1045
00:43:29,610 --> 00:43:33,000
all the more visuals for your
students to latch on to even as they

1046
00:43:33,000 --> 00:43:35,310
might struggle with those same topics.

1047
00:43:35,310 --> 00:43:37,530
Something like Scratch,
meanwhile, so Scratch

1048
00:43:37,530 --> 00:43:40,950
has been meant again to be this
practical, fun, accessible opportunity

1049
00:43:40,950 --> 00:43:42,490
to bring material to life.

1050
00:43:42,490 --> 00:43:45,240
And even though some of your
students might have already used

1051
00:43:45,240 --> 00:43:48,720
Scratch or Scratch Junior as
kids in school or at home,

1052
00:43:48,720 --> 00:43:52,532
it's still an opportunity to elevate
it intellectually to make clear

1053
00:43:52,532 --> 00:43:54,990
that it's not just a game or
something to poke around with.

1054
00:43:54,990 --> 00:43:56,190
It is computer science.

1055
00:43:56,190 --> 00:43:58,740
It is an example of
programming, certainly,

1056
00:43:58,740 --> 00:44:02,400
that's much more accessible than what
they're about to see weeks later.

1057
00:44:02,400 --> 00:44:05,190
And here too, we have fun,
especially in that first class,

1058
00:44:05,190 --> 00:44:08,730
where if you're trying to convince
students who might not necessarily

1059
00:44:08,730 --> 00:44:12,300
even consider computer science for
them demographically, academically,

1060
00:44:12,300 --> 00:44:16,330
or otherwise, Scratch is just a nice
way to put everyone on the same playing

1061
00:44:16,330 --> 00:44:16,830
field.

1062
00:44:16,830 --> 00:44:19,800
And you might remember
from week 0, it's great

1063
00:44:19,800 --> 00:44:23,940
when you can get students literally
jumping on stage and implementing this.

1064
00:44:23,940 --> 00:44:27,367
Recall that I think he was trying
to hit the Whack-a-mole, so

1065
00:44:27,367 --> 00:44:29,950
to speak, as we say in English,
where the thing was moving up,

1066
00:44:29,950 --> 00:44:30,930
down, left, and right.

1067
00:44:30,930 --> 00:44:32,280
So just this idea too.

1068
00:44:32,280 --> 00:44:35,160
It's not maybe as high
information content

1069
00:44:35,160 --> 00:44:38,010
as something like tearing the
phone book for binary search.

1070
00:44:38,010 --> 00:44:38,812
But it's just fun.

1071
00:44:38,812 --> 00:44:40,270
It makes students want to be there.

1072
00:44:40,270 --> 00:44:42,145
It makes them want to
come back the next day,

1073
00:44:42,145 --> 00:44:45,750
and we particularly do these kinds of
things at the beginning of the class

1074
00:44:45,750 --> 00:44:50,290
as students are trying to figure out
if this is indeed a world for them.

1075
00:44:50,290 --> 00:44:52,710
With that said, binary
itself, of course,

1076
00:44:52,710 --> 00:44:54,210
is something we talk about early on.

1077
00:44:54,210 --> 00:44:57,070
And this too is an opportunity
to bring students up on stage.

1078
00:44:57,070 --> 00:44:58,950
So here, for instance,
didn't have paper.

1079
00:44:58,950 --> 00:45:02,470
We actually had found plastic numbers
with light bulbs that lighted up.

1080
00:45:02,470 --> 00:45:07,890
And we had our students represent the 1s
place, 2s place, 4s place, and 8 place

1081
00:45:07,890 --> 00:45:11,160
in a way that just allows us to
get some audience participation.

1082
00:45:11,160 --> 00:45:15,567
And really, pedagogically, for the
students in the audience or the puppets

1083
00:45:15,567 --> 00:45:16,275
in the audience--

1084
00:45:16,275 --> 00:45:16,775
[LAUGHTER]

1085
00:45:16,775 --> 00:45:21,000
--to see the students
on stage as themselves

1086
00:45:21,000 --> 00:45:25,890
sort of imagining what would I
do in that student's position?

1087
00:45:25,890 --> 00:45:29,460
So they're engaging a little
more actively within than in just

1088
00:45:29,460 --> 00:45:33,670
listening to someone like me
talk about these kinds of ideas.

1089
00:45:33,670 --> 00:45:37,320
So debugging, we quickly
transition to now our week 2,

1090
00:45:37,320 --> 00:45:40,800
and we tell students about print
f and print later in Python.

1091
00:45:40,800 --> 00:45:46,170
We introduce them to debug50, which
is CS50 specific, but all it does

1092
00:45:46,170 --> 00:45:49,920
is automatically open the built-in
Visible Studio Code debugger.

1093
00:45:49,920 --> 00:45:53,730
So that too is not CS50 specific, but
we make it a little easier to use.

1094
00:45:53,730 --> 00:45:57,165
And then of course, we
introduce them to, in our case,

1095
00:45:57,165 --> 00:46:02,595
a seven-foot rubber duck standing on
stage, an inflatable duck in this case.

1096
00:46:02,595 --> 00:46:04,470
These are sometimes--
well, actually, they've

1097
00:46:04,470 --> 00:46:06,600
gotten very hard to find at that scale.

1098
00:46:06,600 --> 00:46:10,590
But we also have, of course, these
tinier little ducks that we actually

1099
00:46:10,590 --> 00:46:11,700
give out to students.

1100
00:46:11,700 --> 00:46:12,870
And they don't even have to be that big.

1101
00:46:12,870 --> 00:46:15,390
You can find online or you can
make ones [? own ?] out of paper

1102
00:46:15,390 --> 00:46:16,682
or the like, tiny little ducks.

1103
00:46:16,682 --> 00:46:20,550
The goal is to give students recall
some inanimate objects, something cute,

1104
00:46:20,550 --> 00:46:22,780
something memorable just
to put on their shelf

1105
00:46:22,780 --> 00:46:25,200
so when they don't have a
friend or roommate or teacher

1106
00:46:25,200 --> 00:46:28,990
available to answer questions, they can
just start talking through their ideas.

1107
00:46:28,990 --> 00:46:32,550
And there's a reason that we
do this to steer into this.

1108
00:46:32,550 --> 00:46:36,330
And this is kind of ridiculous that
we have this seven-foot duck among all

1109
00:46:36,330 --> 00:46:37,560
our teaching supplies.

1110
00:46:37,560 --> 00:46:39,750
But the goal is to just
normalize this, not just

1111
00:46:39,750 --> 00:46:43,260
to tell students, hey, go find
something inanimate to talk to.

1112
00:46:43,260 --> 00:46:46,110
But to say, hey, if I can stand
there for three hours in front

1113
00:46:46,110 --> 00:46:49,470
of this goofy duck, you can certainly
try it as a debugging technique.

1114
00:46:49,470 --> 00:46:52,560
And some students do take that
to heart and indeed attest

1115
00:46:52,560 --> 00:46:55,140
that this little guy
proves helpful for them

1116
00:46:55,140 --> 00:46:59,040
sometimes because they just hear the
illogic in something they're saying,

1117
00:46:59,040 --> 00:47:01,920
and the proverbial light bulb goes on.

1118
00:47:01,920 --> 00:47:03,550
How about now arrays?

1119
00:47:03,550 --> 00:47:07,380
So arrays are one of the first data
structures that we introduce students

1120
00:47:07,380 --> 00:47:09,970
to, specifically in C in our case.

1121
00:47:09,970 --> 00:47:12,782
And we introduced them initially
in the abstract like this.

1122
00:47:12,782 --> 00:47:14,490
And you might recall
too that [INAUDIBLE]

1123
00:47:14,490 --> 00:47:16,170
even more of the computer's memory.

1124
00:47:16,170 --> 00:47:19,860
But we try to focus on just a few
bytes at a time left to right.

1125
00:47:19,860 --> 00:47:24,060
And from this though, we try to
connect it to something metaphorical,

1126
00:47:24,060 --> 00:47:25,800
like closed doors.

1127
00:47:25,800 --> 00:47:27,928
Like in the US, it's very
common to have hallways

1128
00:47:27,928 --> 00:47:30,220
filled with lockers, where
the kids can put their books

1129
00:47:30,220 --> 00:47:31,840
and their backpacks and the like.

1130
00:47:31,840 --> 00:47:33,840
And so we try to give
them that mental model

1131
00:47:33,840 --> 00:47:37,980
to latch onto like they used to have
maybe in middle school or high school.

1132
00:47:37,980 --> 00:47:40,920
And now some years,
most recently this year,

1133
00:47:40,920 --> 00:47:45,617
we were fortunate to find,
let's see, seven actual lockers.

1134
00:47:45,617 --> 00:47:47,700
These aren't even the big
ones, though they're not

1135
00:47:47,700 --> 00:47:50,510
fun to move across
campus, seven big lockers.

1136
00:47:50,510 --> 00:47:53,440
But the point is that
the door is closed.

1137
00:47:53,440 --> 00:47:57,000
You can't see all of the numbers
at once with this bird's-eye view.

1138
00:47:57,000 --> 00:48:00,220
You have to deliberately
index into it one at a time.

1139
00:48:00,220 --> 00:48:02,230
And this too, of course,
involves not just me

1140
00:48:02,230 --> 00:48:04,890
but a student potentially
coming on up to act this out,

1141
00:48:04,890 --> 00:48:07,140
lending itself to that memorable moment.

1142
00:48:07,140 --> 00:48:10,890
But this is the perfect example,
too, of things where it doesn't

1143
00:48:10,890 --> 00:48:13,350
need to be as high budget as this.

1144
00:48:13,350 --> 00:48:15,600
The fact that I brought paper
today with those numbers

1145
00:48:15,600 --> 00:48:18,262
is exactly what we used
to do back in the day.

1146
00:48:18,262 --> 00:48:20,220
We might just have the
students turn it around.

1147
00:48:20,220 --> 00:48:22,090
When it's closed, they turn it this way.

1148
00:48:22,090 --> 00:48:24,510
So even though we're fortunate
in Cambridge sometimes

1149
00:48:24,510 --> 00:48:28,710
to have seven-feet ducks and
seven of these red lockers,

1150
00:48:28,710 --> 00:48:33,570
paper and pencil and tape is all we used
in my first several years of teaching

1151
00:48:33,570 --> 00:48:36,870
CS50 because that's what I had in
home or we had there on campus.

1152
00:48:36,870 --> 00:48:41,100
So all of these examples are
meant to be quite accessible.

1153
00:48:41,100 --> 00:48:44,770
Now, they didn't know we were
going to do that demo at first.

1154
00:48:44,770 --> 00:48:47,550
So here's a discussion of
bubble sorted selection sort.

1155
00:48:47,550 --> 00:48:50,730
Here, of course, we have those same
plastic numbers that we used back home,

1156
00:48:50,730 --> 00:48:52,950
but paper certainly
suffices for this too.

1157
00:48:52,950 --> 00:48:56,970
But this is an opportunity, again, to
get the audience viewing themselves

1158
00:48:56,970 --> 00:49:00,750
as maybe thinking, my god, thank god
I'm not up there on stage doing this.

1159
00:49:00,750 --> 00:49:01,770
[LAUGHTER]

1160
00:49:01,770 --> 00:49:04,350
But they think to themselves,
how would they do that?

1161
00:49:04,350 --> 00:49:06,840
Or just like you all
were wonderfully yelling

1162
00:49:06,840 --> 00:49:10,620
like a game show up here, just
rooting for the participants

1163
00:49:10,620 --> 00:49:12,780
to actually sort themselves properly.

1164
00:49:12,780 --> 00:49:15,450
That is probably a memory
that will not leave you,

1165
00:49:15,450 --> 00:49:17,550
will not leave them for some time.

1166
00:49:17,550 --> 00:49:20,820
And I daresay, it's a lot more fun
to have that memory about something

1167
00:49:20,820 --> 00:49:23,760
as arcane as bubble
sort or selection sort.

1168
00:49:23,760 --> 00:49:26,040
These are not topics
that you go home and tell

1169
00:49:26,040 --> 00:49:27,750
mom and dad about all that commonly.

1170
00:49:27,750 --> 00:49:30,270
But you might tell mom
and dad and your friends

1171
00:49:30,270 --> 00:49:32,490
about what you did in
your CS class today

1172
00:49:32,490 --> 00:49:35,910
when this sort of hilarity
but educational presentation

1173
00:49:35,910 --> 00:49:37,860
came to life in this way.

1174
00:49:37,860 --> 00:49:41,940
Now, merge sort, recall, was harder
than those two algorithms too.

1175
00:49:41,940 --> 00:49:44,940
And it's especially harder for
students to wrap their mind

1176
00:49:44,940 --> 00:49:45,930
around what's going on.

1177
00:49:45,930 --> 00:49:47,700
And we often try different techniques.

1178
00:49:47,700 --> 00:49:49,410
So while I talk about it, for instance.

1179
00:49:49,410 --> 00:49:50,790
And I might show the pseudocode.

1180
00:49:50,790 --> 00:49:54,270
I might then pull up one of those
web-based animations with the graphics

1181
00:49:54,270 --> 00:49:56,320
or the YouTube video that's showing it.

1182
00:49:56,320 --> 00:49:59,530
That's deliberate too because some
students are very visual learners.

1183
00:49:59,530 --> 00:50:00,480
Some are very audible.

1184
00:50:00,480 --> 00:50:02,410
Some are very intellectual about it.

1185
00:50:02,410 --> 00:50:06,000
And so by just trying 1, 2, 3
different approaches, hopefully,

1186
00:50:06,000 --> 00:50:08,190
we're getting most of
the students on board.

1187
00:50:08,190 --> 00:50:11,970
With this example here, this is
just a metal shelf we put together.

1188
00:50:11,970 --> 00:50:15,120
This allows us to convey
very visually the merge sort

1189
00:50:15,120 --> 00:50:18,810
that the key to its speed
is you have more space.

1190
00:50:18,810 --> 00:50:22,770
And bubble sort and selection sort
just use in-place swapping here.

1191
00:50:22,770 --> 00:50:25,200
We only need as many
bytes if we had people.

1192
00:50:25,200 --> 00:50:27,810
But merge sort, you need at
least twice as much space.

1193
00:50:27,810 --> 00:50:31,230
Now, just for convenience, I
actually use four times as much space

1194
00:50:31,230 --> 00:50:31,920
in this demo.

1195
00:50:31,920 --> 00:50:36,000
But I could go down, up, down,
up as I do those merging.

1196
00:50:36,000 --> 00:50:38,520
So this too, having a couple
of shelves is certainly

1197
00:50:38,520 --> 00:50:41,460
something that should be
discoverable most anywhere.

1198
00:50:41,460 --> 00:50:44,400
We talk about issues
of scope, for instance.

1199
00:50:44,400 --> 00:50:47,730
Recall that the issue of scope means
where can you use the variable?

1200
00:50:47,730 --> 00:50:50,100
And the short answer,
at least in C is, if you

1201
00:50:50,100 --> 00:50:52,480
declare a variable
inside of curly braces,

1202
00:50:52,480 --> 00:50:55,080
you can only use it inside
of those curly braces.

1203
00:50:55,080 --> 00:50:57,510
You can't use it in some
other function or file.

1204
00:50:57,510 --> 00:51:00,630
So we talk about scope
before a lot with students

1205
00:51:00,630 --> 00:51:02,460
because of our discussion of memory.

1206
00:51:02,460 --> 00:51:05,940
But at that point, as well as
for our solving algorithms,

1207
00:51:05,940 --> 00:51:07,500
we need to be able to--

1208
00:51:07,500 --> 00:51:10,790
for our sorting algorithms, we
need to be able to swap values.

1209
00:51:10,790 --> 00:51:13,950
So you might recall that we
really focus on swapping things.

1210
00:51:13,950 --> 00:51:18,117
And this is a demo I've always liked
where we actually use glasses of water.

1211
00:51:18,117 --> 00:51:19,200
We get some food coloring.

1212
00:51:19,200 --> 00:51:22,210
Just choose two different colors
that ideally are visible by students,

1213
00:51:22,210 --> 00:51:23,420
especially with color blindness.

1214
00:51:23,420 --> 00:51:25,020
So you want to choose those carefully.

1215
00:51:25,020 --> 00:51:27,395
And then you can have fun with
this, as you might recall,

1216
00:51:27,395 --> 00:51:29,770
like don't give the student
three glasses at first.

1217
00:51:29,770 --> 00:51:30,480
Give them two.

1218
00:51:30,480 --> 00:51:31,500
See what happens.

1219
00:51:31,500 --> 00:51:32,520
One year, it was funny.

1220
00:51:32,520 --> 00:51:35,100
When I did this, the student
just got a little creative.

1221
00:51:35,100 --> 00:51:38,160
And she just went like this
and moved them slopping them.

1222
00:51:38,160 --> 00:51:39,450
It's not really what I meant.

1223
00:51:39,450 --> 00:51:42,490
We wanted them to, of course,
pour it left and right.

1224
00:51:42,490 --> 00:51:43,990
But this is a fun example too.

1225
00:51:43,990 --> 00:51:48,280
In case your mind is racing, I also
thought I'd be really clever one year

1226
00:51:48,280 --> 00:51:51,130
because it turns out-- we
don't teach this now in CS50--

1227
00:51:51,130 --> 00:51:53,500
using bitwise operators.

1228
00:51:53,500 --> 00:51:57,040
If some of you are familiar, there's
an operation called XOR for exclusive

1229
00:51:57,040 --> 00:52:00,580
or, which allows you to operate
in C on individual bits,

1230
00:52:00,580 --> 00:52:02,710
not just integers or chars or the like.

1231
00:52:02,710 --> 00:52:06,670
You can actually swap two
values in C, if you're clever,

1232
00:52:06,670 --> 00:52:08,800
without needing a temporary variable.

1233
00:52:08,800 --> 00:52:11,830
You can use this other operator
that we don't use currently in CS50,

1234
00:52:11,830 --> 00:52:13,480
but it's a pretty cool trick.

1235
00:52:13,480 --> 00:52:16,120
And so I thought, years ago,
that I'd try to simulate this

1236
00:52:16,120 --> 00:52:17,860
by being very scientifically clever.

1237
00:52:17,860 --> 00:52:22,028
And so I used one glass of
oil and one glass of water

1238
00:52:22,028 --> 00:52:24,070
because I vaguely remembered
from chemistry class

1239
00:52:24,070 --> 00:52:25,780
that these two things shouldn't mix.

1240
00:52:25,780 --> 00:52:28,270
Of course, it mixes but messily.

1241
00:52:28,270 --> 00:52:29,685
We got some bubbles, as I recall.

1242
00:52:29,685 --> 00:52:32,560
So I was trying to prove-- to be
very clever, pour one into the other

1243
00:52:32,560 --> 00:52:33,730
then dump the other out.

1244
00:52:33,730 --> 00:52:36,760
It didn't work, so sometimes
these demonstrations backfire.

1245
00:52:36,760 --> 00:52:38,860
So another moment I
would encourage you to do

1246
00:52:38,860 --> 00:52:42,620
is to test things in advance,
not in front of your students.

1247
00:52:42,620 --> 00:52:47,020
But again, that too just lends itself
all the more to a memorable moment.

1248
00:52:47,020 --> 00:52:48,640
Well, what about memory itself?

1249
00:52:48,640 --> 00:52:52,367
In the US, we very commonly have on
long roads these kinds of mailboxes.

1250
00:52:52,367 --> 00:52:55,450
So they all follow a similar shape,
and so it's very familiar to students.

1251
00:52:55,450 --> 00:53:00,140
And we use these as representative
of how we might store values.

1252
00:53:00,140 --> 00:53:02,680
Now, these I did happen to go
to the local hardware store.

1253
00:53:02,680 --> 00:53:04,930
But you could mimic this
with a picture thereof

1254
00:53:04,930 --> 00:53:06,820
or just a cardboard box of the like.

1255
00:53:06,820 --> 00:53:11,080
And so we use this to give students
just a more concrete visual

1256
00:53:11,080 --> 00:53:13,780
of what we mean when we say an address.

1257
00:53:13,780 --> 00:53:15,970
We can tell them it's
like a mailbox address,

1258
00:53:15,970 --> 00:53:20,080
but there's a little something special
or more memorable about showing

1259
00:53:20,080 --> 00:53:21,220
that actual thing.

1260
00:53:21,220 --> 00:53:26,410
And what I do too is you might
have, at least in American football

1261
00:53:26,410 --> 00:53:28,720
games back home, as
we discussed pointers,

1262
00:53:28,720 --> 00:53:31,240
these foam fingers tend to
come out, maybe in soccer games

1263
00:53:31,240 --> 00:53:32,570
as well around the world.

1264
00:53:32,570 --> 00:53:34,030
You're like, you're a number one.

1265
00:53:34,030 --> 00:53:37,300
We just use it as a big pointer,
not to say we're number one.

1266
00:53:37,300 --> 00:53:39,470
Rather, the value is over there.

1267
00:53:39,470 --> 00:53:42,010
So this is just again a
silly visual that we're

1268
00:53:42,010 --> 00:53:44,470
very careful to choose our
school colors and the like,

1269
00:53:44,470 --> 00:53:47,290
whereby this pointer,
p, might be pointing

1270
00:53:47,290 --> 00:53:50,990
at some other value, some
number, like n over there.

1271
00:53:50,990 --> 00:53:55,630
So just acting things out, taking a few
moments to do exactly that same thing.

1272
00:53:55,630 --> 00:53:59,260
But at the same time-- and this
might have been a discomfort for some

1273
00:53:59,260 --> 00:54:00,070
of you--

1274
00:54:00,070 --> 00:54:02,832
would you get very low
levels sometimes in CS50.

1275
00:54:02,832 --> 00:54:03,790
And this is deliberate.

1276
00:54:03,790 --> 00:54:07,600
In fact, one of the reasons why we
don't use just Python in the class

1277
00:54:07,600 --> 00:54:11,140
is because I think it's a really missed
opportunity for students to understand

1278
00:54:11,140 --> 00:54:14,990
at a lower level what's going
on inside of a computer.

1279
00:54:14,990 --> 00:54:18,520
And if you only learn Python and
that's the only language you ever

1280
00:54:18,520 --> 00:54:20,628
learn and then use, you can use a list.

1281
00:54:20,628 --> 00:54:21,670
You can use a dictionary.

1282
00:54:21,670 --> 00:54:24,040
But do you ever really
understand what it is?

1283
00:54:24,040 --> 00:54:25,780
Maybe conceptually at a high level.

1284
00:54:25,780 --> 00:54:30,100
But there's something about, I think,
pedagogically just showing students

1285
00:54:30,100 --> 00:54:31,660
what's going on underneath the hood.

1286
00:54:31,660 --> 00:54:34,870
It [? don't ?] abstract everything
away, that they'll get it.

1287
00:54:34,870 --> 00:54:38,470
Even though it might be very technical--
and pointers are a hard topic--

1288
00:54:38,470 --> 00:54:40,510
the result is like, wow.

1289
00:54:40,510 --> 00:54:44,170
That light bulb does go off when
in one line of code in Python

1290
00:54:44,170 --> 00:54:49,390
you can re-implement the entirety of
your speller problem set code in C.

1291
00:54:49,390 --> 00:54:51,790
And so that too is
very deliberate to not

1292
00:54:51,790 --> 00:54:55,250
be fearful of just going into the
weeds sometimes with students.

1293
00:54:55,250 --> 00:54:58,810
So for instance, here is the
very technical, pictoral way

1294
00:54:58,810 --> 00:55:03,010
of describing a pointer p, storing
the address of some value n,

1295
00:55:03,010 --> 00:55:04,930
storing the specific number 50.

1296
00:55:04,930 --> 00:55:07,240
But again, we can abstract
that away with a number.

1297
00:55:07,240 --> 00:55:10,330
And then at that point, is when
the foam finger comes out in class,

1298
00:55:10,330 --> 00:55:14,530
and I start pointing at it
between those two mailboxes.

1299
00:55:14,530 --> 00:55:17,560
Later on in the class, too, you
might recall this demonstration,

1300
00:55:17,560 --> 00:55:20,680
and there's so many good little
videos like this on YouTube

1301
00:55:20,680 --> 00:55:22,275
and other universities websites.

1302
00:55:22,275 --> 00:55:24,400
Look for these things, and
hang on to these things.

1303
00:55:24,400 --> 00:55:26,770
Share these kinds of
things with each other.

1304
00:55:26,770 --> 00:55:30,490
This, of course, was Vicki, as I
recall, made by a friend of ours

1305
00:55:30,490 --> 00:55:33,910
at Stanford University, like in his
basement with a little cardboard box

1306
00:55:33,910 --> 00:55:39,670
and some clay that acts out of what can
go wrong when you actually use pointers

1307
00:55:39,670 --> 00:55:40,870
incorrectly.

1308
00:55:40,870 --> 00:55:45,280
And then toward the end of CS50, we
introduce more sophisticated topics,

1309
00:55:45,280 --> 00:55:47,060
data structures, like hashing.

1310
00:55:47,060 --> 00:55:50,290
So recall that hashing means
you take as input some value,

1311
00:55:50,290 --> 00:55:54,910
maybe a person's name, and you
decide what bucket it goes into.

1312
00:55:54,910 --> 00:55:57,640
Like this is the A bucket,
the B bucket, the Z bucket.

1313
00:55:57,640 --> 00:56:00,400
Or what we choose is,
I went online and I

1314
00:56:00,400 --> 00:56:03,220
looked for playing cards
like that you might

1315
00:56:03,220 --> 00:56:06,280
gamble with that I thought it would
be more fun and more visual to search

1316
00:56:06,280 --> 00:56:08,290
for jumbo playing cards.

1317
00:56:08,290 --> 00:56:11,170
And so we indeed have
these 18-inch cards

1318
00:56:11,170 --> 00:56:13,322
that I can use very
visibly in the class.

1319
00:56:13,322 --> 00:56:15,280
We literally went to the
hardware store and got

1320
00:56:15,280 --> 00:56:17,170
some buckets that looked like this.

1321
00:56:17,170 --> 00:56:21,875
And we introduced students to hashing
by literally bucketizing the values.

1322
00:56:21,875 --> 00:56:24,250
And that's a technical term
a lot of engineers would use,

1323
00:56:24,250 --> 00:56:26,250
even though it's a little
abstract for students.

1324
00:56:26,250 --> 00:56:28,960
But if you use actual
buckets, you decrease

1325
00:56:28,960 --> 00:56:34,470
that gap between the idea and
the actual incarnation thereof.

1326
00:56:34,470 --> 00:56:37,410
Lastly, among topics,
maybe race conditions.

1327
00:56:37,410 --> 00:56:40,170
Now, this is where things
really get sophisticated

1328
00:56:40,170 --> 00:56:41,800
in an introductory course.

1329
00:56:41,800 --> 00:56:46,440
And as we tell students, CS50 is
really a combination of what in the US

1330
00:56:46,440 --> 00:56:51,840
and in many countries is called CS1
and CS2 combined because we introduce

1331
00:56:51,840 --> 00:56:53,880
students to software-based programming.

1332
00:56:53,880 --> 00:56:56,400
But we also touch on data
structures and algorithms

1333
00:56:56,400 --> 00:56:59,730
quite a bit that many schools
separate into two separate courses.

1334
00:56:59,730 --> 00:57:01,710
So by the end of the
class, we're nonetheless

1335
00:57:01,710 --> 00:57:04,890
talking about very
sophisticated topics like this

1336
00:57:04,890 --> 00:57:08,470
that often come up in databases,
be it SQL-like or otherwise.

1337
00:57:08,470 --> 00:57:13,200
So here is the tiniest
refrigerator we've yet found.

1338
00:57:13,200 --> 00:57:15,900
We were fortunate a couple
of years ago during COVID,

1339
00:57:15,900 --> 00:57:19,650
we were collaborating with some
friends at the theater on campus

1340
00:57:19,650 --> 00:57:22,350
where they had a whole
warehouse of actual props

1341
00:57:22,350 --> 00:57:25,560
that were used in plays and musicals
that had been used on campus.

1342
00:57:25,560 --> 00:57:29,220
So in some years we've used an actual
refrigerator that was as tall as me.

1343
00:57:29,220 --> 00:57:31,260
It turns out it's a lot
easier to carry around

1344
00:57:31,260 --> 00:57:36,070
a foot-tall, plastic
refrigerator here so as to paint

1345
00:57:36,070 --> 00:57:37,320
the same picture for students.

1346
00:57:37,320 --> 00:57:41,970
This, recall, was the scenario
in which-- what had I run out of

1347
00:57:41,970 --> 00:57:43,354
if you recall?

1348
00:57:43,354 --> 00:57:44,230
AUDIENCE: Database.

1349
00:57:44,230 --> 00:57:47,410
DAVID MALAN: Oh, database, yes, but
what was I pretending to run out of

1350
00:57:47,410 --> 00:57:49,523
and I needed to go to
the store to get more of.

1351
00:57:49,523 --> 00:57:49,986
AUDIENCE: Milk.

1352
00:57:49,986 --> 00:57:50,986
DAVID MALAN: Milk, yeah.

1353
00:57:50,986 --> 00:57:53,180
So I picked a beverage
and said I was out of it.

1354
00:57:53,180 --> 00:57:55,470
I had to go to the store to get it.

1355
00:57:55,470 --> 00:57:59,540
But if I don't leave a note or
if I don't lock the database,

1356
00:57:59,540 --> 00:58:03,200
my roommate, for instance, would come
home, open the variable, if you will,

1357
00:58:03,200 --> 00:58:07,550
and inspect its value, make a decision
based on the exact same value as I did.

1358
00:58:07,550 --> 00:58:11,243
And that's when a race condition
arises because one of us

1359
00:58:11,243 --> 00:58:12,410
is going to come back first.

1360
00:58:12,410 --> 00:58:15,160
The other is going to then arrive,
and then we have too much milk.

1361
00:58:15,160 --> 00:58:17,840
This is exactly what happens
in the world of databases.

1362
00:58:17,840 --> 00:58:20,180
And in fact, I actually
learned this topic myself.

1363
00:58:20,180 --> 00:58:22,940
And a former professor of
mine gave us this example

1364
00:58:22,940 --> 00:58:26,360
of a refrigerator in an operating
systems class that I took 20

1365
00:58:26,360 --> 00:58:27,360
some odd years ago.

1366
00:58:27,360 --> 00:58:29,780
And so here's an
opportunity too, I think,

1367
00:58:29,780 --> 00:58:33,500
to not be scared of or disinclined
to even introduce students

1368
00:58:33,500 --> 00:58:34,940
to advanced topics.

1369
00:58:34,940 --> 00:58:38,990
I think especially if you can base it
in something metaphorical, something

1370
00:58:38,990 --> 00:58:42,630
physical, something
theatrical, if you will.

1371
00:58:42,630 --> 00:58:47,795
So that's a whirlwind tour of just some
select topics as to the [? line. ?]

1372
00:58:47,795 --> 00:58:48,556
AUDIENCE: No.

1373
00:58:48,556 --> 00:58:50,560
[INTERPOSING VOICES]

1374
00:58:50,560 --> 00:58:51,310
DAVID MALAN: What?

1375
00:58:51,310 --> 00:58:51,810
No?

1376
00:58:51,810 --> 00:58:52,353
No way?

1377
00:58:52,353 --> 00:58:54,844
[LAUGHTER]

1378
00:58:54,844 --> 00:58:58,498
It is so much better being a
teacher than a student [INAUDIBLE]..

1379
00:58:58,498 --> 00:59:00,440
[LAUGHTER]

1380
00:59:00,440 --> 00:59:04,055
But if there's any questions on
those memorable moments or the why,

1381
00:59:04,055 --> 00:59:07,940
I am presenting topics like those.

1382
00:59:07,940 --> 00:59:10,790
These are meant to just be
examples to get you thinking.

1383
00:59:10,790 --> 00:59:13,620
Certainly, you've spent the past
six months on all of the topics.

1384
00:59:13,620 --> 00:59:14,337
Yeah.

1385
00:59:14,337 --> 00:59:20,798
AUDIENCE: So last year
my class [INAUDIBLE]

1386
00:59:20,798 --> 00:59:25,289
they thought that it would
be easier [INAUDIBLE]..

1387
00:59:25,289 --> 00:59:25,956
DAVID MALAN: OK.

1388
00:59:25,956 --> 00:59:28,570
AUDIENCE: [INAUDIBLE].

1389
00:59:28,570 --> 00:59:33,360
Right now, I'd also like
[INAUDIBLE] see the [INAUDIBLE]..

1390
00:59:33,360 --> 00:59:34,912
What do you think [INAUDIBLE]?

1391
00:59:34,912 --> 00:59:37,080


1392
00:59:37,080 --> 00:59:38,580
DAVID MALAN: That's a good question.

1393
00:59:38,580 --> 00:59:41,280
For those who couldn't hear,
you've started with save.

1394
00:59:41,280 --> 00:59:44,673
You then switched to Kotlin so as to
introduce object-oriented programming.

1395
00:59:44,673 --> 00:59:45,840
Then you switched to Python.

1396
00:59:45,840 --> 00:59:48,570
And so the question is,
should we maybe go back to C?

1397
00:59:48,570 --> 00:59:50,010
Should we continue using Kotlin?

1398
00:59:50,010 --> 00:59:51,360
I think it depends on the goals.

1399
00:59:51,360 --> 00:59:53,880
Kotlin is particularly
conducive to mobile apps

1400
00:59:53,880 --> 00:59:56,218
nowadays, at least that's
what Google, for instance,

1401
00:59:56,218 --> 00:59:57,510
has been pushing in that space.

1402
00:59:57,510 --> 01:00:00,870
And everything is in object, really,
in that space now, unlike Java.

1403
01:00:00,870 --> 01:00:04,290
So I think that's helpful if
you want your students focusing

1404
01:00:04,290 --> 01:00:05,655
on mobile in particular.

1405
01:00:05,655 --> 01:00:10,023
AUDIENCE: Yeah, because for the
second year they have to [INAUDIBLE]..

1406
01:00:10,023 --> 01:00:10,690
DAVID MALAN: OK.

1407
01:00:10,690 --> 01:00:12,175
AUDIENCE: [INAUDIBLE].

1408
01:00:12,175 --> 01:00:15,150


1409
01:00:15,150 --> 01:00:16,950
DAVID MALAN: And I
think this is where I'll

1410
01:00:16,950 --> 01:00:19,825
be careful too because I think in
the world of programming languages,

1411
01:00:19,825 --> 01:00:22,650
it's very much a religious
debate as to which language is

1412
01:00:22,650 --> 01:00:23,940
best, which you should use.

1413
01:00:23,940 --> 01:00:27,510
But I would say that, if you
introduce students first to C,

1414
01:00:27,510 --> 01:00:30,870
a very common next language
would be something like C++,

1415
01:00:30,870 --> 01:00:35,160
which isn't technically a superset but
does add additional features on top

1416
01:00:35,160 --> 01:00:35,700
of C.

1417
01:00:35,700 --> 01:00:40,770
So for instance, you could spend maybe
less time, maybe in this first class,

1418
01:00:40,770 --> 01:00:44,213
introducing students to C. And then
maybe in the last week, the last two

1419
01:00:44,213 --> 01:00:46,880
weeks, last four weeks, whatever
seems appropriate curricularly,

1420
01:00:46,880 --> 01:00:50,610
you could say that,
well, structs in C only

1421
01:00:50,610 --> 01:00:54,010
get us so far because there's no
functions or methods built into them.

1422
01:00:54,010 --> 01:00:57,480
So it turns out you can use this other
language, which is almost just like C

1423
01:00:57,480 --> 01:00:58,920
but has classes.

1424
01:00:58,920 --> 01:01:00,240
And you can make these objects.

1425
01:01:00,240 --> 01:01:02,310
So you can start to
bridge one or the other

1426
01:01:02,310 --> 01:01:05,340
without completely changing
syntax from one to the other.

1427
01:01:05,340 --> 01:01:08,310
Or instead, if you liked
your experience with Python

1428
01:01:08,310 --> 01:01:10,710
and maybe you still start
with C, you could focus more

1429
01:01:10,710 --> 01:01:12,897
on the object-oriented
aspects of Python.

1430
01:01:12,897 --> 01:01:14,730
And so for instance,
some of you might know.

1431
01:01:14,730 --> 01:01:19,020
We actually have a class in CS50
called CS50P, CS50's introduction

1432
01:01:19,020 --> 01:01:20,220
to programming and Python.

1433
01:01:20,220 --> 01:01:24,930
And we spend like an entire module
on the object-oriented aspects of OOP

1434
01:01:24,930 --> 01:01:25,740
in that class.

1435
01:01:25,740 --> 01:01:27,810
We don't touch it in CS50.

1436
01:01:27,810 --> 01:01:31,320
So I think I would decide based
on what you want-- where you

1437
01:01:31,320 --> 01:01:32,820
want your students writing the code.

1438
01:01:32,820 --> 01:01:35,980
Like if it is a mobile app, then
maybe just focusing really on--

1439
01:01:35,980 --> 01:01:36,480
Kotlin.

1440
01:01:36,480 --> 01:01:37,380
Make sense?

1441
01:01:37,380 --> 01:01:42,496
AUDIENCE: Yeah, [INAUDIBLE]
and [INAUDIBLE]..

1442
01:01:42,496 --> 01:01:43,163
DAVID MALAN: OK.

1443
01:01:43,163 --> 01:01:45,628
AUDIENCE: So [INAUDIBLE]
then [INAUDIBLE]..

1444
01:01:45,628 --> 01:01:49,572
They have two [? markers ?] [INAUDIBLE].

1445
01:01:49,572 --> 01:01:52,540
So [INAUDIBLE].

1446
01:01:52,540 --> 01:01:53,930
DAVID MALAN: Gotcha.

1447
01:01:53,930 --> 01:01:55,430
AUDIENCE: [INAUDIBLE].

1448
01:01:55,430 --> 01:01:59,820
Right now, [INAUDIBLE] because--

1449
01:01:59,820 --> 01:02:02,070
DAVID MALAN: I think, if
there's no one right answer--

1450
01:02:02,070 --> 01:02:04,940
and I would encourage you as a group to,
like during today's breaks, tomorrow's

1451
01:02:04,940 --> 01:02:07,648
lunch, and [INAUDIBLE],, have that
chat and solicit more opinions

1452
01:02:07,648 --> 01:02:08,640
than just mine.

1453
01:02:08,640 --> 01:02:12,200
But those are the kinds of thoughts
that I would bring to the conversation.

1454
01:02:12,200 --> 01:02:13,050
Yeah.

1455
01:02:13,050 --> 01:02:16,956
AUDIENCE: What is the
reason behind [INAUDIBLE]??

1456
01:02:16,956 --> 01:02:22,383


1457
01:02:22,383 --> 01:02:24,258
DAVID MALAN: Well, which
aspect [INAUDIBLE]??

1458
01:02:24,258 --> 01:02:26,090
AUDIENCE: [INAUDIBLE].

1459
01:02:26,090 --> 01:02:28,460
DAVID MALAN: Oh, the
Harvard preps video.

1460
01:02:28,460 --> 01:02:32,660
OK, so you might recall in
week 8 we showed the prank

1461
01:02:32,660 --> 01:02:35,360
that Yale did on Harvard
by having us hold up

1462
01:02:35,360 --> 01:02:37,580
an offensive sign to all of the guests.

1463
01:02:37,580 --> 01:02:45,140
So the motivation for it really
was, one, safetyschool.org recall

1464
01:02:45,140 --> 01:02:47,070
was one of the domains
that we played with.

1465
01:02:47,070 --> 01:02:50,810
And I ran the command that showed
us that safetyschool.org actually

1466
01:02:50,810 --> 01:02:55,010
issues an HTTP redirect to Yale.edu.

1467
01:02:55,010 --> 01:02:57,170
And that's kind of funny, I think.

1468
01:02:57,170 --> 01:02:59,660
But the catch is because
we in CS50 back home

1469
01:02:59,660 --> 01:03:02,330
also had Yale students
at Yale University,

1470
01:03:02,330 --> 01:03:04,580
not quite fair if we only pick on one.

1471
01:03:04,580 --> 01:03:07,520
So I looked up a similar
prank, and that one

1472
01:03:07,520 --> 01:03:10,320
was maybe the best prank
put on Harvard before.

1473
01:03:10,320 --> 01:03:11,842
So we introduced that as well.

1474
01:03:11,842 --> 01:03:13,550
That is certainly
something you can omit,

1475
01:03:13,550 --> 01:03:16,092
especially if your students
don't care about Harvard or Yale.

1476
01:03:16,092 --> 01:03:19,950
But the motivation was to make it an
even playing field and picking on both.

1477
01:03:19,950 --> 01:03:20,450
Yeah.

1478
01:03:20,450 --> 01:03:26,724
AUDIENCE: Yeah, OK, [INAUDIBLE]
amazingly both [INAUDIBLE] CS50

1479
01:03:26,724 --> 01:03:38,660
is [INAUDIBLE], yeah?

1480
01:03:38,660 --> 01:03:41,845
But what is the story behind the
[INAUDIBLE] [? episode ?] so I am

1481
01:03:41,845 --> 01:03:42,470
so [? sorry. ?]

1482
01:03:42,470 --> 01:03:43,350
DAVID MALAN: OK.

1483
01:03:43,350 --> 01:03:48,520
AUDIENCE: I thought of the [INAUDIBLE],,
and [INAUDIBLE] or [INAUDIBLE]..

1484
01:03:48,520 --> 01:03:51,970
And [INAUDIBLE].

1485
01:03:51,970 --> 01:03:59,060
And I think, I [INAUDIBLE] it starts
[? out ?] of there are a [INAUDIBLE]..

1486
01:03:59,060 --> 01:04:05,530
There are [INAUDIBLE].

1487
01:04:05,530 --> 01:04:06,685
There are [INAUDIBLE].

1488
01:04:06,685 --> 01:04:11,460
There are [INAUDIBLE].

1489
01:04:11,460 --> 01:04:17,510
How is CS50 [INAUDIBLE]
make a good [INAUDIBLE]??

1490
01:04:17,510 --> 01:04:24,070
And it's [INAUDIBLE]
won't be the problem.

1491
01:04:24,070 --> 01:04:25,100
DAVID MALAN: Sure.

1492
01:04:25,100 --> 01:04:31,440
AUDIENCE: No [INAUDIBLE] never
has a feature [INAUDIBLE]

1493
01:04:31,440 --> 01:04:35,300
the this problem set [INAUDIBLE].

1494
01:04:35,300 --> 01:04:38,480
DAVID MALAN: Oh, yes, of
course, you can and should use--

1495
01:04:38,480 --> 01:04:42,542
AUDIENCE: Can we adopt or take
the problem set and [INAUDIBLE]

1496
01:04:42,542 --> 01:04:45,780
problem set to [INAUDIBLE]?

1497
01:04:45,780 --> 01:04:48,720
DAVID MALAN: Thank you, and yes, the
answer to all questions like that

1498
01:04:48,720 --> 01:04:49,590
would be yes.

1499
01:04:49,590 --> 01:04:52,530
The material is yours
to use as you see fit.

1500
01:04:52,530 --> 01:04:54,270
[APPLAUSE]

1501
01:04:54,270 --> 01:04:56,940
And what we'll discuss actually
tomorrow in more detail

1502
01:04:56,940 --> 01:04:59,520
is just how many problems
are available, some of which

1503
01:04:59,520 --> 01:05:01,420
are used for CS50 for teachers.

1504
01:05:01,420 --> 01:05:04,800
There are yet other labs, as we
call them, or practice problems.

1505
01:05:04,800 --> 01:05:09,270
And you're free, certainly, to use
some, all of those, none of those,

1506
01:05:09,270 --> 01:05:11,222
and really adapt them
to your own students.

1507
01:05:11,222 --> 01:05:12,930
And in fact, Margaret,
tomorrow will talk

1508
01:05:12,930 --> 01:05:15,090
about her own experience
with her students

1509
01:05:15,090 --> 01:05:18,780
changing the schedule of the
class, picking and choosing some

1510
01:05:18,780 --> 01:05:20,530
of the problems more so than others.

1511
01:05:20,530 --> 01:05:21,660
So more of that to come.

1512
01:05:21,660 --> 01:05:23,820
And in fact, it's a
perfect segue way to what

1513
01:05:23,820 --> 01:05:26,610
I thought I'd propose is just
some of the motivation behind some

1514
01:05:26,610 --> 01:05:28,920
of those problem sets
that you kindly note.

1515
01:05:28,920 --> 01:05:31,320
So the very first you
might remember is really

1516
01:05:31,320 --> 01:05:33,820
one of my favorite games
from my own childhood,

1517
01:05:33,820 --> 01:05:36,930
even though I'm showing my
age, and perhaps now yours,

1518
01:05:36,930 --> 01:05:40,170
is the fact that this is a very
two-dimensional game versus what

1519
01:05:40,170 --> 01:05:41,250
kids have nowadays.

1520
01:05:41,250 --> 01:05:43,200
But Mario is with us in many forms.

1521
01:05:43,200 --> 01:05:45,750
But this is an example
of a problem where

1522
01:05:45,750 --> 01:05:50,190
you have to make that half pyramid
using like hashtags and ASCII marks,

1523
01:05:50,190 --> 01:05:51,100
if you will.

1524
01:05:51,100 --> 01:05:55,290
And this is an example of a problem
that could very easily be very boring.

1525
01:05:55,290 --> 01:05:59,190
If you just ask students to print
out a pyramid with these hashes

1526
01:05:59,190 --> 01:06:00,210
that looks like this.

1527
01:06:00,210 --> 01:06:03,240
OK, but there's something
more, I think, and something

1528
01:06:03,240 --> 01:06:06,390
special about just giving
them something to latch onto,

1529
01:06:06,390 --> 01:06:10,170
that it's not as simple and boring
as a black and white pyramid made out

1530
01:06:10,170 --> 01:06:10,860
of hash tags.

1531
01:06:10,860 --> 01:06:14,130
But it's like the beginnings of
this game that they might know

1532
01:06:14,130 --> 01:06:16,900
or already love or
something familiar to them.

1533
01:06:16,900 --> 01:06:20,220
And so almost always, when Carter
and I write in courses problem sets,

1534
01:06:20,220 --> 01:06:22,442
we try to find that hook.

1535
01:06:22,442 --> 01:06:24,150
It's not enough to
come up with the code.

1536
01:06:24,150 --> 01:06:25,358
It's like, what is the angle?

1537
01:06:25,358 --> 01:06:28,470
What is the image we're going to put
at the very top of the problem set?

1538
01:06:28,470 --> 01:06:31,380
What's the silly YouTube video
that's just there for fun

1539
01:06:31,380 --> 01:06:34,770
to click on, to motivate you
with some music or some TV

1540
01:06:34,770 --> 01:06:38,870
or some movie clip or the like, just
something to make it very real and fun,

1541
01:06:38,870 --> 01:06:41,760
even though it's like
fun for Mary Poppins.

1542
01:06:41,760 --> 01:06:44,460
A spoonful of sugar makes
the medicine go down.

1543
01:06:44,460 --> 01:06:47,850
Actually, incorporating just a
little bit of fun for a problem

1544
01:06:47,850 --> 01:06:50,610
set that is still just
for loops, just code that

1545
01:06:50,610 --> 01:06:53,820
does this, which in and of itself
might not be nearly as engaging.

1546
01:06:53,820 --> 01:06:58,230
So Mario is sort of representative
exactly that mindset.

1547
01:06:58,230 --> 01:07:00,450
We also-- and not all
of you might have done

1548
01:07:00,450 --> 01:07:03,360
this-- there's the more comfortable
version of this problem where

1549
01:07:03,360 --> 01:07:04,477
we take the same idea.

1550
01:07:04,477 --> 01:07:07,560
And it's still going to involve some
for loops and maybe some conditionals

1551
01:07:07,560 --> 01:07:09,570
that will make it a little harder.

1552
01:07:09,570 --> 01:07:12,930
But it's the type of
problem where it's just

1553
01:07:12,930 --> 01:07:15,240
kind of turning the knob a little bit.

1554
01:07:15,240 --> 01:07:18,600
It's not making it crazy difficult
in that week 1 of the class.

1555
01:07:18,600 --> 01:07:21,660
But it's kind of difficult
for many students

1556
01:07:21,660 --> 01:07:24,420
to figure out, OK, it's
very easy to do this.

1557
01:07:24,420 --> 01:07:26,310
Probably pretty easy to do this.

1558
01:07:26,310 --> 01:07:29,430
Starts to get a little annoying
to do this in the middle.

1559
01:07:29,430 --> 01:07:31,020
You have to think a little harder.

1560
01:07:31,020 --> 01:07:32,530
And that's exactly the point.

1561
01:07:32,530 --> 01:07:35,370
And so this is why we have more
comfortable versions of some

1562
01:07:35,370 --> 01:07:39,450
of our problems is so that students
who are very uncomfortable,

1563
01:07:39,450 --> 01:07:43,170
have no prior programming experience,
we want to give them a very low floor.

1564
01:07:43,170 --> 01:07:46,500
So it doesn't take much
to get into the class.

1565
01:07:46,500 --> 01:07:48,855
But for students who have
been programming for a while

1566
01:07:48,855 --> 01:07:50,730
or think they've been
programming for a while

1567
01:07:50,730 --> 01:07:53,250
and they're just more
confident, justly or not,

1568
01:07:53,250 --> 01:07:57,150
they have sort of a higher ceiling,
so they don't walk into the same room

1569
01:07:57,150 --> 01:07:58,720
and have no room to grow.

1570
01:07:58,720 --> 01:08:00,870
But the ceiling is higher
for them, and that's

1571
01:08:00,870 --> 01:08:03,520
what we mean by these
more comfortable problems.

1572
01:08:03,520 --> 01:08:07,410
So a low floor for less comfortable,
but a high ceiling for those more

1573
01:08:07,410 --> 01:08:07,920
comfortable.

1574
01:08:07,920 --> 01:08:11,610
And so Mario captures exactly that
idea at the start of the class.

1575
01:08:11,610 --> 01:08:13,320
Anyone recall?

1576
01:08:13,320 --> 01:08:14,057
Very [INAUDIBLE].

1577
01:08:14,057 --> 01:08:15,722
[INTERPOSING VOICES]

1578
01:08:15,722 --> 01:08:17,180
DAVID MALAN: We're not [INAUDIBLE].

1579
01:08:17,180 --> 01:08:19,037
[INTERPOSING VOICES]

1580
01:08:19,037 --> 01:08:20,393


1581
01:08:20,393 --> 01:08:23,939
--CS50, but this is an
example in week 2 of the class

1582
01:08:23,939 --> 01:08:29,490
where recall we introduced arrays
and the beginnings of memory and data

1583
01:08:29,490 --> 01:08:30,029
structures.

1584
01:08:30,029 --> 01:08:35,399
And it's very easy to make arrays
and conditionals and loops boring.

1585
01:08:35,399 --> 01:08:38,790
And I honestly daresay from my own
experience textbooks are very good.

1586
01:08:38,790 --> 01:08:41,470
Many textbooks are very good
at making things boring.

1587
01:08:41,470 --> 01:08:45,130
But if you contextualize that
same problem and find that hook,

1588
01:08:45,130 --> 01:08:47,880
all right, well, all we want
students really to practice this week

1589
01:08:47,880 --> 01:08:52,080
is strings but treating them as arrays.

1590
01:08:52,080 --> 01:08:54,450
How could we actually make
those strings interesting?

1591
01:08:54,450 --> 01:08:56,399
So it occurred to us
some years ago that,

1592
01:08:56,399 --> 01:09:00,000
why don't we turn it into an example
of cryptography and encryption

1593
01:09:00,000 --> 01:09:03,788
and have a narrative around it and
bring the excitement to students even

1594
01:09:03,788 --> 01:09:05,580
though, at the end of
the day, they're just

1595
01:09:05,580 --> 01:09:07,439
writing for loops and conditionals.

1596
01:09:07,439 --> 01:09:11,460
But hopefully, they're getting better at
those building blocks at the same time.

1597
01:09:11,460 --> 01:09:15,450
Now, we transition in
week 4 to imagery, and you

1598
01:09:15,450 --> 01:09:18,420
can't escape the popularity
of Instagram and TikTok

1599
01:09:18,420 --> 01:09:20,460
and similar platforms
around the world nowadays

1600
01:09:20,460 --> 01:09:24,000
that have filters that change
the colors or do fun things

1601
01:09:24,000 --> 01:09:25,359
with labels and the like.

1602
01:09:25,359 --> 01:09:27,880
And so we use this is an
opportunity, of course,

1603
01:09:27,880 --> 01:09:32,550
to introduce low-level for
idle IO, input and output,

1604
01:09:32,550 --> 01:09:34,620
reading a file, changing
it, and the like.

1605
01:09:34,620 --> 01:09:39,090
We deliberately choose the simplest file
format we can for images, like a BMP

1606
01:09:39,090 --> 01:09:42,220
file, even though no one
really uses them much nowadays.

1607
01:09:42,220 --> 01:09:46,529
But a BMP file's way simpler
than a JPEG or even a ping, PNG.

1608
01:09:46,529 --> 01:09:49,990
So we use bitmap because it has
a very well-defined structure

1609
01:09:49,990 --> 01:09:51,240
that we introduce students to.

1610
01:09:51,240 --> 01:09:54,970
And of course, if I advanced
here, now it's in black and white.

1611
01:09:54,970 --> 01:09:57,240
Now, we've detected all of the edges.

1612
01:09:57,240 --> 01:10:00,720
And even though this
too is a bunch of loops

1613
01:10:00,720 --> 01:10:03,030
but it's also a bunch of
functions because this

1614
01:10:03,030 --> 01:10:07,020
is one of the first problems where we
now give students distribution code.

1615
01:10:07,020 --> 01:10:08,880
And so we imagine the
class, [? too, ?] is

1616
01:10:08,880 --> 01:10:12,300
this notion of scaffolding, much like
you're doing repairs on a building.

1617
01:10:12,300 --> 01:10:15,170
You start to build up those metal
platforms or wooden platforms

1618
01:10:15,170 --> 01:10:16,920
so that the humans can
go up and up and up

1619
01:10:16,920 --> 01:10:18,900
and work on the outside of the building.

1620
01:10:18,900 --> 01:10:22,320
Scaffolding, for us, really means,
at the beginning of the class,

1621
01:10:22,320 --> 01:10:24,360
we really just give
students an empty file

1622
01:10:24,360 --> 01:10:27,270
because we really want them to
go from nothing to something.

1623
01:10:27,270 --> 01:10:31,230
But if they have to start from
scratch every week-- no pun intended--

1624
01:10:31,230 --> 01:10:35,670
there's only so far they can go in
just seven day's time or maybe 14 day's

1625
01:10:35,670 --> 01:10:36,250
time.

1626
01:10:36,250 --> 01:10:41,550
So eventually, we do introduce them to
library code, like the CS50 library,

1627
01:10:41,550 --> 01:10:43,650
and thereafter,
distribution code, like code

1628
01:10:43,650 --> 01:10:47,070
that we write in comment that
they should read and understand.

1629
01:10:47,070 --> 01:10:49,680
But then we have them
start filling in blanks,

1630
01:10:49,680 --> 01:10:52,380
helping them realize how
they can start to structure

1631
01:10:52,380 --> 01:10:54,900
bigger, more sophisticated
programs without spending

1632
01:10:54,900 --> 01:10:56,700
a month implementing that program.

1633
01:10:56,700 --> 01:10:59,700
If we had a month, I don't think
that would be a bad approach.

1634
01:10:59,700 --> 01:11:02,100
But if time is limited,
we pick and choose

1635
01:11:02,100 --> 01:11:04,420
exactly where we want our focus to be.

1636
01:11:04,420 --> 01:11:07,800
So with this image
problem set, so we focus

1637
01:11:07,800 --> 01:11:10,560
on exactly that, the
manipulation of files

1638
01:11:10,560 --> 01:11:12,690
but still using those same primitives.

1639
01:11:12,690 --> 01:11:15,090
This demarcates the start
of what kind of file?

1640
01:11:15,090 --> 01:11:16,172
AUDIENCE: [INAUDIBLE].

1641
01:11:16,172 --> 01:11:17,130
DAVID MALAN: Say again.

1642
01:11:17,130 --> 01:11:19,060
AUDIENCE: [INAUDIBLE].

1643
01:11:19,060 --> 01:11:20,310
DAVID MALAN: [INAUDIBLE] that.

1644
01:11:20,310 --> 01:11:20,850
AUDIENCE: [INAUDIBLE].

1645
01:11:20,850 --> 01:11:21,725
DAVID MALAN: Not RGB.

1646
01:11:21,725 --> 01:11:22,690
AUDIENCE: [INAUDIBLE].

1647
01:11:22,690 --> 01:11:23,940
DAVID MALAN: It's hexadecimal.

1648
01:11:23,940 --> 01:11:25,245
AUDIENCE: Hexadecimal.

1649
01:11:25,245 --> 01:11:26,550
Hexadecimal.

1650
01:11:26,550 --> 01:11:30,140
DAVID MALAN: I'm not sure
I'm hearing the file format.

1651
01:11:30,140 --> 01:11:31,640
This is not a bitmap.

1652
01:11:31,640 --> 01:11:32,165
It's a?

1653
01:11:32,165 --> 01:11:32,990
AUDIENCE: JPEG.

1654
01:11:32,990 --> 01:11:34,740
DAVID MALAN: J-- oh,
I heard it over here.

1655
01:11:34,740 --> 01:11:35,660
JPEG.

1656
01:11:35,660 --> 01:11:36,600
It's a JPEG.

1657
01:11:36,600 --> 01:11:39,240
So these are the first
three bytes of any JPEG,

1658
01:11:39,240 --> 01:11:43,400
like a photograph that you might take
and store on a digital media card,

1659
01:11:43,400 --> 01:11:45,573
much like our own recover assignment.

1660
01:11:45,573 --> 01:11:47,240
So what these numbers are-- don't worry.

1661
01:11:47,240 --> 01:11:50,330
If you've already forgotten
what hexadecimal is, that's OK.

1662
01:11:50,330 --> 01:11:52,370
But the point is that--
and this honestly

1663
01:11:52,370 --> 01:11:54,500
was the best slide I can
come up with for recover,

1664
01:11:54,500 --> 01:11:55,970
which is really hard
because you can't see what

1665
01:11:55,970 --> 01:11:57,595
you're recovering until you recover it.

1666
01:11:57,595 --> 01:12:02,105
So this is just meant to trigger a
recollection of that recover problem

1667
01:12:02,105 --> 01:12:04,640
set, which for me was actually
inspired by real life.

1668
01:12:04,640 --> 01:12:08,570
So like 20 years ago, a friend
of mine had a digital camera

1669
01:12:08,570 --> 01:12:10,150
before we were all carrying phones.

1670
01:12:10,150 --> 01:12:13,280
He had a proper digital camera with
a compact flash part and the like

1671
01:12:13,280 --> 01:12:14,780
that somehow got corrupted.

1672
01:12:14,780 --> 01:12:18,260
Something went wrong, and he lost
like 100 or 1,000 photos, something

1673
01:12:18,260 --> 01:12:19,170
significant.

1674
01:12:19,170 --> 01:12:22,310
And so he and I figured
out by doing some googling

1675
01:12:22,310 --> 01:12:25,490
and poking around that we
can actually write code in C

1676
01:12:25,490 --> 01:12:28,310
to do exactly what you all
did with recover, which

1677
01:12:28,310 --> 01:12:31,400
was to iterate over file,
top to bottom, left to right,

1678
01:12:31,400 --> 01:12:32,840
looking for that pattern.

1679
01:12:32,840 --> 01:12:35,600
And just with high probability,
if you see that pattern,

1680
01:12:35,600 --> 01:12:38,990
statistically, odds [INAUDIBLE] means,
oh, there's one of my friends JPEGs,

1681
01:12:38,990 --> 01:12:40,430
there's another, there's another.

1682
01:12:40,430 --> 01:12:44,600
And I think we recovered like
97% of his JPEGs this way.

1683
01:12:44,600 --> 01:12:48,110
A few years later, I took
overseas CS50, and we introduced

1684
01:12:48,110 --> 01:12:49,910
exactly the same problem set.

1685
01:12:49,910 --> 01:12:52,070
And I actually tell
that story to students

1686
01:12:52,070 --> 01:12:54,620
often to make the point
that some of these problems

1687
01:12:54,620 --> 01:12:56,480
are actually real-world solutions.

1688
01:12:56,480 --> 01:13:00,050
And funny enough, after 16 years,
I've gotten multiple emails

1689
01:13:00,050 --> 01:13:05,090
from alumni, former students, who
wrote to thank us because they too

1690
01:13:05,090 --> 01:13:09,620
accidentally deleted some files, or they
had their memory card get corrupted.

1691
01:13:09,620 --> 01:13:12,290
And they literally used their
problem set [? for ?] code

1692
01:13:12,290 --> 01:13:14,930
to recover their own
photographs, which does not

1693
01:13:14,930 --> 01:13:16,280
happen for everyone, certainly.

1694
01:13:16,280 --> 01:13:20,960
But it, again, attests to just how
real world some of these problems are.

1695
01:13:20,960 --> 01:13:24,270
We try to introduce
students to other domains.

1696
01:13:24,270 --> 01:13:27,050
So you might not know, and
I'm not very good at biology.

1697
01:13:27,050 --> 01:13:31,680
But last time I studied biology
was in ninth grade in high school.

1698
01:13:31,680 --> 01:13:32,180
[LAUGHTER]

1699
01:13:32,180 --> 01:13:35,502
So thankfully, I leaned on a former
colleague, Brian, to help with this.

1700
01:13:35,502 --> 01:13:37,710
So you know from the
[? Walthers, ?] this, of course,

1701
01:13:37,710 --> 01:13:39,680
is an example of our DNA problem set.

1702
01:13:39,680 --> 01:13:41,240
And this too is intentional.

1703
01:13:41,240 --> 01:13:44,330
We try as much as we can, even
though we're a computer science

1704
01:13:44,330 --> 01:13:47,690
class, to intersect our
ourselves with other fields.

1705
01:13:47,690 --> 01:13:50,030
And I am not an expert
in most other fields,

1706
01:13:50,030 --> 01:13:53,900
but this is why I ask lots of questions
of colleagues or teachers like you

1707
01:13:53,900 --> 01:13:56,973
when we do workshops like these
just to get the germ of an idea

1708
01:13:56,973 --> 01:13:59,390
because odds are, if you've
been teaching for a few years,

1709
01:13:59,390 --> 01:14:02,180
sometimes you don't need to hear
a whole lecture, ironically.

1710
01:14:02,180 --> 01:14:04,820
You just need to hear that one
sentence, that one thought,

1711
01:14:04,820 --> 01:14:06,890
that one picture, and
you're like, aha, I

1712
01:14:06,890 --> 01:14:08,900
can turn that into a
homework assignment.

1713
01:14:08,900 --> 01:14:12,333
And so we're constantly on the
lookout for that from other fields,

1714
01:14:12,333 --> 01:14:15,000
talking to friends in the math
department, chemistry department,

1715
01:14:15,000 --> 01:14:17,000
humanities, or the like.

1716
01:14:17,000 --> 01:14:19,460
And then lastly, of course, is--

1717
01:14:19,460 --> 01:14:21,570
[LAUGHTER]

1718
01:14:21,570 --> 01:14:22,395
--problem set 9.

1719
01:14:22,395 --> 01:14:26,700


1720
01:14:26,700 --> 01:14:28,110
I actually checked.

1721
01:14:28,110 --> 01:14:32,280
If you bought Netflix stock at the
moment we shipped this problem set,

1722
01:14:32,280 --> 01:14:35,142
you would have made money
in the past few months.

1723
01:14:35,142 --> 01:14:36,600
And funny enough, I've looked back.

1724
01:14:36,600 --> 01:14:39,142
Years ago, we used to use what
are called penny stocks, which

1725
01:14:39,142 --> 01:14:42,360
are very low-price stocks
that generally mean

1726
01:14:42,360 --> 01:14:43,960
the company might go out of business.

1727
01:14:43,960 --> 01:14:46,470
But funny enough, we
had this map years ago.

1728
01:14:46,470 --> 01:14:49,877
Any time you chose, not Netflix, but
penny stocks, they always went way up.

1729
01:14:49,877 --> 01:14:51,960
And it would have been
this fascinating experience

1730
01:14:51,960 --> 01:14:53,252
to actually buy your own stock.

1731
01:14:53,252 --> 01:14:56,010
But in this case, we got
lucky again with Netflix,

1732
01:14:56,010 --> 01:14:59,530
but this is meant to be the
final problem set for students

1733
01:14:59,530 --> 01:15:00,780
that serves a couple of goals.

1734
01:15:00,780 --> 01:15:03,390
One, it's meant to introduce
them to web [INAUDIBLE]

1735
01:15:03,390 --> 01:15:07,770
so that at the end of the class, if they
never CS again, they have the ability,

1736
01:15:07,770 --> 01:15:11,160
not just to write programs in C in
a black and white terminal window,

1737
01:15:11,160 --> 01:15:15,910
but full-fledged applications
using common, nowadays, technology.

1738
01:15:15,910 --> 01:15:18,450
But it also pedagogically
is meant to be,

1739
01:15:18,450 --> 01:15:20,220
and as it might have
been for many of you,

1740
01:15:20,220 --> 01:15:23,220
a starting point for
their final project.

1741
01:15:23,220 --> 01:15:25,740
Most of our students
back home in Cambridge

1742
01:15:25,740 --> 01:15:30,570
who use a web-based final project,
start with their own problems 9 code,

1743
01:15:30,570 --> 01:15:32,790
or they go back to the
original distribution code.

1744
01:15:32,790 --> 01:15:35,490
They delete all the stuff
that's specific to finance

1745
01:15:35,490 --> 01:15:37,330
or the API and the like.

1746
01:15:37,330 --> 01:15:40,560
But they keep the overall
structure and then use--

1747
01:15:40,560 --> 01:15:41,770
they start changing things.

1748
01:15:41,770 --> 01:15:45,210
And that's exactly what a
aspiring programmer should do

1749
01:15:45,210 --> 01:15:49,200
is stand on the shoulders of libraries
and maybe things they've seen before

1750
01:15:49,200 --> 01:15:50,728
but start to make it their own.

1751
01:15:50,728 --> 01:15:52,770
And so for us that's really
what that problem set

1752
01:15:52,770 --> 01:15:55,500
serves as is this
offboarding of students

1753
01:15:55,500 --> 01:15:59,130
curricularly so that they can
build something of their very own.

1754
01:15:59,130 --> 01:16:01,620
But we've given them just
enough of that scaffolding.

1755
01:16:01,620 --> 01:16:05,780
This is the weak 9 of the scaffolding
being built outside of the building

1756
01:16:05,780 --> 01:16:06,710
here.

1757
01:16:06,710 --> 01:16:12,470
All right, lastly, we have back home
a series of events, one of which

1758
01:16:12,470 --> 01:16:15,690
you saw came in a little
early, called CS50 Fair.

1759
01:16:15,690 --> 01:16:19,550
But it would probably give you a sense
of some of these more unusual social

1760
01:16:19,550 --> 01:16:23,270
or cultural aspects of the class that
we don't do, admittedly, via Zoom.

1761
01:16:23,270 --> 01:16:25,980
These are really meant to be
done in Cambridge at Harvard,

1762
01:16:25,980 --> 01:16:30,860
in New Haven at Yale, here in Jakarta
or your own towns with your own schools.

1763
01:16:30,860 --> 01:16:33,320
And the first of those,
as I alluded to earlier,

1764
01:16:33,320 --> 01:16:35,300
is what we call CS50 Puzzle Day.

1765
01:16:35,300 --> 01:16:39,560
So several years ago, we decided
to start our school year at Harvard

1766
01:16:39,560 --> 01:16:42,480
by distributing a packet
of puzzles to students.

1767
01:16:42,480 --> 01:16:45,770
So if they sign up for this-- they
don't even have to be taking CS50--

1768
01:16:45,770 --> 01:16:49,610
they arrive in our case on a
Saturday afternoon around lunchtime.

1769
01:16:49,610 --> 01:16:52,880
We then hand them a
printed packet of puzzles,

1770
01:16:52,880 --> 01:16:55,253
and those puzzles are
not jigsaw puzzles.

1771
01:16:55,253 --> 01:16:57,170
They are logic problems,
but they have nothing

1772
01:16:57,170 --> 01:17:00,200
to do with programming and nothing
to do with computer science.

1773
01:17:00,200 --> 01:17:04,730
And indeed, the messaging of the event
is to come one, come all and just

1774
01:17:04,730 --> 01:17:06,500
collaborate on some fun problems.

1775
01:17:06,500 --> 01:17:09,350
Now, it helps that we typically
try to find some food for them.

1776
01:17:09,350 --> 01:17:11,090
We deliver some pizzas and the like.

1777
01:17:11,090 --> 01:17:14,540
We typically have some prizes
that we maybe ask a local company

1778
01:17:14,540 --> 01:17:18,770
to sponsor so that we can award
to the folks who solve the most

1779
01:17:18,770 --> 01:17:20,540
puzzles over the course of three hours.

1780
01:17:20,540 --> 01:17:23,000
But really, this event is
meant to send a message

1781
01:17:23,000 --> 01:17:26,150
that computer science,
programming, computer science

1782
01:17:26,150 --> 01:17:27,710
is not about programming.

1783
01:17:27,710 --> 01:17:30,020
It really is about problem
solving, and you don't even

1784
01:17:30,020 --> 01:17:31,820
need your laptop or your phone.

1785
01:17:31,820 --> 01:17:34,010
You just get some friends
and some paper and pencil.

1786
01:17:34,010 --> 01:17:37,160
And indeed, that's what we'll do for
fun tomorrow morning over breakfast

1787
01:17:37,160 --> 01:17:40,160
is just experience a little bit of
that if you've not done it already

1788
01:17:40,160 --> 01:17:41,670
with us online.

1789
01:17:41,670 --> 01:17:44,690
And so in Cambridge, for instance,
we're fortunate to usually get

1790
01:17:44,690 --> 01:17:48,300
300 to 600 students because we
invite not just our students

1791
01:17:48,300 --> 01:17:49,560
but their friends too.

1792
01:17:49,560 --> 01:17:52,910
So this is one of my favorite memories
at the end of every semester here.

1793
01:17:52,910 --> 01:17:55,160
You have a whole bunch of
students looking this way

1794
01:17:55,160 --> 01:17:59,210
because on the projector here we were
walking them through the solutions

1795
01:17:59,210 --> 01:18:02,750
to the problem, which we'll do tomorrow,
for instance, at some point too.

1796
01:18:02,750 --> 01:18:05,060
And it's just the neatest
most inspiring thing

1797
01:18:05,060 --> 01:18:07,880
to see a whole bunch of
smart people delighting

1798
01:18:07,880 --> 01:18:10,730
in just solving problems together.

1799
01:18:10,730 --> 01:18:14,690
And they none of them need higher
programming experience in CS.

1800
01:18:14,690 --> 01:18:16,820
What they do for the
2 and 1/2 hours prior

1801
01:18:16,820 --> 01:18:20,270
to that is just a little bit of
this in a classroom, in a building,

1802
01:18:20,270 --> 01:18:22,400
anywhere on campus, inside or outside.

1803
01:18:22,400 --> 01:18:25,513
They get together in groups
of two or three or four.

1804
01:18:25,513 --> 01:18:27,680
They try to give themselves
a little bit of a buffer

1805
01:18:27,680 --> 01:18:29,690
so they can whisper and
talk about the problems

1806
01:18:29,690 --> 01:18:31,220
to try to be the team next to them.

1807
01:18:31,220 --> 01:18:33,830
But it's just students, smart
students getting together

1808
01:18:33,830 --> 01:18:37,220
trying to solve some problems
that they've never seen before.

1809
01:18:37,220 --> 01:18:41,420
Toward the end of the semester, we
have what we call a CS50 hackathon.

1810
01:18:41,420 --> 01:18:44,330
And a hackathon is,
for us, an opportunity

1811
01:18:44,330 --> 01:18:47,150
for students to gather,
in our case, overnight.

1812
01:18:47,150 --> 01:18:50,270
We start at 7:00 PM,
and we end at 7:00 AM.

1813
01:18:50,270 --> 01:18:54,380
So it's a long night all together in
one of the larger buildings on campus.

1814
01:18:54,380 --> 01:18:57,450
And it's an opportunity for them
to work on their final project.

1815
01:18:57,450 --> 01:19:00,710
So odds are, most of you worked
on your final projects at home

1816
01:19:00,710 --> 01:19:03,230
or at the office or the like alone.

1817
01:19:03,230 --> 01:19:05,630
That's fine, and you still
created those final projects.

1818
01:19:05,630 --> 01:19:08,255
But wouldn't it have been nice
if we could have gotten together

1819
01:19:08,255 --> 01:19:09,950
today and started working on those?

1820
01:19:09,950 --> 01:19:13,430
But that's what this event is all about
just to get smart people together,

1821
01:19:13,430 --> 01:19:16,113
people who might have bugs,
have questions of each other

1822
01:19:16,113 --> 01:19:18,530
and lean on each other because
every student at that point

1823
01:19:18,530 --> 01:19:20,730
is pretty much doing
something on their own.

1824
01:19:20,730 --> 01:19:22,730
Maybe they have a partner
or two, but everyone's

1825
01:19:22,730 --> 01:19:23,880
working on something different.

1826
01:19:23,880 --> 01:19:25,130
So it really is collaborative.

1827
01:19:25,130 --> 01:19:28,070
And this is different from
what industry tends to do.

1828
01:19:28,070 --> 01:19:31,040
A lot of companies sponsor
hackathons, which are great too.

1829
01:19:31,040 --> 01:19:32,540
But those tend to be competitive.

1830
01:19:32,540 --> 01:19:34,830
And CS50's back home is not competitive.

1831
01:19:34,830 --> 01:19:35,720
There's no prizes.

1832
01:19:35,720 --> 01:19:36,860
Everyone gets pizza.

1833
01:19:36,860 --> 01:19:40,190
Everyone gets desserts and the like,
and there's no reward at the end other

1834
01:19:40,190 --> 01:19:41,450
than you finished.

1835
01:19:41,450 --> 01:19:44,510
You took CS50 by having
finished your project,

1836
01:19:44,510 --> 01:19:47,430
and not necessarily that night,
but having begun or done well.

1837
01:19:47,430 --> 01:19:51,890
And here, for instance, are some
students around probably midnight.

1838
01:19:51,890 --> 01:19:53,990
And here is a student around 5:00 AM.

1839
01:19:53,990 --> 01:19:56,420
[LAUGHTER]

1840
01:19:56,420 --> 01:19:59,692
And the last memory
and the last tradition

1841
01:19:59,692 --> 01:20:01,400
that I thought I'd
share with you is what

1842
01:20:01,400 --> 01:20:04,740
you saw playing before we
began today, the CS50 Fair.

1843
01:20:04,740 --> 01:20:06,680
This is something that
we put on hold back

1844
01:20:06,680 --> 01:20:08,510
home for like three
years because of COVID

1845
01:20:08,510 --> 01:20:11,510
but just resumed it in December of 2022.

1846
01:20:11,510 --> 01:20:14,870
And the vision here was modeled
originally on what in the US

1847
01:20:14,870 --> 01:20:18,320
is commonly like a middle school
science fair where the kids get together

1848
01:20:18,320 --> 01:20:21,530
and they demonstrate something that
glows or something that explodes

1849
01:20:21,530 --> 01:20:24,480
or maybe a volcano they built
or something fun like that.

1850
01:20:24,480 --> 01:20:27,590
But in our case, the students
bring their laptops or their phones

1851
01:20:27,590 --> 01:20:29,360
depending on what
their final project is.

1852
01:20:29,360 --> 01:20:31,760
And we play fun music like
we were playing earlier.

1853
01:20:31,760 --> 01:20:33,350
We inflate balloons.

1854
01:20:33,350 --> 01:20:34,850
We bring some candy and snacks.

1855
01:20:34,850 --> 01:20:38,720
And in our case, too, we try to
invite companies just to be there--

1856
01:20:38,720 --> 01:20:39,710
they have tables--

1857
01:20:39,710 --> 01:20:43,580
just to talk to students about
future opportunities in technology.

1858
01:20:43,580 --> 01:20:46,220
Maybe not so applicable for
middle school students, but yes,

1859
01:20:46,220 --> 01:20:49,350
for university students and maybe
for high school students too.

1860
01:20:49,350 --> 01:20:53,520
And so this too has been a secret
ingredient for us over the years.

1861
01:20:53,520 --> 01:20:57,560
If you're in a town or a city where
there are some technology companies

1862
01:20:57,560 --> 01:20:59,510
or if you have
connections to folks who--

1863
01:20:59,510 --> 01:21:02,060
colleagues who are now
in industry, I wouldn't

1864
01:21:02,060 --> 01:21:06,520
hesitate to just ask companies for
support, to have them bring the pizza,

1865
01:21:06,520 --> 01:21:08,530
to have them send over
some snacks, to have

1866
01:21:08,530 --> 01:21:10,990
them send some T-shirts with
their company's logo on it,

1867
01:21:10,990 --> 01:21:13,910
but things to just give students
and engage them all the more.

1868
01:21:13,910 --> 01:21:16,450
And strategically, what we
often do is we don't just

1869
01:21:16,450 --> 01:21:20,200
ask them to, please, provide the
pizza, or please, send some T-shirts.

1870
01:21:20,200 --> 01:21:22,660
We invite them to join us
at some of these events.

1871
01:21:22,660 --> 01:21:26,980
We invite them to give a Tech Talk,
maybe a 20-minute or 30-minute talk

1872
01:21:26,980 --> 01:21:27,730
for students.

1873
01:21:27,730 --> 01:21:31,090
We invite them to join us for
a lunch or dinner with students

1874
01:21:31,090 --> 01:21:35,150
just to chat about using technology
and programming in the real world.

1875
01:21:35,150 --> 01:21:38,030
So depending on where you are and
what companies might be nearby,

1876
01:21:38,030 --> 01:21:41,590
I want you to know, I think there's
some really interesting opportunities

1877
01:21:41,590 --> 01:21:43,430
to collaborate in that way.

1878
01:21:43,430 --> 01:21:46,000
With that said, we don't
typically invite companies

1879
01:21:46,000 --> 01:21:49,120
to our office hours or the
sections or recitations

1880
01:21:49,120 --> 01:21:50,680
that we keep purely academic.

1881
01:21:50,680 --> 01:21:53,560
But for these more social, these
more collaborative environments,

1882
01:21:53,560 --> 01:21:58,880
we do open the door, not only to our
students, but also the bigger world

1883
01:21:58,880 --> 01:22:00,120
as well.

1884
01:22:00,120 --> 01:22:05,120
So here is just a photograph of one
such fair just before the pandemic.

1885
01:22:05,120 --> 01:22:08,450
Here is exactly what students do the
whole time, standing at a laptop,

1886
01:22:08,450 --> 01:22:10,040
smiling, being asked questions.

1887
01:22:10,040 --> 01:22:12,770
And just to add a little twist
to things, what we do here too

1888
01:22:12,770 --> 01:22:17,960
is everyone who attends this particular
event gets a blank card, a raffle card,

1889
01:22:17,960 --> 01:22:20,960
that's got like 10 unhappy faces on it.

1890
01:22:20,960 --> 01:22:25,520
But we give to all of our CS50 students
little yellow smiley face stickers.

1891
01:22:25,520 --> 01:22:28,830
And the idea is that any time--
and attendee, whether it's

1892
01:22:28,830 --> 01:22:32,850
a teaching fellow or a student
or another professor or a parent

1893
01:22:32,850 --> 01:22:36,420
comes by and asks the student for
a demonstration of their project,

1894
01:22:36,420 --> 01:22:41,520
the social contract is that the student
gives that attendee a yellow sticker.

1895
01:22:41,520 --> 01:22:45,150
And every sticker entitles you
to one entry in the raffle,

1896
01:22:45,150 --> 01:22:47,310
and we typically ask
some friends in industry,

1897
01:22:47,310 --> 01:22:49,770
could you give us some prizes
that we can raffle off?

1898
01:22:49,770 --> 01:22:54,000
And what it really does socially is
just grease the wheels, especially

1899
01:22:54,000 --> 01:22:57,150
for students who might be more
introverted or less comfortable, it

1900
01:22:57,150 --> 01:23:00,760
just gives them an excuse to walk
up to a stranger and say, hey,

1901
01:23:00,760 --> 01:23:01,800
can I see your project?

1902
01:23:01,800 --> 01:23:04,887
And they end up, invariably,
delighting in what they're seeing.

1903
01:23:04,887 --> 01:23:06,720
They also get that
sticker, and so it's sort

1904
01:23:06,720 --> 01:23:09,210
of a social greasing of the wheels.

1905
01:23:09,210 --> 01:23:12,150
So we do try to think about
these things both inside

1906
01:23:12,150 --> 01:23:13,500
and outside of the classroom.

1907
01:23:13,500 --> 01:23:16,800
And this was just CS50
really in an hour and a half.

1908
01:23:16,800 --> 01:23:19,860
You, of course, have spent six
months living and breathing it.

1909
01:23:19,860 --> 01:23:24,210
But our hope is that to in reviewing
these problem sets, these languages,

1910
01:23:24,210 --> 01:23:27,630
these memorable moments, you just
have more of a sense of the why.

1911
01:23:27,630 --> 01:23:30,240
And if you disagree with some
of the why, that too is fine.

1912
01:23:30,240 --> 01:23:33,070
React to it by making
something your own.

1913
01:23:33,070 --> 01:23:35,640
So allow me to flip
here to our final slide,

1914
01:23:35,640 --> 01:23:40,238
and we still have a few minutes before
we take a break for any questions.

1915
01:23:40,238 --> 01:23:41,280
Yeah, let's go over here.

1916
01:23:41,280 --> 01:23:42,592
I'll bounce back and forth.

1917
01:23:42,592 --> 01:23:46,840
AUDIENCE: Actually, this
is a question [INAUDIBLE]..

1918
01:23:46,840 --> 01:23:52,690
Can [? we ?] deliver the [INAUDIBLE]?

1919
01:23:52,690 --> 01:23:54,430
How long does [INAUDIBLE]?

1920
01:23:54,430 --> 01:23:59,115


1921
01:23:59,115 --> 01:24:02,505
And how long [INAUDIBLE]
because [INAUDIBLE]..

1922
01:24:02,505 --> 01:24:08,154
We [? want ?] [INAUDIBLE] be swept
away [? without ?] [INAUDIBLE]??

1923
01:24:08,154 --> 01:24:13,382


1924
01:24:13,382 --> 01:24:14,590
DAVID MALAN: Well, thank you.

1925
01:24:14,590 --> 01:24:16,298
You're too kind, and I--

1926
01:24:16,298 --> 01:24:18,690
[LAUGHTER]

1927
01:24:18,690 --> 01:24:20,940
Carter can attest that
they're far from perfect

1928
01:24:20,940 --> 01:24:24,870
because, in fact, one of the things he
and I do and Brian and I used to do is,

1929
01:24:24,870 --> 01:24:27,810
after every lecture is
painful, but we will then

1930
01:24:27,810 --> 01:24:32,170
walk through all of the slides and
write down to-do's, like a to-do list

1931
01:24:32,170 --> 01:24:34,980
for all of the mistakes I
made, all of the regrets I had.

1932
01:24:34,980 --> 01:24:39,780
And every week, we have a long laundry
list of imperfections, if I may.

1933
01:24:39,780 --> 01:24:41,967
And some years we could
rewatch the videos,

1934
01:24:41,967 --> 01:24:43,925
which is a horrible
experience, to watch this--

1935
01:24:43,925 --> 01:24:44,425
[LAUGHTER]

1936
01:24:44,425 --> 01:24:45,880
--on video [INAUDIBLE].

1937
01:24:45,880 --> 01:24:50,250
But with that said, the
way I myself prepare,

1938
01:24:50,250 --> 01:24:54,360
every term, and CS50 in particular,
is I start by looking literally

1939
01:24:54,360 --> 01:24:56,880
at this list of things
I wish I had done better

1940
01:24:56,880 --> 01:24:59,550
because, especially if it's
been a semester or even a year

1941
01:24:59,550 --> 01:25:03,630
since I taught the class, it is so
valuable to have a list of things

1942
01:25:03,630 --> 01:25:07,140
I know I want to change even
if I didn't remember it.

1943
01:25:07,140 --> 01:25:11,160
Two, what I do is I look through
my previous year's slides,

1944
01:25:11,160 --> 01:25:13,260
and I just start to think
through, is this how I

1945
01:25:13,260 --> 01:25:15,300
would present this material this year?

1946
01:25:15,300 --> 01:25:17,970
And invariably, I start
moving things around,

1947
01:25:17,970 --> 01:25:20,830
or I start hiding slides
because I don't like doing that.

1948
01:25:20,830 --> 01:25:23,670
And every year, even after 16 years,
if you look through the slides,

1949
01:25:23,670 --> 01:25:25,003
there's definitely similarities.

1950
01:25:25,003 --> 01:25:29,490
And like 70% of the class might stay
the same, 60%, 80%, something like that.

1951
01:25:29,490 --> 01:25:33,190
But I'm constantly regretting how I
taught something the previous year.

1952
01:25:33,190 --> 01:25:36,850
And so I'm striving for my
white whale, so to speak,

1953
01:25:36,850 --> 01:25:39,430
trying to find the
perfect version of CS50,

1954
01:25:39,430 --> 01:25:42,330
which is only to say that
I very carefully think

1955
01:25:42,330 --> 01:25:44,580
through things from start to finish.

1956
01:25:44,580 --> 01:25:47,730
I then look through the source
code that I wrote the past year.

1957
01:25:47,730 --> 01:25:50,190
And sometimes, with the
source code, I actually

1958
01:25:50,190 --> 01:25:52,620
start that from scratch
because I find, honestly,

1959
01:25:52,620 --> 01:25:54,630
even after doing this
all these years, I'd

1960
01:25:54,630 --> 01:25:57,840
like to think I'm getting better even
at C and certain other languages,

1961
01:25:57,840 --> 01:26:01,950
or industry trends are changing
with some of the later material,

1962
01:26:01,950 --> 01:26:03,850
and so it needs to be updated.

1963
01:26:03,850 --> 01:26:06,660
But at least in my case,
I don't write things down.

1964
01:26:06,660 --> 01:26:10,860
If you see me flipping here, all I
have is a printout of the slides.

1965
01:26:10,860 --> 01:26:13,290
There's no notes or script
or anything like that,

1966
01:26:13,290 --> 01:26:15,750
which is fine if that's the
type of teacher you are and you

1967
01:26:15,750 --> 01:26:18,240
want that outline or if you
want to script things out.

1968
01:26:18,240 --> 01:26:23,320
I tend to go with the flow, if you will.

1969
01:26:23,320 --> 01:26:24,780
But it's each their own.

1970
01:26:24,780 --> 01:26:27,900
Carter has a different style, Guy
and Margaret have a different style.

1971
01:26:27,900 --> 01:26:29,280
I would find your own.

1972
01:26:29,280 --> 01:26:31,133
But it takes practice.

1973
01:26:31,133 --> 01:26:32,050
AUDIENCE: [INAUDIBLE].

1974
01:26:32,050 --> 01:26:34,000
DAVID MALAN: Yeah, over here.

1975
01:26:34,000 --> 01:26:36,186
Sure.

1976
01:26:36,186 --> 01:26:42,920
AUDIENCE: In almost
every known [INAUDIBLE]..

1977
01:26:42,920 --> 01:26:49,340
And we just add necessary
code to [INAUDIBLE]..

1978
01:26:49,340 --> 01:26:52,430
I wonder what's the reason--

1979
01:26:52,430 --> 01:26:54,100
which one more effective?

1980
01:26:54,100 --> 01:26:57,700
Do we give the student--

1981
01:26:57,700 --> 01:27:01,240
we let the student code
from the start to the end?

1982
01:27:01,240 --> 01:27:04,318
Or give them the template like
you did, each one [INAUDIBLE]??

1983
01:27:04,318 --> 01:27:06,110
DAVID MALAN: That's a
really good question.

1984
01:27:06,110 --> 01:27:09,310
So to recap, toward the
middle of the semester onward,

1985
01:27:09,310 --> 01:27:12,310
we tend to give students starter
code or template code or distribution

1986
01:27:12,310 --> 01:27:13,300
code, same idea.

1987
01:27:13,300 --> 01:27:16,690
And we often have to-do's or
blanks that they need to fill in.

1988
01:27:16,690 --> 01:27:17,960
Should we do that or not?

1989
01:27:17,960 --> 01:27:19,900
I think it depends
partly on your students

1990
01:27:19,900 --> 01:27:22,760
and partly what you want the
focus of that week to be.

1991
01:27:22,760 --> 01:27:25,720
So for me, it's important
in the beginning of CS50

1992
01:27:25,720 --> 01:27:27,640
that you start with a blank file.

1993
01:27:27,640 --> 01:27:30,212
I want them to understand,
from start to finish,

1994
01:27:30,212 --> 01:27:32,920
that what they see on the screen,
even if it's just Hello, world,

1995
01:27:32,920 --> 01:27:39,070
is entirely of their own doing, no
magic or things they don't understand.

1996
01:27:39,070 --> 01:27:41,380
But as I said earlier,
especially with C,

1997
01:27:41,380 --> 01:27:45,908
it's hard to do fun, engaging homework
problems in a language like C and even

1998
01:27:45,908 --> 01:27:47,950
in Python if you're only
using a terminal window,

1999
01:27:47,950 --> 01:27:51,940
and still, you give students some
libraries or some starter code.

2000
01:27:51,940 --> 01:27:54,520
And I would say our own view
on this has been changing.

2001
01:27:54,520 --> 01:27:57,640
And just this spring,
we've been going back

2002
01:27:57,640 --> 01:28:02,280
and adding least
comfortable versions of some

2003
01:28:02,280 --> 01:28:05,520
of the problems which, for us, means
providing a little more starter code.

2004
01:28:05,520 --> 01:28:08,400
And for us, this is an
opportunity for those students

2005
01:28:08,400 --> 01:28:11,550
who are somewhat self-selecting,
if they really feel uncomfortable,

2006
01:28:11,550 --> 01:28:14,910
we give them a bit more of the solution
and guide them step by step through it.

2007
01:28:14,910 --> 01:28:18,090
But some other students who have either
been programming for years or they

2008
01:28:18,090 --> 01:28:21,040
just they want a challenge, and then you
probably have students just like that,

2009
01:28:21,040 --> 01:28:23,910
especially if they like the field,
we give them less starter code.

2010
01:28:23,910 --> 01:28:27,100
And we allow them to have
this higher ceiling instead.

2011
01:28:27,100 --> 01:28:29,200
So I think it depends on your students.

2012
01:28:29,200 --> 01:28:32,340
But for us, it's very important
to me that our problem sets

2013
01:28:32,340 --> 01:28:34,590
get interesting or stay interesting.

2014
01:28:34,590 --> 01:28:38,580
And I don't think you can do that if
you give them a blank file every week

2015
01:28:38,580 --> 01:28:40,260
to start with.

2016
01:28:40,260 --> 01:28:42,510
Other questions.

2017
01:28:42,510 --> 01:28:43,270
Let me go here.

2018
01:28:43,270 --> 01:28:44,937
Let me-- some new hands first, if I may.

2019
01:28:44,937 --> 01:28:47,520
AUDIENCE: Yeah, [INAUDIBLE]
thank you for the chance.

2020
01:28:47,520 --> 01:28:48,270
DAVID MALAN: Sure.

2021
01:28:48,270 --> 01:28:52,130
AUDIENCE: I want to ask
you about [INAUDIBLE]

2022
01:28:52,130 --> 01:28:55,540
if we want to [INAUDIBLE]
that evening, we

2023
01:28:55,540 --> 01:29:00,000
must make the students feel
comfortable and make them understand

2024
01:29:00,000 --> 01:29:03,600
what happened in their [INAUDIBLE].

2025
01:29:03,600 --> 01:29:06,112
And I have some problem at my school.

2026
01:29:06,112 --> 01:29:06,984
DAVID MALAN: Sure.

2027
01:29:06,984 --> 01:29:10,820
AUDIENCE: VS code is too
heavy to teach my [INAUDIBLE]

2028
01:29:10,820 --> 01:29:13,533
in my computer [INAUDIBLE].

2029
01:29:13,533 --> 01:29:14,200
DAVID MALAN: OK.

2030
01:29:14,200 --> 01:29:16,330
AUDIENCE: And can you--

2031
01:29:16,330 --> 01:29:20,960
I think if they just understand
what happened [INAUDIBLE],,

2032
01:29:20,960 --> 01:29:22,393
but it's not [? grandfathered. ?]

2033
01:29:22,393 --> 01:29:23,060
DAVID MALAN: OK.

2034
01:29:23,060 --> 01:29:30,020
AUDIENCE: [INAUDIBLE] was they
can't program a single [INAUDIBLE]

2035
01:29:30,020 --> 01:29:31,700
it will work like that.

2036
01:29:31,700 --> 01:29:42,095
Can you give me a citation
by using another [INAUDIBLE]

2037
01:29:42,095 --> 01:29:46,290
to teach my students
without the VS code?

2038
01:29:46,290 --> 01:29:49,350
DAVID MALAN: Sure, so VS code
is very heavyweight [? and ?]

2039
01:29:49,350 --> 01:29:52,620
so on your school's
computer lab computers.

2040
01:29:52,620 --> 01:29:55,733
So VS code itself can be downloaded
for free for Mac and Windows,

2041
01:29:55,733 --> 01:29:57,150
which I think you're referring to.

2042
01:29:57,150 --> 01:30:00,940
But what Code Spaces is,
code.CS50.IO, in our case,

2043
01:30:00,940 --> 01:30:03,250
it's just a browser-based
version thereof.

2044
01:30:03,250 --> 01:30:07,680
And so long as the computers are
within five or six years old,

2045
01:30:07,680 --> 01:30:11,340
it should be OK so long as you have a
good enough internet connection, which

2046
01:30:11,340 --> 01:30:12,210
not everyone does.

2047
01:30:12,210 --> 01:30:13,990
And I do realize that's a challenge.

2048
01:30:13,990 --> 01:30:17,580
So in terms of other text
editors, let me probably follow up

2049
01:30:17,580 --> 01:30:20,077
with an email with some
links to something like this

2050
01:30:20,077 --> 01:30:21,660
because there are lighter weight ones.

2051
01:30:21,660 --> 01:30:24,630
Like on Windows,
Notepad++ comes to mind.

2052
01:30:24,630 --> 01:30:29,010
It's not as popular nowadays as
VS code, but there's others too.

2053
01:30:29,010 --> 01:30:31,945
And if I forget, just email me
tomorrow to remind me of that.

2054
01:30:31,945 --> 01:30:34,320
I think we have time for maybe
one or two more questions.

2055
01:30:34,320 --> 01:30:41,642
AUDIENCE: [INAUDIBLE]
days ago [INAUDIBLE]..

2056
01:30:41,642 --> 01:30:42,350
DAVID MALAN: Yes.

2057
01:30:42,350 --> 01:30:43,267
AUDIENCE: [INAUDIBLE].

2058
01:30:43,267 --> 01:30:47,805
[INAUDIBLE] I use other [INAUDIBLE]?

2059
01:30:47,805 --> 01:30:48,930
DAVID MALAN: Good question.

2060
01:30:48,930 --> 01:30:51,610
So in this class, as well as with
our undergraduates back home,

2061
01:30:51,610 --> 01:30:54,680
we ask them at the start of the
term to bucketize themselves

2062
01:30:54,680 --> 01:30:57,310
among those less comfortable,
more comfortable, somewhere

2063
01:30:57,310 --> 01:31:00,910
in between, and in our case, most
recently, least comfortable as well.

2064
01:31:00,910 --> 01:31:04,210
Generally, that's been
sufficient detail for us,

2065
01:31:04,210 --> 01:31:07,540
and we don't give them a test or
a quiz or any kind of assessment

2066
01:31:07,540 --> 01:31:10,160
like that because I think
most students know what

2067
01:31:10,160 --> 01:31:13,510
bucket they fall into because those
who are less comfortable or least

2068
01:31:13,510 --> 01:31:16,600
comfortable, they're uncomfortable
just even being in the class

2069
01:31:16,600 --> 01:31:17,860
on that first day.

2070
01:31:17,860 --> 01:31:20,253
By contrast, the students
who are more comfortable

2071
01:31:20,253 --> 01:31:23,170
are the kids that have been programming
since they were six years old,

2072
01:31:23,170 --> 01:31:24,430
or they're highly confident.

2073
01:31:24,430 --> 01:31:26,560
And so they know who they are.

2074
01:31:26,560 --> 01:31:28,580
And our answer to the
students who are like,

2075
01:31:28,580 --> 01:31:30,700
I don't know which group
I'm in, by definition,

2076
01:31:30,700 --> 01:31:32,570
they are somewhere in between.

2077
01:31:32,570 --> 01:31:36,250
And so for us, we have either
these three buckets or now four,

2078
01:31:36,250 --> 01:31:40,270
which can help just in our case-- and
we can't do this in all classrooms.

2079
01:31:40,270 --> 01:31:42,820
It can help you group
students so that they're only

2080
01:31:42,820 --> 01:31:46,092
among students who are similarly
uncomfortable, similarly comfortable,

2081
01:31:46,092 --> 01:31:47,800
so they don't feel
like they're competing

2082
01:31:47,800 --> 01:31:50,410
with the smarter kids or the
slower kids in the class, which

2083
01:31:50,410 --> 01:31:52,560
is not healthy for anyone.

2084
01:31:52,560 --> 01:31:53,790
Other questions?

2085
01:31:53,790 --> 01:31:55,551
Yeah.

2086
01:31:55,551 --> 01:31:57,012
AUDIENCE: [INAUDIBLE].

2087
01:31:57,012 --> 01:32:12,333


2088
01:32:12,333 --> 01:32:13,250
DAVID MALAN: OK, yeah.

2089
01:32:13,250 --> 01:32:17,460
AUDIENCE: [INAUDIBLE] all [INAUDIBLE]?

2090
01:32:17,460 --> 01:32:20,430


2091
01:32:20,430 --> 01:32:22,680
DAVID MALAN: Vis a vis a
matter of academic honesty?

2092
01:32:22,680 --> 01:32:22,980
AUDIENCE: Yeah.

2093
01:32:22,980 --> 01:32:24,730
DAVID MALAN: Yeah,
that's a good question.

2094
01:32:24,730 --> 01:32:27,780
So the question is about whether
it's a Harvard thing or a CS50 thing,

2095
01:32:27,780 --> 01:32:29,790
this emphasis on academic honesty.

2096
01:32:29,790 --> 01:32:33,330
It is especially CS50 focused.

2097
01:32:33,330 --> 01:32:35,670
Harvard, for instance,
has its own honor code

2098
01:32:35,670 --> 01:32:38,987
where across all courses and
departments students are not supposed

2099
01:32:38,987 --> 01:32:40,320
to be copying each other's work.

2100
01:32:40,320 --> 01:32:42,060
They should be adhering
to certain rules.

2101
01:32:42,060 --> 01:32:45,150
In CS50, we philosophically,
for many years

2102
01:32:45,150 --> 01:32:47,730
since I took over and
even before my time,

2103
01:32:47,730 --> 01:32:50,910
proactively look for instances
of academic dishonesty

2104
01:32:50,910 --> 01:32:51,970
for a couple of reasons.

2105
01:32:51,970 --> 01:32:54,512
And the first and foremost is
just fairness to other students

2106
01:32:54,512 --> 01:32:56,925
because we want them to
be meeting us halfway.

2107
01:32:56,925 --> 01:32:59,550
We're fortunate back home to have
a lot of teaching assistants,

2108
01:32:59,550 --> 01:33:02,620
as Carter noted, a lot of
resources and support for students.

2109
01:33:02,620 --> 01:33:06,270
And if we're going to provide this, we
want them meeting us halfway and taking

2110
01:33:06,270 --> 01:33:07,530
advantage of those resources.

2111
01:33:07,530 --> 01:33:10,500
Where even in a smaller class,
coming to me as the teacher

2112
01:33:10,500 --> 01:33:13,380
and not turning to
someone else's solution.

2113
01:33:13,380 --> 01:33:15,630
Now, with that said, what
we try to teach students

2114
01:33:15,630 --> 01:33:19,110
over the course of the
semester is where the line is.

2115
01:33:19,110 --> 01:33:21,810
They're absolutely should be
googling for certain things.

2116
01:33:21,810 --> 01:33:25,590
They should be googling for
how to write a for loop in C

2117
01:33:25,590 --> 01:33:29,400
or how to implement a
conditional in Python

2118
01:33:29,400 --> 01:33:34,530
or function that makes HTTP requests
in Python, like very commodity things.

2119
01:33:34,530 --> 01:33:39,180
What they shouldn't be doing is
how to print a pyramid for Mario

2120
01:33:39,180 --> 01:33:40,410
or very specific things.

2121
01:33:40,410 --> 01:33:44,580
Or any time they get a search result,
where clearly it's a CS50 problem,

2122
01:33:44,580 --> 01:33:46,560
and CS50 might even
be mentioned somewhere

2123
01:33:46,560 --> 01:33:49,980
in the post, that's the point at
which, OK, you've found your way there

2124
01:33:49,980 --> 01:33:50,850
accidentally.

2125
01:33:50,850 --> 01:33:52,470
That's when you close the tab.

2126
01:33:52,470 --> 01:33:55,900
And trying to teach students that
leaning on each other for help,

2127
01:33:55,900 --> 01:33:58,320
asking questions of us and
others for help is fine.

2128
01:33:58,320 --> 01:34:02,010
But copying someone else's work
and presenting it as their own--

2129
01:34:02,010 --> 01:34:07,410
and then in our case, letting 72 or more
hours pass and not realizing, darn it,

2130
01:34:07,410 --> 01:34:10,830
I really shouldn't have done
that even though I was very tired

2131
01:34:10,830 --> 01:34:13,440
and stressed at the time
and not coming forward.

2132
01:34:13,440 --> 01:34:16,290
At that point, we take
more punitive approaches

2133
01:34:16,290 --> 01:34:20,010
because if students aren't
ethically meeting us that way,

2134
01:34:20,010 --> 01:34:22,410
then we try with the
last measure we have.

2135
01:34:22,410 --> 01:34:25,060
And the goal ultimately, especially
for an introductory course,

2136
01:34:25,060 --> 01:34:28,560
which for us at the university level
is one of the first four courses

2137
01:34:28,560 --> 01:34:31,440
that many first-year,
freshman students take,

2138
01:34:31,440 --> 01:34:34,750
this is where-- we're the
funnel leading to other courses.

2139
01:34:34,750 --> 01:34:37,140
So we try to place a lot
of that effort there.

2140
01:34:37,140 --> 01:34:39,730
And we'll talk more about
this over time as well.

2141
01:34:39,730 --> 01:34:41,237
Maybe one final question, if we may.

2142
01:34:41,237 --> 01:34:44,070
Let me do one-on-one because we
already chatted, but how about here?

2143
01:34:44,070 --> 01:34:45,386
[LAUGHTER]

2144
01:34:45,386 --> 01:34:46,820
AUDIENCE: [INAUDIBLE].

2145
01:34:46,820 --> 01:34:53,574


2146
01:34:53,574 --> 01:34:55,053
So [INAUDIBLE]?

2147
01:34:55,053 --> 01:35:05,910


2148
01:35:05,910 --> 01:35:08,040
DAVID MALAN: So for
the final project, we

2149
01:35:08,040 --> 01:35:12,420
encourage students to take their
finance code or our starter code

2150
01:35:12,420 --> 01:35:13,710
and make it their own.

2151
01:35:13,710 --> 01:35:16,840
That's very much blessed and
encouraged at that point.

2152
01:35:16,840 --> 01:35:20,130
What would be inappropriate
for a final project is

2153
01:35:20,130 --> 01:35:22,860
downloading someone
else's project from GitHub

2154
01:35:22,860 --> 01:35:26,160
or elsewhere and then just
saying, I made this code.

2155
01:35:26,160 --> 01:35:29,430
What is OK would be to download
someone's code perhaps,

2156
01:35:29,430 --> 01:35:32,242
especially if it's open source
in a lab, but make clear

2157
01:35:32,242 --> 01:35:34,200
to their teaching fellow,
in our case, or to me

2158
01:35:34,200 --> 01:35:37,150
as the teacher what they added to it.

2159
01:35:37,150 --> 01:35:40,050
For instance, treating it more
like a library, that's reasonable.

2160
01:35:40,050 --> 01:35:43,020
And as you can imagine, the
whole point of taking a class

2161
01:35:43,020 --> 01:35:45,990
or being your students is for
students to learn something.

2162
01:35:45,990 --> 01:35:49,240
And it's not meant to be an exercise in
simply submitting someone else's work

2163
01:35:49,240 --> 01:35:52,710
but going from some starting
point to some endpoint.

2164
01:35:52,710 --> 01:35:55,470
So what we try to do with
students even more so in person

2165
01:35:55,470 --> 01:35:58,170
back home is help them
navigate that line.

2166
01:35:58,170 --> 01:36:01,350
And many of you have probably played
with or heard about Racine's rules

2167
01:36:01,350 --> 01:36:04,350
like ChatGPT, which
honestly, for us teachers,

2168
01:36:04,350 --> 01:36:06,150
is going to make things a little harder.

2169
01:36:06,150 --> 01:36:09,900
It doesn't make things fundamentally
any different because there's always--

2170
01:36:09,900 --> 01:36:13,020
whoa, there's always-- for the
past 20 years there's been Google.

2171
01:36:13,020 --> 01:36:15,210
And for the past 100
plus years, there's been

2172
01:36:15,210 --> 01:36:17,040
other human beings in the classroom.

2173
01:36:17,040 --> 01:36:20,340
But it does make it
easier, tools like ChatGPT,

2174
01:36:20,340 --> 01:36:23,550
to misbehave anonymously
because you're just asking

2175
01:36:23,550 --> 01:36:25,500
the internet very specific questions.

2176
01:36:25,500 --> 01:36:27,300
And I hope-- and we're
not there yet, but I

2177
01:36:27,300 --> 01:36:31,400
think the educational
opportunity of ChatGPT, Co-pilot,

2178
01:36:31,400 --> 01:36:33,150
if you've heard these
terms, is that we're

2179
01:36:33,150 --> 01:36:36,870
going to have many more virtual
TAs, and not bad virtual

2180
01:36:36,870 --> 01:36:39,960
TAs where it just tries to autocomplete
the answer to your question

2181
01:36:39,960 --> 01:36:46,470
in like an FAQ or a knowledge base
but would be able to have students

2182
01:36:46,470 --> 01:36:50,430
highlight the starter code and have
the computer explain it to them instead

2183
01:36:50,430 --> 01:36:52,757
of needing to ask me or Carter or you.

2184
01:36:52,757 --> 01:36:54,840
And so the goal there, I
think for us, [INAUDIBLE]

2185
01:36:54,840 --> 01:36:57,150
of these tools over the
next one to two years

2186
01:36:57,150 --> 01:37:02,205
is to actually leverage the positive
aspects so that your software, your VS

2187
01:37:02,205 --> 01:37:05,550
code, your student's code
can answer, let's say,

2188
01:37:05,550 --> 01:37:09,900
70% of the introductory questions
so that one of you, who's

2189
01:37:09,900 --> 01:37:12,917
running around to 30 or 20
students or more in the class,

2190
01:37:12,917 --> 01:37:15,000
can focus really on the
harder questions, the more

2191
01:37:15,000 --> 01:37:17,170
sophisticated questions as well.

2192
01:37:17,170 --> 01:37:19,513
So all this and more tomorrow as well.

2193
01:37:19,513 --> 01:37:21,930
But why don't we go ahead and
take a 30-minute break here.

2194
01:37:21,930 --> 01:37:24,060
There's cookies outside,
thanks to our hosts.

2195
01:37:24,060 --> 01:37:25,545
And we'll resume at 4:30 PM.

2196
01:37:25,545 --> 01:37:29,355
[APPLAUSE]

2197
01:37:29,355 --> 01:37:34,000