一
00:00:09,136 - > 00:00:13,056
>>大卫：欢迎您，我的名字是
大卫马兰，这是CS50。

2
00:00:13,056 - > 00:00:16,246
而且，这是不是你
典型的高中计算机

3
00:00:16,246 - > 00:00:17,346
科学课程。

4
00:00:17,346 - > 00:00:19,276
这当然是一个小
一些特别的东西。

5
00:00:19,636 - > 00:00:20,936
它不是因为
我教了。

6
00:00:20,936 - > 00:00:23,066
这是因为这是一
对，我们想的，

7
00:00:23,066 - > 00:00:27,206
这些罕见的课程，实际上
这么多挤你的大脑

8
00:00:27,206 - > 00:00:28,466
这么多和你的时间表

9
00:00:28,466 - > 00:00:31,756
到学期结束时你
真正聪明的感觉。

10
00:00:31,926 - > 00:00:33,206
所以，这是我的感受

11
00:00:33,206 - > 00:00:36,476
当我自己把这个
当然，早在1996年。

12
00:00:36,476 - > 00:00:37,646
我是政府的一个重大

13
00:00:37,646 - > 00:00:42,806
当时这里
住在马瑟楼。

14
00:00:44,006 - > 00:00:44,346
而且，一

15
00:00:44,346 - > 00:00:44,413
[打气]

16
00:00:44,413 - > 00:00:46,356
由于是外，
有5人。

17
00:00:46,856 - > 00:00:50,886
所以，我是一个政府
在主要的时间。

18
00:00:50,886 - > 00:00:51,876
我是一个政府的主要

19
00:00:51,876 - > 00:00:53,246
因为我一直
喜欢历史。

20
00:00:53,246 - > 00:00:55,196
我喜欢的宪法
法在高中。

21
00:00:55,196 - > 00:00:58,256
所以，我在这条道路出发
新生一年做我做什么

22
00:00:58,316 - > 00:01:00,246
最好的，做什么我知道我很喜欢。

23
00:01:00,466 - > 00:01:02,376
而且我一直
一个怪胎位，

24
00:01:02,516 - > 00:01:04,186
我一直胡说
电脑。

25
00:01:04,186 - > 00:01:06,846
不过，我自己，或许
具有讽刺意味的回顾，

26
00:01:06,846 - > 00:01:09,276
我一直认为谁的家伙
服用计算机科学

27
00:01:09,276 - > 00:01:12,906
在我高中时，我
朋友，真正的爱好者。

28
00:01:13,206 - > 00:01:16,646
然而，最后终于，大二
今年，我参加这个小课程

29
00:01:16,646 - > 00:01:19,726
这实际上所谓CS50
我把我吓坏了自己

30
00:01:19,726 - > 00:01:20,346
大学一年级。

31
00:01:20,536 - > 00:01:22,156
我是一个用户
当时的助理。

32
00:01:22,636 - > 00:01:25,006
所以，我肯定
已经提前出线，至少，

33
00:01:25,006 - > 00:01:27,726
对属于这些人，这些爱好者

34
00:01:27,726 - > 00:01:29,946
我是谁嘲笑
在高中。

35
00:01:30,326 - > 00:01:31,216
不过，我很害怕。

36
00:01:31,326 - > 00:01:34,966
目前，它有这种声誉
当时，也许仍

37
00:01:34,966 - > 00:01:37,616
部分，这是一个，
这是一个可怕的过程。

38
00:01:37,616 - > 00:01:38,396
这是一个大量的工作。

39
00:01:38,396 - > 00:01:41,566
这很难，然而，它的一
这些东西在那里，我的上帝，

40
00:01:42,026 - > 00:01:44,176
树皮远
不如其咬。

41
00:01:44,176 - > 00:01:46,446
我发现自己大二
今年，第一次，

42
00:01:46,746 - > 00:01:48,266
其实找功课的乐趣。

43
00:01:48,506 - > 00:01:51,026
而我并不是说这只是
在球场本课程给你。

44
00:01:51,026 - > 00:01:52,956
这是一个真正的
实现了我。

45
00:01:53,236 - > 00:01:55,416
现在，我认为在一
点，我没有越线

46
00:01:55,416 - > 00:01:59,276
到那里我真正geekdum
实际使用期待

47
00:01:59,276 - > 00:02:01,736
到星期五晚上，因为
我蜷缩在前面

48
00:02:01,736 - > 00:02:05,176
我的小MacBook和
工作CS50的习题。

49
00:02:05,496 - > 00:02:08,466
因此，在这一点上，我想我
显然越线。

50
00:02:08,466 - > 00:02:10,996
而且，我们的目标在这个过程中
是不是把你的所有

51
00:02:10,996 - > 00:02:13,926
该人，
但是，我只想说

52
00:02:13,926 - > 00:02:16,676
有一个小东西
特别对这个过程中，

53
00:02:16,676 - > 00:02:18,776
有点与众不同
关于计算机科学

54
00:02:18,776 - > 00:02:20,186
特别是在一般
这些天。

55
00:02:20,186 - > 00:02:22,496
而且，我们越驯化
所有钻进技术，

56
00:02:22,736 - > 00:02:24,766
我们进行了更多的玩具
围绕在我们的口袋里

57
00:02:24,766 - > 00:02:25,936
这本身就是计算机。

58
00:02:25,936 - > 00:02:28,826
我的意思是，我的iPhone实际上是
一个更高性能的计算机

59
00:02:28,936 - > 00:02:30,616
比我的笔记本上大学。

60
00:02:30,806 - > 00:02:33,496
你可以做很多的整洁
事情这些事情。

61
00:02:33,496 - > 00:02:34,786
现在，大部分
我们在这个房间，

62
00:02:34,956 - > 00:02:38,146
可能只是使用其他人
软件，其他人的工具，

63
00:02:38,366 - > 00:02:41,156
其他人的解决方案
因为我们去解决问题

64
00:02:41,286 - > 00:02:43,236
到iTunes，我们下载
一些应用程序的应用程序商店

65
00:02:43,236 - > 00:02:45,006
我们可以做和沃拉
一件整洁。

66
00:02:45,196 - > 00:02:46,476
但是，由最终的
这学期，

67
00:02:46,946 - > 00:02:50,106
你可以成为人
这样做解决问题。

68
00:02:50,106 - > 00:02:53,316
你可以成为解决人
有些问题，建立该应用程序，

69
00:02:53,636 - > 00:02:55,526
这一段的软件，
该工具，或者，

70
00:02:55,526 - > 00:02:58,476
一只是使我感到有趣，娱你。

71
00:02:58,476 - > 00:03:01,156
例如，控制，
就是说，你的iTunes资料库

72
00:03:01,156 - > 00:03:02,946
从你的房子
显然是一个应用程序

73
00:03:03,116 - > 00:03:06,476
已经存在，或者您可以
找到航天飞机安排更

74
00:03:06,476 - > 00:03:07,566
易实例。

75
00:03:07,806 - > 00:03:09,666
所以，事实上，其中一个
我做的第一件事

76
00:03:09,666 - > 00:03:13,036
在采取CS50是
再次，它可能是

77
00:03:13,036 - > 00:03:15,596
在这一点上周五
晚上和周六的晚上，

78
00:03:15,596 - > 00:03:17,526
有这个机会
当时

79
00:03:17,526 - > 00:03:19,156
在哈佛
穿梭巴士运行。

80
00:03:19,156 - > 00:03:21,496
而且，为了这一天，他们仍
印有时间表。

81
00:03:21,526 - > 00:03:23,336
但是，确实没有
手段寻找在线

82
00:03:23,336 - > 00:03:24,436
进行下一次航天飞机的。

83
00:03:24,666 - > 00:03:26,486
现在，我不在乎，
因为即使我住

84
00:03:26,486 - > 00:03:29,486
在马瑟我不是在那些
谁普遍采取了航天飞机。

85
00:03:29,486 - > 00:03:31,606
但是，我有很多朋友
在Pfoho的实例。

86
00:03:31,606 - > 00:03:33,906
而其中一个人问我，
我认为在一个点。

87
00:03:33,906 - > 00:03:33,973
[打气]

88
00:03:33,973 - > 00:03:35,306
好吧Pfoho更好
显然比马瑟。

89
00:03:35,416 - > 00:03:37,846
所以，我的朋友一类

90
00:03:37,846 - > 00:03:40,566
让我的思想也许我可以
写一个小程序来样

91
00:03:40,566 - > 00:03:42,646
帮助我的朋友检查
航天飞机的时间表。

92
00:03:42,646 - > 00:03:45,736
就这样诞生了
笨拙的男孩名叫穿梭，

93
00:03:46,496 - > 00:03:49,786
这个词汇具有片
徘徊的一些数字

94
00:03:49,786 - > 00:03:51,726
至少在两年
一些高年级。

95
00:03:51,726 - > 00:03:54,686
在当时，这是这
小命令行程序

96
00:03:54,956 - > 00:03:56,156
类似的精神到DOS。

97
00:03:56,156 - > 00:03:57,746
这是运行
一个UNIX环境。

98
00:03:57,916 - > 00:03:59,336
因此，它不是很性感的。

99
00:03:59,336 - > 00:04:01,266
你刚才输入的一对夫妇
命令，它告诉你

100
00:04:01,266 - > 00:04:02,286
当航天飞机进行。

101
00:04:02,506 - > 00:04:05,056
那么，这些天的1
更复杂一点。

102
00:04:05,226 - > 00:04:07,826
而且，它实际上代表
恰恰类型

103
00:04:07,826 - > 00:04:10,146
学生的项目
在课程结束

104
00:04:10,146 - > 00:04:11,526
制定了以任期届满。

105
00:04:11,526 - > 00:04:15,276
所以，这是版本4，一些
15年以后，Shuttleboy。

106
00:04:15,676 - > 00:04:17,826
似乎是谷歌地图
那里是一个有点慢。

107
00:04:17,826 - > 00:04:20,386
但对你谁拥有这些
离开这里后级

108
00:04:20,746 - > 00:04:23,086
去，说，从
纪念馆，需要

109
00:04:23,086 - > 00:04:24,626
去到，也就是说，四。

110
00:04:24,906 - > 00:04:28,016
嗯，你可以离开
如果在两分钟，

111
00:04:28,016 - > 00:04:29,616
这实在是不
为你工作只是还没有，

112
00:04:29,866 - > 00:04:32,856
或者你有许多其他
选择，你可能会喜欢的。

113
00:04:32,856 - > 00:04:35,286
此外，即将推出，我们可以
这个球场由CS50，

114
00:04:35,286 - > 00:04:37,756
这将是相同的
能力的短信。

115
00:04:37,976 - > 00:04:39,756
您可以文本Shuttleboy
通过电话。

116
00:04:39,756 - > 00:04:40,936
你可以Shuttleboy。

117
00:04:41,486 - > 00:04:43,106
CS50的电话号码
今年，好，

118
00:04:43,266 - > 00:04:47,156
这是令人惊讶
可用617 -臭虫CS50。

119
00:04:47,666 - > 00:04:49,276
所以，这将问世。

120
00:04:49,756 - > 00:04:50,786
所以，不要只是打电话

121
00:04:50,786 - > 00:04:52,896
但因为我
斥责得到，

122
00:04:53,016 - > 00:04:54,926
现在它被路由

123
00:04:54,926 - > 00:04:57,386
我们的系统头教学
研究员的手机。

124
00:04:57,616 - > 00:04:59,076
所以，你就把他
如果您有问题

125
00:04:59,076 - > 00:05:00,436
现在关于航天飞机的时间表。

126
00:05:00,656 - > 00:05:02,356
但是，这将很快
实施。

127
00:05:03,546 - > 00:05:06,026
因此，其他的事情，其实，这
今年夏天我们自己用了

128
00:05:06,026 - > 00:05:09,236
在真正的准备
这学期是一大堆

129
00:05:09,236 - > 00:05:11,746
其他问题
我们要解决的问题。

130
00:05:11,786 - > 00:05:13,726
例如，有一
很多的东西，去

131
00:05:13,726 - > 00:05:15,566
在这校园
在某一天。

132
00:05:15,566 - > 00:05:17,666
而事实上，提出另
这样，有一大堆

133
00:05:17,666 - > 00:05:18,976
去的东西就在这个校园

134
00:05:18,976 - > 00:05:20,846
当然，我从未
利用。

135
00:05:21,066 - > 00:05:23,516
而且，即使我现在
有多少事情淹没

136
00:05:23,516 - > 00:05:24,926
这是正在进行，校园，

137
00:05:25,176 - > 00:05:27,076
我似乎仍然没有
找到时间。

138
00:05:27,356 - > 00:05:29,706
但是，沃拉，甚至
在那里，CS50的演讲。

139
00:05:29,706 - > 00:05:32,766
这就是你的，所以这是
1，这是一个计划，我们说

140
00:05:32,966 - > 00:05:34,816
聚集所有
在校园的事件。

141
00:05:34,816 - > 00:05:36,566
这已被
其他学生的东西

142
00:05:36,566 - > 00:05:38,466
在这同一课程
自行解决。

143
00:05:38,686 - > 00:05:40,606
而且，我们已经与
校园其他实体

144
00:05:40,606 - > 00:05:41,846
要真正做到这一点。

145
00:05:41,846 - > 00:05:44,426
但是，对于CS50点
这个词是所有

146
00:05:44,426 - > 00:05:47,086
我们对这些小程序
一直在研究这是否一

147
00:05:47,366 - > 00:05:50,326
还是一个聚集
所有哈佛大学的新闻

148
00:05:50,326 - > 00:05:51,906
在一个地方，所有
在谷歌新闻，

149
00:05:52,096 - > 00:05:54,166
所有这一切都将
有什么所谓的API，

150
00:05:54,656 - > 00:05:56,686
应用编程
接口。

151
00:05:56,686 - > 00:05:59,306
而这只是幻想
说话能力

152
00:05:59,516 - > 00:06:01,646
让其他人，
人们在这个房间，

153
00:06:01,846 - > 00:06:03,956
其实做什么
用同样的数据。

154
00:06:03,956 - > 00:06:05,646
因此，到任期届满，如果你决定

155
00:06:05,646 - > 00:06:08,306
最终的项目实施
相关的新闻或事件

156
00:06:08,306 - > 00:06:10,206
或地图，以及我们在
至少作为一门课程，

157
00:06:10,206 - > 00:06:12,846
将所有的
今年提供方便你

158
00:06:12,846 - > 00:06:15,506
同一个接口，一个排序
功能，可以这么说，

159
00:06:15,506 - > 00:06:19,436
软件，您可以使用
你自己的项目上面去

160
00:06:19,436 - > 00:06:22,016
及以后的学生，
或许，已经在过去的时代

161
00:06:22,206 - > 00:06:24,556
因为这个框架
未设立了他们。

162
00:06:24,556 - > 00:06:26,906
再次，所有这一切
开始，对我来说至少

163
00:06:27,246 - > 00:06:29,706
大约15年前
实施Shuttleboy。

164
00:06:29,706 - > 00:06:31,636
我当时我的电子邮件
朋友肯在Pfoho。

165
00:06:31,636 - > 00:06:33,206
我说：嘿，你认为什么？

166
00:06:33,206 - > 00:06:33,936
这有用吗？

167
00:06:33,936 - > 00:06:36,446
他寄给列于
Pfoho开放清单和沃拉，

168
00:06:36,446 - > 00:06:38,676
所有这些年后，我很
显然仍然挤奶

169
00:06:38,976 - > 00:06:39,686
此项目。

170
00:06:39,686 - > 00:06:42,106
而关于它整洁东西，
而这也正是一门课程

171
00:06:42,106 - > 00:06:44,306
像这样的工程和
计算机科学，我认为，

172
00:06:44,306 - > 00:06:47,136
有点特别，是，
当您做您的家作品

173
00:06:47,136 - > 00:06:49,666
当你做你的项目
在这个过程中，你知道，

174
00:06:49,666 - > 00:06:52,656
其中很多，是的，你会提出
一旁，没有真正再次使用。

175
00:06:52,656 - > 00:06:54,286
但是，它的一些，你会的。

176
00:06:54,346 - > 00:06:57,186
而有这样真的
强大的东西，至少对于我来说，

177
00:06:57,406 - > 00:06:59,656
这真是令人兴奋的事情，
当您做什么

178
00:06:59,856 - > 00:07:03,446
其实和其他人照顾，
其他人不只是微笑

179
00:07:03,446 - > 00:07:05,036
并拍拍你的
背部，然后就想

180
00:07:05,036 - > 00:07:05,766
对自己的生活。

181
00:07:05,766 - > 00:07:08,976
他们实际上使用了什么你
在他们自己的生活，即使它的

182
00:07:08,976 - > 00:07:11,766
作为愚蠢或某事
刚刚发现那样简单

183
00:07:11,766 - > 00:07:12,816
当他们可以离开这里

184
00:07:12,816 - > 00:07:14,726
赶上下一个
穿梭于四。

185
00:07:14,726 - > 00:07:17,516
因此，到任期届满，这是一
对本课程的目标;

186
00:07:17,516 - > 00:07:20,196
授权你家伙刚
确定是否有问题

187
00:07:20,196 - > 00:07:22,306
它在校园内或
希望远远超出了校园，

188
00:07:22,646 - > 00:07:25,666
和自己的实际使用
技巧，你自己的头脑和解决

189
00:07:25,666 - > 00:07:28,816
在一些问题
部分技术。

190
00:07:29,216 - > 00:07:32,026
因此，这也是一门课程
正如我们所说的教学大纲

191
00:07:32,026 - > 00:07:35,366
和正式课程
说明，教你如何

192
00:07:35,366 - > 00:07:37,416
想和它教你如何

193
00:07:37,416 - > 00:07:39,286
解决问题
更有效率。

194
00:07:39,536 - > 00:07:40,356
那么，是什么意思？

195
00:07:40,356 - > 00:07:42,476
那么，当你有600
兆赫在你的口袋

196
00:07:42,476 - > 00:07:44,356
或3千兆赫
在你的办公桌在家里，

197
00:07:44,646 - > 00:07:47,056
你可以解决很多
问题只是有效

198
00:07:47,096 - > 00:07:48,336
剪切蛮力。

199
00:07:48,616 - > 00:07:50,526
但是，有一个很多
在这个世界上的问题，

200
00:07:50,766 - > 00:07:54,156
无论是搜索，
也就是说，Facebook的网络

201
00:07:54,156 - > 00:07:55,756
或通过谷歌互联网，

202
00:07:55,756 - > 00:07:58,706
它不事有多快
您的特定的计算机上，

203
00:07:58,706 - > 00:08:00,866
有没有办法你在地狱
要搜寻数十亿

204
00:08:00,866 - > 00:08:03,886
迅速的网页，除非
实际上，你这个办法

205
00:08:03,886 - > 00:08:05,496
聪明的问题。

206
00:08:05,496 - > 00:08:06,916
你不只是搜索，
例如，

207
00:08:06,916 - > 00:08:09,876
所有在网上的巨大清单
地球上从上页

208
00:08:09,876 - > 00:08:11,876
上下期待
相关的东西

209
00:08:11,876 - > 00:08:14,776
到任何您的搜索字词
寻找希望谷歌

210
00:08:14,776 - > 00:08:17,006
大概和谷歌
和Facebook和任何

211
00:08:17,006 - > 00:08:19,476
有这些大型实体
聪明人的思维很多

212
00:08:19,476 - > 00:08:21,856
他们如何能
查找数据更迅速，

213
00:08:22,106 - > 00:08:24,626
他们如何能处理信息
更有效率，并

214
00:08:24,656 - > 00:08:27,196
如何他们可以一般
返回结果更迅速

215
00:08:27,456 - > 00:08:28,266
所以，你可以做的是，

216
00:08:28,266 - > 00:08:30,546
更有趣的事情
与这些设备。

217
00:08:30,546 - > 00:08:33,916
因此，我们的意思是什么，不过，
由如何，教人如何

218
00:08:33,916 - > 00:08:36,526
更仔细地思考，
更复杂的运算。

219
00:08:36,756 - > 00:08:39,686
那么，这个小视觉
似乎总是一个好做法。

220
00:08:39,686 - > 00:08:40,816
而且，这似乎是令人难忘。

221
00:08:40,926 - > 00:08:43,126
而我什至问刚
昨天由以前的学生，

222
00:08:43,126 - > 00:08:45,466
哦，你要怎么办
电话簿的事情了。

223
00:08:45,466 - > 00:08:48,896
而我几乎当场
决定好吗肯定我们将建立

224
00:08:48,896 - > 00:08:49,646
电话簿的事情。

225
00:08:49,646 - > 00:08:52,266
他问我，当你
它撕了一半的权利，

226
00:08:52,636 - > 00:08:55,006
我想好耶技术
我们撕了一半，但它不

227
00:08:55,006 - > 00:08:58,056
的方式，在计算机
科学的方法，我将能

228
00:08:58,056 - > 00:08:59,366
要撕毁这一半的东西。

229
00:08:59,366 - > 00:09:02,426
因此，这里是问题
我们提出了一些时间。

230
00:09:02,426 - > 00:09:03,336
所以，这里的电话簿。

231
00:09:03,336 - > 00:09:05,366
它有至少一
一千多页。

232
00:09:05,616 - > 00:09:08,296
而眼下的简单目标
世界是很现实地发现，

233
00:09:08,616 - > 00:09:09,806
也就是说，一个人在这里。

234
00:09:09,806 - > 00:09:12,586
因此，迈克史密斯，最后
所以起的名字与南，

235
00:09:12,586 - > 00:09:14,416
我是一个典型的人，我
拿起这个电话本。

236
00:09:14,416 - > 00:09:17,156
而且那里的人，什么
你，一个典型的人，

237
00:09:17,156 - > 00:09:19,856
如何开始寻找迈克
史密斯显然不知道

238
00:09:19,856 - > 00:09:21,816
提前哪一页
其实他是。

239
00:09:22,346 - > 00:09:26,096
对，所以你大概去
在中间，右。

240
00:09:26,096 - > 00:09:29,956
而在这个故事中的点，
我可能在N的或M的，

241
00:09:29,956 - > 00:09:32,006
你知道，大约有一半
方法通过电话簿。

242
00:09:32,356 - > 00:09:34,646
原来，我最后一次做
这个例子中我不知为何

243
00:09:34,646 - > 00:09:36,056
本人在陪同部分。

244
00:09:36,056 - > 00:09:38,646
因此，它实际上不是同样
通过并购之间平衡

245
00:09:38,646 - > 00:09:41,646
和N到Z但是，今天，
我们是，事实上，在M的，

246
00:09:41,956 - > 00:09:43,116
没事的话，现在我在M的。

247
00:09:43,176 - > 00:09:44,576
但是，什么是我现在只是外卖

248
00:09:44,576 - > 00:09:46,006
作为一个正常的人
过街的？

249
00:09:46,046 - > 00:09:47,306
下次我去哪里
麦克史密斯。

250
00:09:48,026 - > 00:09:51,736
[听不清]因此，只要
可能在今年上半年，权利，

251
00:09:51,736 - > 00:09:55,886
因为S之前，米就这样，
这就是视觉戏剧。

252
00:09:55,886 - > 00:09:57,896
这不是真的
它撕了一半，右。

253
00:09:57,896 - > 00:09:58,956
我种被骗
沿着中心。

254
00:09:59,236 - > 00:10:02,986
但是，我们现在知道，迈克
至少是没有的一半。

255
00:10:03,086 - > 00:10:06,196
我们可以从字面上抛出
离开了问题的一半。

256
00:10:06,196 - > 00:10:08,676
而我离开了这个问题
这从根本上仍是

257
00:10:08,676 - > 00:10:10,906
同样的事情，找到迈克
史密斯在一个真正的大书。

258
00:10:11,096 - > 00:10:12,996
但是，问题在于
现在的一半。

259
00:10:12,996 - > 00:10:15,666
如果它有1000页
以前，现在它有500个。

260
00:10:15,866 - > 00:10:17,416
你知道吗，我可以做
同样的事情了。

261
00:10:17,596 - > 00:10:20,426
我可以种递归或
反复做同样的事情。

262
00:10:20,696 - > 00:10:24,856
现在，我不太在
我在南吨因此，

263
00:10:24,856 - > 00:10:26,246
哦，我有点过分了。

264
00:10:26,246 - > 00:10:30,126
不过，我现在知道，迈克
不正确的，有准备

265
00:10:30,126 - > 00:10:32,216
总有一天要在一些类
我只是不能撕裂大坝的事情，

266
00:10:32,216 - > 00:10:32,486
我敢打赌。

267
00:10:32,726 - > 00:10:34,666
但现在，我知道他
不正确的。

268
00:10:34,896 - > 00:10:36,646
所以，现在的问题
已进驻。

269
00:10:36,646 - > 00:10:39,706
所以，我已经经历了一个由
万到500至250页。

270
00:10:39,706 - > 00:10:41,976
再次，如果你继续
逻辑，继续进行数学，

271
00:10:42,236 - > 00:10:44,136
我砍本
问题的一半，一半，

272
00:10:44,416 - > 00:10:47,896
半直到最后我现在不是
将找不到任何史密斯

273
00:10:47,896 - > 00:10:51,196
在所有的，不可能的，或者我要去
要找到一个我要找的。

274
00:10:51,316 - > 00:10:53,476
但是，这一点，那么，随之所
的问题，这是没有更好

275
00:10:53,476 - > 00:10:57,606
较简单的办法只
他说，你知道，阿，不，乙，

276
00:10:57,606 - > 00:11:00,566
没有开始，从左至右
通过将线性书？

277
00:11:00,756 - > 00:11:01,776
嗯，是的本能。

278
00:11:01,916 - > 00:11:03,246
这将是一个快得多。

279
00:11:03,526 - > 00:11:04,326
但是，如何少得多？

280
00:11:04,856 - > 00:11:09,056
嗯，如果我有1000页
电话簿或让我们说1024

281
00:11:09,056 - > 00:11:10,746
对于那些你们谁
像两个大国，

282
00:11:10,966 - > 00:11:13,446
可能我有多少时间
这个问题要分裂

283
00:11:13,446 - > 00:11:16,326
在发现前半
史密斯先生？

284
00:11:17,176 - > 00:11:17,276
>> 10。

285
00:11:17,686 - > 00:11:18,826
>>大卫：那么，10，正确的。

286
00:11:18,826 - > 00:11:22,746
如果你有1024个网页和你
分裂的一半，一半，

287
00:11:22,746 - > 00:11:24,926
一半，一半，我该怎么做
这意味着我去10倍

288
00:11:24,926 - > 00:11:27,346
从1000页
我要找的人

289
00:11:27,346 - > 00:11:29,096
在短短的10页转。

290
00:11:29,096 - > 00:11:31,076
这就是一种整洁，
但是，你知道，如果你觉得

291
00:11:31,076 - > 00:11:32,426
关于它，你一直在做
你这生活的一切。

292
00:11:32,426 - > 00:11:33,246
这不是戏剧化了。

293
00:11:33,386 - > 00:11:35,826
但现在，该电话簿
不只是波士顿，

294
00:11:35,826 - > 00:11:38,036
它是为整个
美国和整个世界

295
00:11:38,036 - > 00:11:40,616
这一点已
在这数十亿的网页，

296
00:11:40,706 - > 00:11:43,436
所以想象一个电话簿
与40亿页。

297
00:11:43,776 - > 00:11:47,176
多少翻页我
将不得不做最大限度

298
00:11:47,176 - > 00:11:50,196
找到一个迈克史密斯
40亿页电话簿？

299
00:11:50,196 - > 00:11:52,196
>>“注销基地2。

300
00:11:52,446 - > 00:11:53,606
>>大卫：那是啊，
如果你是那种

301
00:11:53,606 - > 00:11:55,406
类型的数学
这是日志基地2。

302
00:11:55,406 - > 00:11:56,936
但是，如果你认为4
亿至20.0亿

303
00:11:56,936 - > 00:11:58,626
1亿元，因此
一个50亿美元。

304
00:11:58,626 - > 00:12:01,556
我的意思，实际上
自己去惠特尔斯

305
00:12:01,556 - > 00:12:02,706
向下相当非常快。

306
00:12:02,706 - > 00:12:05,796
事实上32 halvings
甚至在电话簿

307
00:12:05,796 - > 00:12:08,326
从4亿元，我会
坐下来一页。

308
00:12:08,326 - > 00:12:10,226
这就是当这东西
变得强大，我想。

309
00:12:10,226 - > 00:12:12,146
这是当这些
想法得到令人信服

310
00:12:12,146 - > 00:12:14,436
当你可以有一个4
亿页的问题

311
00:12:14,676 - > 00:12:18,376
并在32个步骤，你可以找到
你的人正在寻找。

312
00:12:18,476 - > 00:12:21,746
因此，这就是我们的意思时
我们说，你将学会如何

313
00:12:21,746 - > 00:12:23,986
更仔细地思考，
更复杂的运算，

314
00:12:23,986 - > 00:12:25,776
更加智能化
关于解决问题。

315
00:12:25,986 - > 00:12:28,266
而当巨大的回报
你其实可以做到这一点，

316
00:12:28,266 - > 00:12:29,856
再次，这
点的谷歌

317
00:12:29,856 - > 00:12:31,756
世界Facebooks
谁拥有豪华

318
00:12:31,756 - > 00:12:33,126
有庞大的数据集。

319
00:12:33,456 - > 00:12:35,486
你一定要态度
这些问题

320
00:12:35,486 - > 00:12:38,726
这样，否则的话
根本行不通的。

321
00:12:39,136 - > 00:12:43,016
那么，什么是什么做的
学生实际记得？

322
00:12:43,676 - > 00:12:46,436
我，我们喜欢做的事情
是一个有点傻，有时

323
00:12:46,436 - > 00:12:47,676
排序的边缘走了

324
00:12:47,676 - > 00:12:50,166
什么是否则
大量的新材料。

325
00:12:50,166 - > 00:12:53,166
因此，他实际上，这
以前的学生给我这个链接

326
00:12:53,166 - > 00:12:56,016
我继续努力，只为
踢，然后后悔

327
00:12:56,016 - > 00:12:58,306
到了最后，拉
在uTube了这里。

328
00:12:58,306 - > 00:13:01,366
所以，我以为我会分享
一个非计算机科学家手段

329
00:13:01,366 - > 00:13:03,736
当他的眼泪一电话簿
了一半。

330
00:13:04,516 - > 00:13:25,959
[笑]

331
00:13:26,459 - > 00:13:47,902
[沉默]

332
00:13:48,402 - > 00:14:09,845
[听不清]

333
00:14:10,346 - > 00:14:15,396
>>你知道超过200页的，可爱的
清理线，合法眼泪。

334
00:14:15,696 - > 00:14:17,696
[笑]

335
00:14:17,996 - > 00:14:22,186
>>大卫：所以，我想，
他的工作方式了。

336
00:14:22,186 - > 00:14:27,216
因此，我离开了这个
当然，所有这些年前

337
00:14:27,426 - > 00:14:30,316
是的，Shuttleboy，然后是
在计算机科学学位，

338
00:14:30,346 - > 00:14:31,976
然后是一博士
在计算机科学。

339
00:14:31,976 - > 00:14:32,976
而这不是我们所想

340
00:14:32,976 - > 00:14:34,706
把大多数学生
在这个过程中进入。

341
00:14:34,706 - > 00:14:37,186
你们中的大多数在此
当然不会去

342
00:14:37,186 - > 00:14:39,056
在一个主修计算机科学。

343
00:14:39,056 - > 00:14:40,686
一些你可能
未成年人，但对一些

344
00:14:40,686 - > 00:14:42,146
这将是你
终端课程。

345
00:14:42,146 - > 00:14:44,856
这也无所谓
这当然是因为，事实上，

346
00:14:44,856 - > 00:14:47,956
在结构化的方式
即使您只需支付您的会费

347
00:14:47,956 - > 00:14:49,986
数个月的
你真的焦点

348
00:14:49,986 - > 00:14:53,746
你真的拿那么多
走出这当然可以，

349
00:14:53,996 - > 00:14:56,256
你愿意，实际上是
装备精良回去

350
00:14:56,336 - > 00:14:59,056
你的经济学世界，
生物学，心理学，

351
00:14:59,056 - > 00:15:02,326
应用数学，实际
使最终使用的是什么

352
00:15:02,516 - > 00:15:04,806
作为一门课程感兴趣
我们希望从概念

353
00:15:05,016 - > 00:15:07,426
因为它是从根本上
实用。

354
00:15:07,876 - > 00:15:11,056
这也是值得的
或许有点罕见的。

355
00:15:11,056 - > 00:15:13,306
我以为我会分享一些
评论说，学生

356
00:15:13,306 - > 00:15:16,736
从去年秋天在此提出
过去几年线索指南时问

357
00:15:16,736 - > 00:15:18,766
你想什么
告诉未来的学生。

358
00:15:18,766 - > 00:15:20,386
好吧，如果你还没有
看着这些评论，

359
00:15:20,386 - > 00:15:23,166
一名学生说，这当然
将有相当数量的

360
00:15:23,166 - > 00:15:23,786
你的时间了。

361
00:15:24,066 - > 00:15:26,966
但是，如果你把你的工作纳入
一个全新的世界，一个整体，

362
00:15:26,966 - > 00:15:30,156
如果你把工作，如果你
把工作纳入，好吧，

363
00:15:30,156 - > 00:15:33,906
所以这是他的语法不是我的，
所以如果你把在工作投入，

364
00:15:33,906 - > 00:15:36,176
一个全新的世界
将开放给你。

365
00:15:36,176 - > 00:15:39,276
我多么惊人
据悉仅12周。

366
00:15:39,736 - > 00:15:42,606
另一位学生写道：
你最好借此

367
00:15:42,606 - > 00:15:43,686
否则你会后悔的。

368
00:15:44,056 - > 00:15:48,196
另一个说，多一点
说穿了，它会踢你屁股

369
00:15:48,196 - > 00:15:49,296
，让你感觉很好。

370
00:15:49,886 - > 00:15:53,596
然后最终，这一个是
或许是我只能

371
00:15:53,596 - > 00:15:56,976
显示文字，但是，
这里从倒数第二。

372
00:15:57,516 - > 00:16:03,626
[笑]

373
00:16:04,126 - > 00:16:06,436
所以，我不知道
你有很多朋友

374
00:16:06,436 - > 00:16:08,866
谁参加这个课程，但我们
种做了很大的破坏

375
00:16:08,866 - > 00:16:10,716
去年的学生。

376
00:16:10,806 - > 00:16:14,166
我们介绍，在一开始，
一些讲座，一些测验，

377
00:16:14,166 - > 00:16:16,426
一对夫妇的问题集，
这lolcats概念。

378
00:16:17,416 - > 00:16:19,066
你看不到什么
我可以在这里看到

379
00:16:19,066 - > 00:16:21,306
但在一个时刻，你会看到
一个年轻的男子名叫幸福的猫

380
00:16:21,956 - > 00:16:25,076
谁是领袖
所谓lolcat。

381
00:16:25,076 - > 00:16:27,116
这是一
愚蠢的互联网前锋

382
00:16:27,116 - > 00:16:30,546
坦率地说，我觉得
二分法

383
00:16:30,546 - > 00:16:32,996
这两位先生之间
在这里，我们现在已

384
00:16:32,996 - > 00:16:34,126
也许是在屏幕上。

385
00:16:34,126 - > 00:16:34,193
[笑]

386
00:16:34,193 - > 00:16:40,856
其中最不恰当的
利用这项最新的战场。

387
00:16:41,024 - > 00:16:44,604
而且，我们为什么不使一小
更真实一点个人

388
00:16:44,604 - > 00:16:48,494
这个概念其实解决
一个更有效的问题。

389
00:16:48,494 - > 00:16:51,614
阿天一个简单的问题
任何学校是坐下

390
00:16:51,694 - > 00:16:53,734
或站起来，并开始
计数的学生，

391
00:16:53,734 - > 00:16:55,054
各种各样的权利唱名。

392
00:16:55,054 - > 00:16:57,044
那么，最天真
但尽管如此，

393
00:16:57,044 - > 00:17:01,054
一个非常正确的做法
教师可以采取的一，二，

394
00:17:01,104 - > 00:17:03,454
三，四，五，六，七，

395
00:17:03,454 - > 00:17:05,014
我们会在这儿
相当一段时间。

396
00:17:05,234 - > 00:17:07,274
那么，什么是边缘
这甚至改善

397
00:17:07,274 - > 00:17:08,374
您可能
这样做的孩子吗？

398
00:17:08,374 - > 00:17:09,904
您是如何计算的人快？

399
00:17:11,064 - > 00:17:12,894
而且，不要开始阅读
从我自己的指令？

400
00:17:13,324 - > 00:17:14,404
你有什么
这样做的孩子吗？

401
00:17:14,774 - > 00:17:18,484
三三两两地开始计数，权利，
所以我很喜欢在两个好，

402
00:17:18,484 - > 00:17:19,914
四，六，八，十，12。

403
00:17:20,104 - > 00:17:22,094
所以，这事
有趣的权利。

404
00:17:22,154 - > 00:17:24,634
因此，如何一多
改进是什么？

405
00:17:26,074 - > 00:17:27,444
因此，它的明显
两个因素。

406
00:17:27,444 - > 00:17:29,004
我现在只要花那么多时间的一半。

407
00:17:29,184 - > 00:17:31,234
但是，你知道，我们会
发现这整个学期，

408
00:17:31,584 - > 00:17:34,754
大不了，喜欢你的加速
只要运行时间的一个因素

409
00:17:34,754 - > 00:17:36,674
是不是所有的2
有趣

410
00:17:36,674 - > 00:17:38,904
因为这里的模拟
在计算机世界

411
00:17:38,904 - > 00:17:41,314
我是我是一个CPU
计算机，以及赫克，

412
00:17:41,314 - > 00:17:43,604
如果我只是等待12
个月，18个月，

413
00:17:43,604 - > 00:17:46,374
我的电脑也只是
能够自然，由数

414
00:17:46,374 - > 00:17:48,174
我的千兆赫
在我能

415
00:17:48,174 - > 00:17:49,884
数人
这个房间更快。

416
00:17:50,094 - > 00:17:54,064
因此，这些种类，这些种类
线性加速比的因素，如

417
00:17:54,064 - > 00:17:57,064
两因素三，即使
因子10，谁在乎？

418
00:17:57,064 - > 00:17:59,334
对，我们可以抛出
在硬件的问题。

419
00:17:59,334 - > 00:18:00,354
我们可以等待的事情了。

420
00:18:00,354 - > 00:18:01,764
我们可以发展得更快的机器。

421
00:18:01,994 - > 00:18:04,544
但是，理智，是啊
这是一种聪明

422
00:18:04,604 - > 00:18:06,564
但它并没有真正
从根本上改变

423
00:18:06,564 - > 00:18:07,124
的问题。

424
00:18:07,124 - > 00:18:09,814
我还是会从左边
到右，从前到后。

425
00:18:10,034 - > 00:18:11,404
这真的是相同的算法。

426
00:18:11,404 - > 00:18:12,924
但是，我提供的
我们可以做得更好。

427
00:18:12,924 - > 00:18:14,654
我们可以做的比这更聪明

428
00:18:14,654 ---> 00:18:18,104
and do fundamentally a
faster implementation.

429
00:18:18,104 ---> 00:18:19,204
But, to demonstrate this,

430
00:18:19,494 ---> 00:18:21,444
we need you to humor
us for just a moment.

431
00:18:21,684 ---> 00:18:22,684
And it's at this point

432
00:18:22,684 ---> 00:18:25,164
where it'll be me talking
less and you talking more.

433
00:18:25,164 ---> 00:18:27,704
But I do need you to
execute step one together,

434
00:18:27,704 ---> 00:18:30,164
which is if you would
humor us, please stand up.

435
00:18:31,634 ---> 00:18:34,494
The directions here on the
board, you know are, okay,

436
00:18:34,494 ---> 00:18:36,514
a couple of you have
to sit down.

437
00:18:37,284 ---> 00:18:41,404
Those of you in back,
there we go, alright.

438
00:18:41,804 ---> 00:18:42,824
Thank you.

439
00:18:42,824 ---> 00:18:44,554
So, the program here
is before you.

440
00:18:44,554 ---> 00:18:46,814
You are now the computers
executing this program.

441
00:18:46,814 ---> 00:18:48,934
It's fairly self
explanatory at this point.

442
00:18:48,934 ---> 00:18:50,754
Yes, you should be number one.

443
00:18:51,184 ---> 00:18:53,644
Get it? Right, many of you are
probably thinking this already

444
00:18:53,644 ---> 00:18:54,994
anyway, first freshman year.

445
00:18:55,484 ---> 00:18:58,794
So, think to yourself,
you're the number one.

446
00:18:58,794 ---> 00:19:01,574
So, step three here, pair
off with someone standing,

447
00:19:01,764 ---> 00:19:03,784
add your two numbers
together and adopt that sum

448
00:19:03,784 ---> 00:19:05,754
as your new number and
we'll do a sanity check.

449
00:19:06,494 ---> 00:19:41,524
[ Noises from crowd ]

450
00:19:42,024 ---> 00:19:47,184
Do you know how many we have?

451
00:19:47,184 ---> 00:19:47,314
>> [Inaudible]

452
00:19:47,314 ---> 00:19:47,464
>> No [inaudible].

453
00:19:47,784 ---> 00:19:57,014
>> We need to have
an answer key.

454
00:19:57,014 ---> 00:19:57,214
[ Silence ]

455
00:19:57,214 ---> 00:19:57,954
>> Yeah.

456
00:19:58,494 ---> 00:20:17,534
[ Noises from crowd ]

457
00:20:18,034 ---> 00:20:20,454
>> David: At this point
the algorithm should be

458
00:20:20,454 ---> 00:20:21,724
winding down.

459
00:20:22,494 ---> 00:20:32,544
[ Noises from crowd ]

460
00:20:33,044 ---> 00:20:46,024
Maybe we should have gone
with my approach after all.

461
00:20:46,274 ---> 00:20:46,534
>> 43.

462
00:20:47,104 ---> 00:20:49,864
>> 163.

463
00:20:50,814 ---> 00:20:56,274
>> David: Ooh arithmetic in
front of 300 plus people.

464
00:20:56,274 ---> 00:20:56,341
[ Laughter ]

465
00:20:56,341 ---> 00:21:00,964
What's our final
tally going to be?

466
00:21:00,964 ---> 00:21:01,514
>> 180.

467
00:21:01,514 ---> 00:21:01,581
[ Laughter ]

468
00:21:01,581 ---> 00:21:02,474
>> 1,200.

469
00:21:03,934 ---> 00:21:08,224
>> 386.

470
00:21:09,344 ---> 00:21:14,114
>> David: 386, and are
you the last one standing?

471
00:21:14,114 ---> 00:21:16,404
Is that everyone?

472
00:21:16,644 ---> 00:21:17,314
Do you know the answer?

473
00:21:17,314 ---> 00:21:17,524
>> What?

474
00:21:17,954 ---> 00:21:22,794
>> David: Do you know
what the answer is?

475
00:21:22,924 ---> 00:21:25,194
We didn't bring an
answer key with us so,

476
00:21:26,114 ---> 00:21:31,034
386 is in fact precisely the
right answer for the first time.

477
00:21:31,517 ---> 00:21:33,517
[ Cheering ]

478
00:21:34,000 ---> 00:21:36,000
[掌声]

479
00:21:36,484 ---> 00:21:37,024
That's okay.

480
00:21:37,024 ---> 00:21:37,091
[掌声]

481
00:21:37,091 ---> 00:21:39,154
Very, very nicely done.

482
00:21:39,154 ---> 00:21:40,734
So, what was the takeaway

483
00:21:40,734 ---> 00:21:42,554
because that definitely
felt a little slower

484
00:21:42,554 ---> 00:21:43,584
than my very simple

485
00:21:43,584 ---> 00:21:46,204
but nonetheless very correct
approach of just going onesies

486
00:21:46,204 ---> 00:21:48,784
and twosies and just getting it
done with from left to right.

487
00:21:49,104 ---> 00:21:50,664
But, what did we
really just do there?

488
00:21:50,664 ---> 00:21:53,454
Well, if there were roughly,
let's say, 400 of you standing

489
00:21:53,454 ---> 00:21:56,184
at one point, and then
half of you, very quickly,

490
00:21:56,184 ---> 00:21:57,784
from what I could tell,
wanted to sit down.

491
00:21:57,784 ---> 00:22:01,554
So, half of you sat down,
we went from 400 to 200 then

492
00:22:01,554 ---> 00:22:05,154
to 100 then to 50 then to 25.

493
00:22:05,374 ---> 00:22:07,784
So again, there's
that same divide

494
00:22:07,784 ---> 00:22:09,864
and conquer idea we
had with the phonebook.

495
00:22:09,864 ---> 00:22:13,044
Again, with every iteration we
halved the size of the problem,

496
00:22:13,044 ---> 00:22:14,104
we halved it, we halved it.

497
00:22:14,344 ---> 00:22:17,594
So, in theory, your algorithm
should've been much faster

498
00:22:17,774 ---> 00:22:20,744
than my linear approach because
my approach would've taken say

499
00:22:20,844 ---> 00:22:24,764
400 steps or maybe if I'm
slightly clever 200 steps.

500
00:22:25,024 ---> 00:22:28,644
But, yours would've taken far
fewer, right from 400 to 200,

501
00:22:28,644 ---> 00:22:34,634
100, 50, 25, 13, six;
so fewer than ten steps

502
00:22:34,634 ---> 00:22:36,854
in the end versus my 200 or 400.

503
00:22:36,854 ---> 00:22:39,984
And there's the germ of a
really interesting idea.

504
00:22:39,984 ---> 00:22:42,954
And yes, mathematically what you
just did was something that's a

505
00:22:42,954 ---> 00:22:45,714
little logarithmic in
nature by log base two,

506
00:22:45,714 ---> 00:22:47,194
we divided in two and two again.

507
00:22:47,194 ---> 00:22:48,974
And we'll revisit this
later in this semester.

508
00:22:49,174 ---> 00:22:51,994
But therein lies again a very
intelligent implementation.

509
00:22:51,994 ---> 00:22:53,664
And, we are just
scratching the surface

510
00:22:53,664 ---> 00:22:57,744
of the very clever the very
intelligent efficient approaches

511
00:22:58,064 ---> 00:23:00,164
to problems that we
might ultimately solve.

512
00:23:00,484 ---> 00:23:04,494
So, who are the people you
just chatted with if briefly?

513
00:23:04,494 ---> 00:23:07,674
A common concern in a course
like this is that everyone

514
00:23:07,674 ---> 00:23:09,404
to the left of you and
everyone to the right

515
00:23:09,404 ---> 00:23:12,014
of you must clearly
know more than you.

516
00:23:12,014 ---> 00:23:13,604
Well, that's absolutely
not the case.

517
00:23:13,604 ---> 00:23:14,744
And in fact, in recent years,

518
00:23:14,774 ---> 00:23:16,754
this course has made a
concerted effort to reach

519
00:23:16,754 ---> 00:23:19,454
out to those less
comfortable, so to speak.

520
00:23:19,634 ---> 00:23:22,174
And by that, we mean not people
who've never touched a computer

521
00:23:22,174 ---> 00:23:24,074
before because that's
really hard to find

522
00:23:24,074 ---> 00:23:26,504
around here these days,
but folks who use email,

523
00:23:26,504 ---> 00:23:28,314
use Facebook, maybe
even right now

524
00:23:28,314 ---> 00:23:31,644
but are not necessarily
quite sure what to do

525
00:23:31,644 ---> 00:23:34,314
when something goes wrong
or when they are asked

526
00:23:34,314 ---> 00:23:37,594
about anything technological,
you know, the hands go up

527
00:23:37,714 ---> 00:23:39,144
or they kind of push
the hardware

528
00:23:39,144 ---> 00:23:42,384
to a friend who's perhaps
more versed in it than they.

529
00:23:42,384 ---> 00:23:45,794
Well, these are some statistics
from last year's semester.

530
00:23:45,794 ---> 00:23:49,494
So, when asked, when we asked
our 400 so students last year,

531
00:23:49,874 ---> 00:23:52,424
you know, what is your level of
comfort coming into this class,

532
00:23:52,424 ---> 00:23:56,784
well 34% wrote themselves down
as among those less comfortable.

533
00:23:56,784 ---> 00:23:59,654
So, if you have come into this
room and are still thinking now,

534
00:23:59,904 ---> 00:24:02,554
that, you know what, this term
less comfortable describes me,

535
00:24:02,804 ---> 00:24:04,994
know that you are in
very good company.

536
00:24:04,994 ---> 00:24:06,994
But, realize too that, if
you're coming in this course

537
00:24:06,994 ---> 00:24:10,254
with a background in computer
science and you were really

538
00:24:10,254 ---> 00:24:13,194
that geek in middle school and
high school who was writing code

539
00:24:13,194 ---> 00:24:15,314
and teaching yourselves
languages, well that's fine too

540
00:24:15,314 ---> 00:24:17,884
because there's definitely
a nontrivial sized audience

541
00:24:17,884 ---> 00:24:20,954
with that background as
well, about 13%, last term.

542
00:24:21,104 ---> 00:24:23,144
And then, there's everybody
else, sort of someone

543
00:24:23,144 ---> 00:24:24,784
who doesn't think
they're less comfortable,

544
00:24:24,784 ---> 00:24:26,894
they definitely don't think
they're more comfortable

545
00:24:26,894 ---> 00:24:29,364
but they're just in a course
to get something out of it.

546
00:24:29,364 ---> 00:24:32,034
So, realize this course
does draw quite the spectrum

547
00:24:32,034 ---> 00:24:32,584
of students.

548
00:24:32,714 ---> 00:24:36,034
And, to put this in more
concrete terms, 71% of students,

549
00:24:36,034 ---> 00:24:38,514
last year, had zero
courses behind them.

550
00:24:38,804 ---> 00:24:40,754
So, if you're entering this
course thinking oh everyone

551
00:24:40,754 ---> 00:24:43,334
who takes CS50 was a
computer science whiz

552
00:24:43,334 ---> 00:24:44,794
in high school, it's
not the case.

553
00:24:44,934 ---> 00:24:47,554
Most people are presumably
just interested in it.

554
00:24:47,554 ---> 00:24:50,094
And a few, yes, absolutely
have taken some courses, some,

555
00:24:50,354 ---> 00:24:53,174
or at least one person
last year had taken five

556
00:24:53,174 ---> 00:24:54,334
courses previously.

557
00:24:54,594 ---> 00:24:56,634
So, we definitely have some
outliers but again the meat

558
00:24:56,634 ---> 00:24:59,674
of the curve is in those
lower values altogether.

559
00:24:59,874 ---> 00:25:01,794
And another interesting
statistic we shared

560
00:25:01,794 ---> 00:25:03,864
over the past couple of
years is the gender ratio.

561
00:25:03,864 ---> 00:25:06,434
So, historically, at least in
computer science, there is a bit

562
00:25:06,434 ---> 00:25:07,954
of a male female skew.

563
00:25:07,954 ---> 00:25:10,924
I couple of years ago it was
much more marked than last year.

564
00:25:10,924 ---> 00:25:12,904
So, we're almost now
at the %40 level.

565
00:25:12,904 ---> 00:25:15,994
And if I can throw down a
gauntlet just for the sake

566
00:25:15,994 ---> 00:25:18,034
of having a third
pie chart next year,

567
00:25:18,034 ---> 00:25:19,364
that's even more equitable.

568
00:25:19,534 ---> 00:25:22,014
I would point out that
there's absolutely no reason

569
00:25:22,014 ---> 00:25:24,134
from the courses
perspective that males

570
00:25:24,134 ---> 00:25:25,474
and females shouldn't
be enrolling

571
00:25:25,474 ---> 00:25:26,284
in this kind of course.

572
00:25:26,534 ---> 00:25:29,714
In relatively equal numbers
and realize to 38 percent,

573
00:25:29,744 ---> 00:25:32,464
48 percent, we're actually quite
pleased to see that we're almost

574
00:25:32,464 ---> 00:25:37,014
at that, at least,
statistically even value of 50%.

575
00:25:37,054 ---> 00:25:39,104
So, if you are, in fact,
female, do rest assure too

576
00:25:39,104 ---> 00:25:41,804
that this is not, in fact,
a male dominated class.

577
00:25:42,314 ---> 00:25:46,324
Well, this just so happens
to be CS50's 20th birthday.

578
00:25:46,574 ---> 00:25:48,234
I, well thank you.

579
00:25:48,584 ---> 00:25:50,584
[ Cheering ]

580
00:25:50,934 ---> 00:25:52,934
[掌声]

581
00:25:53,284 ---> 00:25:55,554
That's very nice of you
because we brought cake

582
00:25:55,554 ---> 00:25:56,434
for you actually.

583
00:25:56,634 ---> 00:25:58,324
And so, when you exit
here later today,

584
00:25:58,464 ---> 00:26:01,024
you'll actually get
a chance to meet many

585
00:26:01,024 ---> 00:26:03,164
of the courses teaching
fellows who'll be lingering

586
00:26:03,164 ---> 00:26:03,784
in the hallway.

587
00:26:03,784 ---> 00:26:06,924
And yes it'll be a nice
sort of incentivized way

588
00:26:06,924 ---> 00:26:08,064
of meeting the teaching fellows.

589
00:26:08,284 ---> 00:26:11,354
But, we do take a trip
up to a little bakery

590
00:26:11,354 ---> 00:26:14,434
and again consistent with the
course is playful nature while

591
00:26:14,434 ---> 00:26:16,984
nonetheless is expecting
nontrivial amount

592
00:26:16,984 ---> 00:26:18,714
of work while we're
having that fun.

593
00:26:18,864 ---> 00:26:20,364
But, we do have one of
these cakes for you.

594
00:26:20,364 ---> 00:26:20,431
[ Laughter ]

595
00:26:20,431 ---> 00:26:23,604
So, if you're laughing that's
actually good because even

596
00:26:23,604 ---> 00:26:25,474
if you're among one of
those less comfortable

597
00:26:25,474 ---> 00:26:26,754
at least you're aware of it.

598
00:26:27,244 ---> 00:26:31,184
Those of you in the 14 percent
might prefer this flavor.

599
00:26:31,184 ---> 00:26:31,334
[ Laughter ]

600
00:26:31,334 ---> 00:26:35,354
And then, if you don't know what
the hell is going on right now,

601
00:26:35,354 ---> 00:26:43,384
we also have this
for the rest of you.

602
00:26:43,384 ---> 00:26:43,451
[ Cheering ]

603
00:26:43,451 ---> 00:26:43,518
[掌声]

604
00:26:43,518 ---> 00:26:47,584
So, those are being chopped up
into pieces outside as we speak.

605
00:26:47,584 ---> 00:26:49,614
So again, let's take
things up a notch

606
00:26:49,614 ---> 00:26:52,514
and at least introduce
some basic tenant

607
00:26:52,514 ---> 00:26:53,664
that we'll then take for granted

608
00:26:53,664 ---> 00:26:55,154
in the remaining
of this semester.

609
00:26:55,154 ---> 00:26:58,524
So, we all probably know that
computers ultimately boil

610
00:26:58,524 ---> 00:27:01,984
down somehow to zeros and
ones, these things called bits.

611
00:27:01,984 ---> 00:27:02,694
What does that mean?

612
00:27:02,834 ---> 00:27:04,664
Well you can think of it
frankly as a light bulb,

613
00:27:04,664 ---> 00:27:07,254
a bit is a light bulb that's
either on or it's off.

614
00:27:07,254 ---> 00:27:09,484
It's a switch, it's
either on or it's off.

615
00:27:09,484 ---> 00:27:11,564
Now, computer scientists
generally think of off

616
00:27:11,564 ---> 00:27:13,884
as the number zero
arbitrarily and the,

617
00:27:13,884 ---> 00:27:15,974
and the notion of on as one.

618
00:27:16,274 ---> 00:27:17,654
So, if you throw a light switch

619
00:27:17,654 ---> 00:27:20,234
on that's one turn
it off that's a zero.

620
00:27:20,444 ---> 00:27:23,034
Or, equivalently, turn the
light on that's the value

621
00:27:23,034 ---> 00:27:25,554
of true turn it off
that's the value of false.

622
00:27:25,554 ---> 00:27:26,514
So, these are just synonyms.

623
00:27:26,724 ---> 00:27:30,984
At the end of the day, yes, all
computation, all stuff that goes

624
00:27:30,984 ---> 00:27:33,984
on underneath the hood in a
computer does ultimately boil

625
00:27:33,984 ---> 00:27:35,154
down to zeros and ones.

626
00:27:35,154 ---> 00:27:36,254
And, when you stop
to think about it,

627
00:27:36,454 ---> 00:27:38,904
it's pretty dam remarkable
what the world has done

628
00:27:39,114 ---> 00:27:41,034
with these basic building
blocks including some

629
00:27:41,034 ---> 00:27:42,674
of the devices you're
holding in your hand.

630
00:27:42,864 ---> 00:27:44,894
Well, why are zeros
and ones useful?

631
00:27:44,894 ---> 00:27:46,314
My God, even in the
real world we

632
00:27:46,314 ---> 00:27:48,474
at least have ten
digits, zero through nine.

633
00:27:48,734 ---> 00:27:49,724
Why so limited?

634
00:27:49,904 ---> 00:27:51,954
Well in hardware
terms it's very easy.

635
00:27:51,954 ---> 00:27:54,204
It's much easier to
represent two states, right.

636
00:27:54,204 ---> 00:27:56,704
If computers are plugged
into the wall, usually,

637
00:27:56,914 ---> 00:28:00,304
you have this easy
source of binary nature.

638
00:28:00,304 ---> 00:28:01,284
It's either on or off.

639
00:28:01,284 ---> 00:28:03,194
Electricity is flowing
or it's not.

640
00:28:03,374 ---> 00:28:05,224
So, that's kind of one
of the initial reasons

641
00:28:05,224 ---> 00:28:07,414
that the world went with just
zeros and ones in computers.

642
00:28:07,414 ---> 00:28:09,174
But, you can use them
as building blocks.

643
00:28:09,454 ---> 00:28:12,304
So, this actually is a little
small on the screen here

644
00:28:12,524 ---> 00:28:15,644
but we can count in binary or we
can represent anything we want

645
00:28:15,644 ---> 00:28:18,704
in binary just as we can,
say, decimal, just as we can,

646
00:28:18,704 ---> 00:28:20,354
even in fact, with
alphabetical letters.

647
00:28:20,514 ---> 00:28:21,884
And so, here's the quick system.

648
00:28:21,884 ---> 00:28:24,964
In just a couple minutes time
you'll now know how to count,

649
00:28:24,964 ---> 00:28:27,484
how to write, how
to speak binary much

650
00:28:27,484 ---> 00:28:28,654
like your own laptop.

651
00:28:28,654 ---> 00:28:31,724
Well, you have, in the world
of binary, sort of just

652
00:28:31,724 ---> 00:28:34,344
like grade school
columns or values.

653
00:28:34,344 ---> 00:28:36,954
So, in grade school we learn
this is the ones column this is

654
00:28:36,954 ---> 00:28:39,464
the tens column, the
hundreds column and so forth.

655
00:28:39,674 ---> 00:28:42,084
In other words, why
is the number we know

656
00:28:42,324 ---> 00:28:46,344
as 123 the number 123?

657
00:28:46,344 ---> 00:28:48,364
Well, my teacher taught me
this is the ones column,

658
00:28:48,364 ---> 00:28:50,694
this was the tens,
this was the hundreds.

659
00:28:50,914 ---> 00:28:51,884
Well what did that mean?

660
00:28:51,884 ---> 00:28:54,064
Well, to figure out
what the total value is

661
00:28:54,064 ---> 00:28:56,594
of what is otherwise
the string of digits,

662
00:28:56,594 ---> 00:28:57,884
just hash marks on the board.

663
00:28:58,214 ---> 00:29:02,024
Well, we have one 100,
so that's 1 times 100

664
00:29:02,264 ---> 00:29:03,934
and then plus what two 10's

665
00:29:03,974 ---> 00:29:09,434
so that's 2 times 10 plus three
ones, so that's 3 times 1, okay,

666
00:29:09,774 ---> 00:29:11,694
so I seem to have gotten
back to where I started.

667
00:29:11,784 ---> 00:29:16,124
But, this very simple process
of just multiplying the digits

668
00:29:16,354 ---> 00:29:19,344
by the value of the column
is exactly what binary is

669
00:29:19,344 ---> 00:29:19,864
all about.

670
00:29:19,864 ---> 00:29:22,984
But, in binary you use powers
of two not powers of ten.

671
00:29:23,224 ---> 00:29:25,194
So, here's a series
of eight light bulbs.

672
00:29:25,474 ---> 00:29:29,064
Computer scientists like to use
values like two and eight and 16

673
00:29:29,064 ---> 00:29:32,824
and 24 and 32 because they're
all generally convenient values

674
00:29:32,824 ---> 00:29:33,164
to use.

675
00:29:33,404 ---> 00:29:35,074
So, when we talk
about eight values

676
00:29:35,074 ---> 00:29:36,664
in sequence this is
like called the byte.

677
00:29:37,084 ---> 00:29:39,424
And these days we rarely
talk in just bytes,

678
00:29:39,424 ---> 00:29:42,554
we talk megabytes gigabytes
and terabytes these days.

679
00:29:42,584 ---> 00:29:44,104
But it's all ultimately
the same thing.

680
00:29:44,324 ---> 00:29:48,714
Here's eight bits AKA one
byte, just simple jargon.

681
00:29:49,034 ---> 00:29:50,604
So, all of these
light bulbs are off.

682
00:29:50,604 ---> 00:29:52,544
So, the math is actually
really easy.

683
00:29:52,544 ---> 00:29:54,624
So there on the right,
though it's small to see,

684
00:29:54,624 ---> 00:29:56,944
is the one's column, the
twos, the fours, the eights,

685
00:29:57,004 ---> 00:29:59,664
the 16s, 32s, 64s, 128s.

686
00:29:59,934 ---> 00:30:01,644
Alright, maybe it's hard
to memorize at first

687
00:30:01,644 ---> 00:30:03,784
but it's just multiplied
by two from right to left.

688
00:30:03,784 ---> 00:30:05,044
So, you can always
recreate this.

689
00:30:05,284 ---> 00:30:08,824
Well, they're all off so
that's 0 times placeholder,

690
00:30:08,824 ---> 00:30:10,014
0 times placeholder.

691
00:30:10,184 ---> 00:30:13,804
So, this is the number
0 represented in binary.

692
00:30:13,804 ---> 00:30:16,244
In other words, how do you
write the number we know

693
00:30:16,244 ---> 00:30:17,734
as 0 in binary?

694
00:30:18,034 ---> 00:30:22,514
Well, one, two, three, four,
five, six, seven, eight,

695
00:30:22,784 ---> 00:30:24,304
and technically just
like in decimal,

696
00:30:24,534 ---> 00:30:27,384
all of these leading zeros,
they don't add anything

697
00:30:27,444 ---> 00:30:29,394
to the formula they're
just there

698
00:30:29,394 ---> 00:30:31,304
because we arbitrarily
decided we want eight

699
00:30:31,304 ---> 00:30:32,324
of these things in a row, right.

700
00:30:32,324 ---> 00:30:33,624
If they're physical
objects, we have eight

701
00:30:33,624 ---> 00:30:34,764
so they've got to all be off.

702
00:30:34,764 ---> 00:30:36,524
So, we could've just
gotten away with one zero.

703
00:30:36,814 ---> 00:30:38,324
Well how do you represent
the number one?

704
00:30:38,594 ---> 00:30:40,794
Well, instinctively you're going
to throw one of the switches.

705
00:30:40,794 ---> 00:30:41,894
You're going to turn a bulb on.

706
00:30:42,134 ---> 00:30:44,934
So, there is the number one
because we now put a one,

707
00:30:45,294 ---> 00:30:48,054
a light bulb that's on,
in the one's position.

708
00:30:48,234 ---> 00:30:49,474
How are we going
to represent two?

709
00:30:49,474 ---> 00:30:52,354
Well, we're actually going to
throw two switches now at least

710
00:30:52,354 ---> 00:30:53,794
versus this state,
we have to turn

711
00:30:53,794 ---> 00:30:56,004
on the two's column
turn off the ones column

712
00:30:56,284 ---> 00:30:59,644
and now we have the value
of one in the twos column.

713
00:30:59,644 ---> 00:31:01,384
So, that's the total
value of two.

714
00:31:01,704 ---> 00:31:04,034
Now, a quick mental exercise;
what's going to happen

715
00:31:04,034 ---> 00:31:05,024
with the next sequence?

716
00:31:05,024 ---> 00:31:06,524
How do I present
the number three?

717
00:31:06,824 ---> 00:31:08,364
Well, I need one
from the twos column,

718
00:31:08,364 ---> 00:31:10,324
one from the threes
column and ah ha.

719
00:31:10,324 ---> 00:31:11,964
So, now I've incremented
that one.

720
00:31:12,174 ---> 00:31:13,824
And now, this same
basic pattern repeats.

721
00:31:13,824 ---> 00:31:14,774
What's the number four?

722
00:31:14,874 ---> 00:31:17,014
Well let's see, I just need
a one in the fours column

723
00:31:17,014 ---> 00:31:18,864
and then zeros in
the twos and ones.

724
00:31:19,234 ---> 00:31:21,134
So then, it continues that way.

725
00:31:21,134 ---> 00:31:22,524
And, it's just this
sequence of steps.

726
00:31:22,714 ---> 00:31:25,864
And in the notion of binary is
really not all that complicated.

727
00:31:25,864 ---> 00:31:27,484
At the top there we
have eight zeros.

728
00:31:27,854 ---> 00:31:29,874
Below that we have
seven zeros and a one.

729
00:31:30,114 ---> 00:31:32,214
Below that we have
six zeros, a one,

730
00:31:32,494 ---> 00:31:34,204
and a zero and that's binary.

731
00:31:34,454 ---> 00:31:38,164
Now, thankfully, we computer
scientists, we programmers

732
00:31:38,164 ---> 00:31:41,674
by terms end are not going to
often be writing in binary,

733
00:31:41,674 ---> 00:31:43,694
talking in binary,
thinking in binary

734
00:31:43,894 ---> 00:31:47,204
because we've built many layers
of the traction on top of that.

735
00:31:47,204 ---> 00:31:49,434
In fact, people rarely
talk about bits except

736
00:31:49,434 ---> 00:31:51,344
in a networking context
they talk about bytes

737
00:31:51,404 ---> 00:31:53,144
because one bit,
not that useful,

738
00:31:53,354 ---> 00:31:55,444
eight bits these days
still not that useful,

739
00:31:55,444 ---> 00:31:56,484
but at least eight bits,

740
00:31:56,484 ---> 00:31:59,914
one byte is at least getting
us toward more useful units

741
00:31:59,914 ---> 00:32:00,484
of measure.

742
00:32:00,764 ---> 00:32:02,734
But, when we start looking
underneath the hood,

743
00:32:02,814 ---> 00:32:05,324
when we do certain problems
such as look at files

744
00:32:05,324 ---> 00:32:06,764
and look perhaps
at network traffic,

745
00:32:07,014 ---> 00:32:08,304
it will become interesting

746
00:32:08,304 ---> 00:32:10,844
to know how you're representing
data because you're going

747
00:32:10,844 ---> 00:32:13,774
to have to figure out how to
display that same information.

748
00:32:13,774 ---> 00:32:16,954
And, in fact, we, if we
only have zeros and ones,

749
00:32:17,164 ---> 00:32:21,744
how do we go about representing,
say alphabetical letters?

750
00:32:21,744 ---> 00:32:23,994
Well, we're going to
have to have some mapping

751
00:32:24,104 ---> 00:32:25,774
between binary and letters.

752
00:32:25,824 ---> 00:32:27,564
But that's as of yet unclear.

753
00:32:27,564 ---> 00:32:30,464
But to hammer this point
home and to give me a break

754
00:32:30,464 ---> 00:32:33,614
from speaking at, I thought
I'd pause for a moment and see

755
00:32:33,614 ---> 00:32:35,774
if we can't recruit
eight volunteers,

756
00:32:36,134 ---> 00:32:37,344
one byte eight people.

757
00:32:37,674 ---> 00:32:41,224
Can I get eight people for
whom it is not too awkward

758
00:32:41,224 ---> 00:32:41,754
to come on up.

759
00:32:41,804 ---> 00:32:45,384
good, good one, two, three,
four, five, six, seven,

760
00:32:45,384 ---> 00:32:48,464
eight very enthusiastic
eight, come on down.

761
00:32:49,024 ---> 00:32:51,584
So, you all, for just a
moment here, oh and you have

762
00:32:51,644 ---> 00:32:53,914
to be willing to not be on
the internet because there is

763
00:32:53,914 ---> 00:32:55,294
in fact a camera in
the back of this room.

764
00:32:55,634 ---> 00:32:58,114
So, turn back now if you
don't want to be on the,

765
00:32:58,374 ---> 00:33:00,314
hello mom, in perpetuity.

766
00:33:01,134 ---> 00:33:05,084
So, let's see, you here
will be the 128th column.

767
00:33:05,344 ---> 00:33:08,504
And let me ask that you
simply hold this before you.

768
00:33:08,504 ---> 00:33:10,124
And actually, if you could
scooch this way just a little

769
00:33:10,124 ---> 00:33:12,484
bit, then I will
get out of your way.

770
00:33:12,484 ---> 00:33:14,174
You'll be the 64's column,

771
00:33:15,074 ---> 00:33:18,164
you shall be the 32's
column and the 16's.

772
00:33:18,424 ---> 00:33:25,444
32's, 16s, 8's, 4's,
2's and 1's.

773
00:33:25,444 ---> 00:33:26,134
All right.

774
00:33:26,134 ---> 00:33:28,414
So perfectly lined up with
the place holders from before,

775
00:33:28,574 ---> 00:33:30,614
but we need a little bit of
mapping, so a quick set up.

776
00:33:30,844 ---> 00:33:34,754
We just need an arbitrary way
of mapping binary numbers,

777
00:33:34,754 ---> 00:33:37,314
which really could be converted
very easily to decimal numbers.

778
00:33:37,314 ---> 00:33:39,734
So we need a way of
converting numbers to letters

779
00:33:39,804 ---> 00:33:42,524
if our computers are actually
going to show us emails

780
00:33:42,794 ---> 00:33:46,604
or type URL's or actually
display non numeric information.

781
00:33:46,764 ---> 00:33:49,934
And, in fact, there is a system
for that, it's called ASCII,

782
00:33:50,204 ---> 00:33:53,044
an acronym whose meaning is not

783
00:33:53,044 ---> 00:33:56,354
so interesting, but
whose utility is.

784
00:33:56,554 ---> 00:33:58,984
This is just a mapping
from letters to numbers

785
00:33:58,984 ---> 00:34:00,984
and there's actually a lot
more numbers on the screen,

786
00:34:00,984 ---> 00:34:02,484
and you guys, don't
worry, aren't going to have

787
00:34:02,524 ---> 00:34:04,174
to test yourselves with
this in just a moment.

788
00:34:04,424 ---> 00:34:06,324
But there's a mapping
between numbers and letters

789
00:34:06,324 ---> 00:34:07,884
and I'm just going to get
us started by pointing

790
00:34:07,884 ---> 00:34:08,664
out a couple of these.

791
00:34:08,954 ---> 00:34:12,284
The numbers of interest
right now are going to be,

792
00:34:12,284 ---> 00:34:14,084
whoops, are going to be this.

793
00:34:14,854 ---> 00:34:17,434
Whoops. So in this column
here, I can't seem to zoom

794
00:34:17,434 ---> 00:34:19,124
in simultaneously,
we have decimal.

795
00:34:19,194 ---> 00:34:19,964
Dec for decimal.

796
00:34:20,134 ---> 00:34:22,384
And then we have the character
on the right hand side.

797
00:34:22,614 ---> 00:34:25,084
So if I hop over into this
column, thought it's a bit small

798
00:34:25,084 ---> 00:34:28,834
on the screen, the number
65 represents what letter?

799
00:34:30,024 ---> 00:34:32,484
Capital A. And the number 97?

800
00:34:33,134 ---> 00:34:35,714
Lowercase A. All right.

801
00:34:35,714 ---> 00:34:38,644
So those two alone, right,
so do not go home and try

802
00:34:38,644 ---> 00:34:39,854
to remember ASCII chart.

803
00:34:39,854 ---> 00:34:42,164
Come quiz time, do not try
memorizing an ASCII chart.

804
00:34:42,374 ---> 00:34:45,864
Memorize two, 65 is capital
A and 97 is lowercase A.

805
00:34:46,044 ---> 00:34:47,884
And from there you can
bootstrap yourself to all

806
00:34:47,884 ---> 00:34:49,184
of the other alphabetical
characters.

807
00:34:49,404 ---> 00:34:51,534
But all this chart says, and
I just downloaded this chart

808
00:34:51,534 ---> 00:34:54,084
from ASCIItable.com, this
is a standard that's been

809
00:34:54,084 ---> 00:34:55,544
around for many,
many, many years,

810
00:34:55,684 ---> 00:34:57,224
but most computers still use it.

811
00:34:57,394 ---> 00:34:58,784
What we now have is a means

812
00:34:58,784 ---> 00:35:02,194
of encoding alphabetical
information using what's

813
00:35:02,194 ---> 00:35:03,184
ultimately numeric.

814
00:35:03,184 ---> 00:35:05,814
So if these guys are just
switches, light bulbs,

815
00:35:06,064 ---> 00:35:08,614
computers, we can
actually convey messages.

816
00:35:08,904 ---> 00:35:10,974
So each of you has
some hints on the back.

817
00:35:11,364 ---> 00:35:13,574
We're going to have three rounds
here where these guys are going

818
00:35:13,574 ---> 00:35:15,884
to spell out in English,
in ASCII,

819
00:35:16,104 ---> 00:35:18,014
a very short message,
a three letter word.

820
00:35:18,754 ---> 00:35:21,364
It will involve them
either raising their hand,

821
00:35:21,364 ---> 00:35:24,274
thereby representing a one or
just standing there awkwardly,

822
00:35:24,274 ---> 00:35:25,994
thereby representing a zero.

823
00:35:26,484 ---> 00:35:28,754
So why don't we proceed
immediately with round one

824
00:35:28,904 ---> 00:35:31,014
and you can either raise
or not raise your hands.

825
00:35:31,704 ---> 00:35:35,064
So the audience doesn't
get off the hook.

826
00:35:35,104 ---> 00:35:37,964
What number are they
currently representing?

827
00:35:39,174 ---> 00:35:39,954
66. Right.

828
00:35:39,954 ---> 00:35:42,864
Not hard because we have a one,
a hand up in the 64s column,

829
00:35:42,864 ---> 00:35:44,214
a hand up in the 2's column.

830
00:35:44,214 ---> 00:35:47,094
64 times one plus
two times one is 66.

831
00:35:47,124 ---> 00:35:48,254
They're representing
the number 6,

832
00:35:48,254 ---> 00:35:52,264
which means the first letter
is B. So not too bad, right?

833
00:35:52,674 ---> 00:35:53,234
Round two.

834
00:35:53,314 ---> 00:35:56,654
First letter was a B.

835
00:35:56,654 ---> 00:35:56,824
[ Laughter ]

836
00:35:56,824 ---> 00:36:01,104
>> Seventy Nine.

837
00:36:02,454 ---> 00:36:04,374
>> David: Can someone
second that?

838
00:36:04,374 ---> 00:36:04,924
Yes. All right.

839
00:36:04,924 ---> 00:36:10,084
So 79, which means
it's now an O. So B,O.

840
00:36:10,084 ---> 00:36:10,984
There's a third letter.

841
00:36:10,984 ---> 00:36:13,284
Actually that is kind of, yeah.

842
00:36:14,114 ---> 00:36:14,644
Third round.

843
00:36:14,834 ---> 00:36:15,724
Third and final round.

844
00:36:15,864 ---> 00:36:19,594
What number is this?

845
00:36:22,244 ---> 00:36:23,374
I heard an 87.

846
00:36:23,674 ---> 00:36:24,394
Someone else agree?

847
00:36:25,434 ---> 00:36:25,924
All right, yeah.

848
00:36:26,134 ---> 00:36:27,764
This is in fact 87,
which maps to,

849
00:36:27,764 ---> 00:36:30,984
and this is a very
clever set up at

850
00:36:30,984 ---> 00:36:34,184
which point you all
B, O, W, it's bow.

851
00:36:34,384 ---> 00:36:34,834
Very good.

852
00:36:35,104 ---> 00:36:37,194
So actually besides
that little souvenir,

853
00:36:38,784 ---> 00:36:40,794
that was not a very
enthusiastic applause,

854
00:36:40,794 ---> 00:36:42,004
so I'll take care of you.

855
00:36:42,254 ---> 00:36:44,074
So we do have a little something
for these guys here now

856
00:36:44,074 ---> 00:36:44,764
that they just appeared

857
00:36:44,764 ---> 00:36:47,424
on center stage doing perhaps
the geekiest thing they could.

858
00:36:47,914 ---> 00:36:49,894
So maybe if we could
humor them if only

859
00:36:49,894 ---> 00:36:51,364
because I'm feeling a
little bit awkward now.

860
00:36:51,364 ---> 00:36:52,954
A little round of applause
for these guys here.

861
00:36:53,494 ---> 00:36:59,624
[掌声]

862
00:37:00,124 ---> 00:37:00,764
All yours.

863
00:37:00,764 ---> 00:37:01,124
All right.

864
00:37:01,284 ---> 00:37:02,314
Thank you very much.

865
00:37:02,364 ---> 00:37:08,554
So, so, it turns out that we
can take this one step further,

866
00:37:08,764 ---> 00:37:11,624
but you are now entering
a community of people

867
00:37:11,794 ---> 00:37:13,954
who understand things like this.

868
00:37:14,494 ---> 00:37:23,164
[ Silence ]

869
00:37:23,664 ---> 00:37:25,344
It's slowly spreading, yes?

870
00:37:25,479 ---> 00:37:27,479
[ Laughter ]

871
00:37:27,614 ---> 00:37:29,274
It's not cool that you
understand this now.

872
00:37:29,714 ---> 00:37:31,944
So we've already done some
damage here today, but yes,

873
00:37:32,394 ---> 00:37:34,354
there is now such a
thing as geek humor

874
00:37:34,354 ---> 00:37:36,864
that you might just catch
a little bit more on to.

875
00:37:36,864 ---> 00:37:38,944
So what are we going to do
throughout this semester?

876
00:37:39,154 ---> 00:37:44,044
So there's 12 weeks, zero
index, so 13 weeks in total.

877
00:37:44,044 ---> 00:37:45,354
You'll find throughout
the semester

878
00:37:45,354 ---> 00:37:48,244
that computer scientists tend
to count starting from zero

879
00:37:48,244 ---> 00:37:49,964
for reasons that will
soon become clear.

880
00:37:50,174 ---> 00:37:52,434
But what we're going to do this
week, starting this Friday,

881
00:37:52,434 ---> 00:37:54,304
is introduce you to programming.

882
00:37:54,304 ---> 00:37:56,954
Now you may already be coming
at this course with a background

883
00:37:56,954 ---> 00:37:58,644
in the same, and
that's perfectly fine,

884
00:37:58,644 ---> 00:37:59,714
but we'll also be able

885
00:37:59,714 ---> 00:38:01,844
to introduce some more
sophisticated topics

886
00:38:01,844 ---> 00:38:03,804
than are typically
covered, things like events

887
00:38:03,804 ---> 00:38:05,774
and threading, so just
to toss out a couple

888
00:38:05,774 ---> 00:38:07,264
of buzz words for
those unfamiliar.

889
00:38:07,404 ---> 00:38:09,494
But what we're going
to do is not dive

890
00:38:09,494 ---> 00:38:12,764
into what the typically
traditional language like Java

891
00:38:12,764 ---> 00:38:17,084
or C++ or C sharp catch phrases
that you might have heard

892
00:38:17,084 ---> 00:38:19,444
in the past, but we're going to
use a programming environment,

893
00:38:19,444 ---> 00:38:21,034
a graphical programming
environment

894
00:38:21,034 ---> 00:38:23,934
that was actually
developed by MIT's media lab.

895
00:38:23,934 ---> 00:38:26,354
And this is an environment
that allows you to program,

896
00:38:26,354 ---> 00:38:30,024
quite literally, by dragging
and dropping puzzle pieces

897
00:38:30,024 ---> 00:38:31,444
that fit together logically

898
00:38:31,444 ---> 00:38:33,634
that lets you implement
these things called loops

899
00:38:33,634 ---> 00:38:35,494
and conditions and
Boolean expressions

900
00:38:35,734 ---> 00:38:38,664
and you can actually, on
day one, after this Friday,

901
00:38:38,884 ---> 00:38:40,834
write a program that
actually some

902
00:38:40,834 ---> 00:38:42,394
of your friends might
care about.

903
00:38:42,484 ---> 00:38:43,604
So in yester year, say

904
00:38:43,604 ---> 00:38:46,674
when you've taken a computer
science course in high school,

905
00:38:46,874 ---> 00:38:49,504
odds are one of your first
programs was the equivalent

906
00:38:49,504 ---> 00:38:51,704
of hello world, like wow mom,

907
00:38:51,704 ---> 00:38:54,864
I just made the computer type
some characters on the screen.

908
00:38:54,864 ---> 00:38:56,984
It's a very underwhelming
experience.

909
00:38:57,294 ---> 00:39:00,824
Much more interesting is it to
implement a little something

910
00:39:00,824 ---> 00:39:04,114
like this, as one of
last year's students did.

911
00:39:04,644 ---> 00:39:07,114
So I give you the work
of a former classmate.

912
00:39:07,434 ---> 00:39:10,954
It's a love story, of sorts,
about dancing cookies.

913
00:39:11,494 ---> 00:40:25,544
[音乐]

914
00:40:26,044 ---> 00:40:27,684
So this was actually
from a student

915
00:40:27,714 ---> 00:40:29,004
who had never programmed before.

916
00:40:29,004 ---> 00:40:30,854
And just to give you a
teaser of this interface,

917
00:40:30,854 ---> 00:40:33,104
and we're only going to
use this for one week time,

918
00:40:33,104 ---> 00:40:35,114
really to get the
comfort levels up

919
00:40:35,114 ---> 00:40:36,294
and to really get folks excited

920
00:40:36,294 ---> 00:40:38,484
about what you can actually
make these machines do,

921
00:40:38,694 ---> 00:40:41,244
this is an environment where
you'll be programming by,

922
00:40:41,244 ---> 00:40:43,034
for at least a week,
just dragging

923
00:40:43,034 ---> 00:40:45,154
and dropping puzzle
pieces that fit together,

924
00:40:45,334 ---> 00:40:47,144
as we'll see, in
a logical fashion.

925
00:40:47,144 ---> 00:40:50,114
And it lets you do fun,
silly things quickly.

926
00:40:50,114 ---> 00:40:52,554
And for any of you who are a
little bit familiar with things

927
00:40:52,554 ---> 00:40:56,564
like Java and C++, it's
usually a good semester or two

928
00:40:56,564 ---> 00:40:59,754
or three before you finally
get to start writing something

929
00:40:59,754 ---> 00:41:02,884
that another person might
actually enjoy watching.

930
00:41:02,884 ---> 00:41:06,674
Well, in week one of the course,
or the second week, zero index,

931
00:41:06,834 ---> 00:41:09,214
where we dive into a little
more traditional environment.

932
00:41:09,214 ---> 00:41:10,854
In this course we'll
spend much of our time

933
00:41:10,854 ---> 00:41:13,454
on a language called
C. This is one

934
00:41:13,454 ---> 00:41:15,634
of the earliest languages
that, unlike Java,

935
00:41:15,914 ---> 00:41:19,924
actually gives us much greater
access for better or for worse,

936
00:41:19,924 ---> 00:41:22,604
to manipulating hardware
and actual memory,

937
00:41:22,604 ---> 00:41:24,204
and we can do a lot
of damage with that.

938
00:41:24,384 ---> 00:41:27,974
In fact, any time you read of
web servers being exploited

939
00:41:27,974 ---> 00:41:29,524
or computers being hacked into,

940
00:41:29,754 ---> 00:41:32,254
very often to this
day it's the result

941
00:41:32,464 ---> 00:41:36,804
of people having run software
in a language called C or C++

942
00:41:37,164 ---> 00:41:41,334
without sufficient care given to
what are called buffer overruns

943
00:41:41,334 ---> 00:41:44,934
or lengths of arrays, so some
fairly technical concepts

944
00:41:44,934 ---> 00:41:46,544
that are not that
hard to understand,

945
00:41:46,764 ---> 00:41:49,634
but there's been a lot of
humans making a lot of mistakes

946
00:41:49,634 ---> 00:41:53,074
for years and with this language
we'll actually understand some

947
00:41:53,074 ---> 00:41:55,514
of those security implications.

948
00:41:55,774 ---> 00:41:57,354
But each week, typically,

949
00:41:57,354 ---> 00:41:59,774
we'll introduce also
an interesting domain

950
00:41:59,774 ---> 00:42:01,784
that will inspire that
week's problem set.

951
00:42:01,784 ---> 00:42:06,004
So we'll also take a look this
week at the field of cryptology,

952
00:42:06,244 ---> 00:42:10,074
cryptanalysis, the notion that
you can encipher information

953
00:42:10,074 ---> 00:42:12,024
in such a way that people
can't read your messages,

954
00:42:12,374 ---> 00:42:14,524
but if clever enough
perhaps you can, in fact,

955
00:42:14,584 ---> 00:42:16,934
crack what are otherwise
secret messages.

956
00:42:17,154 ---> 00:42:20,674
In week three we'll then look
at some basic fundamentals

957
00:42:20,674 ---> 00:42:23,404
of computer science like
searching and sorting

958
00:42:23,404 ---> 00:42:25,934
and we'll actually
look at this notion

959
00:42:25,934 ---> 00:42:27,754
of recursion, how
to debug things.

960
00:42:27,754 ---> 00:42:31,624
In short, we'll take things up
to the level of problem solving

961
00:42:31,744 ---> 00:42:33,804
and not so much about
mere syntax

962
00:42:34,084 ---> 00:42:36,754
and implementing short little
cookie cutter programs.

963
00:42:36,754 ---> 00:42:40,114
In week four we'll
introduce more sophisticated

964
00:42:40,114 ---> 00:42:40,834
problems still.

965
00:42:41,094 ---> 00:42:43,124
What does it mean
to manage memory?

966
00:42:43,154 ---> 00:42:45,604
What does it mean to
run out of memory?

967
00:42:45,604 ---> 00:42:48,424
What does it mean to
actually segfault,

968
00:42:48,424 ---> 00:42:50,654
if you've heard this expression,
and odds are you haven't,

969
00:42:50,654 ---> 00:42:52,304
but very bad things
happen and frankly

970
00:42:52,304 ---> 00:42:55,174
by terms end you'll understand
terms like my code segfaulted

971
00:42:55,404 ---> 00:43:00,084
which actually is generally
not going to be a good thing.

972
00:43:00,084 ---> 00:43:02,414
But then again, we'll introduce
some domain specific stuff.

973
00:43:02,414 ---> 00:43:03,014
So actually one

974
00:43:03,014 ---> 00:43:05,234
of my internships during
graduate school was to work

975
00:43:05,234 ---> 00:43:08,374
for the local Middlesex County
District Attorney's office doing

976
00:43:08,424 ---> 00:43:11,034
forensic investigations
in a digital sense.

977
00:43:11,074 ---> 00:43:13,084
The local Mass state
police would bring

978
00:43:13,084 ---> 00:43:16,514
to our office hard drives and
floppy disks and sometimes

979
00:43:16,514 ---> 00:43:18,624
for no reason mice
and keyboards.

980
00:43:18,624 ---> 00:43:21,624
And we would be tasked
with finding evidence.

981
00:43:21,744 ---> 00:43:25,694
Now it turns out, maybe just
an FYI, that the criminals

982
00:43:25,694 ---> 00:43:28,674
in Cambridge, Massachusetts,
at least,

983
00:43:28,944 ---> 00:43:30,474
not necessarily that clever.

984
00:43:30,474 ---> 00:43:32,644
Very often our forensic
analysis boiled

985
00:43:32,644 ---> 00:43:34,684
down to booting the computer
up and double clicking

986
00:43:34,684 ---> 00:43:37,934
on the My Documents folder,
and therein laid the evidence.

987
00:43:38,464 ---> 00:43:41,214
But what we'll do this
week is give you a sense

988
00:43:41,214 ---> 00:43:43,164
of what it actually means
to store information

989
00:43:43,164 ---> 00:43:44,954
on a hard drive,
on a flash drive,

990
00:43:44,954 ---> 00:43:48,764
and why can't otherwise
private information be disclosed

991
00:43:48,764 ---> 00:43:51,914
to third parties when you drop
off a computer to be repaired

992
00:43:51,914 ---> 00:43:53,754
or even when you discard it.

993
00:43:53,804 ---> 00:43:55,394
Well someone might
very well be sifting

994
00:43:55,394 ---> 00:43:57,364
through those hard drives
and it's really not that hard

995
00:43:57,364 ---> 00:43:59,614
to find data if you
know how to look for it.

996
00:43:59,814 ---> 00:44:01,674
Well, in week five we'll look

997
00:44:01,674 ---> 00:44:05,154
at more sophisticated data
structures, tools and techniques

998
00:44:05,154 ---> 00:44:07,074
that you can use ala phone books

999
00:44:07,074 ---> 00:44:11,894
and ala searching huge data
sets much more intelligently.

1000
00:44:11,894 ---> 00:44:14,524
And the week's problem set
will task you competitively

1001
00:44:14,734 ---> 00:44:17,514
to see just how fast the
code you can write is

1002
00:44:17,694 ---> 00:44:19,504
and how little memory
you can use.

1003
00:44:19,774 ---> 00:44:23,294
Toward terms end though we'll
take things up to a higher level

1004
00:44:23,294 ---> 00:44:26,024
in terms of programming
languages and put C behind us

1005
00:44:26,254 ---> 00:44:28,614
and introduce a web programming
language known as PHP,

1006
00:44:29,184 ---> 00:44:31,284
one of the popular
languages these days.

1007
00:44:31,284 ---> 00:44:33,364
Much of Facebook is
still written in PHP,

1008
00:44:33,364 ---> 00:44:36,514
at least outward facing, and
it's just a very easy language

1009
00:44:36,514 ---> 00:44:39,524
to learn quickly once
you already know another.

1010
00:44:39,524 ---> 00:44:42,134
So with PHP we'll be
able to solve problems

1011
00:44:42,134 ---> 00:44:44,664
and implement websites
that do interesting things.

1012
00:44:44,664 ---> 00:44:46,474
The news site I showed
you, the events site,

1013
00:44:46,714 ---> 00:44:47,594
the shuttle boy site,

1014
00:44:47,594 ---> 00:44:50,454
all of those all happen
to be written in PHP.

1015
00:44:50,454 ---> 00:44:52,314
But by no means is
that prerequisite.

1016
00:44:52,314 ---> 00:44:54,174
What you'll also find
throughout this course is

1017
00:44:54,174 ---> 00:44:57,564
that you're not going to exit
this course knowing C. You're

1018
00:44:57,564 ---> 00:44:59,634
not going to exit this
course knowing PHP.

1019
00:44:59,634 ---> 00:45:03,184
Those are not interesting
skills to claim, but knowing how

1020
00:45:03,184 ---> 00:45:06,564
to program, knowing how to use
data structures and algorithms

1021
00:45:06,564 ---> 00:45:09,244
in an interesting way,
that's a compelling story.

1022
00:45:09,244 ---> 00:45:11,464
Even I, all these years
later, throughout college

1023
00:45:11,464 ---> 00:45:14,804
and graduate school, the only
time I ever learned a language

1024
00:45:15,054 ---> 00:45:18,744
was probably in CS50 where it
was still taught in C and CS51,

1025
00:45:18,744 ---> 00:45:20,654
which is one of the
successor courses.

1026
00:45:20,714 ---> 00:45:24,764
Everywhere along the way since
has been go learn this language

1027
00:45:24,764 ---> 00:45:26,094
and then work on
this problem set

1028
00:45:26,154 ---> 00:45:28,264
because computer science
is not supposed to be

1029
00:45:28,264 ---> 00:45:31,324
about here's a language, let's
spend seven weeks teaching you

1030
00:45:31,324 ---> 00:45:32,604
where the semi colons are.

1031
00:45:32,764 ---> 00:45:34,734
There are much more
interesting ideas out there.

1032
00:45:34,804 ---> 00:45:35,804
Databases, for one.

1033
00:45:35,804 ---> 00:45:37,684
And in week two we'll
introduce you

1034
00:45:37,684 ---> 00:45:41,384
to this query language
called SQL that'll allow you

1035
00:45:41,594 ---> 00:45:43,114
to store information
in databases

1036
00:45:43,114 ---> 00:45:45,124
and actually implement
some fairly interesting

1037
00:45:45,404 ---> 00:45:46,244
final projects.

1038
00:45:46,274 ---> 00:45:47,394
The week after we'll look

1039
00:45:47,394 ---> 00:45:49,244
at what's called
client side programming,

1040
00:45:49,244 ---> 00:45:52,074
doing interesting things
on a user's computer,

1041
00:45:52,074 ---> 00:45:53,974
taking advantage of
their CPU cycles,

1042
00:45:54,244 ---> 00:45:57,084
doing things ala Google
maps and these websites

1043
00:45:57,084 ---> 00:45:58,774
that actually use JavaScript,

1044
00:45:58,774 ---> 00:46:00,354
which is actually a
language we'll introduce

1045
00:46:00,354 ---> 00:46:03,224
to let you do client side
things, make more interesting,

1046
00:46:03,224 ---> 00:46:05,874
more sophisticated user
interfaces, but at the end

1047
00:46:05,874 ---> 00:46:08,374
of the day have to be really
mindful when implemented

1048
00:46:08,564 ---> 00:46:11,794
of a lot of sticky issues
like network speeds,

1049
00:46:11,794 ---> 00:46:13,584
network performance
and security.

1050
00:46:13,814 ---> 00:46:16,684
So it's not about again just
coding something up that's fun

1051
00:46:16,684 ---> 00:46:19,184
to use or pretty to look
at, but actually thinking

1052
00:46:19,184 ---> 00:46:21,524
about the design that'll
be the interesting process.

1053
00:46:21,664 ---> 00:46:24,844
And then, the end result
aesthetically will often be a

1054
00:46:24,844 ---> 00:46:27,164
really neat toy to show
yourself or a friend.

1055
00:46:27,164 ---> 00:46:29,604
And then we'll look at hardware.

1056
00:46:29,604 ---> 00:46:30,734
We're going to take for granted

1057
00:46:30,734 ---> 00:46:32,694
that there are these
physical boxes throughout much

1058
00:46:32,734 ---> 00:46:35,934
of the semester that will
do what we tell them to do.

1059
00:46:36,324 ---> 00:46:37,464
But how are they doing that.

1060
00:46:37,464 ---> 00:46:39,464
So we'll actually take a
peak under the hood and talk

1061
00:46:39,464 ---> 00:46:42,984
about what a compiler really
is, what a CPU really is

1062
00:46:42,984 ---> 00:46:46,324
and actually consider what's
making all of this fanciness

1063
00:46:46,324 ---> 00:46:49,424
from stupid YouTube
videos on down possible.

1064
00:46:50,014 ---> 00:46:51,254
So what are the expectations?

1065
00:46:51,254 ---> 00:46:52,584
Attending lectures and sessions,

1066
00:46:52,924 ---> 00:46:55,794
completing nine problem sets
assigned roughly weekly,

1067
00:46:55,794 ---> 00:46:57,994
two quizzes, the final
project and there is

1068
00:46:57,994 ---> 00:46:59,464
in fact no final exam.

1069
00:46:59,464 ---> 00:47:02,824
Grades, it's always a question,
broken down as follows here.

1070
00:47:02,824 ---> 00:47:04,174
You can take the
course pass-fail.

1071
00:47:04,174 ---> 00:47:06,994
But let me say it here, and
I've said it many times.

1072
00:47:07,254 ---> 00:47:09,864
I personally care relatively
little about grades.

1073
00:47:09,914 ---> 00:47:11,764
I think they are
a wonderful, well,

1074
00:47:11,914 ---> 00:47:15,344
they are a useful pedagogical
tool with which to motivate

1075
00:47:15,344 ---> 00:47:18,704
and unfortunately sometimes
de-motivate, but you'll find

1076
00:47:18,704 ---> 00:47:22,494
in this course that at the
end of the day it's more

1077
00:47:22,494 ---> 00:47:26,464
about seeing how far you can
go from weeks zero to week 12,

1078
00:47:26,464 ---> 00:47:28,464
as we say in the
syllabus than it is

1079
00:47:28,464 ---> 00:47:30,934
about absolutely ranking
all students in this course.

1080
00:47:30,934 ---> 00:47:33,244
So if you're coming into
this course among those less

1081
00:47:33,244 ---> 00:47:36,154
comfortable, though a large
demographic do not assume

1082
00:47:36,344 ---> 00:47:39,404
that that's automatically
putting you in the lower third

1083
00:47:39,564 ---> 00:47:41,194
of the so called distribution.

1084
00:47:41,194 ---> 00:47:44,464
At terms end do I sit down
with the TF's and discuss each

1085
00:47:44,464 ---> 00:47:45,614
and every one of the students.

1086
00:47:45,784 ---> 00:47:48,984
We take into account
where a student came from,

1087
00:47:49,184 ---> 00:47:51,574
what kind of trajectory
they were actually on and so

1088
00:47:51,574 ---> 00:47:55,024
at the end of the day please
focus more on, and I don't mean

1089
00:47:55,024 ---> 00:47:56,934
to sound too grand,
the process of learning

1090
00:47:57,144 ---> 00:47:58,154
and less on the numeric's.

1091
00:47:58,254 ---> 00:48:00,604
And you'll actually see
that we grade problem sets,

1092
00:48:00,604 ---> 00:48:04,074
in particular, very coarsely,
whereby along three axis,

1093
00:48:04,074 ---> 00:48:07,634
you will get a score
of 1, 2, 3, 4, or 5,

1094
00:48:07,674 ---> 00:48:09,354
where 3, is in fact good.

1095
00:48:09,604 ---> 00:48:13,574
3 is not C. 3 is good,
4 is better, 5 is best.

1096
00:48:13,574 ---> 00:48:16,344
But more on that as the
problem sets are released.

1097
00:48:16,714 ---> 00:48:19,934
So the course's website is where
you will find, as in most cases,

1098
00:48:19,934 ---> 00:48:23,504
a whole lot of useful things,
if not silly things, too.

1099
00:48:23,684 ---> 00:48:25,414
And we have the luxury,
as computer scientists

1100
00:48:25,414 ---> 00:48:27,244
of implementing it ourselves.

1101
00:48:27,244 ---> 00:48:27,924
So over the course

1102
00:48:27,924 ---> 00:48:30,234
of the semester you will
see various new features

1103
00:48:30,234 ---> 00:48:30,754
rolling out.

1104
00:48:30,754 ---> 00:48:32,064
You'll find out over the
course of the semester

1105
00:48:32,064 ---> 00:48:34,594
that the bulletin board
is a wonderful place,

1106
00:48:34,594 ---> 00:48:35,914
certainly in the
course of this size,

1107
00:48:35,914 ---> 00:48:38,384
to turn when you have
questions about the problem set,

1108
00:48:38,544 ---> 00:48:41,394
questions about some
computer science concept.

1109
00:48:41,394 ---> 00:48:43,844
You'll be able to check your
grades, download all handouts

1110
00:48:44,034 ---> 00:48:46,514
in advance of lecture typically
will I post the slides,

1111
00:48:46,514 ---> 00:48:48,144
if you're the type who
wants to scribble on notes.

1112
00:48:48,414 ---> 00:48:51,154
But as you've seen, usually
I shy away from long lists

1113
00:48:51,154 ---> 00:48:54,054
of details and more
like pictures of cats

1114
00:48:54,284 ---> 00:48:56,284
and other visual cues.

1115
00:48:56,704 ---> 00:48:59,794
So you'll find, too, that we
will provide printouts of code

1116
00:48:59,794 ---> 00:49:02,294
when we actually think it
particularly advantageous

1117
00:49:02,294 ---> 00:49:03,554
to write right on the paper.

1118
00:49:03,844 ---> 00:49:07,204
Software, videos will be
available, usually around 1 to 2

1119
00:49:07,204 ---> 00:49:09,254
to 3 days maximally
after each lecture.

1120
00:49:09,504 ---> 00:49:12,114
So the courses are being filmed
and every lecture will go online

1121
00:49:12,334 ---> 00:49:14,664
in various formats
including QuickTime and MP3's

1122
00:49:14,664 ---> 00:49:16,534
for downloads to iPods and such.

1123
00:49:16,774 ---> 00:49:17,824
And also you will find a link

1124
00:49:17,824 ---> 00:49:19,584
to download what we call
the virtual terminal room,

1125
00:49:19,824 ---> 00:49:22,324
which as you'll see is related
to virtual office hours.

1126
00:49:22,634 ---> 00:49:25,044
Books are expensive and in
the computer world also not

1127
00:49:25,044 ---> 00:49:25,644
that useful.

1128
00:49:25,894 ---> 00:49:30,104
They are on the shelves of
the coop, although we're told

1129
00:49:30,104 ---> 00:49:33,214
that last year they ordered
like 120 books for the course

1130
00:49:33,474 ---> 00:49:36,374
and 30 were actually purchased,
but this perhaps speak

1131
00:49:36,554 ---> 00:49:39,344
to the fact that there are
places like Amazon.com,

1132
00:49:39,344 ---> 00:49:42,764
so if you are the type who
actually enjoys the sort

1133
00:49:42,764 ---> 00:49:45,564
of support structure that a book
provides, if you like to read

1134
00:49:45,564 ---> 00:49:47,774
up more than say a course's
typical materials offer,

1135
00:49:47,774 ---> 00:49:50,304
by all means, procure
one or more of the books

1136
00:49:50,344 ---> 00:49:52,164
that we recommend
here and discuss more

1137
00:49:52,164 ---> 00:49:53,354
in detail in the syllabus.

1138
00:49:53,604 ---> 00:49:55,454
But realize there
are so many resources

1139
00:49:55,454 ---> 00:49:57,214
that this course
provides in printed form

1140
00:49:57,214 ---> 00:49:58,804
and electronic form, and my God,

1141
00:49:58,804 ---> 00:50:00,114
there's the whole
internet out there.

1142
00:50:00,364 ---> 00:50:02,314
Books are not something
that are required

1143
00:50:02,314 ---> 00:50:03,404
for this particular course.

1144
00:50:03,984 ---> 00:50:05,844
Lectures, in general, will
be Monday's and Wednesday's,

1145
00:50:06,064 ---> 00:50:08,784
except for this Friday
and next Friday,

1146
00:50:09,044 ---> 00:50:10,964
simply because of shopping
period and Labor Day.

1147
00:50:10,964 ---> 00:50:13,494
So we'll meet this Friday,
next Wednesday, next Friday,

1148
00:50:13,694 ---> 00:50:16,214
but there after this is just
a Monday, Wednesday course.

1149
00:50:16,514 ---> 00:50:18,934
So this little visual cue
here is to remind me that yes,

1150
00:50:19,044 ---> 00:50:22,124
we do distribute videos in
QuickTime formats, MP3's,

1151
00:50:22,174 ---> 00:50:25,034
fun ways that you can, if
you're actually this type,

1152
00:50:25,194 ---> 00:50:27,714
maybe in the 14 percent, watch
a computer science lecture

1153
00:50:27,714 ---> 00:50:35,204
on your iPod, but it reminded
me that at terms end last year,

1154
00:50:35,204 ---> 00:50:37,124
the course culminates
in final projects,

1155
00:50:37,124 ---> 00:50:39,354
in which students can design
most anything they want,

1156
00:50:39,354 ---> 00:50:41,424
and we actually had some
students tackle some

1157
00:50:41,424 ---> 00:50:42,504
iPhone applications.

1158
00:50:42,714 ---> 00:50:45,434
Some one of these at least
is now in the Apple store.

1159
00:50:45,434 ---> 00:50:46,274
It's called Rover.

1160
00:50:46,394 ---> 00:50:48,894
It's been adopted
essentially by Harvard agencies

1161
00:50:48,894 ---> 00:50:49,994
and it's the iPhone version

1162
00:50:49,994 ---> 00:50:51,974
of the unofficial guide
to life at Harvard.

1163
00:50:51,974 ---> 00:50:53,104
They did a brilliant job.

1164
00:50:53,774 ---> 00:50:56,034
I bring this slide
up too, just to point

1165
00:50:56,304 ---> 00:50:58,504
out what other technologies
might very well be

1166
00:50:58,504 ---> 00:50:59,264
down the road.

1167
00:50:59,264 ---> 00:51:00,964
Some of you may have
seen this before,

1168
00:51:00,964 ---> 00:51:03,094
but just to give you a
teaser of apparently what's

1169
00:51:03,094 ---> 00:51:06,764
in the pipeline, I thought
I would offer this brief

1170
00:51:07,354 ---> 00:51:09,654
distraction here.

1171
00:51:10,494 ---> 00:51:32,554
[音乐]

1172
00:51:33,054 ---> 00:51:36,764
>> With the MacBook wheel,
Apple has replaced the keyboard

1173
00:51:36,764 ---> 00:51:39,284
with a sleek, touch
sensitive click wheel.

1174
00:51:39,504 ---> 00:51:42,344
Apple CEO Steve Jobs
introduced the product yesterday

1175
00:51:42,614 ---> 00:51:43,974
at the annual Mac Expo.

1176
00:51:44,304 ---> 00:51:47,444
Senior product innovator says
the MacBook wheel will make

1177
00:51:47,574 ---> 00:51:49,094
typing a thing of the past.

1178
00:51:49,094 ---> 00:51:51,534
>> At Apple our philosophy is
create products that are simple

1179
00:51:51,534 ---> 00:51:54,474
to use and nothing's more simple
than a single giant button.

1180
00:51:54,754 ---> 00:51:56,634
>> Gilman showed me how
the revolutionary new

1181
00:51:56,634 ---> 00:51:57,344
computer works.

1182
00:51:57,704 ---> 00:52:00,414
>> Gilman: Just open the
intuit-type alphabet menu here,

1183
00:52:01,064 ---> 00:52:04,794
scroll to the letter you need
and center click to select it

1184
00:52:05,424 ---> 00:52:07,074
and click again to capitalize

1185
00:52:07,624 ---> 00:52:09,784
and repeat this process
for each new letter.

1186
00:52:09,784 ---> 00:52:11,194
It couldn't be simpler.

1187
00:52:14,214 ---> 00:52:16,414
You could also let the
predictive sentence technology

1188
00:52:16,534 ---> 00:52:17,564
complete the sentence for you.

1189
00:52:17,944 ---> 00:52:21,344
>> Gilman says the MacBook wheel
has also simplified organization

1190
00:52:21,344 ---> 00:52:23,684
of files, so searching your
hard drive will be a snap.

1191
00:52:24,204 ---> 00:52:26,444
>> Gilman: Just press both
sides of the wheel concurrently

1192
00:52:26,794 ---> 00:52:29,124
and center click and there,
you have an alphabetical list

1193
00:52:29,124 ---> 00:52:31,084
of every file on
your hard drive.

1194
00:52:31,274 ---> 00:52:33,194
Everything is just a
few hundred clicks away.

1195
00:52:33,414 ---> 00:52:36,174
>> Apple is calling the MacBook
wheel the most intuitive product

1196
00:52:36,424 ---> 00:52:37,364
every designed.

1197
00:52:37,544 ---> 00:52:38,684
>> Here at Apple
we like to think

1198
00:52:38,684 ---> 00:52:40,884
that we're giving customers
features they don't even know

1199
00:52:40,884 ---> 00:52:41,624
they want yet.

1200
00:52:41,914 ---> 00:52:44,134
>> While the MacBook wheel won't
hit the shelves for another 3

1201
00:52:44,134 ---> 00:52:46,784
to 15 months, many apple
users already have it

1202
00:52:46,784 ---> 00:52:47,494
on their wish list.

1203
00:52:47,714 ---> 00:52:50,064
>> I'll buy almost anything
[inaudible] and made by Apple.

1204
00:52:50,244 ---> 00:52:52,304
>> Alex [inaudible] was one
of the lucky few to get to try

1205
00:52:52,304 ---> 00:52:55,424
out a MacWheel and spent
45 minutes typing an email

1206
00:52:55,424 ---> 00:52:56,004
to his friend.

1207
00:52:56,324 ---> 00:52:57,934
>> I never really realized
how much I hated keyboards

1208
00:52:57,934 ---> 00:52:59,174
until I saw this thing.

1209
00:52:59,174 ---> 00:53:02,994
>> I like how it automatically
says, sent with a MacBook Wheel,

1210
00:53:02,994 ---> 00:53:04,344
so people automatically
know you have one.

1211
00:53:04,464 ---> 00:53:06,994
>> With a price tag of
just under 2600 dollars

1212
00:53:07,024 ---> 00:53:09,704
for the lowest end MacBook
Wheel, it is an investment.

1213
00:53:10,214 ---> 00:53:12,834
But the super thin laptop
features numerous innovations,

1214
00:53:12,834 ---> 00:53:15,154
like the new ultra thin
hummingbird battery,

1215
00:53:15,474 ---> 00:53:16,854
which can power the
MacBook Wheel

1216
00:53:16,904 ---> 00:53:19,454
for a fill 19 minutes before
needing to be recharged

1217
00:53:19,614 ---> 00:53:22,234
and the computer is virtually
unbreakable unless dropped

1218
00:53:22,234 ---> 00:53:22,604
or hit.

1219
00:53:22,884 ---> 00:53:24,664
But Apple isn't resting
on its laurels,

1220
00:53:24,664 ---> 00:53:26,904
Bryan Gilman says they're
already hard at work

1221
00:53:26,904 ---> 00:53:28,774
on the next generation
of the MacBook Wheel,

1222
00:53:28,774 ---> 00:53:31,344
which will be four ounces
lighter due to its lack

1223
00:53:31,414 ---> 00:53:32,904
of streaming hard
drive or wheel.

1224
00:53:32,904 ---> 00:53:35,214
For the Ugly news
Network, I'm Jeff Tate.

1225
00:53:35,504 ---> 00:53:36,254
>> Thank you for that, Jeff.

1226
00:53:36,364 ---> 00:53:38,024
It remains to be seen
if the wheel will catch

1227
00:53:38,234 ---> 00:53:40,504
on in the business world
where people use computers

1228
00:53:40,504 ---> 00:53:43,024
for actual work and not
just dicking around.

1229
00:53:43,274 ---> 00:53:44,774
Moving on, police warn.

1230
00:53:44,774 ---> 00:53:45,554
>> David: So I've
seen that thing

1231
00:53:45,554 ---> 00:53:47,774
at least a half a dozen
times now, including once

1232
00:53:47,774 ---> 00:53:51,064
at like two a.m. last night and
I was scrolling down on YouTube

1233
00:53:51,064 ---> 00:53:52,514
and literally like
an hour prior,

1234
00:53:52,514 ---> 00:53:55,514
some guy in all seriousness
posted, just a wheel?

1235
00:53:55,514 ---> 00:53:57,484
That's the stupidest
product I've ever seen.

1236
00:53:57,484 ---> 00:53:58,194
[ Laughter ]

1237
00:53:58,194 ---> 00:54:02,754
And then the rants ensued
in the thread thereafter.

1238
00:54:03,084 ---> 00:54:05,464
So besides lectures
there are also sections

1239
00:54:05,464 ---> 00:54:06,764
and it is your teaching fellow

1240
00:54:06,764 ---> 00:54:08,554
and the course's course
assistants that you will get

1241
00:54:08,554 ---> 00:54:11,354
to know very well over the
course of this semester.

1242
00:54:11,804 ---> 00:54:14,024
Sectioning won't begin
for a week or so's time.

1243
00:54:14,024 ---> 00:54:15,784
More on that in the
lectures to come.

1244
00:54:15,784 ---> 00:54:18,034
But know that the course will
have several different tracks

1245
00:54:18,264 ---> 00:54:20,854
of sections, much like First
Knight's has for music.

1246
00:54:21,114 ---> 00:54:24,164
Sections targeted more at
those less comfortable,

1247
00:54:24,354 ---> 00:54:26,644
those more comfortable and
those somewhere in between.

1248
00:54:26,824 ---> 00:54:30,254
And we also offer most Sunday
nights before a problem set is

1249
00:54:30,294 ---> 00:54:33,784
due on the following Friday is
what we call code walkthrough's

1250
00:54:33,784 ---> 00:54:36,574
where one of the course's
teaching fellows will lead a

1251
00:54:36,574 ---> 00:54:39,424
session targeted specifically
at the week's problem set

1252
00:54:39,424 ---> 00:54:41,964
and will help you answer the
question where do I begin,

1253
00:54:42,094 ---> 00:54:43,174
how should I approach this?

1254
00:54:43,174 ---> 00:54:45,694
And that too will be filmed
and made available online

1255
00:54:45,924 ---> 00:54:47,904
and always linked on
the course's website.

1256
00:54:48,224 ---> 00:54:50,394
So this course has a huge staff.

1257
00:54:50,594 ---> 00:54:53,644
Our staff is larger than
Harvard's average class size.

1258
00:54:53,644 ---> 00:54:55,824
We have over 50 people
involved in the production

1259
00:54:55,824 ---> 00:54:57,264
of this course on
a weekly basis.

1260
00:54:57,544 ---> 00:55:00,514
Some of them teaching fellows
who hold sections, grade work,

1261
00:55:00,704 ---> 00:55:02,124
hold office hours and more.

1262
00:55:02,124 ---> 00:55:04,984
Course assistants who are former
students, who are offering

1263
00:55:04,984 ---> 00:55:08,384
on a volunteer basis in fact
multiple hours of office hours

1264
00:55:08,384 ---> 00:55:09,554
in the computer lab per week.

1265
00:55:09,864 ---> 00:55:11,534
System administrators,
folks doing all

1266
00:55:11,534 ---> 00:55:12,984
of our AV and video production.

1267
00:55:12,984 ---> 00:55:14,824
Someone who will actually
be taking notes for you.

1268
00:55:15,104 ---> 00:55:18,304
So it is actually my
opinion that scribbling

1269
00:55:18,304 ---> 00:55:19,524
down almost every
word that someone

1270
00:55:19,524 ---> 00:55:21,584
like me says is not a very
good use of one's time.

1271
00:55:21,584 ---> 00:55:23,824
It's much more interesting
I think to actually engage

1272
00:55:24,044 ---> 00:55:25,964
with what's on the screen,
what's being presented.

1273
00:55:25,964 ---> 00:55:29,134
And so what we will do as a
course is post PDF's online

1274
00:55:29,134 ---> 00:55:31,864
within a couple of days of
lectures of scribe notes,

1275
00:55:31,864 ---> 00:55:33,834
which is essentially an
authoritative version

1276
00:55:33,834 ---> 00:55:38,234
of course notes, unedited,
but documenting what went

1277
00:55:38,234 ---> 00:55:41,544
on in lecture that day, thereby
hopefully freeing your minds

1278
00:55:41,544 ---> 00:55:44,724
and pencils from
jotting information down.

1279
00:55:44,904 ---> 00:55:46,014
We have some of our team here.

1280
00:55:46,014 ---> 00:55:47,924
Most of our team is
actually shopping courses.

1281
00:55:47,924 ---> 00:55:49,774
But if a few of your guys
would like to come on stage

1282
00:55:49,774 ---> 00:55:52,164
for a moment with our
head teaching fellow

1283
00:55:52,164 ---> 00:55:53,534
and assistant head
teaching fellow.

1284
00:55:53,684 ---> 00:55:56,914
Allow me to ask the latter
to say a quick hello.

1285
00:55:57,494 ---> 00:56:02,624
And as these guys come up
in absentia allow me to say

1286
00:56:02,624 ---> 00:56:06,144
that also on staff this year
besides the folks you see here

1287
00:56:06,144 ---> 00:56:10,774
are Alex, Alice, Andrew, Batul,
Charlotte, Chris, Dan, Dan,

1288
00:56:10,774 ---> 00:56:16,294
Daniel, David, David, David,
Derek, Dev, Didi, Doug, Drew,

1289
00:56:16,294 ---> 00:56:21,374
Erica, Fil, Glen, Greg, Janice,
Jason, Jean, Jeff, Jesse, John,

1290
00:56:21,374 ---> 00:56:25,394
John, Jonathan, Jordan, Josh,
Karim, Kelly, Ken, Kent,

1291
00:56:25,654 ---> 00:56:30,194
Kyu Bok, Lee, Madhura, Marta,
Matthew, Michael, Michelle,

1292
00:56:30,194 ---> 00:56:34,714
Mike, Mike, Nathan, Patrick,
Peter, Peyton, Rose, Saba,

1293
00:56:34,924 ---> 00:56:38,794
Sanjay, Shannon, Stacey,
Ted, Wellie, Yair and me.

1294
00:56:39,684 ---> 00:56:42,004
So our course is teaching
fellows and course assistants,

1295
00:56:42,004 ---> 00:56:45,644
Cansu and Yuhki, would you
like to say a quick hello?

1296
00:56:46,194 ---> 00:56:48,574
>> Hi. It's definitely
a great honor

1297
00:56:48,574 ---> 00:56:50,624
to be back here for
the third time.

1298
00:56:51,044 ---> 00:56:53,654
And if you're one of those
who are like less comfortable.

1299
00:56:53,654 ---> 00:56:53,721
[ Laughter ]

1300
00:56:53,721 ---> 00:57:00,254
I think I can [inaudible].

1301
00:57:00,654 ---> 00:57:00,754
Okay.

1302
00:57:00,754 ---> 00:57:00,821
[ Laughter ]

1303
00:57:00,821 ---> 00:57:03,444
If you're one of
those [inaudible].

1304
00:57:03,444 ---> 00:57:07,094
There's no need to be afraid.

1305
00:57:07,094 ---> 00:57:09,764
I walked in here two years ago
with no experience what so ever,

1306
00:57:09,794 ---> 00:57:14,394
and I thought that I was
like dumb and I was sure

1307
00:57:14,394 ---> 00:57:15,594
that I was going
to fail the class.

1308
00:57:15,594 ---> 00:57:18,824
And I came back for
the third time.

1309
00:57:18,904 ---> 00:57:21,184
I did not fail the class.

1310
00:57:22,544 ---> 00:57:25,554
This course is great because
it has such a good community.

1311
00:57:25,554 ---> 00:57:30,274
As you can tell by the
names listed by David.

1312
00:57:30,274 ---> 00:57:32,984
All the CA's and TF's
are here to help you.

1313
00:57:32,984 ---> 00:57:36,574
So if you have any questions
at all, just come up to us.

1314
00:57:36,574 ---> 00:57:40,564
Not taking this class because
it's hard is not a good excuse.

1315
00:57:42,234 ---> 00:57:43,424
So, hi.

1316
00:57:43,424 ---> 00:57:45,034
>> [Inaudible].

1317
00:57:45,034 ---> 00:57:51,224
>> Hi, so well both
as a student and TF,

1318
00:57:51,224 ---> 00:57:55,254
I've really enjoyed being
a part of this course.

1319
00:57:55,254 ---> 00:57:58,724
And even though it's a course
that requires a lot of work

1320
00:57:58,774 ---> 00:58:01,274
from you, we've put a lot of
work in to it for you as well

1321
00:58:01,274 ---> 00:58:03,874
to make it as enjoyable
and as fun as possible.

1322
00:58:03,964 ---> 00:58:08,914
So, we really hope that all
of you stay and take part

1323
00:58:09,104 ---> 00:58:11,174
in this very special experience.

1324
00:58:11,674 ---> 00:58:11,874
>> Thanks.

1325
00:58:11,874 ---> 00:58:14,044
>> David: So you will find,
thank you, all of you,

1326
00:58:14,044 ---> 00:58:15,014
you will meet them
in the hallway

1327
00:58:15,014 ---> 00:58:16,154
in just a few minutes as well.

1328
00:58:16,474 ---> 00:58:18,414
So you'll find that this
course, perhaps more

1329
00:58:18,414 ---> 00:58:21,064
so than many is very
much a shared experience.

1330
00:58:21,064 ---> 00:58:22,324
This is not a competitive
course.

1331
00:58:22,324 ---> 00:58:23,714
This is not your premed course.

1332
00:58:23,994 ---> 00:58:26,084
This is a course which
ultimately yes is

1333
00:58:26,084 ---> 00:58:28,564
about doing independent
work, as you'll see each week

1334
00:58:28,604 ---> 00:58:29,714
by way of the problem sets.

1335
00:58:30,054 ---> 00:58:32,264
But you can't help but
to get close to someone

1336
00:58:32,514 ---> 00:58:35,504
when you're fighting with
some bug and banging your head

1337
00:58:35,544 ---> 00:58:39,714
against the computer
screen proverbially to try

1338
00:58:39,714 ---> 00:58:41,084
to track down some bug.

1339
00:58:41,324 ---> 00:58:43,804
And I think you'll find that
past students will concur

1340
00:58:43,804 ---> 00:58:45,614
that you exit this
course with a lot

1341
00:58:45,614 ---> 00:58:48,494
of friends among students
and also on staff.

1342
00:58:48,724 ---> 00:58:50,004
So where does that happen?

1343
00:58:50,244 ---> 00:58:51,844
Well, within office
hours in the basement

1344
00:58:51,844 ---> 00:58:53,864
of the science center there's
some large computer labs

1345
00:58:53,864 ---> 00:58:56,664
and we pretty much take them
over five nights a week.

1346
00:58:56,834 ---> 00:58:59,454
These won't start for some
time, and this, to be honest,

1347
00:58:59,494 ---> 00:59:00,854
is perhaps the most
beautiful picture

1348
00:59:00,854 ---> 00:59:02,174
of the science center
I've ever seen.

1349
00:59:02,604 ---> 00:59:04,604
[ Laughter ]

1350
00:59:05,034 ---> 00:59:07,024
It does not look like
that on the inside.

1351
00:59:07,134 ---> 00:59:11,524
But it is a place where a good
percentage of students do choose

1352
00:59:11,524 ---> 00:59:14,014
to spend time to get one
on one assistance with each

1353
00:59:14,014 ---> 00:59:15,444
of the week's problem sets.

1354
00:59:15,444 ---> 00:59:19,504
Each week we will offer more
than 100 hours of assistance one

1355
00:59:19,504 ---> 00:59:21,854
on one in the science
center per the schedule

1356
00:59:21,854 ---> 00:59:23,144
that will eventually go online.

1357
00:59:23,394 ---> 00:59:26,344
And for those of you who live,
say in the quad, or in Mather,

1358
00:59:26,344 ---> 00:59:28,044
or who just don't want
to trek all the way

1359
00:59:28,044 ---> 00:59:29,894
to the science center to
ask that quick question,

1360
00:59:30,144 ---> 00:59:32,624
we also offer what are
called virtual office hours,

1361
00:59:32,624 ---> 00:59:35,134
much like remote technical
support where you'll be able

1362
00:59:35,134 ---> 00:59:38,364
to log into a glorified
chat room, in which yes,

1363
00:59:38,364 ---> 00:59:40,474
you can type back and
forth with a TF or a CA,

1364
00:59:40,474 ---> 00:59:43,264
but you can also share your
screen or share control

1365
00:59:43,264 ---> 00:59:45,224
of your mouse with them
subject to your consent

1366
00:59:45,434 ---> 00:59:47,814
so that they can help you
troubleshoot any problem

1367
00:59:47,814 ---> 00:59:49,654
or any question you
have remotely.

1368
00:59:49,654 ---> 00:59:51,814
To give you a sense of what's
involved in the course,

1369
00:59:52,084 ---> 00:59:53,724
these are statistics
from last year.

1370
00:59:53,724 ---> 00:59:55,814
So you will, I think
it's quite fair to say,

1371
00:59:55,814 ---> 00:59:57,414
work your ass off
in this course.

1372
00:59:57,624 ---> 00:59:59,304
But per my promise
from the start,

1373
00:59:59,584 ---> 01:00:01,744
this is one of those experiences

1374
01:00:01,984 ---> 01:00:04,544
that I don't think a
typical student regrets.

1375
01:00:04,684 ---> 01:00:06,784
If you flip through, for
instance, the Q Guide forms

1376
01:00:06,814 ---> 01:00:09,884
that are all on the course's
website, you'll find that only

1377
01:00:10,134 ---> 01:00:12,074
by putting in the
time to a course

1378
01:00:12,074 ---> 01:00:14,934
like this do you
really exit having felt

1379
01:00:14,934 ---> 01:00:16,334
like you got something out of it

1380
01:00:16,334 ---> 01:00:19,704
and frankly might very well
even have emerged even smarter.

1381
01:00:19,984 ---> 01:00:23,324
So what does it mean to
actually write programs

1382
01:00:23,364 ---> 01:00:24,944
and implement problem sets?

1383
01:00:24,944 ---> 01:00:26,764
Well, the first problem
set last year,

1384
01:00:27,054 ---> 01:00:28,244
a quick retrospective here,

1385
01:00:28,244 ---> 01:00:30,484
was to implement your very
own programming scratch.

1386
01:00:30,684 ---> 01:00:32,534
And we spend just the first
week there, and the goal is

1387
01:00:32,534 ---> 01:00:34,834
to implement your own
game or animation or art

1388
01:00:35,064 ---> 01:00:37,104
or anything that appeals to you.

1389
01:00:37,104 ---> 01:00:40,214
In week one, then do you
implement some basic C programs

1390
01:00:40,254 ---> 01:00:42,554
to get acclimated to some
more traditional programming

1391
01:00:42,554 ---> 01:00:44,224
environments at the
command line,

1392
01:00:44,224 ---> 01:00:47,004
at Linux so you get comfortable
with some of these basics

1393
01:00:47,004 ---> 01:00:49,004
that will certainly serve
you well in the long run.

1394
01:00:49,294 ---> 01:00:51,704
Last year's Problem Set
2 was about cryptography.

1395
01:00:51,944 ---> 01:00:55,274
We gave students the opportunity
to implement some ciphers,

1396
01:00:55,274 ---> 01:00:57,684
some algorithms that let
them encrypt information.

1397
01:00:57,914 ---> 01:01:00,424
And we also offered some
students the opportunity

1398
01:01:00,424 ---> 01:01:01,284
to do the opposite.

1399
01:01:01,554 ---> 01:01:03,324
Each problem set,
many problem sets,

1400
01:01:03,324 ---> 01:01:05,484
as you'll see are
implemented in two editions.

1401
01:01:05,694 ---> 01:01:08,514
A standard edition that we
expect almost everyone to do,

1402
01:01:08,514 ---> 01:01:09,734
say 90 percent of the class.

1403
01:01:10,194 ---> 01:01:12,974
And then a hacker edition,
which presents the material

1404
01:01:12,974 ---> 01:01:14,564
from a more sophisticated angle,

1405
01:01:14,564 ---> 01:01:16,294
expects perhaps a
bit more clever work

1406
01:01:16,294 ---> 01:01:17,654
for those more experienced,

1407
01:01:17,904 ---> 01:01:19,934
and for this one did
those students get handed

1408
01:01:19,934 ---> 01:01:23,714
in the hacker edition
pre existing user names

1409
01:01:23,714 ---> 01:01:26,304
and passwords in encrypted
form and they had to figure

1410
01:01:26,494 ---> 01:01:27,824
out what those passwords for.

1411
01:01:27,824 ---> 01:01:30,844
We actually got into trouble for
this a few years ago because all

1412
01:01:30,844 ---> 01:01:32,764
of the sudden FAS
Computer Services saw

1413
01:01:32,764 ---> 01:01:38,904
like 50 people running a crack
program on nice.fas.Harvard.edu,

1414
01:01:39,174 ---> 01:01:41,704
so they now have been given a
heads up for programs like that.

1415
01:01:42,094 ---> 01:01:44,574
Last year students
implemented the game of 15.

1416
01:01:44,794 ---> 01:01:46,824
Not all that much fun to
play as a party favorite,

1417
01:01:46,824 ---> 01:01:48,484
moving the numbers
up down, left, right,

1418
01:01:48,584 ---> 01:01:50,114
but a real stepping stone

1419
01:01:50,114 ---> 01:01:52,194
to implementing something
interactive

1420
01:01:52,244 ---> 01:01:54,264
that involves a human
and the hacker edition

1421
01:01:54,264 ---> 01:01:56,654
for this one had students
implementing God mode,

1422
01:01:56,654 ---> 01:01:59,484
which actually solved
this thing for the human,

1423
01:01:59,484 ---> 01:02:02,594
maybe cheat mode is the
more apt term, in Sudoku,

1424
01:02:02,814 ---> 01:02:05,604
which was a step up toward that,
where we provided the students,

1425
01:02:05,604 ---> 01:02:08,384
you, with a framework
with a whole bunch of code

1426
01:02:08,384 ---> 01:02:11,184
that you needed to first
understand before taking things

1427
01:02:11,184 ---> 01:02:13,044
the final mile and
implementing some

1428
01:02:13,044 ---> 01:02:14,394
of the remaining functionality.

1429
01:02:14,644 ---> 01:02:17,034
And then we dabbled in
forensics and this grew

1430
01:02:17,034 ---> 01:02:20,444
out of a real world experience
between me and a friend.

1431
01:02:20,674 ---> 01:02:22,914
For this problem set last
year, this buddy and I,

1432
01:02:22,914 ---> 01:02:25,044
who he being a particularly
good photographer,

1433
01:02:25,284 ---> 01:02:29,604
strolled around campus and we
shot photographs of unique,

1434
01:02:29,774 ---> 01:02:33,484
non obvious, but
identifiable places on campus.

1435
01:02:33,484 ---> 01:02:34,904
And this was using
his digital camera.

1436
01:02:34,904 ---> 01:02:36,324
All of these JPEGs got stored

1437
01:02:36,324 ---> 01:02:37,854
on a digital flash
card or what not.

1438
01:02:38,134 ---> 01:02:40,754
And then I accidentally
formatting the thing,

1439
01:02:40,754 ---> 01:02:41,474
or erased it.

1440
01:02:41,584 ---> 01:02:44,514
Well, it turns out formatting
something or erasing something,

1441
01:02:44,514 ---> 01:02:45,914
usually means neither.

1442
01:02:45,914 ---> 01:02:48,134
It just means doing
a little bit of work

1443
01:02:48,254 ---> 01:02:50,374
to make the human think
their data has been erased,

1444
01:02:50,374 ---> 01:02:51,974
when in reality it hasn't.

1445
01:02:52,384 ---> 01:02:53,604
It's just been forgotten.

1446
01:02:53,934 ---> 01:02:56,624
And so we tasked last year's
students with writing a program

1447
01:02:56,624 ---> 01:03:01,214
in C to actually recover
these photos for my friend.

1448
01:03:01,214 ---> 01:03:03,294
We gave everyone a
forensic image, so to speak,

1449
01:03:03,294 ---> 01:03:06,104
a big file representing that
compact flash card, and they had

1450
01:03:06,104 ---> 01:03:08,114
to recover the several
dozen photographs.

1451
01:03:08,114 ---> 01:03:10,314
And they also had to solve
this little murder mystery.

1452
01:03:10,604 ---> 01:03:12,624
We provided folks
with this image here.

1453
01:03:13,714 ---> 01:03:17,384
Those of you who've seen
this before might be doing

1454
01:03:17,384 ---> 01:03:19,654
that squinting thing right now
where you're trying to look

1455
01:03:19,754 ---> 01:03:22,184
through the picture, well
you look pretty awkward,

1456
01:03:22,184 ---> 01:03:23,764
because this is not
a magic eye puzzle.

1457
01:03:23,764 ---> 01:03:25,314
This is just random red noise

1458
01:03:25,314 ---> 01:03:29,484
that actually has behind
it an actual message.

1459
01:03:29,484 ---> 01:03:33,844
And it turns out, I think
it was Colonel, let's see,

1460
01:03:33,844 ---> 01:03:35,014
I've got my little
solution here.

1461
01:03:35,014 ---> 01:03:36,724
Last year it was Colonel Mustard

1462
01:03:36,784 ---> 01:03:38,734
in the study with
the candlestick.

1463
01:03:38,884 ---> 01:03:41,634
And this was the murder
message recovered by students

1464
01:03:41,634 ---> 01:03:42,784
who wrote code to do so.

1465
01:03:42,784 ---> 01:03:44,694
And then in Problem
Set 6 last year.

1466
01:03:44,694 ---> 01:03:45,604
We challenged students

1467
01:03:45,604 ---> 01:03:48,504
with implementing the fastest
spell checker possible.

1468
01:03:48,504 ---> 01:03:49,414
What do we mean by that?

1469
01:03:49,774 ---> 01:03:54,054
Well, we handed the students
a big text file containing 140

1470
01:03:54,114 ---> 01:03:58,424
plus thousand English words,
and we said write a program

1471
01:03:58,424 ---> 01:04:01,914
that loads all of these words
into memory, but very quickly

1472
01:04:01,914 ---> 01:04:05,024
and very efficiently
can tell us yea or nay,

1473
01:04:05,214 ---> 01:04:08,274
is this document perfectly
spelled or are there errors?

1474
01:04:08,274 ---> 01:04:10,694
And what we provided was a
testing framework, a harness,

1475
01:04:11,004 ---> 01:04:14,144
that students, if they wanted
to compete, could run their code

1476
01:04:14,144 ---> 01:04:16,914
against some benchmarks,
against some testing programs

1477
01:04:16,944 ---> 01:04:17,604
that we wrote.

1478
01:04:17,814 ---> 01:04:20,394
And then, ranked on the
course's website from fastest

1479
01:04:20,394 ---> 01:04:23,274
to slowest were the
running times,

1480
01:04:23,424 ---> 01:04:25,614
the amount of time it took
for each student's code

1481
01:04:25,614 ---> 01:04:28,094
to actually execute,
complete opt in.

1482
01:04:28,094 ---> 01:04:29,274
It's by no means required.

1483
01:04:29,484 ---> 01:04:32,814
And we took a bullet for the
team and made sure that one

1484
01:04:32,814 ---> 01:04:35,694
of our own teaching fellows
intentionally, I think,

1485
01:04:35,694 ---> 01:04:37,294
was at the very bottom
of the list.

1486
01:04:37,694 ---> 01:04:39,204
So, there was definitely
a lower bound.

1487
01:04:39,204 ---> 01:04:41,984
But the odd, the funny
thing was we saw this

1488
01:04:41,984 ---> 01:04:45,734
in the cue guide evaluation,
this problem set of all things,

1489
01:04:45,974 ---> 01:04:48,764
was apparently the one that
people sunk the most time into.

1490
01:04:48,984 ---> 01:04:51,624
Not because it took any longer
than all the other p sets,

1491
01:04:51,854 ---> 01:04:54,444
but they would come back from
like dinner, look at the board,

1492
01:04:54,444 ---> 01:04:57,074
and realize dam my friend,
my roommate just ever

1493
01:04:57,074 ---> 01:04:59,984
so slightly inch higher than me
and so it incentivized people

1494
01:04:59,984 ---> 01:05:02,524
if only to one up their
friends and roommates.

1495
01:05:03,164 ---> 01:05:05,684
In Problem Set 7, last
year, we asked students

1496
01:05:05,684 ---> 01:05:08,964
to implement their own E*Trade
like website, whereby you had

1497
01:05:08,964 ---> 01:05:10,194
to create a website using

1498
01:05:10,194 ---> 01:05:12,864
that language call PHP
a database called mysql

1499
01:05:13,374 ---> 01:05:17,224
that actually lets people log
in and then manage a portfolio

1500
01:05:17,224 ---> 01:05:19,124
of stocks, buy stocks
quote unquote,

1501
01:05:19,204 ---> 01:05:21,344
sell stocks quote
unquote, get stock quotes.

1502
01:05:21,344 ---> 01:05:21,974
And from where?

1503
01:05:22,194 ---> 01:05:24,504
Well, we have the students;
we had the student patch

1504
01:05:24,504 ---> 01:05:27,394
into Yahoo Finance where they
grabbed merely the Real time

1505
01:05:27,394 ---> 01:05:29,974
stock quotes to actually
simulate the process

1506
01:05:30,334 ---> 01:05:31,844
of buying and trading stocks.

1507
01:05:31,844 ---> 01:05:35,004
Unfortunately some students,
perhaps some economics majors

1508
01:05:35,004 ---> 01:05:37,174
or just folks with too
much free time figured

1509
01:05:37,174 ---> 01:05:38,644
out last year how
to gain the system.

1510
01:05:38,904 ---> 01:05:41,414
So, even though we gave
everyone 10,000 virtual dollars,

1511
01:05:41,694 ---> 01:05:46,044
I think our winner turned
teaching fellow this year

1512
01:05:46,044 ---> 01:05:49,754
actually, right don't push them
away make them one of your own,

1513
01:05:49,894 ---> 01:05:52,634
for a billion dollars
something like that ridiculous.

1514
01:05:53,084 ---> 01:05:54,774
Turns out we weren't
really checking whether

1515
01:05:54,774 ---> 01:05:56,534
or not people were
trading after hours.

1516
01:05:56,794 ---> 01:06:00,204
And it turns out that also,
Yahoo stalk quotes are not

1517
01:06:00,204 ---> 01:06:02,044
in fact perfectly
Real time which means

1518
01:06:02,044 ---> 01:06:04,794
if you just have a real E*Trade
account you can see the future

1519
01:06:05,004 ---> 01:06:06,484
and see where the
stocks are going.

1520
01:06:06,484 ---> 01:06:06,551
[ Laughter ]

1521
01:06:06,551 ---> 01:06:11,974
So, apparently you can exploit
that if you put your mind to it.

1522
01:06:12,174 ---> 01:06:13,394
and then, in Problem Set 8,

1523
01:06:13,394 ---> 01:06:15,364
the course's final
problem set last year,

1524
01:06:15,614 ---> 01:06:18,744
we had students implement a mash
up where they take Google News

1525
01:06:18,744 ---> 01:06:22,514
and Google Maps and mash them
together using JavaScript,

1526
01:06:22,514 ---> 01:06:25,674
PHP and SQL in such a way
that they had a website

1527
01:06:25,674 ---> 01:06:27,724
that they could find
all of the local news

1528
01:06:27,724 ---> 01:06:31,174
from whether it's zip
code 02138 or 90210.

1529
01:06:31,174 ---> 01:06:34,334
And, you would actually pull
the local current even articles

1530
01:06:34,604 ---> 01:06:36,794
by this thing called
XML and integrate it

1531
01:06:36,794 ---> 01:06:38,434
into the view of a Google Map.

1532
01:06:38,904 ---> 01:06:42,404
And then, at very course's
end was the true climax

1533
01:06:42,404 ---> 01:06:42,954
of the course.

1534
01:06:42,984 ---> 01:06:45,174
This course culminates
in final projects,

1535
01:06:45,174 ---> 01:06:47,014
which ultimately will
be your opportunity

1536
01:06:47,014 ---> 01:06:49,894
to design your very own piece
of software, designed by you

1537
01:06:50,124 ---> 01:06:51,644
or two or three friends.

1538
01:06:51,824 ---> 01:06:55,594
And the course then climaxes
with the new and improved,

1539
01:06:55,594 ---> 01:06:59,024
with the second annual
computer science 50 fair

1540
01:06:59,024 ---> 01:07:01,084
which last year was an
exhibition across the street

1541
01:07:01,084 ---> 01:07:02,344
in one of the engineering
buildings

1542
01:07:02,594 ---> 01:07:06,484
with 300 laptops atop
tables, popcorn was popping,

1543
01:07:06,484 ---> 01:07:08,484
music was playing, stress balls

1544
01:07:08,484 ---> 01:07:10,774
with CS50's logo were
being thrown around.

1545
01:07:11,074 ---> 01:07:13,324
And this was an opportunity
for our 300 plus students

1546
01:07:13,324 ---> 01:07:16,364
to exhibit their final projects
not only to each other but also

1547
01:07:16,364 ---> 01:07:19,724
to some 900 attendees in total.

1548
01:07:19,724 ---> 01:07:21,774
And we also invited
some recruiters as well.

1549
01:07:21,774 ---> 01:07:24,044
So, that is what you have to
look forward in this course.

1550
01:07:24,234 ---> 01:07:27,024
You also have cake to look
forward to in the hallway.

1551
01:07:27,284 ---> 01:07:29,934
This is CS50 and we'll
see you on Friday.

1552
01:07:30,494 ---> 01:07:38,498
[掌声]