1
00:00:00,000 --> 00:00:01,872


2
00:00:01,872 --> 00:00:07,810
SPEAKER: This is CS50, and this is
CS50 Explained, Behind the Pedagogy.

3
00:00:07,810 --> 00:00:13,060
So many of you have probably taken CS50
or heard of CS50 in some form already.

4
00:00:13,060 --> 00:00:15,900
And so that then is
what of CS50, if you've

5
00:00:15,900 --> 00:00:19,530
actually gone through the courses,
lectures, and/or problem sets, that

6
00:00:19,530 --> 00:00:20,800
is programming assignments.

7
00:00:20,800 --> 00:00:23,040
But this session during
our educator workshop

8
00:00:23,040 --> 00:00:25,600
is meant to be a glimpse at the why.

9
00:00:25,600 --> 00:00:29,910
Why, for better or for worse,
have I, have we, CS50's team,

10
00:00:29,910 --> 00:00:34,090
made some of the pedagogical and
curricular decisions that we have.

11
00:00:34,090 --> 00:00:36,760
Ultimately, it's up to you as a
teacher in your own classroom,

12
00:00:36,760 --> 00:00:39,630
whether to adopt or
adapt or neither of those

13
00:00:39,630 --> 00:00:41,182
when it comes to each of these ideas.

14
00:00:41,182 --> 00:00:43,140
But at least we thought
we would share with you

15
00:00:43,140 --> 00:00:46,390
some of the thinking behind
our own conscious decisions.

16
00:00:46,390 --> 00:00:51,100
So CS50 itself is a fairly traditional
undergraduate class here in person.

17
00:00:51,100 --> 00:00:52,600
It's among Harvard's largest.

18
00:00:52,600 --> 00:00:54,930
So pictured here is
beautiful Sanders Theater,

19
00:00:54,930 --> 00:00:57,210
this old building on
campus in which we're

20
00:00:57,210 --> 00:00:59,740
fortunate to be able
to give our lectures.

21
00:00:59,740 --> 00:01:03,080
But the course is structured
with other resources as well.

22
00:01:03,080 --> 00:01:07,630
And everything that we do nowadays,
curricularly, technologically

23
00:01:07,630 --> 00:01:10,610
is freely available as open
courseware, so to speak.

24
00:01:10,610 --> 00:01:13,660
That is to say it costs
teachers nothing to use

25
00:01:13,660 --> 00:01:17,710
any and all of these materials
and these tools as well.

26
00:01:17,710 --> 00:01:21,460
CS50x, now in terms of
nomenclature, is essentially

27
00:01:21,460 --> 00:01:24,350
what we call the free version of CS50.

28
00:01:24,350 --> 00:01:27,710
So they are one in the same
curricularly and technologically.

29
00:01:27,710 --> 00:01:31,870
But whereas we might say a Harvard
or Yale student takes CS50 on campus,

30
00:01:31,870 --> 00:01:35,450
anyone online would
take CS50x off campus.

31
00:01:35,450 --> 00:01:38,150
But curricularly and
technologically they are the same.

32
00:01:38,150 --> 00:01:42,910
And all of the courses materials live at
this URL, as well as on other platforms

33
00:01:42,910 --> 00:01:46,660
that you might know, like edX
and YouTube, Apple TV, Google

34
00:01:46,660 --> 00:01:50,150
TV, and other platforms
over the time as well.

35
00:01:50,150 --> 00:01:52,330
Now, in terms of other
nomenclature, there's

36
00:01:52,330 --> 00:01:56,770
an adaptation of the class called CS50
AP, which for those of you in the United

37
00:01:56,770 --> 00:02:01,510
States in particular is an endorsed
implementation of the AP Computer

38
00:02:01,510 --> 00:02:04,720
Science Principles
curriculum framework, which

39
00:02:04,720 --> 00:02:08,560
is to say that high school students
can take CS50 either online

40
00:02:08,560 --> 00:02:11,260
or through their own
school for AP credit,

41
00:02:11,260 --> 00:02:15,040
if their school will administer
ultimately the exam so that they

42
00:02:15,040 --> 00:02:16,400
can get that credit.

43
00:02:16,400 --> 00:02:20,560
All of those materials are available
at this URL on CS50's own website.

44
00:02:20,560 --> 00:02:26,530
And in essence, CS50 AP includes
CS50x, plus some additional materials

45
00:02:26,530 --> 00:02:31,330
from a course that we have long called
CS50T, an introduction to technology,

46
00:02:31,330 --> 00:02:34,750
more broadly, that has
additional material that the AP

47
00:02:34,750 --> 00:02:37,210
test might expect of students.

48
00:02:37,210 --> 00:02:38,980
Pictured here is one
of my favorite photos

49
00:02:38,980 --> 00:02:41,140
over the years whereby
we gathered in New York

50
00:02:41,140 --> 00:02:43,630
City with a number of
public and private schools

51
00:02:43,630 --> 00:02:46,180
years ago with some of our
teachers and our network

52
00:02:46,180 --> 00:02:48,910
to have a hackathon for
our high school students.

53
00:02:48,910 --> 00:02:53,230
Pictured here just a few weeks back
are about 300 teachers from Indonesia

54
00:02:53,230 --> 00:02:55,450
who teach middle school
and/or high school

55
00:02:55,450 --> 00:02:58,030
and are going to be teaching
now introductory computer

56
00:02:58,030 --> 00:02:59,690
science in their own classrooms.

57
00:02:59,690 --> 00:03:02,080
So some of CS50's team
and I flew to Indonesia

58
00:03:02,080 --> 00:03:07,310
to lead a workshop like this one in
person for those teachers in Jakarta.

59
00:03:07,310 --> 00:03:10,160
And lastly, pictured here are
some of our students in Nicaragua.

60
00:03:10,160 --> 00:03:12,940
So where they have been
taking CS50 largely

61
00:03:12,940 --> 00:03:15,010
in Spanish with some
of their own teachers

62
00:03:15,010 --> 00:03:17,920
there, as well as working
their way through the courses,

63
00:03:17,920 --> 00:03:22,390
problem sets, final projects, ultimately
to exhibit their own CS50 certificate

64
00:03:22,390 --> 00:03:23,530
at the end of the course.

65
00:03:23,530 --> 00:03:25,900
And most recently, as
CS50 actually begun

66
00:03:25,900 --> 00:03:28,810
giving talks and professional
development in companies,

67
00:03:28,810 --> 00:03:31,720
like General Electric
and others, whereby

68
00:03:31,720 --> 00:03:34,420
the goal is to really uplift
people more broadly when

69
00:03:34,420 --> 00:03:37,480
it comes to understanding,
technology, computing,

70
00:03:37,480 --> 00:03:39,410
and programming in particular.

71
00:03:39,410 --> 00:03:45,100
Now, for those of you unfamiliar,
besides CS50x, and in turn CS50 AP,

72
00:03:45,100 --> 00:03:48,250
CS50 has a whole
curriculum now of courses

73
00:03:48,250 --> 00:03:54,320
that you can take either before CS50
or after CS50 in either of those forms.

74
00:03:54,320 --> 00:03:56,440
So, for instance, just
to rattle these off,

75
00:03:56,440 --> 00:04:00,550
we have a course that focuses
particularly on programming with Python,

76
00:04:00,550 --> 00:04:04,510
a course that focuses on web
programming with Python and Javascript,

77
00:04:04,510 --> 00:04:06,700
a course that focuses
on game development,

78
00:04:06,700 --> 00:04:10,570
one that focuses on artificial
intelligence with Python, one of which

79
00:04:10,570 --> 00:04:13,270
is an introduction to
computer science for lawyers

80
00:04:13,270 --> 00:04:17,320
or for business professionals or
for technologists, really consumers,

81
00:04:17,320 --> 00:04:19,010
or citizens more generally.

82
00:04:19,010 --> 00:04:21,970
Hot off the press is a
new course on programming

83
00:04:21,970 --> 00:04:24,580
with R, very popular
language for data science

84
00:04:24,580 --> 00:04:26,780
that's about to launch
in just a few days.

85
00:04:26,780 --> 00:04:30,370
A course on programming with Scratch,
particularly for younger students

86
00:04:30,370 --> 00:04:34,540
a course on databases
with SQL, a language

87
00:04:34,540 --> 00:04:36,320
via which you can manipulate data.

88
00:04:36,320 --> 00:04:41,090
And then lastly, for now, a course
on cyber security specifically.

89
00:04:41,090 --> 00:04:44,020
So even though today and
tomorrow we will focus primarily

90
00:04:44,020 --> 00:04:49,960
on CS50x, and in turn CS50 AP, is
really the computer science backbone

91
00:04:49,960 --> 00:04:55,490
that these courses, either lead to or
extend from after you've taken them,

92
00:04:55,490 --> 00:04:58,180
all of these courses, all
of these resources and tools

93
00:04:58,180 --> 00:05:02,820
are similarly available to you for
free as indeed open courseware.

94
00:05:02,820 --> 00:05:03,750
But there's a lot.

95
00:05:03,750 --> 00:05:06,060
In those courses in
CS50 itself, indeed, you

96
00:05:06,060 --> 00:05:08,640
might recall if you've
watched CS50's own lectures,

97
00:05:08,640 --> 00:05:13,770
we display this picture here, which is
a fire hydrant connected to a drinking

98
00:05:13,770 --> 00:05:14,530
faucet.

99
00:05:14,530 --> 00:05:16,980
And the idea is, and
this is a photograph down

100
00:05:16,980 --> 00:05:21,480
the road from MIT, that taking CS50,
like getting an education from MIT,

101
00:05:21,480 --> 00:05:23,290
is like drinking from a fire hose.

102
00:05:23,290 --> 00:05:26,520
It's really going to hit you with
a lot of material, a lot of water

103
00:05:26,520 --> 00:05:29,350
that you might not be able
to take down all at once.

104
00:05:29,350 --> 00:05:32,130
But that's not really
the goal ultimately.

105
00:05:32,130 --> 00:05:34,380
Rather, the goal is that exposure.

106
00:05:34,380 --> 00:05:36,420
And that reality that
over time there's going

107
00:05:36,420 --> 00:05:40,650
to be so much more to learn, and among
the goals of CS50 is to teach students

108
00:05:40,650 --> 00:05:43,650
and in turn teachers
how to teach themselves

109
00:05:43,650 --> 00:05:46,980
this material, which is never
going away insofar as it's only

110
00:05:46,980 --> 00:05:48,840
going to continue to change.

111
00:05:48,840 --> 00:05:51,480
Now, as for the language,
the programming languages

112
00:05:51,480 --> 00:05:53,460
that we use in CS50,
we actually do start

113
00:05:53,460 --> 00:05:57,358
with Scratch, a very student friendly
graphical programming language

114
00:05:57,358 --> 00:05:59,400
that many kids around the
world nowadays are even

115
00:05:59,400 --> 00:06:02,150
using in middle school, if not younger.

116
00:06:02,150 --> 00:06:05,260
But we use it to talk about
programming fundamentals,

117
00:06:05,260 --> 00:06:09,700
like functions and loops and
arguments and conditionals

118
00:06:09,700 --> 00:06:13,000
and other programming
constructs that are still

119
00:06:13,000 --> 00:06:16,220
going to be present in most every
other language we talk about.

120
00:06:16,220 --> 00:06:19,270
But in Scratch, there's no
semicolons, there's no parentheses,

121
00:06:19,270 --> 00:06:23,050
there's no sort of syntactic stupidity
that just tends to get in the way

122
00:06:23,050 --> 00:06:26,030
and gets very frustrating
when students are confused.

123
00:06:26,030 --> 00:06:29,980
So we get rid of that early on,
spending just a day, maybe a week

124
00:06:29,980 --> 00:06:33,160
or slightly more on
this particular domain.

125
00:06:33,160 --> 00:06:36,490
For those unfamiliar, it's indeed this
drag and drop programming interface

126
00:06:36,490 --> 00:06:40,030
that really isn't too
young of a platform,

127
00:06:40,030 --> 00:06:41,600
even for the oldest of students.

128
00:06:41,600 --> 00:06:45,140
Indeed, we use this with our
own university students here.

129
00:06:45,140 --> 00:06:47,980
It allows us to implement
Hello, World as quite simply

130
00:06:47,980 --> 00:06:50,210
as a couple of puzzle pieces like that.

131
00:06:50,210 --> 00:06:52,600
But then we do transition
in CS50 fairly quickly

132
00:06:52,600 --> 00:06:54,850
to a more traditional
text based language,

133
00:06:54,850 --> 00:06:58,467
an older language called C, which
is not very common nowadays.

134
00:06:58,467 --> 00:07:00,050
It looks a little something like this.

135
00:07:00,050 --> 00:07:04,840
Much of the world, I daresay, has moved
to use Java, or most recently Python,

136
00:07:04,840 --> 00:07:06,590
perhaps other languages as well.

137
00:07:06,590 --> 00:07:09,880
But the appeal of something
like C to us is, one,

138
00:07:09,880 --> 00:07:14,830
we can actually pretty readily make
an analogy between Scratch and C,

139
00:07:14,830 --> 00:07:18,070
even by color coding it, as
I have done the code here.

140
00:07:18,070 --> 00:07:21,160
Even though there's a lot more
syntax going on here, of course

141
00:07:21,160 --> 00:07:25,670
this program is functionally the same
and just prints out Hello, World.

142
00:07:25,670 --> 00:07:28,810
And so when we go from Scratch
to C, among my favorite things

143
00:07:28,810 --> 00:07:33,190
to do pedagogically is to show students
these very user friendly puzzle

144
00:07:33,190 --> 00:07:37,600
pieces in Scratch, and say in C,
it just looks a little different,

145
00:07:37,600 --> 00:07:38,930
like this here on the right.

146
00:07:38,930 --> 00:07:40,310
Yes, it looks scarier.

147
00:07:40,310 --> 00:07:43,810
Yes, it's harder to memorize at
first with all of this punctuation,

148
00:07:43,810 --> 00:07:46,130
but it's the exact same idea.

149
00:07:46,130 --> 00:07:49,900
And we try to give students early on
this mental hook, this mental comfort,

150
00:07:49,900 --> 00:07:53,950
so that even if they're frustrated by
or struggling with some of the syntax,

151
00:07:53,950 --> 00:07:58,270
it's the same darn ideas as they
were the previous week with respect

152
00:07:58,270 --> 00:08:01,610
to functions and loops and
conditionals and so much more.

153
00:08:01,610 --> 00:08:03,760
Indeed, here is a
conditional that starts

154
00:08:03,760 --> 00:08:07,900
to look even more cryptic on right, but
is the exact same thing as the puzzle

155
00:08:07,900 --> 00:08:09,190
pieces at left.

156
00:08:09,190 --> 00:08:13,960
But C now educationally also
allows us to go at a lower level

157
00:08:13,960 --> 00:08:14,960
and pretty quickly.

158
00:08:14,960 --> 00:08:19,390
And in fact, among the most
empowering things I hope about CS50

159
00:08:19,390 --> 00:08:23,360
is that we actually don't
abstract that much away.

160
00:08:23,360 --> 00:08:26,860
At the end of the day, what's nice
about C, I do think pedagogically,

161
00:08:26,860 --> 00:08:28,370
is that there's no magic.

162
00:08:28,370 --> 00:08:31,480
You don't just write one line of
code and a whole lot of functionality

163
00:08:31,480 --> 00:08:33,320
happens for free for you.

164
00:08:33,320 --> 00:08:36,669
If you want to have a
list of information,

165
00:08:36,669 --> 00:08:39,100
if you want to have
a hash table of data,

166
00:08:39,100 --> 00:08:41,197
you have to implement that yourself.

167
00:08:41,197 --> 00:08:43,030
Now, that's not necessarily
something you're

168
00:08:43,030 --> 00:08:47,240
going to want to do or even have
to do professionally long term.

169
00:08:47,240 --> 00:08:50,470
But the fact that in this course,
we give students this bottom up

170
00:08:50,470 --> 00:08:54,340
understanding of what is going on
underneath the hood of the computer,

171
00:08:54,340 --> 00:08:57,350
we do think intellectually
is incredibly empowering.

172
00:08:57,350 --> 00:09:00,580
So we present students, for
instance, this grid of memory,

173
00:09:00,580 --> 00:09:02,870
RAM, so to speak,
inside of your computer.

174
00:09:02,870 --> 00:09:06,970
And we propose to them that if we
want to maintain some kind of ordering

175
00:09:06,970 --> 00:09:09,320
and association among these
data, we can, of course,

176
00:09:09,320 --> 00:09:13,760
implement the scary old linked
lists like this using pointers.

177
00:09:13,760 --> 00:09:15,730
But at the end of the
day, there's no magic.

178
00:09:15,730 --> 00:09:17,060
This is just numbers.

179
00:09:17,060 --> 00:09:19,910
And those numbers are
just bits, zeros and ones.

180
00:09:19,910 --> 00:09:24,010
And because we try in the course to
scaffold things from building blocks

181
00:09:24,010 --> 00:09:28,750
to building block to building block,
layering ideas on top of one another,

182
00:09:28,750 --> 00:09:32,650
the hope is that when students
transition thereafter to a higher level

183
00:09:32,650 --> 00:09:37,420
language like Python, they still
understand what is actually going on,

184
00:09:37,420 --> 00:09:40,982
and they appreciate now what
tools they've been provided with.

185
00:09:40,982 --> 00:09:43,940
And they're not just kind of mimicking
what they've seen on the screen.

186
00:09:43,940 --> 00:09:47,720
They know what Python, they know
what their own code is doing.

187
00:09:47,720 --> 00:09:50,150
So one of my favorite
exercises, in fact, is this.

188
00:09:50,150 --> 00:09:53,990
This is a bit of a spoiler, if
you've not finished CS50x yourself.

189
00:09:53,990 --> 00:09:59,290
But this code here in about a dozen
lines of code in Python is essentially

190
00:09:59,290 --> 00:10:03,500
an implementation of problem
set 5 in CS50x currently,

191
00:10:03,500 --> 00:10:08,390
which is to implement a spell checker in
C and implement your very own hash table

192
00:10:08,390 --> 00:10:13,850
for like 100,000 plus words in English
that daresay takes most students 5

193
00:10:13,850 --> 00:10:17,935
hours, 10 hours, 15, 20 hours
to implement and get right.

194
00:10:17,935 --> 00:10:21,710
But in Python, and I do this
deliberately in class, 60 seconds, type,

195
00:10:21,710 --> 00:10:25,940
type, type, done implementing
the same spell checker in Python,

196
00:10:25,940 --> 00:10:28,380
because that entire
hash table, of course,

197
00:10:28,380 --> 00:10:31,460
is reduced to that one line
of code at the very top

198
00:10:31,460 --> 00:10:34,010
there, where we use a
Python set that we could

199
00:10:34,010 --> 00:10:37,190
use even a list or a dictionary
or some other structure

200
00:10:37,190 --> 00:10:41,100
to implement that data structure
containing all of those words.

201
00:10:41,100 --> 00:10:44,720
And it's that moment where students
see and appreciate and sort of shake

202
00:10:44,720 --> 00:10:48,230
their fist metaphorically in class
when they realize, oh my God,

203
00:10:48,230 --> 00:10:52,050
why did we just spend 10 to
20 hours implementing it in C.

204
00:10:52,050 --> 00:10:55,040
But the difference is that
our students, we do hope,

205
00:10:55,040 --> 00:10:59,840
understand now at a very real
level what all of this code

206
00:10:59,840 --> 00:11:02,020
is actually doing for them.

207
00:11:02,020 --> 00:11:05,770
We transition toward the end of the
CS50, of course, to web programming.

208
00:11:05,770 --> 00:11:08,580
And this too is motivated
by the reality nowadays

209
00:11:08,580 --> 00:11:12,670
that it's just useful to be able
to write code for web contexts.

210
00:11:12,670 --> 00:11:14,860
It's not even the
actual web necessarily.

211
00:11:14,860 --> 00:11:17,580
Increasingly, do mobile
devices, for instance,

212
00:11:17,580 --> 00:11:22,830
have applications written in them using
languages like HTML, CSS, and JavaScript

213
00:11:22,830 --> 00:11:27,790
for cross-platform support across
Android and iOS in particular.

214
00:11:27,790 --> 00:11:30,150
So we introduced students,
of course, to this structure

215
00:11:30,150 --> 00:11:33,430
of HTML, the bones that allow
you to structure a page.

216
00:11:33,430 --> 00:11:37,110
But we very quickly transitioned to
Flask, which for those unfamiliar

217
00:11:37,110 --> 00:11:39,010
is a micro framework.

218
00:11:39,010 --> 00:11:43,560
It's code that standardizes how
you implement a web application,

219
00:11:43,560 --> 00:11:45,190
but it's fairly lightweight.

220
00:11:45,190 --> 00:11:48,360
There's fairly little
Flask-specific stuff

221
00:11:48,360 --> 00:11:52,450
that students have to master in order
to make their very own web application,

222
00:11:52,450 --> 00:11:55,500
unlike something like
Django or other frameworks

223
00:11:55,500 --> 00:11:57,340
that just tend to be heavier weight.

224
00:11:57,340 --> 00:11:59,970
And indeed, this too is
a pedagogical decision.

225
00:11:59,970 --> 00:12:03,640
We want students to become
familiar with a framework.

226
00:12:03,640 --> 00:12:07,320
We want them to get exposure to
some real world web applications.

227
00:12:07,320 --> 00:12:10,350
But we don't want to spend a
week, a month, a course teaching

228
00:12:10,350 --> 00:12:14,190
them a specific framework,
something like Django or the like,

229
00:12:14,190 --> 00:12:17,710
which might be very useful and
very applicable professionally.

230
00:12:17,710 --> 00:12:19,250
But that's not the point, right?

231
00:12:19,250 --> 00:12:21,625
That's the point at which you
should be going and reading

232
00:12:21,625 --> 00:12:22,930
the documentation is needed.

233
00:12:22,930 --> 00:12:25,590
What we care about in the
context of web programming

234
00:12:25,590 --> 00:12:28,740
is what is the browser doing,
what is the server doing, what

235
00:12:28,740 --> 00:12:32,620
is HTTP, what is the framework
doing to facilitate all of that.

236
00:12:32,620 --> 00:12:37,110
And how are HTML, CSS,
JavaScript and Python all

237
00:12:37,110 --> 00:12:40,200
solving different problems in this case.

238
00:12:40,200 --> 00:12:43,830
Now, ultimately, the software that
we have students use in the course

239
00:12:43,830 --> 00:12:45,137
has evolved over time.

240
00:12:45,137 --> 00:12:47,970
And if you've been with us as a
teacher in some form over the years,

241
00:12:47,970 --> 00:12:51,210
you'll know that the technology,
the platforms we ourselves use

242
00:12:51,210 --> 00:12:52,330
has been evolving.

243
00:12:52,330 --> 00:12:56,190
Most recently, we have students
using Visual Studio Code or VS

244
00:12:56,190 --> 00:12:59,070
Code, which is a very
popular text editor,

245
00:12:59,070 --> 00:13:02,730
increasingly really an IDE, or
integrated development environment,

246
00:13:02,730 --> 00:13:05,130
because with things called
extensions or plugins,

247
00:13:05,130 --> 00:13:08,710
you can really add a lot more
functionality to the environment.

248
00:13:08,710 --> 00:13:12,180
And so what we ourselves do for
students is we can figure this for them

249
00:13:12,180 --> 00:13:16,020
in the cloud using a third party
tool called GitHub Codespaces.

250
00:13:16,020 --> 00:13:20,190
What's nice about GitHub Codespaces is
that whether you're using it for CS50

251
00:13:20,190 --> 00:13:24,000
or any of your own classes,
any verified teacher

252
00:13:24,000 --> 00:13:28,570
can use GitHub Codespaces and
related tools completely for free.

253
00:13:28,570 --> 00:13:31,140
So if you're using this
through CS50 or on your own,

254
00:13:31,140 --> 00:13:33,310
you can use these tools in the cloud.

255
00:13:33,310 --> 00:13:35,950
And this too is a very
pedagogical decision.

256
00:13:35,950 --> 00:13:39,090
All too often in introductory
technical courses,

257
00:13:39,090 --> 00:13:41,610
students might have to
download some piece of software

258
00:13:41,610 --> 00:13:43,720
or install it and configure it.

259
00:13:43,720 --> 00:13:46,200
Sometimes that works out
well, but the reality

260
00:13:46,200 --> 00:13:49,950
is there's so many darn
versions of Mac OS and Windows

261
00:13:49,950 --> 00:13:52,050
and even other operating
systems that you're

262
00:13:52,050 --> 00:13:54,460
going to run into
technical difficulties,

263
00:13:54,460 --> 00:13:58,380
certainly if you have a
medium number of students.

264
00:13:58,380 --> 00:14:01,890
If you have just a handful, might not
be such a big deal to get everyone up

265
00:14:01,890 --> 00:14:06,240
and running on their own Macs or PCs,
especially if they need offline access.

266
00:14:06,240 --> 00:14:09,950
But if you're fortunate to have
pretty good internet access in school,

267
00:14:09,950 --> 00:14:14,090
at home or at work, more generally,
using something in the cloud

268
00:14:14,090 --> 00:14:16,860
is certainly very
turnkey and convenient.

269
00:14:16,860 --> 00:14:20,558
So we use this so we can standardize
students' programming environments.

270
00:14:20,558 --> 00:14:23,600
And for those of you who teach not
just introductory courses, but perhaps

271
00:14:23,600 --> 00:14:27,510
higher level, more advanced courses as
well, we'll talk over the coming days.

272
00:14:27,510 --> 00:14:30,380
And we have documentation online
via which you can actually

273
00:14:30,380 --> 00:14:35,480
use Codespaces and customize it yourself
for courses even unrelated to CS50

274
00:14:35,480 --> 00:14:36,330
as well.

275
00:14:36,330 --> 00:14:38,360
But within the classroom,
and what we really

276
00:14:38,360 --> 00:14:41,360
wanted to share in this
first session today

277
00:14:41,360 --> 00:14:45,140
is like what the point is of
a lot of the demonstrations,

278
00:14:45,140 --> 00:14:49,890
a lot of the decisions that we make
on camera or really in class itself.

279
00:14:49,890 --> 00:14:54,800
And the goal for me as a teacher now
has been to create as best I can,

280
00:14:54,800 --> 00:14:59,960
as many as I can of these memorable
moments, sort of visual memories

281
00:14:59,960 --> 00:15:04,050
that stick in students' head long
after the course itself is over,

282
00:15:04,050 --> 00:15:08,250
so that for the most sophisticated
topics, complicated, difficult topics

283
00:15:08,250 --> 00:15:11,010
in the class, they have some
kind of mental framework

284
00:15:11,010 --> 00:15:13,650
that they can fall back on
that just gives them greater

285
00:15:13,650 --> 00:15:17,400
comfort an understanding of some
topic that might otherwise be far too

286
00:15:17,400 --> 00:15:20,080
abstract or complex to recall.

287
00:15:20,080 --> 00:15:22,950
So, for instance, binary search
is perhaps one of the first

288
00:15:22,950 --> 00:15:24,160
that we introduced in class.

289
00:15:24,160 --> 00:15:26,400
And you might remember
scenes like this here.

290
00:15:26,400 --> 00:15:30,160
It's getting increasingly hard
to find these here phone books.

291
00:15:30,160 --> 00:15:34,100
And I think quite soon, we
might solicit via the internet

292
00:15:34,100 --> 00:15:36,600
that if you have phone books
of your own that you don't need

293
00:15:36,600 --> 00:15:39,280
or colleagues or friends,
please do mail them to us.

294
00:15:39,280 --> 00:15:40,780
They're also getting fairly thin.

295
00:15:40,780 --> 00:15:43,750
So it's not all that compelling
to tear these things in half.

296
00:15:43,750 --> 00:15:46,350
But what's nice about
phone books is that they're

297
00:15:46,350 --> 00:15:48,640
still with us in digital form.

298
00:15:48,640 --> 00:15:50,850
Whether you have an
iPhone or Android device,

299
00:15:50,850 --> 00:15:54,930
you have a contacts or address-book app
that still has people's names from A

300
00:15:54,930 --> 00:15:57,040
to Z sorted alphabetically.

301
00:15:57,040 --> 00:16:01,240
A phone book, then, is just a physical
incarnation of that same idea.

302
00:16:01,240 --> 00:16:02,503
I hope you won't mind.

303
00:16:02,503 --> 00:16:04,420
I don't think I'm going
to tear this one today

304
00:16:04,420 --> 00:16:05,810
because I kind of need it in the fall.

305
00:16:05,810 --> 00:16:07,602
So we're going to hang
on to this one here.

306
00:16:07,602 --> 00:16:11,570
But you can see a dramatically
torn in any of our videos online.

307
00:16:11,570 --> 00:16:13,780
We, of course, talked
with students about binary

308
00:16:13,780 --> 00:16:16,090
and indeed try to give
them a sense of really

309
00:16:16,090 --> 00:16:18,520
at the end of the day, what
is a computer doing, how is it

310
00:16:18,520 --> 00:16:20,147
storing information.

311
00:16:20,147 --> 00:16:23,230
And so even though we function, of
course, in the human world with decimal

312
00:16:23,230 --> 00:16:25,810
primarily, among our
goals with teaching binary

313
00:16:25,810 --> 00:16:29,690
is also to create one of these memorable
moments after that same phone book.

314
00:16:29,690 --> 00:16:32,290
So pictured here, for instance,
is some of our students

315
00:16:32,290 --> 00:16:36,040
in a prior year holding up
their hand to represent a one

316
00:16:36,040 --> 00:16:39,770
or just standing there with their
hand down to represent a zero.

317
00:16:39,770 --> 00:16:41,780
Now, we do this with sheets of paper.

318
00:16:41,780 --> 00:16:45,940
In this case, I print 1 on some of
the sheets or 0 on the other sheets

319
00:16:45,940 --> 00:16:49,450
as a sort of visual cue to tell them
or the audience what it is they're

320
00:16:49,450 --> 00:16:50,360
representing.

321
00:16:50,360 --> 00:16:51,530
You don't even need that.

322
00:16:51,530 --> 00:16:53,990
Sometimes we use light
bulbs that are on or off.

323
00:16:53,990 --> 00:16:58,060
I went on amazon.com one year and found
some plastic light up numbers which we

324
00:16:58,060 --> 00:17:02,440
can similarly use as well to ultimately
have students represent the ones place,

325
00:17:02,440 --> 00:17:08,960
the twos place, the fours place,
eights, 16s, 32, 64 128s place.

326
00:17:08,960 --> 00:17:12,760
The tension, I think, ultimately, is,
how many minutes, how much class time

327
00:17:12,760 --> 00:17:14,920
do you actually spend
on these demonstrations

328
00:17:14,920 --> 00:17:18,859
when you could have just written
it on the board in chalk or marker?

329
00:17:18,859 --> 00:17:21,430
But that's really left to
you, to me, the teacher,

330
00:17:21,430 --> 00:17:24,819
to decide to read the
room as to what feels

331
00:17:24,819 --> 00:17:27,550
like an appropriate balance
of spending good time on these

332
00:17:27,550 --> 00:17:30,490
to create memorable moments
versus taking too much time

333
00:17:30,490 --> 00:17:32,830
at the expense of other discussions.

334
00:17:32,830 --> 00:17:36,400
Now, when it comes to debugging
too, you might recognize

335
00:17:36,400 --> 00:17:40,577
or might wonder why rubber ducks
seem to be everywhere in CS50.

336
00:17:40,577 --> 00:17:42,910
We've actually been giving
these little rubber ducks out

337
00:17:42,910 --> 00:17:46,270
to students for quite a bit of
time now in class physically,

338
00:17:46,270 --> 00:17:49,310
and they also line the stage
in this photograph here.

339
00:17:49,310 --> 00:17:51,400
Here is simply a much
bigger version of the same,

340
00:17:51,400 --> 00:17:53,108
because there's this
thing in programming

341
00:17:53,108 --> 00:17:56,410
called rubber-duck debugging,
whereby if you or a student

342
00:17:56,410 --> 00:17:59,590
are struggling to solve some
problem or understand something,

343
00:17:59,590 --> 00:18:04,400
you're encouraged to have a conversation
with a rubber duck and sound it out.

344
00:18:04,400 --> 00:18:06,650
Tell the duck what
problems you're having.

345
00:18:06,650 --> 00:18:08,240
Ask the duck any questions.

346
00:18:08,240 --> 00:18:09,890
Odds are it won't actually reply.

347
00:18:09,890 --> 00:18:13,150
But through that process of
talking through the problem,

348
00:18:13,150 --> 00:18:15,760
the presumption is that
light bulb will go off

349
00:18:15,760 --> 00:18:18,820
and you'll realize some
illogic in your thinking,

350
00:18:18,820 --> 00:18:22,310
and you will have solved the
problem just by verbalizing it.

351
00:18:22,310 --> 00:18:24,200
Well, nowadays we do this digitally.

352
00:18:24,200 --> 00:18:26,560
We've had a chat bot that
will quack back at students,

353
00:18:26,560 --> 00:18:30,527
and most recently, one that will speak
English or even other human languages

354
00:18:30,527 --> 00:18:31,360
back to the student.

355
00:18:31,360 --> 00:18:34,180
And indeed, more on that over
the course of today and tomorrow,

356
00:18:34,180 --> 00:18:38,200
because now underlying these
ducks is artificial intelligence.

357
00:18:38,200 --> 00:18:41,350
But at a lower level, of course, we
introduce students to data structures,

358
00:18:41,350 --> 00:18:43,010
among the simplest being an array.

359
00:18:43,010 --> 00:18:45,700
We try to remind students
that an array is really

360
00:18:45,700 --> 00:18:49,850
just leveraging that same model we
discussed in the context of memory.

361
00:18:49,850 --> 00:18:53,650
But technically, a computer can
only look at one location at a time,

362
00:18:53,650 --> 00:18:54,380
typically.

363
00:18:54,380 --> 00:18:59,080
And so we liken locations in memory
to doors, like lockers in a gym

364
00:18:59,080 --> 00:19:02,680
or in the hallway where students might
keep their books in their backpacks.

365
00:19:02,680 --> 00:19:06,570
We have been fortunate
to find at a local store

366
00:19:06,570 --> 00:19:10,810
a whole bunch of tiny gym lockers that
aren't very convenient to move around.

367
00:19:10,810 --> 00:19:15,090
But we nonetheless set them
up on stage and allow students

368
00:19:15,090 --> 00:19:18,840
to then visualize and
hear all the more what

369
00:19:18,840 --> 00:19:22,380
we mean when we say a computer can
only look at one location at a time

370
00:19:22,380 --> 00:19:25,950
as we go from left to right
opening those same doors.

371
00:19:25,950 --> 00:19:27,780
We talk about sorting information.

372
00:19:27,780 --> 00:19:31,170
And here too, a fun opportunity
to have students come up on stage

373
00:19:31,170 --> 00:19:32,370
and sort themselves.

374
00:19:32,370 --> 00:19:35,160
Pictured here are some of our
students holding plastic light

375
00:19:35,160 --> 00:19:39,040
up numbers that represent a
number from 0 to 7 in this case.

376
00:19:39,040 --> 00:19:42,480
And it's a fun exercise to, one,
have them just go sort themselves.

377
00:19:42,480 --> 00:19:44,020
And usually it's a little chaotic.

378
00:19:44,020 --> 00:19:46,180
But as smart humans, they figure it out.

379
00:19:46,180 --> 00:19:49,720
But then I ask them, well, what
was the algorithm you used.

380
00:19:49,720 --> 00:19:51,900
And really, no one can
kind of put their finger

381
00:19:51,900 --> 00:19:54,490
on what just happened
chaotically on the stage.

382
00:19:54,490 --> 00:19:59,010
So we try to formalize it with something
like selection sort or bubble sort

383
00:19:59,010 --> 00:20:01,320
or more advanced algorithm as well.

384
00:20:01,320 --> 00:20:03,120
When we get two pointers,
we try to, again,

385
00:20:03,120 --> 00:20:06,240
to give students these memorable
moments and these mental models

386
00:20:06,240 --> 00:20:10,150
by likening it to pointing
from one thing to another.

387
00:20:10,150 --> 00:20:12,270
So I picked up from a
local hardware store,

388
00:20:12,270 --> 00:20:14,820
called Home Depot here,
a couple of mailboxes

389
00:20:14,820 --> 00:20:17,040
physically that you get postal mail in.

390
00:20:17,040 --> 00:20:18,850
But we set them up on stage here.

391
00:20:18,850 --> 00:20:21,930
So Carter and I were playing
the roles of actually

392
00:20:21,930 --> 00:20:26,848
accessing the contents of these memory
locations represented by mailboxes.

393
00:20:26,848 --> 00:20:28,890
And because we're at a
university, we have access

394
00:20:28,890 --> 00:20:30,580
to a lot of those foam fingers.

395
00:20:30,580 --> 00:20:32,700
So I had a Harvard foam
finger or a Yale foam

396
00:20:32,700 --> 00:20:35,610
finger that allows me even
more visibly and dramatically

397
00:20:35,610 --> 00:20:38,650
to point from one location to another.

398
00:20:38,650 --> 00:20:40,530
But of course, ultimately
under the hood,

399
00:20:40,530 --> 00:20:44,860
it's just this grid of memory locations,
which we again remind students of.

400
00:20:44,860 --> 00:20:48,380
And even though this kind of
story seems to escalate quickly,

401
00:20:48,380 --> 00:20:50,130
because suddenly it
gets very complicated,

402
00:20:50,130 --> 00:20:54,550
I'm looking at hexadecimal and grids
of memory, it's just the same idea.

403
00:20:54,550 --> 00:20:58,770
And so just like with Scratch
and C, with memory and mailboxes,

404
00:20:58,770 --> 00:21:03,500
we try to give students this very
comfortable, familiar, memorable moment

405
00:21:03,500 --> 00:21:07,540
and mental model, but use that to
allow them to better understand

406
00:21:07,540 --> 00:21:10,450
what's going on underneath
the hood so they really

407
00:21:10,450 --> 00:21:14,180
can appreciate and understand
these so-called abstractions.

408
00:21:14,180 --> 00:21:15,430
We do this again and again.

409
00:21:15,430 --> 00:21:19,670
With hashing, for instance, it's common
to say that you put values into buckets.

410
00:21:19,670 --> 00:21:23,570
So we literally pick up some buckets
from, again, the hardware store.

411
00:21:23,570 --> 00:21:27,590
And in this case, we had some jumbo
playing cards that we found on Amazon.

412
00:21:27,590 --> 00:21:30,530
But you could make these yourself
out of paper and markers.

413
00:21:30,530 --> 00:21:36,130
And we bucketize the values by hashing
based on the suit of these here cards.

414
00:21:36,130 --> 00:21:39,220
But it's important to recognize,
too, especially since we

415
00:21:39,220 --> 00:21:44,320
are fortunate to teach a class like CS50
in this beautiful theater on campus,

416
00:21:44,320 --> 00:21:49,030
that none of this theatricality, none
of this creation of memorable moments

417
00:21:49,030 --> 00:21:52,160
actually requires much in
the way of those resources.

418
00:21:52,160 --> 00:21:54,380
And it certainly doesn't
require a theater.

419
00:21:54,380 --> 00:21:57,370
Indeed, several of those
examples and all of my own

420
00:21:57,370 --> 00:22:01,810
earliest examples didn't have
buckets, didn't have plastic numbers

421
00:22:01,810 --> 00:22:02,720
that light up.

422
00:22:02,720 --> 00:22:04,780
They just had sheets
of paper that I grabbed

423
00:22:04,780 --> 00:22:08,050
from a printer drawn on
with a marker to just make

424
00:22:08,050 --> 00:22:11,110
more real and more visual
what it is that we're

425
00:22:11,110 --> 00:22:14,320
trying to present to our students.

426
00:22:14,320 --> 00:22:17,890
So the problem sets are what
ultimately is where students

427
00:22:17,890 --> 00:22:19,790
spend most of their time in the class.

428
00:22:19,790 --> 00:22:22,810
It's an opportunity to assess their
understanding of the material,

429
00:22:22,810 --> 00:22:27,040
but more importantly, for them to
apply the material to actually problems

430
00:22:27,040 --> 00:22:29,930
and actually learn how to master it.

431
00:22:29,930 --> 00:22:34,870
We try to draw inspiration from
familiar aspects of culture, pop culture

432
00:22:34,870 --> 00:22:35,680
and technology.

433
00:22:35,680 --> 00:22:38,020
Mario, for instance, has
become fairly canonical.

434
00:22:38,020 --> 00:22:42,200
And as you yourself are a
teacher, perhaps a new teacher,

435
00:22:42,200 --> 00:22:45,070
I keep a lookout in my own
life for things like this

436
00:22:45,070 --> 00:22:49,510
that I could use as a hook,
a way of enticing students

437
00:22:49,510 --> 00:22:53,440
into caring about a problem, but
reducing it really to something

438
00:22:53,440 --> 00:22:54,410
that we want to teach.

439
00:22:54,410 --> 00:22:58,780
So here is a fairly involved picture
from the 1980s of the original Nintendo

440
00:22:58,780 --> 00:23:00,142
and Super Mario Brothers.

441
00:23:00,142 --> 00:23:02,350
But what caught my attention
there is, wait a minute,

442
00:23:02,350 --> 00:23:05,620
this pyramid is a fairly
standard structure.

443
00:23:05,620 --> 00:23:08,170
There's some kind of loop via
which you could create it.

444
00:23:08,170 --> 00:23:09,490
That's a problem set.

445
00:23:09,490 --> 00:23:11,002
How do we make it more complicated?

446
00:23:11,002 --> 00:23:13,710
Well, later in the game, there's
two pyramids, slightly different

447
00:23:13,710 --> 00:23:14,770
opposing shapes.

448
00:23:14,770 --> 00:23:17,140
That's a slightly
harder homework problem.

449
00:23:17,140 --> 00:23:19,350
So again, we tend to
look for these hooks,

450
00:23:19,350 --> 00:23:22,770
be it visually, audibly,
experientially, that we

451
00:23:22,770 --> 00:23:26,858
use as motivation for the subsequent
problem, which at the end of the day,

452
00:23:26,858 --> 00:23:29,400
especially for those of us who've
been programming for years,

453
00:23:29,400 --> 00:23:30,820
might be kind of boring, right?

454
00:23:30,820 --> 00:23:33,870
Like writing a for loop or
two is not terribly exciting,

455
00:23:33,870 --> 00:23:38,190
but it can be the first time and it
can be if you know how it's applicable

456
00:23:38,190 --> 00:23:40,690
and care why it is.

457
00:23:40,690 --> 00:23:43,740
We talk about cryptography,
which at the end of the day

458
00:23:43,740 --> 00:23:46,380
really is just an excuse to--

459
00:23:46,380 --> 00:23:51,870
really is just rather a context in
which to discuss string manipulation

460
00:23:51,870 --> 00:23:54,660
and treating strings as
array of characters in C,

461
00:23:54,660 --> 00:23:57,570
and manipulating the underlying
characters as though they're

462
00:23:57,570 --> 00:24:00,000
numbers because of that
equivalence between chars

463
00:24:00,000 --> 00:24:03,220
and ints in a language
like C. So this, of course,

464
00:24:03,220 --> 00:24:07,820
is the plain text that might correspond
to the so-called ciphertext here in.

465
00:24:07,820 --> 00:24:10,780
But again, that context,
that hook is meant

466
00:24:10,780 --> 00:24:15,670
to get students thinking about and
caring about the material at hand.

467
00:24:15,670 --> 00:24:18,830
Photographs and videos
nowadays are everywhere.

468
00:24:18,830 --> 00:24:21,220
And so here's a picture
of a popular location

469
00:24:21,220 --> 00:24:24,910
here on campus that we apply
some Instagram-like filters

470
00:24:24,910 --> 00:24:28,340
to make it black and white
or detect all of the edges.

471
00:24:28,340 --> 00:24:30,340
At the end of the day,
what we really care about

472
00:24:30,340 --> 00:24:34,240
with this homework assignment,
so-called Problem Set 4 in CS50 of late,

473
00:24:34,240 --> 00:24:38,180
is that we want them to
understand file input and output.

474
00:24:38,180 --> 00:24:42,760
We want them to understand bitmap
files and grids of pixels and structs

475
00:24:42,760 --> 00:24:44,510
via which you represent colors.

476
00:24:44,510 --> 00:24:48,070
But again, we use this hook
of Instagram-like filters

477
00:24:48,070 --> 00:24:51,610
to get students caring about and
excited about what problem they're

478
00:24:51,610 --> 00:24:52,870
trying to solve.

479
00:24:52,870 --> 00:24:55,750
Here, we introduce them
to hexadecimal as a hook

480
00:24:55,750 --> 00:24:58,660
to get rather in the
context of data recovery,

481
00:24:58,660 --> 00:25:02,970
to get students interested in actually
recovering photos by really just looking

482
00:25:02,970 --> 00:25:06,690
for patterns of bits pictured there
into their hexadecimal equivalents.

483
00:25:06,690 --> 00:25:10,410
We introduce students to a bit
of biology in the context of DNA

484
00:25:10,410 --> 00:25:13,530
and a sort of mystery
with DNA really to get

485
00:25:13,530 --> 00:25:16,800
them thinking about string
processing, which at a glance,

486
00:25:16,800 --> 00:25:21,060
is not nearly as exciting until we say,
this is Alice's DNA and this is Bob,

487
00:25:21,060 --> 00:25:23,200
and we ask him a question
like who done it.

488
00:25:23,200 --> 00:25:25,200
And then toward the end
of the course, of course

489
00:25:25,200 --> 00:25:28,470
in the context of web
programming, we introduce them

490
00:25:28,470 --> 00:25:32,580
of late to CS50 Finance, a full
fledged web application that

491
00:25:32,580 --> 00:25:36,090
talks to a lightweight
API, a third party service

492
00:25:36,090 --> 00:25:39,670
to get live data so that students,
really, by the end of the course

493
00:25:39,670 --> 00:25:44,310
have built something within the
context and support structure of CS50,

494
00:25:44,310 --> 00:25:48,600
but in a way that they can then
use as a stepping stone to making

495
00:25:48,600 --> 00:25:54,600
their own final project, if not a web
application or mobile app as well.

496
00:25:54,600 --> 00:25:58,830
But now, here on campus and perhaps in
your own schools or communities as well,

497
00:25:58,830 --> 00:26:01,730
we focus also on CS50's community.

498
00:26:01,730 --> 00:26:05,530
I dare say we've tried to make it more
than just a course, more than just

499
00:26:05,530 --> 00:26:07,840
a set of homework
assignments, but really this

500
00:26:07,840 --> 00:26:09,520
shared collective experience.

501
00:26:09,520 --> 00:26:11,950
In part, because it's
meant to be fairly intense

502
00:26:11,950 --> 00:26:14,450
and it is indeed rigorous
for so many students.

503
00:26:14,450 --> 00:26:17,740
And we want there to be
this mix of work and play,

504
00:26:17,740 --> 00:26:20,630
but that ultimately really
brings students together in a way

505
00:26:20,630 --> 00:26:21,620
that they care about.

506
00:26:21,620 --> 00:26:24,370
And so we have this sequence of
events that start with Puzzle Day.

507
00:26:24,370 --> 00:26:26,162
And you some of you
might have participated

508
00:26:26,162 --> 00:26:27,740
in the online version of this.

509
00:26:27,740 --> 00:26:30,790
All the better if you can get your
students, your classmates together,

510
00:26:30,790 --> 00:26:34,303
working on challenge problems,
logical problems together.

511
00:26:34,303 --> 00:26:36,220
Pictured here is among
my favorite photographs

512
00:26:36,220 --> 00:26:39,070
of some of our very smart
students gathering together

513
00:26:39,070 --> 00:26:41,140
to delight in what the solutions are.

514
00:26:41,140 --> 00:26:44,740
Pictured here are some of those same
students struggling with those problems

515
00:26:44,740 --> 00:26:48,290
collaboratively before the
solutions were revealed.

516
00:26:48,290 --> 00:26:51,770
And these puzzles have nothing to do
deliberately with computer science.

517
00:26:51,770 --> 00:26:53,530
This is not a hackathon per se.

518
00:26:53,530 --> 00:26:55,990
It has nothing to do
with programming or CS,

519
00:26:55,990 --> 00:26:59,650
but about problem solving
collaboratively, and especially drawing

520
00:26:59,650 --> 00:27:03,820
in those students less
comfortable at the school

521
00:27:03,820 --> 00:27:08,570
so that they might even follow
their CS50 friends to this event,

522
00:27:08,570 --> 00:27:10,540
learn a little something
about problem solving,

523
00:27:10,540 --> 00:27:13,640
and get interested perhaps
in the field itself.

524
00:27:13,640 --> 00:27:16,930
Now, toward the end of the semester,
as you might know, here at Harvard,

525
00:27:16,930 --> 00:27:20,240
as well as at Yale, do we-- once
students have a programming background,

526
00:27:20,240 --> 00:27:24,580
we do have a proper hackathon,
a 12-hour event, in our case,

527
00:27:24,580 --> 00:27:30,160
during which students can work, ideally
excitedly, on their final projects,

528
00:27:30,160 --> 00:27:32,050
their capstone experience.

529
00:27:32,050 --> 00:27:35,170
We have a tradition
of ending the evening,

530
00:27:35,170 --> 00:27:40,040
which for us starts at 7:00 PM at night
and ends at 7:00 AM in the morning.

531
00:27:40,040 --> 00:27:42,520
But any students who are still
awake with enough energy,

532
00:27:42,520 --> 00:27:47,530
we invite to a local pancake place,
the International House of Pancakes,

533
00:27:47,530 --> 00:27:50,740
where such memories as
these await ultimately

534
00:27:50,740 --> 00:27:53,990
after a long night of
actual problem solving.

535
00:27:53,990 --> 00:27:57,490
And then, lastly, do we end our
semester with the so-called CS50

536
00:27:57,490 --> 00:28:01,240
Fair, which is really inspired by what
some of your own schools back in the day

537
00:28:01,240 --> 00:28:04,060
might have held as middle
school science fairs,

538
00:28:04,060 --> 00:28:07,810
where you show off the volcano that
you built at home demonstrating

539
00:28:07,810 --> 00:28:09,770
some chemical concept from class.

540
00:28:09,770 --> 00:28:11,560
Well, we have students
bring their laptops

541
00:28:11,560 --> 00:28:15,550
and we invite friends, alumni,
recruiters from industry.

542
00:28:15,550 --> 00:28:18,280
We turn on some music, we
serve some popcorn and candy,

543
00:28:18,280 --> 00:28:21,970
and we invite students and
faculty and staff across campus

544
00:28:21,970 --> 00:28:26,750
to exhibit and see our
students' final projects.

545
00:28:26,750 --> 00:28:29,060
And so scenes like
this are not uncommon.

546
00:28:29,060 --> 00:28:33,190
Every CS50 student has their same
laptop or phone on which they're

547
00:28:33,190 --> 00:28:35,420
displaying the work that they created.

548
00:28:35,420 --> 00:28:39,010
We use this too, as an opportunity
to potentially recruit new students

549
00:28:39,010 --> 00:28:42,160
to get them interested in what
their friends have clearly

550
00:28:42,160 --> 00:28:45,310
created over the course of
just three months, in our case.

551
00:28:45,310 --> 00:28:50,380
We include typically a raffle, whereby
we give all of our CS50 students

552
00:28:50,380 --> 00:28:54,670
a sheet of paper that has some
placeholders for stickers,

553
00:28:54,670 --> 00:28:57,620
and we also give our CS50
students some stickers.

554
00:28:57,620 --> 00:29:00,310
And the idea is that
for any person who's

555
00:29:00,310 --> 00:29:03,760
attending that asks them
about their final project,

556
00:29:03,760 --> 00:29:05,920
the student should give
that person a sticker.

557
00:29:05,920 --> 00:29:10,420
And every sticker represents one entry
in a raffle with fabulous prizes,

558
00:29:10,420 --> 00:29:11,750
whatever those might be.

559
00:29:11,750 --> 00:29:16,360
And the goal, honestly, of this raffle
is just to grease the wheels socially,

560
00:29:16,360 --> 00:29:21,550
break the ice for students and attendees
to give them a fun excuse to go up

561
00:29:21,550 --> 00:29:24,010
and ask about this project
and this one and this one,

562
00:29:24,010 --> 00:29:27,430
so that students, again, care
and take an interest engaging

563
00:29:27,430 --> 00:29:31,450
with their fellow classmates,
staff and students.

564
00:29:31,450 --> 00:29:33,850
So this then was an
overview, ultimately,

565
00:29:33,850 --> 00:29:37,660
we hope, of the course's curriculum
and some of the why behind it,

566
00:29:37,660 --> 00:29:41,020
some of the technical and curricular
decisions behind the languages,

567
00:29:41,020 --> 00:29:43,450
behind the problem sets
and more, as well as

568
00:29:43,450 --> 00:29:47,260
a look behind the motivation
for so many of CS50's events

569
00:29:47,260 --> 00:29:50,270
that we host here in
person and/or online.

570
00:29:50,270 --> 00:29:53,230
Ultimately, again, the goal
in explaining all of this

571
00:29:53,230 --> 00:29:56,140
is to enable you as a teacher
to make your own informed

572
00:29:56,140 --> 00:29:59,710
decision as to whether to
adapt or adopt or neither

573
00:29:59,710 --> 00:30:02,150
of all of these various resources.

574
00:30:02,150 --> 00:30:04,920
But allow us to conclude
officially here.

575
00:30:04,920 --> 00:30:08,330
I'll take a-- we have
a few minutes of break

576
00:30:08,330 --> 00:30:11,610
ahead via which we can now
transition to the next session.

577
00:30:11,610 --> 00:30:14,130
So thank you so much for
joining us this morning.

578
00:30:14,130 --> 00:30:17,040
We will be back in just five
minutes for our next session.

579
00:30:17,040 --> 00:30:20,160
I'm going to hop off camera,
but hop into the chat room.

580
00:30:20,160 --> 00:30:24,680
So if you have any questions for me,
I will appear momentarily in the chat.

581
00:30:24,680 --> 00:30:26,460
But we'll see you in five.

582
00:30:26,460 --> 00:30:30,340
This was CS50 Explained.

583
00:30:30,340 --> 00:30:32,000