1
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>> David: Selamat Datang, nama saya
David malan dan ini CS50.

2
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Dan, ini bukan anda
khas sekolah tinggi komputer

3
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ilmu sahaja.

4
00:00:17,346 --> 00:00:19,276
Kursus ini sedikit
khusus sesuatu.

5
00:00:19,636 --> 00:00:20,936
Dan itu bukan kerana
Aku mengajarkannya.

6
00:00:20,936 --> 00:00:23,066
itu kerana ini adalah salah satu
dari, kita suka berfikir,

7
00:00:23,066 --> 00:00:27,206
mereka jarang program yang benar-benar
meramas otak anda begitu banyak

8
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dan anda begitu banyak jadual

9
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yang pada akhir semester anda
benar-benar merasa lebih pintar.

10
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Jadi, itu yang kurasakan

11
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ketika saya sendiri mengambil ini
Tentu saja kembali pada tahun 1996.

12
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Aku kerajaan besar

13
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pada saat di sini
Rumah tinggal di Mather.

14
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Dan, I.

15
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[Bersorak]

16
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Sebagai adalah lain,
lima orang lain di sana.

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Jadi, saya adalah kerajaan
utama pada ketika itu.

18
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Dan aku kerajaan besar

19
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kerana aku selalu
menyukai sejarah.

20
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Aku suka berperlembagaan
undang-undang di sekolah tinggi.

21
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Maka, aku memulakan jalan ini
mahasiswa baru tahun melakukan apa yang saya lakukan

22
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terbaik, melakukan apa yang aku tahu aku suka.

23
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Dan aku selalu
sedikit geek,

24
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Aku selalu mengoceh
dengan komputer.

25
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Tapi, aku sendiri, mungkin
ironisnya dalam retrospeksi,

26
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Aku akan selalu dilihat orang-orang yang
mengambil ilmu komputer

27
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di SMA saya, saya
teman-teman sebagai Geeks nyata.

28
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Namun, akhirnya itu, sophomore
tahun ini saya mengambil program kecil

29
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disebut CS50 yang sebenarnya
pernah takut pergi sendiri

30
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mahasiswa tahun.

31
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Dan aku pengguna
pembantu pada saat itu.

32
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Jadi, saya pasti
sudah berkelulusan, sekurang-kurangnya,

33
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berada di antara mereka, mereka Geeks

34
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siapa aku mengolok-olok
di sekolah tinggi.

35
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Tapi, saya takut.

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Ada, itu reputasi ini
pada masa dan mungkin masih

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di bahagian yang itu,
itu saja menakutkan.

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Itu banyak bekerja.

39
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Sulit dan belum, itu salah satu
hal-hal di mana, ya Tuhan,

40
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kulit jauh
lebih buruk daripada gigitannya.

41
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Aku mendapati diriku sophomore
tahun, untuk pertama kalinya,

42
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benar-benar termasuk kerja rumah menyenangkan.

43
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Dan aku tidak pernah berkata ini hanya
untuk pitch kursus ini untuk anda.

44
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ini adalah asli
realisasi bagi saya.

45
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Sekarang, saya kira, di salah satu
titik, aku melampaui batas

46
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untuk geekdum benar di mana saya
benar-benar digunakan untuk melihat ke depan

47
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untuk malam Jumaat kerana
Aku bisa bergelung di depan

48
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dari MacBook kecilku dan
bekerja pada masalah CS50's set.

49
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Jadi, pada saat itu, saya fikir saya
sudah jelas melanggar batas.

50
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Dan, kami tujuan dalam kursus ini
tidak untuk menukar kamu semua

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kepada orang itu,
tetapi, hanya untuk mengatakan

52
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bahawa ada sesuatu yang sedikit
khusus tentang kursus ini,

53
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khusus sedikit sesuatu
tentang ilmu komputer

54
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secara umum terutama
hari ini.

55
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Dan, semakin terbiasa kita
semua masuk ke teknologi,

56
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mainan banyak kita membawa
di dalam saku kami

57
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yang semuanya adalah komputer.

58
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Maksudku, iPhone sebenarnya
komputer berprestasi tinggi

59
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dari laptop saya masih kuliah.

60
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Anda boleh melakukan banyak rapi
hal dengan hal-hal ini.

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Dan sekarang, sebahagian besar
kami di bilik ini,

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mungkin hanya menggunakan orang lain
perisian, orang lain alat-alat,

63
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penyelesaian orang lain
masalah kerana kita pergi

64
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untuk iTunes, kita download
beberapa aplikasi dari kedai app

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dan Walla yang dapat kita lakukan
benar-benar rapi sesuatu.

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Namun, pada akhir
semester ini,

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Anda boleh menjadi orang yang
melakukan penyelesaian masalah.

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Anda boleh menjadi orang memecahkan
beberapa masalah, membina aplikasi yang,

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bahawa perisian,
alat yang bahawa, baik,

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satu hanya menghibur aku, menghibur anda.

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contohnya, kawalan,
berkata, iTunes library

72
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dari dengan apartemen anda
jelas sebuah aplikasi

73
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yang sudah ada atau anda boleh
mencari jadual yang lebih shuttle

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dengan contohnya.

75
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Jadi sebenarnya, salah satu
hal-hal pertama yang saya lakukan

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setelah mengambil CS50 adalah
lagi, itu mungkin

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pada saat ini Jumaat
malam dan malam Sabtu,

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ada kesempatan ini
pada saat itu

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mana Harvard
lari shuttle bus.

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Dan, hingga ke hari ini, mereka masih
telah dicetak jadual.

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Tapi, ada yang benar-benar tidak
bererti talian termasuk

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ketika pesawat ulang-alik seterusnya.

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Sekarang, saya tidak peduli,
kerana walaupun aku tinggal

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di Mather aku tidak di antara mereka
yang umumnya memuat ulang-alik.

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Tapi, saya punya banyak teman
di Pfoho misalnya.

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Dan salah satu dari mereka bertanya kepada saya,
Aku berfikir dalam pada satu titik.

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[Bersorak]

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Oke Pfoho lebih baik
dari Mather rupanya.

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Jadi, salah satu teman saya jenis

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yang membuat saya berfikir mungkin aku bisa
menulis sebuah program kecil untuk jenis

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bantuan teman-teman saya cek
jadual shuttle.

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Dan demikianlah lahir
canggung bernama anak shuttle,

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ini adalah sebahagian daripada leksikon yang
tinggal di beberapa nombor

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tahun sekurang-kurangnya di antara
beberapa senior.

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Pada waktu itu, ini adalah ini
program baris perintah kecil

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sama dalam semangat untuk Dos.

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Itu berjalan di
persekitaran UNIX.

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Jadi, tidak terlalu seksi sama sekali.

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Anda hanya menaip beberapa
perintah dan memberitahu anda

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ketika pengangkutan itu.

101
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Well, ini hari ini adalah
sedikit lebih canggih.

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Dan, itu sebenarnya diwakili
dari tepat jenis

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projek yang mahasiswa
di akhir program

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sampai akhir keputusan oleh istilah.

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Jadi, ini adalah versi empat, beberapa
15 tahun kemudian, dari Shuttleboy.

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Sepertinya Google Maps
menjadi agak lambat di sana.

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Tapi, bagi anda yang mempunyai
untuk keluar dari sini selepas kelas

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dan pergi, berkata, dari
Memorial Hall dan perlu

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untuk pergi ke, katakanlah, Quad itu.

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Nah, anda boleh meninggalkan
dalam dua minit jika oleh,

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ini benar-benar tidak
bekerja untuk anda hanya belum,

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atau anda mempunyai banyak lain
Pilihan seperti yang mungkin anda sukai.

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Dan, akan datang, kita dapat
pitch ini dari CS50,

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itu akan sama
kemampuan melalui SMS.

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Anda boleh teks Shuttleboy
melalui telefon.

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Anda menyebut Shuttleboy.

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CS50 nombor telefon
tahun ini, well,

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luar biasa ini
sedia, 617-BUG-CS50.

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Jadi, yang akan segera debut.

120
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Jadi jangan menyebutnya hanya

121
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tapi karena aku sudah
ditegur untuk mendapatkan,

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sekarang ini sedang diarahkan

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mengajar kepala sistem kami
orang itu telefon.

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Jadi, anda hanya akan membawanya
jika anda mempunyai soalan

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tentang jadual kapal sekarang.

126
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Tapi, yang akan segera
dilaksanakan.

127
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Jadi, lain hal, sebenarnya, bahawa
kita sendiri menghabiskan musim panas ini

128
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pada benar-benar dalam persiapan untuk
semester ini adalah sejumlah besar

129
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masalah lain yang
kami ingin menyelesaikan.

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Sebagai contoh, ada
keseluruhan banyak hal yang terjadi

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di kampus ini
pada hari tertentu.

132
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Dan sebenarnya, menempatkan lain
cara, ada jauh

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hal terjadi di kampus ini

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bahawa saya pasti pernah
memanfaatkan.

135
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Dan, walaupun aku sekarang
kewalahan dengan berapa banyak hal

136
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yang terjadi, di kampus,

137
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Aku masih tampak tak pernah
untuk mencari masa.

138
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Tapi, Walla, bahkan
ada, kuliah CS50's.

139
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Itu di mana anda adalah, jadi ini
, Ini adalah program kami menulis

140
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untuk semua agregat
peristiwa di kampus.

141
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Dan ini telah
sesuatu yang lain pelajar

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dalam program yang sama telah
menangani sendiri.

143
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Dan, kami telah bekerja dengan
entiti lain di kampus

144
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untuk benar-benar membuat hal ini terjadi.

145
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Tapi titik untuk CS50
istilah ini adalah bahawa semua

146
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program-program kecil kita
telah bekerja pada apakah ini

147
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atau apakah pertama untuk menggabungkan
semua berita Harvard

148
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di satu tempat, semua
Google News,

149
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semua hal-hal ini akan
untuk memiliki apa yang disebut API's,

150
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pengaturcaraan aplikasi
interface.

151
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Dan ini hanya bintang
kemampuan berbicara

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membiarkan orang lain,
orang di ruangan ini,

153
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benar-benar melakukan sesuatu
dengan data yang sama.

154
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Jadi, dengan syarat akhir, jika anda memutuskan

155
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untuk melaksanakan tugas akhir
berkaitan dengan berita atau peristiwa

156
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atau peta, baik kita, di
sekurang-kurangnya sebagai kursus,

157
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akan membuat semua lebih
dengan tahun ini dengan menyediakan anda

158
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dengan antara muka; semacam
fungsi, sehingga untuk berbicara,

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perisian yang anda boleh gunakan dalam
projek anda sendiri untuk pergi di atas

160
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dan seterusnya di mana pelajar,
mungkin, sudah di masa lalu

161
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kerana rangka kerja ini telah
tidak berada di tempat bagi mereka.

162
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Dan sekali lagi, ini semua
bermula, setidaknya untuk saya,

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sekitar 15 tahun yang lalu
melaksanakan Shuttleboy.

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Saya kemudian diemail saya
kawan Ken di Pfoho.

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Aku berkata hei bagaimana menurutmu?

166
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Adakah ini berguna?

167
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Dia dihantar keluar pada
Pfoho membuka pendaftaran dan Walla,

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bertahun-tahun kemudian aku
tampaknya masih memerah susu

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projek ini.

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Dan hal rapi tentang itu,
dan ini adalah di mana terlalu kursus

171
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seperti ini dalam kejuruteraan dan
ilmu komputer, saya pikir,

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sedikit khusus, adalah bahawa,
apabila anda melakukan pekerjaan rumah anda

173
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dan ketika anda melakukan kerja anda
dalam kursus ini, anda tahu,

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banyak dari mereka, ya, anda akan meletakkan
sebelah dan tidak benar-benar menggunakan.

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Namun, sebahagian, anda akan.

176
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Dan ini benar-benar ada
kuat hal, setidaknya untuk saya,

177
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hal yang sangat menarik,
apabila anda membuat sesuatu

178
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dan orang lain benar-benar peduli,
orang lain tidak hanya tersenyum

179
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dan menepuk anda pada
kembali dan kemudian pergi semacam

180
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tentang kehidupan mereka sendiri.

181
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Mereka benar-benar menggunakan apa yang anda buat
dalam kehidupan mereka walaupun

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untuk sesuatu yang konyol atau
sesederhana hanya mencari

183
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ketika mereka boleh keluar dari sini

184
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untuk menangkap seterusnya
shuttle ke Quad.

185
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Jadi, dengan istilah akhir, itu salah satu
tujuan program ini;

186
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untuk memberdayakan kamu hanya
mengenalpasti beberapa masalah apakah

187
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itu di kampus atau
mudah-mudahan baik luar kampus,

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dan benar-benar menggunakan sendiri
kemahiran, anda sendiri fikiran dan menyelesaikan

189
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bahawa masalah di beberapa
bahagian, teknologi.

190
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Jadi, ini juga kursus
seperti yang kita katakan dalam silabus

191
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dan program rasmi
keterangan yang mengajari anda bagaimana

192
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untuk berfikir dan mengajarkan anda bagaimana

193
00:07:37,416 --> 00:07:39,286
untuk menyelesaikan masalah
lebih efisien.

194
00:07:39,536 --> 00:07:40,356
Nah, apa artinya?

195
00:07:40,356 --> 00:07:42,476
Yah, kalau kau punya 600
megahertz di saku anda

196
00:07:42,476 --> 00:07:44,356
atau tiga gigahertz
bawah meja anda di rumah,

197
00:07:44,646 --> 00:07:47,056
Anda boleh menyelesaikan banyak
masalah cekap hanya

198
00:07:47,096 --> 00:07:48,336
oleh kekerasan luncurkan.

199
00:07:48,616 --> 00:07:50,526
Tapi, ada banyak
masalah di dunia ini,

200
00:07:50,766 --> 00:07:54,156
apakah itu akan mencari,
berkata, Facebook rangkaian

201
00:07:54,156 --> 00:07:55,756
atau internet melalui Google,

202
00:07:55,756 --> 00:07:58,706
bahawa tidak peduli seberapa segera
komputer tertentu anda,

203
00:07:58,706 --> 00:08:00,866
tidak ada cara di neraka anda
akan bilion carian

204
00:08:00,866 --> 00:08:03,886
laman web dengan cepat kecuali
Anda benar-benar pendekatan ini

205
00:08:03,886 --> 00:08:05,496
masalah cerdas.

206
00:08:05,496 --> 00:08:06,916
Anda tidak hanya mencari,
contohnya,

207
00:08:06,916 --> 00:08:09,876
pendaftaran besar dari semua web
laman di bumi dari atas

208
00:08:09,876 --> 00:08:11,876
melihat ke bawah
untuk sesuatu yang berkaitan

209
00:08:11,876 --> 00:08:14,776
untuk istilah carian apa pun yang anda
cari mudah-mudahan Google

210
00:08:14,776 --> 00:08:17,006
dan mungkin Google
dan Facebook dan setiap

211
00:08:17,006 --> 00:08:19,476
ini entiti besar mempunyai
banyak orang pintar berfikir

212
00:08:19,476 --> 00:08:21,856
tentang bagaimana mereka dapat
mencari data lebih cepat,

213
00:08:22,106 --> 00:08:24,626
bagaimana mereka boleh memproses maklumat
lebih efisien, dan,

214
00:08:24,656 --> 00:08:27,196
bagaimana mereka bisa saja umum
memberikan hasil lebih cepat

215
00:08:27,456 --> 00:08:28,266
sehingga yang anda boleh lakukan belum,

216
00:08:28,266 --> 00:08:30,546
yang lebih menarik hal-hal
dengan peranti tersebut.

217
00:08:30,546 --> 00:08:33,916
Jadi, apa yang kita maksud, walaupun,
oleh bagaimana, mengajar orang bagaimana

218
00:08:33,916 --> 00:08:36,526
untuk berfikir lebih hati-hati,
lebih algorithmically.

219
00:08:36,756 --> 00:08:39,686
Well, ini sedikit visual
tampaknya selalu pergi lebih baik.

220
00:08:39,686 --> 00:08:40,816
Dan, tampaknya menjadi kenangan.

221
00:08:40,926 --> 00:08:43,126
Dan Aku bahkan bertanya saja
terakhir oleh bekas pelajar,

222
00:08:43,126 --> 00:08:45,466
oh yang anda akan lakukan
hal buku telefon lagi.

223
00:08:45,466 --> 00:08:48,896
Dan aku cukup banyak di tempat
memutuskan baik pasti kita akan membina

224
00:08:48,896 --> 00:08:49,646
hal buku telefon.

225
00:08:49,646 --> 00:08:52,266
Dan dia bertanya kapan anda
merobek dalam setengah benar,

226
00:08:52,636 --> 00:08:55,006
Aku seperti juga yeah teknikal
merobek kita menjadi dua, tetapi tidak

227
00:08:55,006 --> 00:08:58,056
di jalan, di komputer
ilmu cara saya akan dapat

228
00:08:58,056 --> 00:08:59,366
untuk merobek hal di setengah.

229
00:08:59,366 --> 00:09:02,426
Jadi, di sini masalahnya
bahawa kita dihidangkan untuk beberapa waktu.

230
00:09:02,426 --> 00:09:03,336
Jadi, inilah buku telefon.

231
00:09:03,336 --> 00:09:05,366
It's got setidaknya
ribu atau lebih halaman.

232
00:09:05,616 --> 00:09:08,296
Dan tujuan mudah di tangan
dunia yang sangat nyata adalah untuk mencari,

233
00:09:08,616 --> 00:09:09,806
berkata, orang di sini.

234
00:09:09,806 --> 00:09:12,586
Jadi, Mike Smith, terkini
nama bermula dengan S. Jadi,

235
00:09:12,586 --> 00:09:14,416
Aku seorang manusia biasa, aku
mengambil buku telefon.

236
00:09:14,416 --> 00:09:17,156
Dan orang di luar sana, apa
anda akan, orang yang khas,

237
00:09:17,156 --> 00:09:19,856
lakukan untuk mula mencari Mike
Smith, jelas tidak tahu

238
00:09:19,856 --> 00:09:21,816
dahulu apa laman
dia sebenarnya pada.

239
00:09:22,346 --> 00:09:26,096
Benar, supaya anda pergi kasar
di tengah, kanan.

240
00:09:26,096 --> 00:09:29,956
Dan pada saat ini dalam cerita,
Aku mungkin di N atau M's,

241
00:09:29,956 --> 00:09:32,006
Anda tahu, kira-kira setengah
cara melalui buku telefon.

242
00:09:32,356 --> 00:09:34,646
Ternyata, kali terakhir saya melakukannya
contoh ini saya bisa menemukan

243
00:09:34,646 --> 00:09:36,056
diriku di bahagian pendamping.

244
00:09:36,056 --> 00:09:38,646
Jadi, itu sebenarnya tidak sama
seimbang antara A sampai M

245
00:09:38,646 --> 00:09:41,646
dan N melalui Z. Tapi, hari ini,
kita, pada kenyataannya, di M's,

246
00:09:41,956 --> 00:09:43,116
alright begitu, sekarang aku di M's.

247
00:09:43,176 --> 00:09:44,576
Tapi apa Takeaway saya sekarang hanya

248
00:09:44,576 --> 00:09:46,006
sebagai manusia normal
off dari jalan?

249
00:09:46,046 --> 00:09:47,306
Di mana saya pergi selanjutnya
untuk Mike Smith.

250
00:09:48,026 --> 00:09:51,736
[Terdengar] Dan demikian, hanya
mungkin pada setengah ini, ke kanan,

251
00:09:51,736 --> 00:09:55,886
kerana S datang selepas M. Dengan demikian,
terletak sini drama visual.

252
00:09:55,886 --> 00:09:57,896
Itu tidak benar-benar
merobek-robek menjadi dua, kanan.

253
00:09:57,896 --> 00:09:58,956
Aku agak curang
ke pusat.

254
00:09:59,236 --> 00:10:02,986
Tapi, kita sekarang tahu bahawa Mike
setidaknya tidak di setengah itu.

255
00:10:03,086 --> 00:10:06,196
Kami benar-benar dapat membuang
setengah dari masalah itu.

256
00:10:06,196 --> 00:10:08,676
Dan aku pergi dengan masalah
yang mendasar masih

257
00:10:08,676 --> 00:10:10,906
hal yang sama, termasuk Mike
Smith dalam sebuah buku yang sangat besar.

258
00:10:11,096 --> 00:10:12,996
Tapi, masalahnya adalah
sekarang setengah besar.

259
00:10:12,996 --> 00:10:15,666
Kalau seribu halaman
sebelum, sekarang punya 500.

260
00:10:15,866 --> 00:10:17,416
Kau tahu apa, aku boleh melakukan
hal yang sama lagi.

261
00:10:17,596 --> 00:10:20,426
Aku bisa jenis secara rekursif atau
berkali-kali melakukan hal yang sama.

262
00:10:20,696 --> 00:10:24,856
Sekarang aku tidak cukup pada
S. Aku ada di T. Dengan demikian,

263
00:10:24,856 --> 00:10:26,246
oh aku pergi terlalu jauh.

264
00:10:26,246 --> 00:10:30,126
Tapi, saya tahu sekarang bahawa Mike
tidak ke kanan, akan ada

265
00:10:30,126 --> 00:10:32,216
menjadi beberapa kelas suatu hari di mana
Aku hanya tidak bisa robek hal bendungan,

266
00:10:32,216 --> 00:10:32,486
Aku yakin.

267
00:10:32,726 --> 00:10:34,666
Tapi sekarang, aku tahu dia
tidak ke kanan.

268
00:10:34,896 --> 00:10:36,646
Jadi, sekarang masalahnya
telah empat.

269
00:10:36,646 --> 00:10:39,706
Jadi, saya sudah pergi dari
ribu untuk 500-250 halaman.

270
00:10:39,706 --> 00:10:41,976
Dan lagi, jika anda meneruskan
logik, meneruskan matematik,

271
00:10:42,236 --> 00:10:44,136
Aku memotong ini
masalah dalam setengah, setengah,

272
00:10:44,416 --> 00:10:47,896
setengah sampai akhirnya aku baik
akan tidak termasuk Smith

273
00:10:47,896 --> 00:10:51,196
sama sekali, tidak mungkin, atau aku akan
untuk mencari satu yang saya cari.

274
00:10:51,316 --> 00:10:53,476
Tapi, itu, kemudian, memunculkan
soalan, apakah ini lebih baik

275
00:10:53,476 --> 00:10:57,606
berbanding dengan pendekatan mudah saja
berkata, Anda tahu, A, nope, B,

276
00:10:57,606 --> 00:11:00,566
tidak ada, bermula dari kiri ke kanan
akan linier melalui buku?

277
00:11:00,756 --> 00:11:01,776
Well, secara naluriah ya.

278
00:11:01,916 --> 00:11:03,246
Ini akan jauh lebih cepat.

279
00:11:03,526 --> 00:11:04,326
Tapi, berapa banyak?

280
00:11:04,856 --> 00:11:09,056
Nah, jika saya mempunyai laman seribu
buku telefon atau katakanlah 1.024

281
00:11:09,056 --> 00:11:10,746
bagi anda yang
seperti kekuatan dari dua,

282
00:11:10,966 --> 00:11:13,446
berapa banyak masa yang boleh saya
harus membagi masalah ini

283
00:11:13,446 --> 00:11:16,326
setengah sebelum mendapati
Mr Smith?

284
00:11:17,176 --> 00:11:17,276
>> Sepuluh.

285
00:11:17,686 --> 00:11:18,826
>> David: Jadi, sepuluh, benar.

286
00:11:18,826 --> 00:11:22,746
Jika anda mempunyai 1.024 halaman dan anda
membaginya menjadi dua, dua,

287
00:11:22,746 --> 00:11:24,926
setengah, setengah, saya melakukannya
sepuluh kali yang bermaksud aku pergi

288
00:11:24,926 --> 00:11:27,346
1,000 laman ke
orang yang saya cari

289
00:11:27,346 --> 00:11:29,096
untuk di laman ternyata hanya sepuluh.

290
00:11:29,096 --> 00:11:31,076
Dan yang agak rapi,
tetapi, anda tahu, jika anda berfikir

291
00:11:31,076 --> 00:11:32,426
tentang hal ini anda telah melakukan
ini semua kehidupan anda.

292
00:11:32,426 --> 00:11:33,246
Ini bukan yang dramatik.

293
00:11:33,386 --> 00:11:35,826
Tapi sekarang, bahawa buku telefon
tidak hanya untuk Boston,

294
00:11:35,826 --> 00:11:38,036
itu untuk semua
AS atau seluruh dunia

295
00:11:38,036 --> 00:11:40,616
dan hal ini
milyaran halaman di dalamnya,

296
00:11:40,706 --> 00:11:43,436
jadi bayangkan sebuah buku telefon
dengan empat bilion halaman.

297
00:11:43,776 --> 00:11:47,176
Berapa banyak membalik halaman saya
harus dilakukan secara maksimum

298
00:11:47,176 --> 00:11:50,196
untuk mencari Mike Smith
empat bilion laman buku telefon?

299
00:11:50,196 --> 00:11:52,196
>> Log base dua.

300
00:11:52,446 --> 00:11:53,606
>> David: Jadi yeah,
jika anda jenis

301
00:11:53,606 --> 00:11:55,406
jenis matematik
ini adalah log base dua.

302
00:11:55,406 --> 00:11:56,936
Tapi, jika anda berfikir empat
bilion menjadi dua bilion

303
00:11:56,936 --> 00:11:58,626
untuk satu bilion, sehingga
setengah bilion.

304
00:11:58,626 --> 00:12:01,556
Maksudku, yang benar-benar
pergi whittles sendiri

305
00:12:01,556 --> 00:12:02,706
down pretty darn segera.

306
00:12:02,706 --> 00:12:05,796
Bahkan dengan 32 halvings
dari buku telefon bahkan

307
00:12:05,796 --> 00:12:08,326
daripada empat bilion, saya akan
turun ke satu halaman.

308
00:12:08,326 --> 00:12:10,226
Dan saat itulah hal ini
semakin kuat, saya pikir.

309
00:12:10,226 --> 00:12:12,146
Itulah saat ini
mendapatkan idea-idea menarik

310
00:12:12,146 --> 00:12:14,436
apabila anda boleh mempunyai empat
bilion laman masalah

311
00:12:14,676 --> 00:12:18,376
dan dalam 32 langkah anda dapat mencari
orang yang anda cari.

312
00:12:18,476 --> 00:12:21,746
Dan, itulah yang kita maksud ketika
kita mengatakan bahawa anda akan belajar bagaimana

313
00:12:21,746 --> 00:12:23,986
untuk berfikir lebih hati-hati,
lebih algorithmically,

314
00:12:23,986 --> 00:12:25,776
lebih cerdas
tentang menyelesaikan masalah.

315
00:12:25,986 --> 00:12:28,266
Dan kembali sangat besar ketika
Anda benar-benar boleh melakukan ini,

316
00:12:28,266 --> 00:12:29,856
dan lagi, untuk ini
titik googles

317
00:12:29,856 --> 00:12:31,756
dunia yang Facebooks
yang mewah

318
00:12:31,756 --> 00:12:33,126
mempunyai dataset besar.

319
00:12:33,456 --> 00:12:35,486
Anda harus pendekatan
masalah ini

320
00:12:35,486 --> 00:12:38,726
dengan cara ini dinyatakan itu
hanya tidak akan berjaya.

321
00:12:39,136 --> 00:12:43,016
Nah, apa yang membuat
mahasiswa benar-benar ingat?

322
00:12:43,676 --> 00:12:46,436
Aku, kami ingin melakukan hal-hal yang
yang sedikit kadang-kadang konyol

323
00:12:46,436 --> 00:12:47,676
untuk jenis menghilangkan kegembiraan

324
00:12:47,676 --> 00:12:50,166
dari apa yang dinyatakan
banyak bahan-bahan baru.

325
00:12:50,166 --> 00:12:53,166
Jadi, dia benar-benar, ini
bekas pelajar mengutus aku link ini

326
00:12:53,166 --> 00:12:56,016
yang saya pergi ke depan, hanya untuk
menendang dan kemudian menyesalinya

327
00:12:56,016 --> 00:12:58,306
pada akhirnya, menarik
di utube di sini.

328
00:12:58,306 --> 00:13:01,366
Jadi, saya fikir saya akan berkongsi apa
seorang saintis non-komputer bermaksud

329
00:13:01,366 --> 00:13:03,736
ketika dia air mata buku telefon
setengah.

330
00:13:04,516 --> 00:13:25,959
[Tertawa]

331
00:13:26,459 --> 00:13:47,902
[Diam]

332
00:13:48,402 --> 00:14:09,845
[Tak terdengar]

333
00:14:10,346 --> 00:14:15,396
>> Kau tahu lebih dari 200 halaman, bagus
garis yang bersih, air mata yang sah.

334
00:14:15,696 --> 00:14:17,696
[Tertawa]

335
00:14:17,996 --> 00:14:22,186
>> David: Jadi, saya kira,
jalan bekerja terlalu.

336
00:14:22,186 --> 00:14:27,216
Jadi, apa yang saya keluar dari ini
Tentu saja bertahun-tahun yang lalu

337
00:14:27,426 --> 00:14:30,316
ya, Shuttleboy, dan kemudian ya
gelaran sarjana dalam ilmu komputer,

338
00:14:30,346 --> 00:14:31,976
dan kemudian ya sebuah PHD
dalam ilmu komputer.

339
00:14:31,976 --> 00:14:32,976
Dan bukan itu yang kita cuba

340
00:14:32,976 --> 00:14:34,706
untuk menukar sebahagian besar pelajar
dalam kursus ini ke dalam.

341
00:14:34,706 --> 00:14:37,186
Sebahagian besar dari anda dalam
Tentu saja tidak akan pergi

342
00:14:37,186 --> 00:14:39,056
pada besar dalam ilmu komputer.

343
00:14:39,056 --> 00:14:40,686
Beberapa dari anda mungkin
kecil, tapi untuk beberapa

344
00:14:40,686 --> 00:14:42,146
daripada anda ini akan
kursus terminal.

345
00:14:42,146 --> 00:14:44,856
Dan itu baik-baik saja
kerana program ini adalah, pada kenyataannya,

346
00:14:44,856 --> 00:14:47,956
berstruktur dengan cara di mana
bahkan jika anda hanya membayar yuran anda

347
00:14:47,956 --> 00:14:49,986
selama beberapa bulan dan
Anda benar-benar fokus dalam

348
00:14:49,986 --> 00:14:53,746
dan anda benar-benar memuat sebanyak
keluar dari program ini seperti yang anda boleh,

349
00:14:53,996 --> 00:14:56,256
Anda akan, pada kenyataannya,
dilengkapi dengan baik untuk kembali

350
00:14:56,336 --> 00:14:59,056
untuk dunia anda ekonomi,
biologi, psikologi,

351
00:14:59,056 --> 00:15:02,326
diterapkan matematik, dan benar-benar
memanfaatkan apa yang akhirnya

352
00:15:02,516 --> 00:15:04,806
sebagai sebuah program yang menarik
sebagai kami berharap dapat konseptual

353
00:15:05,016 --> 00:15:07,426
karena secara fundamental
praktikal.

354
00:15:07,876 --> 00:15:11,056
Dan itu juga adalah sesuatu yang
mungkin agak jarang dijumpai.

355
00:15:11,056 --> 00:15:13,306
Saya pikir saya mau berbagi beberapa
Komen bahawa pelajar

356
00:15:13,306 --> 00:15:16,736
dari musim gugur yang lalu dimasukkan ke dalam ini
Manual isyarat tahun terakhir ketika ditanya

357
00:15:16,736 --> 00:15:18,766
tentang apa yang ingin anda
untuk memberitahu para calon mahasiswa.

358
00:15:18,766 --> 00:15:20,386
Nah, jika anda belum
melihat ulasan ini,

359
00:15:20,386 --> 00:15:23,166
kata seorang mahasiswa program ini
akan memakan masa yang lumayan

360
00:15:23,166 --> 00:15:23,786
masa anda up.

361
00:15:24,066 --> 00:15:26,966
tetapi, jika anda memasukkan karya anda ke
seluruh dunia baru, secara keseluruhan,

362
00:15:26,966 --> 00:15:30,156
jika anda meletakkan pekerjaan, jika anda
menempatkan pekerjaan ke dalam, baik,

363
00:15:30,156 --> 00:15:33,906
jadi ini adalah tata bahasa nya bukan milikku,
jadi jika anda menaruh, dimasukkan ke dalam kerja,

364
00:15:33,906 --> 00:15:36,176
seluruh dunia baru
akan terbuka kepada anda.

365
00:15:36,176 --> 00:15:39,276
Amazing betapa aku
belajar hanya dalam 12 minggu.

366
00:15:39,736 --> 00:15:42,606
Seorang murid lain menulis,
Anda lebih baik mengambil ini

367
00:15:42,606 --> 00:15:43,686
atau anda akan menyesalinya.

368
00:15:44,056 --> 00:15:48,196
Lain menulis, lebih sedikit
terus terang, ia akan menendang bokongmu

369
00:15:48,196 --> 00:15:49,296
dan membuat anda merasa besar.

370
00:15:49,886 --> 00:15:53,596
Dan akhirnya, yang satu ini
mungkin sesuatu yang saya hanya boleh

371
00:15:53,596 --> 00:15:56,976
menunjukkan secara bertulis, namun,
kedua dari bawah sini.

372
00:15:57,516 --> 00:16:03,626
[Tertawa]

373
00:16:04,126 --> 00:16:06,436
Jadi, aku tidak yakin apakah
Anda punya banyak teman

374
00:16:06,436 --> 00:16:08,866
yang mengambil kursus ini tapi kami
semacam melakukan banyak kerosakan

375
00:16:08,866 --> 00:16:10,716
untuk pelajar tahun lalu.

376
00:16:10,806 --> 00:16:14,166
Kami diperkenalkan, di awal,
beberapa kuliah, seorang beberapa kuis,

377
00:16:14,166 --> 00:16:16,426
sebuah set beberapa masalah,
idea ini lolcats.

378
00:16:17,416 --> 00:16:19,066
Anda tidak dapat melihat apa
Aku bisa lihat di sini

379
00:16:19,066 --> 00:16:21,306
tapi suatu saat anda akan melihat
seorang pemuda bernama kucing bahagia

380
00:16:21,956 --> 00:16:25,076
yang merupakan pemimpin
yang Lolcat disebut.

381
00:16:25,076 --> 00:16:27,116
Ini adalah salah satu
bodoh ke depan internet

382
00:16:27,116 --> 00:16:30,546
yang menurut saya terus terang
dikotomi yang

383
00:16:30,546 --> 00:16:32,996
antara dua lelaki
di sini dan apa yang kita sekarang mempunyai

384
00:16:32,996 --> 00:16:34,126
pada paparan adalah mungkin.

385
00:16:34,126 --> 00:16:34,193
[Tertawa]

386
00:16:34,193 --> 00:16:40,856
Salah satu yang paling tepat
menggunakan teater ini sampai saat ini.

387
00:16:41,024 --> 00:16:44,604
Dan, kenapa tidak kita membuat sedikit
lebih nyata sedikit lebih peribadi

388
00:16:44,604 --> 00:16:48,494
idea ini benar-benar menyelesaikan
masalah yang lebih efisien.

389
00:16:48,494 --> 00:16:51,614
Masalah sederhana pada hari pertama
setiap sekolah untuk duduk

390
00:16:51,694 --> 00:16:53,734
atau berdiri dan mula
menghitung pelajar,

391
00:16:53,734 --> 00:16:55,054
roll kanan panggilan macam.

392
00:16:55,054 --> 00:16:57,044
Nah, yang paling naif
tapi tetap,

393
00:16:57,044 --> 00:17:01,054
amat benar pendekatan bahawa
guru boleh turun adalah satu, dua,

394
00:17:01,104 --> 00:17:03,454
tiga, empat, lima, enam, tujuh,

395
00:17:03,454 --> 00:17:05,014
dan kami akan berada di sini
beberapa waktu.

396
00:17:05,234 --> 00:17:07,274
Jadi, apa yang marjinal
perbaikan ini bahkan

397
00:17:07,274 --> 00:17:08,374
bahawa anda mungkin
dilakukan sebagai anak-anak?

398
00:17:08,374 --> 00:17:09,904
Bagaimana anda mengira orang lebih cepat?

399
00:17:11,064 --> 00:17:12,894
Dan, jangan mula membaca
dari Arahan saya sendiri?

400
00:17:13,324 --> 00:17:14,404
Apa yang akan anda
dilakukan sebagai anak-anak?

401
00:17:14,774 --> 00:17:18,484
Mulai menghitung berpasangan, ke kanan,
seperti jadi aku cukup bagus di dua,

402
00:17:18,484 --> 00:17:19,914
empat, enam, lapan, sepuluh, 12.

403
00:17:20,104 --> 00:17:22,094
Jadi, itu adalah sesuatu
menarik betul.

404
00:17:22,154 --> 00:17:24,634
Jadi, banyak yang bagaimana
perbaikan adalah bahawa di sana?

405
00:17:26,074 --> 00:17:27,444
Jadi, ini jelas
faktor dua.

406
00:17:27,444 --> 00:17:29,004
Butuh waktu setengah banyak masa.

407
00:17:29,184 --> 00:17:31,234
Tapi, anda tahu apa, kerana kami akan
mencari sepanjang semester ini,

408
00:17:31,584 --> 00:17:34,754
masalah besar, seperti mempercepat anda
waktu berjalan hanya dengan faktor

409
00:17:34,754 --> 00:17:36,674
dua adalah tidak semua
yang menarik

410
00:17:36,674 --> 00:17:38,904
kerana analog di sini
di dunia komputer

411
00:17:38,904 --> 00:17:41,314
bahawa aku adalah aku CPU
komputer, baik sih,

412
00:17:41,314 --> 00:17:43,604
jika aku hanya menunggu 12
bulan, 18 bulan,

413
00:17:43,604 --> 00:17:46,374
Aku komputer hanya akan menjadi
boleh secara alami, dengan nombor

414
00:17:46,374 --> 00:17:48,174
dari gigahertz saya
dalam diriku untuk dapat

415
00:17:48,174 --> 00:17:49,884
untuk mengira orang di
bilik ini lebih cepat.

416
00:17:50,094 --> 00:17:54,064
Jadi, ini macam, jenis ini
dari speedups linier seperti faktor

417
00:17:54,064 --> 00:17:57,064
dua faktor tiga, bahkan
faktor sepuluh, siapa yang peduli?

418
00:17:57,064 --> 00:17:59,334
Benar, kita dapat membuang
masalah hardware.

419
00:17:59,334 --> 00:18:00,354
Kita boleh menunggu hal-hal yang keluar.

420
00:18:00,354 --> 00:18:01,764
Kita bisa mengembangkan mesin lebih cepat.

421
00:18:01,994 --> 00:18:04,544
Tapi, intelektual, yeah
yang agak cerdas

422
00:18:04,604 --> 00:18:06,564
tetapi tidak benar-benar
perubahan fundamental

423
00:18:06,564 --> 00:18:07,124
masalah.

424
00:18:07,124 --> 00:18:09,814
Aku masih akan dari kiri
ke kanan, depan ke belakang.

425
00:18:10,034 --> 00:18:11,404
Ini benar-benar algoritma yang sama.

426
00:18:11,404 --> 00:18:12,924
Tapi, saya menawarkan bahawa
kita bisa berbuat lebih baik.

427
00:18:12,924 --> 00:18:14,654
Kita boleh melakukan lebih cerdas dari ini

428
00:18:14,654 --> 00:18:18,104
dan melakukan mendasar merupakan
pelaksanaan lebih cepat.

429
00:18:18,104 --> 00:18:19,204
Tapi, untuk menunjukkan ini,

430
00:18:19,494 --> 00:18:21,444
kami memerlukan anda untuk humor
kita hanya sesaat.

431
00:18:21,684 --> 00:18:22,684
Dan di titik ini

432
00:18:22,684 --> 00:18:25,164
dimana akan aku berbicara
kurang dan anda berbicara lebih.

433
00:18:25,164 --> 00:18:27,704
Tapi aku ingin kau
menjalankan langkah pertama bersama-sama,

434
00:18:27,704 --> 00:18:30,164
yang jika anda akan
humor kami, sila berdiri.

435
00:18:31,634 --> 00:18:34,494
Penggunaan di sini, di
papan, anda tahu adalah, oke,

436
00:18:34,494 --> 00:18:36,514
beberapa dari anda telah
untuk duduk.

437
00:18:37,284 --> 00:18:41,404
Sesungguhnya orang-orang di belakang,
sana kita pergi, baik-baik saja.

438
00:18:41,804 --> 00:18:42,824
Terima kasih.

439
00:18:42,824 --> 00:18:44,554
Jadi, program di sini
adalah sebelum anda.

440
00:18:44,554 --> 00:18:46,814
Anda sekarang komputer
melaksanakan program ini.

441
00:18:46,814 --> 00:18:48,934
Ini cukup diri
jelas pada masa ini.

442
00:18:48,934 --> 00:18:50,754
Ya, anda harus menjadi nombor satu.

443
00:18:51,184 --> 00:18:53,644
Mendapatkannya? Benar, banyak di antara anda
mungkin berfikir ini sudah

444
00:18:53,644 --> 00:18:54,994
Lagi pula, pelajar-pelajar tahun pertama.

445
00:18:55,484 --> 00:18:58,794
Jadi, berfikir untuk diri sendiri,
Anda nombor satu.

446
00:18:58,794 --> 00:19:01,574
Jadi, langkah ketiga di sini, sepasang
mati dengan berdiri seseorang,

447
00:19:01,764 --> 00:19:03,784
Anda menambah dua nombor
bersama dan mengadopsi jumlah yang

448
00:19:03,784 --> 00:19:05,754
sebagai nombor baru anda dan
kami akan melakukan pemeriksaan kesihatan jiwa.

449
00:19:06,494 --> 00:19:41,524
[Suara dari] orang ramai

450
00:19:42,024 --> 00:19:47,184
Adakah anda tahu berapa banyak yang kita miliki?

451
00:19:47,184 --> 00:19:47,314
>> [] Tak terdengar

452
00:19:47,314 --> 00:19:47,464
>> Tidak terdengar] [.

453
00:19:47,784 --> 00:19:57,014
>> Kita perlu mempunyai
kunci jawaban.

454
00:19:57,014 --> 00:19:57,214
[Diam]

455
00:19:57,214 --> 00:19:57,954
>> Yeah.

456
00:19:58,494 --> 00:20:17,534
[Suara dari] orang ramai

457
00:20:18,034 --> 00:20:20,454
>> Daud: Pada titik ini
algoritma harus

458
00:20:20,454 --> 00:20:21,724
mereda.

459
00:20:22,494 --> 00:20:32,544
[Suara dari] orang ramai

460
00:20:33,044 --> 00:20:46,024
Mungkin kita harus pergi
dengan pendekatan saya setelah semua.

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 geometri dalam
depan 300 orang ditambah.

464
00:20:56,274 --> 00:20:56,341
[Tertawa]

465
00:20:56,341 --> 00:21:00,964
Apa yang kami akhir
pengiraan akan?

466
00:21:00,964 --> 00:21:01,514
>> 180.

467
00:21:01,514 --> 00:21:01,581
[Tertawa]

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
>> Daud: 386, dan
Anda berdiri yang terkini?

471
00:21:14,114 --> 00:21:16,404
Apakah semua orang bahawa?

472
00:21:16,644 --> 00:21:17,314
Adakah anda tahu jawapannya?

473
00:21:17,314 --> 00:21:17,524
>> Apa?

474
00:21:17,954 --> 00:21:22,794
>> Daud: Adakah anda tahu
apa jawabannya?

475
00:21:22,924 --> 00:21:25,194
Kami tidak membawa
kunci jawaban dengan kami sehingga,

476
00:21:26,114 --> 00:21:31,034
386 pada kenyataannya justru
jawapan yang betul untuk pertama kalinya.

477
00:21:31,517 --> 00:21:33,517
[Bersorak]

478
00:21:34,000 --> 00:21:36,000
[Tepuk tangan]

479
00:21:36,484 --> 00:21:37,024
Tidak apa-apa.

480
00:21:37,024 --> 00:21:37,091
[Tepuk tangan]

481
00:21:37,091 --> 00:21:39,154
Sangat, sangat manis.

482
00:21:39,154 --> 00:21:40,734
Jadi, apa yang Takeaway

483
00:21:40,734 --> 00:21:42,554
kerana yang pasti
merasa sedikit lebih lambat

484
00:21:42,554 --> 00:21:43,584
dari saya sangat mudah

485
00:21:43,584 --> 00:21:46,204
tetapi tetap amat benar
pendekatan hanya akan onesies

486
00:21:46,204 --> 00:21:48,784
dan twosies dan hanya mendapatkannya
dilakukan dengan dari kiri ke kanan.

487
00:21:49,104 --> 00:21:50,664
Tapi, apa yang kita
benar-benar hanya lakukan di sana?

488
00:21:50,664 --> 00:21:53,454
Nah, jika ada kasar,
katakanlah, 400 daripada anda berdiri

489
00:21:53,454 --> 00:21:56,184
pada satu titik, dan kemudian
setengah daripada anda, sangat cepat,

490
00:21:56,184 --> 00:21:57,784
dari apa yang saya boleh hantar,
ingin duduk.

491
00:21:57,784 --> 00:22:01,554
Jadi, setengah daripada anda duduk,
kami pergi 400-200 kemudian

492
00:22:01,554 --> 00:22:05,154
hingga 100 lalu ke 50 kemudian ke 25.

493
00:22:05,374 --> 00:22:07,784
Jadi sekali lagi, ada
yang memisahkan sama

494
00:22:07,784 --> 00:22:09,864
dan menawan idea kita
telah dengan buku telefon.

495
00:22:09,864 --> 00:22:13,044
Sekali lagi, dengan iterasi setiap kita
dibelah dua saiz masalah,

496
00:22:13,044 --> 00:22:14,104
kita dibelah dua itu, kita dibelah dua itu.

497
00:22:14,344 --> 00:22:17,594
Jadi, secara teori, algoritma anda
seharusnya sudah jauh lebih cepat

498
00:22:17,774 --> 00:22:20,744
dari pendekatan linier saya kerana
pendekatan saya akan mengatakan telah diambil

499
00:22:20,844 --> 00:22:24,764
400 langkah atau mungkin jika saya
200 langkah sedikit pandai.

500
00:22:25,024 --> 00:22:28,644
Tapi, anda pasti sudah diambil jauh
lebih sedikit, ke kanan 400-200,

501
00:22:28,644 --> 00:22:34,634
100, 50, 25, 13, enam;
sehingga kurang dari sepuluh langkah

502
00:22:34,634 --> 00:22:36,854
di akhir versus saya 200 atau 400.

503
00:22:36,854 --> 00:22:39,984
Dan ada benih dari
benar-benar menarik idea.

504
00:22:39,984 --> 00:22:42,954
Dan ya, secara matematik apa yang anda
hanya lakukan adalah sesuatu yang sangat

505
00:22:42,954 --> 00:22:45,714
sedikit logaritma dalam
alam dengan dasar masuk dua,

506
00:22:45,714 --> 00:22:47,194
kami dibagi dalam dua dan dua lagi.

507
00:22:47,194 --> 00:22:48,974
Dan kami akan kembali ini
kemudian di semester ini.

508
00:22:49,174 --> 00:22:51,994
Namun di situlah letak lagi yang sangat
cerdas pelaksanaan.

509
00:22:51,994 --> 00:22:53,664
Dan, kita hanya
menggaruk permukaan

510
00:22:53,664 --> 00:22:57,744
dari yang sangat cerdas yang sangat
cerdas cekap pendekatan

511
00:22:58,064 --> 00:23:00,164
untuk masalah yang kita
akhirnya bisa menyelesaikan.

512
00:23:00,484 --> 00:23:04,494
Jadi, yang adalah orang yang anda
hanya berbual dengan jika sebentar?

513
00:23:04,494 --> 00:23:07,674
Sebuah keprihatinan bersama dalam suatu kursus
seperti ini adalah semua orang bahawa

514
00:23:07,674 --> 00:23:09,404
di sebelah kiri anda dan
semua orang ke kanan

515
00:23:09,404 --> 00:23:12,014
Anda harus secara jelas
tahu lebih banyak dari anda.

516
00:23:12,014 --> 00:23:13,604
Yah, itu benar-benar
tidak terjadi.

517
00:23:13,604 --> 00:23:14,744
Dan pada kenyataannya, dalam beberapa tahun terakhir,

518
00:23:14,774 --> 00:23:16,754
kursus ini telah melakukan
usaha bersepadu untuk mencapai

519
00:23:16,754 --> 00:23:19,454
kepada mereka yang kurang
nyaman, sehingga untuk berbicara.

520
00:23:19,634 --> 00:23:22,174
Dan dengan itu, kita bererti tidak orang
yang belum pernah menyentuh komputer

521
00:23:22,174 --> 00:23:24,074
dahulu kerana itu
benar-benar sukar untuk mencari

522
00:23:24,074 --> 00:23:26,504
di sini hari ini,
tetapi orang-orang yang menggunakan email,

523
00:23:26,504 --> 00:23:28,314
menggunakan Facebook, mungkin
bahkan sekarang

524
00:23:28,314 --> 00:23:31,644
tetapi tidak
pasti apa yang harus dilakukan

525
00:23:31,644 --> 00:23:34,314
ketika sesuatu berjalan salah
atau ketika mereka diminta

526
00:23:34,314 --> 00:23:37,594
tentang apa-apa teknologi,
Anda tahu, tangan naik

527
00:23:37,714 --> 00:23:39,144
atau mereka jenis push
peranti keras

528
00:23:39,144 --> 00:23:42,384
untuk seorang teman yang mungkin
lebih berpengalaman dalam hal itu daripada mereka.

529
00:23:42,384 --> 00:23:45,794
Well, ini adalah beberapa statistik
dari semester tahun lalu.

530
00:23:45,794 --> 00:23:49,494
Jadi, ketika ditanya, ketika kita tanya
kami 400 pelajar jadi tahun terakhir,

531
00:23:49,874 --> 00:23:52,424
Anda tahu, apa tahap anda
kemudahan datang ke dalam kelas ini,

532
00:23:52,424 --> 00:23:56,784
34% baik menulis sendiri turun
seperti di antara mereka yang kurang selesa.

533
00:23:56,784 --> 00:23:59,654
Jadi, jika anda telah datang ke ini
bilik dan masih berfikir sekarang,

534
00:23:59,904 --> 00:24:02,554
itu, anda tahu apa, istilah
menjelaskan saya kurang selesa,

535
00:24:02,804 --> 00:24:04,994
tahu bahawa anda berada di
sangat baik syarikat.

536
00:24:04,994 --> 00:24:06,994
Tapi, menyedari juga bahawa, jika
Anda akan datang dalam kursus ini

537
00:24:06,994 --> 00:24:10,254
dengan latar belakang komputer
ilmu pengetahuan dan anda benar-benar

538
00:24:10,254 --> 00:24:13,194
yang geek di sekolah menengah dan
sekolah tinggi yang menulis kod

539
00:24:13,194 --> 00:24:15,314
dan pengajaran sendiri
Bahasa, baik itu juga boleh

540
00:24:15,314 --> 00:24:17,884
kerana pasti ada
khalayak berukuran trivial

541
00:24:17,884 --> 00:24:20,954
dengan latar belakang sebagai
baik, sekitar 13% jangka, lalu.

542
00:24:21,104 --> 00:24:23,144
Dan kemudian, semua orang ada
lain, seperti seseorang

543
00:24:23,144 --> 00:24:24,784
yang tidak berfikir
mereka kurang selesa,

544
00:24:24,784 --> 00:24:26,894
mereka pasti tidak berfikir
mereka lebih selesa

545
00:24:26,894 --> 00:24:29,364
tapi mereka hanya dalam suatu kursus
untuk mendapatkan sesuatu dari itu.

546
00:24:29,364 --> 00:24:32,034
Jadi, kursus ini menyedari
tidak cukup menarik spektrum

547
00:24:32,034 --> 00:24:32,584
pelajar.

548
00:24:32,714 --> 00:24:36,034
Dan, untuk menempatkan ini di lebih
istilah konkrit, 71% daripada pelajar,

549
00:24:36,034 --> 00:24:38,514
tahun lalu, telah sifar
kursus di belakang mereka.

550
00:24:38,804 --> 00:24:40,754
Jadi, jika anda memasuki
Tentu saja semua orang berfikir oh

551
00:24:40,754 --> 00:24:43,334
yang mengambil CS50 adalah
ilmu komputer jagoan

552
00:24:43,334 --> 00:24:44,794
di sekolah tinggi, itu
tidak terjadi.

553
00:24:44,934 --> 00:24:47,554
Kebanyakan orang mungkin
hanya tertarik di dalamnya.

554
00:24:47,554 --> 00:24:50,094
Dan beberapa, ya, benar-benar
telah mengambil beberapa program, beberapa,

555
00:24:50,354 --> 00:24:53,174
atau sekurang-kurangnya satu orang
tahun terakhir telah diambil lima

556
00:24:53,174 --> 00:24:54,334
program sebelumnya.

557
00:24:54,594 --> 00:24:56,634
Jadi, kita pasti mempunyai beberapa
outlier tapi sekali lagi daging

558
00:24:56,634 --> 00:24:59,674
kurva yang ada dalam mereka
nilai lebih rendah sama sekali.

559
00:24:59,874 --> 00:25:01,794
Dan lain yang menarik
statistik kita berkongsi

560
00:25:01,794 --> 00:25:03,864
selama beberapa masa lalu
tahun adalah nisbah gender.

561
00:25:03,864 --> 00:25:06,434
Jadi, secara historis, sekurang-kurangnya di
ilmu komputer, ada sedikit

562
00:25:06,434 --> 00:25:07,954
dari laki-laki perempuan miring.

563
00:25:07,954 --> 00:25:10,924
Aku beberapa tahun yang lalu itu
jauh lebih ditandai dari tahun lalu.

564
00:25:10,924 --> 00:25:12,904
Jadi, kita sekarang sudah hampir
pada peringkat 40%.

565
00:25:12,904 --> 00:25:15,994
Dan jika aku bisa melempar menuruni
cabaran hanya untuk demi

566
00:25:15,994 --> 00:25:18,034
mempunyai satu pertiga
pie chart tahun depan,

567
00:25:18,034 --> 00:25:19,364
itu bahkan lebih adil.

568
00:25:19,534 --> 00:25:22,014
Saya akan menunjukkan bahawa
benar-benar ada alasan

569
00:25:22,014 --> 00:25:24,134
dari program
perspektif bahwa laki-laki

570
00:25:24,134 --> 00:25:25,474
dan perempuan seharusnya tidak
harus mendaftarkan

571
00:25:25,474 --> 00:25:26,284
semacam ini tentu saja.

572
00:25:26,534 --> 00:25:29,714
Dalam jumlah yang relatif sama
dan menyedari menjadi 38 peratus,

573
00:25:29,744 --> 00:25:32,464
48 peratus, kita sebenarnya hanya
senang melihat bahawa kami hampir

574
00:25:32,464 --> 00:25:37,014
pada saat itu, sekurang-kurangnya,
bahkan statistik nilai 50%.

575
00:25:37,054 --> 00:25:39,104
Jadi, jika anda, pada kenyataannya,
wanita, melakukan sisanya juga boleh menjamin

576
00:25:39,104 --> 00:25:41,804
yang ini tidak, pada kenyataannya,
kelas didominasi laki-laki.

577
00:25:42,314 --> 00:25:46,324
Well, ini hanya supaya terjadi
menjadi ulang tahun 20 CS50's.

578
00:25:46,574 --> 00:25:48,234
Aku, juga terima kasih.

579
00:25:48,584 --> 00:25:50,584
[Bersorak]

580
00:25:50,934 --> 00:25:52,934
[Tepuk tangan]

581
00:25:53,284 --> 00:25:55,554
Itu sangat baik daripada anda
kerana kami membawa kuih

582
00:25:55,554 --> 00:25:56,434
anda sebenarnya.

583
00:25:56,634 --> 00:25:58,324
Jadi, bila anda keluar
di sini hari ini,

584
00:25:58,464 --> 00:26:01,024
Anda benar-benar akan mendapatkan
kesempatan untuk bertemu banyak

585
00:26:01,024 --> 00:26:03,164
dari program pengajaran
rakan yang akan datang-datang

586
00:26:03,164 --> 00:26:03,784
di lorong.

587
00:26:03,784 --> 00:26:06,924
Dan ya itu akan menjadi menyenangkan
semacam cara insentif

588
00:26:06,924 --> 00:26:08,064
mesyuarat fellows mengajar.

589
00:26:08,284 --> 00:26:11,354
Tapi, kita melakukan perjalanan
sampai kedai roti kecil

590
00:26:11,354 --> 00:26:14,434
dan lagi konsisten dengan
Tentu saja sifat suka bermain sementara

591
00:26:14,434 --> 00:26:16,984
tetap mengharapkan
jumlah trivial

592
00:26:16,984 --> 00:26:18,714
kerja sementara kita
bersenang-senang itu.

593
00:26:18,864 --> 00:26:20,364
Tapi, kami mempunyai salah satu
kuih ini untuk anda.

594
00:26:20,364 --> 00:26:20,431
[Tertawa]

595
00:26:20,431 --> 00:26:23,604
Jadi, jika anda tertawa itu
benar-benar baik kerana bahkan

596
00:26:23,604 --> 00:26:25,474
jika anda di antara salah satu
kurang nyaman mereka

597
00:26:25,474 --> 00:26:26,754
setidaknya kau menyedari hal itu.

598
00:26:27,244 --> 00:26:31,184
Bagi anda di 14 peratus
mungkin lebih suka rasa ini.

599
00:26:31,184 --> 00:26:31,334
[Tertawa]

600
00:26:31,334 --> 00:26:35,354
Kemudian, jika anda tidak tahu apa
neraka yang sedang berlaku sekarang,

601
00:26:35,354 --> 00:26:43,384
kami juga mempunyai
untuk sisa anda.

602
00:26:43,384 --> 00:26:43,451
[Bersorak]

603
00:26:43,451 --> 00:26:43,518
[Tepuk tangan]

604
00:26:43,518 --> 00:26:47,584
Jadi, yang sedang dipotong-potong
menjadi potongan-potongan luar saat kita bicara.

605
00:26:47,584 --> 00:26:49,614
Jadi sekali lagi, mari kita
hal-hal yang membuat takik

606
00:26:49,614 --> 00:26:52,514
dan sekurang-kurangnya memperkenalkan
beberapa penyewa asas

607
00:26:52,514 --> 00:26:53,664
bahawa kita kemudian akan mengambil untuk diberikan

608
00:26:53,664 --> 00:26:55,154
di sisa
semester ini.

609
00:26:55,154 --> 00:26:58,524
Jadi, kita semua mungkin tahu bahawa
akhirnya komputer mendidih

610
00:26:58,524 --> 00:27:01,984
bawah sifar dan entah bagaimana
yang, hal-hal yang disebut bit.

611
00:27:01,984 --> 00:27:02,694
Apa artinya?

612
00:27:02,834 --> 00:27:04,664
Nah anda dapat memikirkannya
terus terang sebagai bola lampu,

613
00:27:04,664 --> 00:27:07,254
sedikit adalah bola lampu itu
baik pada atau batal.

614
00:27:07,254 --> 00:27:09,484
Ini sebuah butang, itu
baik pada atau batal.

615
00:27:09,484 --> 00:27:11,564
Sekarang, saintis komputer
umumnya memikirkan mati

616
00:27:11,564 --> 00:27:13,884
sebagai nombor sifar
dan sewenang-wenangnya,

617
00:27:13,884 --> 00:27:15,974
dan idea sebagai satu.

618
00:27:16,274 --> 00:27:17,654
Jadi, jika anda membaling butang lampu

619
00:27:17,654 --> 00:27:20,234
pada satu giliran
it off itu sifar.

620
00:27:20,444 --> 00:27:23,034
Atau, dengan kata lain, putar
cahaya pada itu nilai

621
00:27:23,034 --> 00:27:25,554
yang benar mematikannya
itulah nilai false.

622
00:27:25,554 --> 00:27:26,514
Jadi, ini hanya sinonim.

623
00:27:26,724 --> 00:27:30,984
Pada akhir hari, ya, semua
perhitungan, semua hal yang terjadi

624
00:27:30,984 --> 00:27:33,984
di bawah kap dalam
komputer tidak akhirnya mendidih

625
00:27:33,984 --> 00:27:35,154
turun ke sifar dan yang.

626
00:27:35,154 --> 00:27:36,254
Dan, apabila anda berhenti
memikirkannya,

627
00:27:36,454 --> 00:27:38,904
it's pretty bendungan luar biasa
apa dunia telah dilakukan

628
00:27:39,114 --> 00:27:41,034
dengan bangunan asas
blok termasuk beberapa

629
00:27:41,034 --> 00:27:42,674
dari peranti anda
memegang di tangan anda.

630
00:27:42,864 --> 00:27:44,894
Nah, kenapa sifar
dan yang berguna?

631
00:27:44,894 --> 00:27:46,314
Ya Tuhan, bahkan dalam
nyata dunia kita

632
00:27:46,314 --> 00:27:48,474
sekurang-kurangnya sepuluh
digit, sifar sampai sembilan.

633
00:27:48,734 --> 00:27:49,724
Mengapa begitu terhad?

634
00:27:49,904 --> 00:27:51,954
Baik dalam peranti keras
hal itu sangat mudah.

635
00:27:51,954 --> 00:27:54,204
Ini jauh lebih mudah
merupakan dua negara, benar.

636
00:27:54,204 --> 00:27:56,704
Jika komputer disambungkan
ke dinding, biasanya,

637
00:27:56,914 --> 00:28:00,304
Anda mempunyai ini mudah
sumber alam binari.

638
00:28:00,304 --> 00:28:01,284
It's on atau off.

639
00:28:01,284 --> 00:28:03,194
Kuasa mengalir
atau tidak.

640
00:28:03,374 --> 00:28:05,224
Jadi, itu satu jenis
alasan awal

641
00:28:05,224 --> 00:28:07,414
bahawa dunia itu hanya dengan
sifar dan yang ada di komputer.

642
00:28:07,414 --> 00:28:09,174
Tapi, anda boleh menggunakannya
sebagai blok bangunan.

643
00:28:09,454 --> 00:28:12,304
Jadi, ini sebenarnya sedikit
kecil di skrin sini

644
00:28:12,524 --> 00:28:15,644
tapi kita boleh mengira dalam binari atau kita
boleh mewakili apa yang kita inginkan

645
00:28:15,644 --> 00:28:18,704
dalam binari seperti yang kita boleh,
berkata, perpuluhan, seperti kita boleh,

646
00:28:18,704 --> 00:28:20,354
bahkan sebenarnya, dengan
huruf abjad.

647
00:28:20,514 --> 00:28:21,884
Jadi, inilah sistem cepat.

648
00:28:21,884 --> 00:28:24,964
Hanya dalam masa beberapa minit
Anda sekarang akan tahu bagaimana cara menghitung,

649
00:28:24,964 --> 00:28:27,484
bagaimana menulis, bagaimana
binari berbicara banyak

650
00:28:27,484 --> 00:28:28,654
seperti laptop anda sendiri.

651
00:28:28,654 --> 00:28:31,724
Nah, anda miliki, di dunia
binari, hanya semacam

652
00:28:31,724 --> 00:28:34,344
seperti sekolah dasar
medan atau nilai-nilai.

653
00:28:34,344 --> 00:28:36,954
Jadi, di sekolah dasar kita belajar
ini adalah yang medan ini

654
00:28:36,954 --> 00:28:39,464
medan puluhan, yang
ratusan medan dan sebagainya.

655
00:28:39,674 --> 00:28:42,084
Dengan kata lain, mengapa
adalah jumlah kita tahu

656
00:28:42,324 --> 00:28:46,344
sebagai 123 nombor 123?

657
00:28:46,344 --> 00:28:48,364
Well, guru saya mengajar
ini adalah yang medan,

658
00:28:48,364 --> 00:28:50,694
ini adalah puluhan,
ini adalah ratusan.

659
00:28:50,914 --> 00:28:51,884
Nah apa artinya?

660
00:28:51,884 --> 00:28:54,064
Nah, untuk mengetahui
apa nilai total

661
00:28:54,064 --> 00:28:56,594
dari apa yang dinyatakan
string digit,

662
00:28:56,594 --> 00:28:57,884
hanya hash tanda di papan tulis.

663
00:28:58,214 --> 00:29:02,024
Yah, kita memiliki satu 100,
jadi itu 1 kali 100

664
00:29:02,264 --> 00:29:03,934
dan kemudian ditambah apa dua 10's

665
00:29:03,974 --> 00:29:09,434
jadi itu 2 kali 10 dan ditambah lagi tiga
orang, jadi itu 3 kali 1, oke,

666
00:29:09,774 --> 00:29:11,694
jadi aku sepertinya mendapatkan
kembali ke tempat saya mulai.

667
00:29:11,784 --> 00:29:16,124
Tapi, ini proses yang sangat mudah
hanya mengalikan angka

668
00:29:16,354 --> 00:29:19,344
oleh nilai medan
adalah apa yang binari

669
00:29:19,344 --> 00:29:19,864
semua tentang.

670
00:29:19,864 --> 00:29:22,984
Tapi, dalam binari anda menggunakan kekuatan
dua tidak kekuatan sepuluh.

671
00:29:23,224 --> 00:29:25,194
Jadi, inilah serangkaian
lapan bola lampu.

672
00:29:25,474 --> 00:29:29,064
Komputer saintis hendak menggunakan
nilai-nilai seperti dua dan lapan dan 16

673
00:29:29,064 --> 00:29:32,824
dan 24 dan 32 kerana mereka
semua nilai-nilai umum yang nyaman

674
00:29:32,824 --> 00:29:33,164
digunakan.

675
00:29:33,404 --> 00:29:35,074
Jadi, ketika kita berbicara
sekitar lapan nilai-nilai

676
00:29:35,074 --> 00:29:36,664
dalam urutan ini
seperti disebut bait.

677
00:29:37,084 --> 00:29:39,424
Dan hari ini kita jarang
bertutur dalam bytes adil,

678
00:29:39,424 --> 00:29:42,554
kita bicara gigabyte Mb
dan terabyte hari ini.

679
00:29:42,584 --> 00:29:44,104
Tapi semua akhirnya
hal yang sama.

680
00:29:44,324 --> 00:29:48,714
Berikut adalah lapan bit AKA pertama
bait, jargon hanya sederhana.

681
00:29:49,034 --> 00:29:50,604
Jadi, semua
bola lampu adalah mati.

682
00:29:50,604 --> 00:29:52,544
Jadi, matematik itu sebenarnya
sangat mudah.

683
00:29:52,544 --> 00:29:54,624
Jadi ada di sebelah kanan,
walaupun kecil untuk melihat,

684
00:29:54,624 --> 00:29:56,944
adalah medan seseorang,
berpasangan, yang merangkak, yang lapan,

685
00:29:57,004 --> 00:29:59,664
itu 16S, 32s, 64s, 128s.

686
00:29:59,934 --> 00:30:01,644
Baiklah, mungkin sukar
menghafal pada awalnya

687
00:30:01,644 --> 00:30:03,784
tapi itu hanya dikalikan
oleh dua dari kanan ke kiri.

688
00:30:03,784 --> 00:30:05,044
Jadi, anda sentiasa boleh
semula ini.

689
00:30:05,284 --> 00:30:08,824
Yah, mereka semua pergi begitu
itu 0 kali placeholder,

690
00:30:08,824 --> 00:30:10,014
0 kali placeholder.

691
00:30:10,184 --> 00:30:13,804
Jadi, ini nombornya
0 terwakili dalam binari.

692
00:30:13,804 --> 00:30:16,244
Dengan kata lain, bagaimana anda
tulis nombor kita tahu

693
00:30:16,244 --> 00:30:17,734
sebagai 0 dalam binari?

694
00:30:18,034 --> 00:30:22,514
Well, satu, dua, tiga, empat,
lima, enam, tujuh, lapan,

695
00:30:22,784 --> 00:30:24,304
dan teknikal sahaja
seperti dalam perpuluhan,

696
00:30:24,534 --> 00:30:27,384
semua sifar terkemuka,
mereka tidak menambah sesuatu

697
00:30:27,444 --> 00:30:29,394
dengan rumus mereka
hanya ada

698
00:30:29,394 --> 00:30:31,304
kerana kita sewenang-wenangnya
memutuskan kami ingin lapan

699
00:30:31,304 --> 00:30:32,324
hal ini berturut-turut, benar.

700
00:30:32,324 --> 00:30:33,624
Jika mereka sedang fizikal
objek, kita mempunyai lapan

701
00:30:33,624 --> 00:30:34,764
sehingga mereka harus semua pergi.

702
00:30:34,764 --> 00:30:36,524
Jadi, kita boleh baru saja
lolos dengan satu sifar.

703
00:30:36,814 --> 00:30:38,324
Nah bagaimana anda mewakili
nombor satu?

704
00:30:38,594 --> 00:30:40,794
Yah, secara naluri anda akan
untuk menghapuskan salah satu switch.

705
00:30:40,794 --> 00:30:41,894
Kau akan mengubah bola lampu di.

706
00:30:42,134 --> 00:30:44,934
Jadi, ada user yang pertama
kerana kita sekarang menempatkan satu,

707
00:30:45,294 --> 00:30:48,054
bola lampu yang ada di,
dalam kedudukan seseorang.

708
00:30:48,234 --> 00:30:49,474
Bagaimana kita akan
untuk mewakili dua?

709
00:30:49,474 --> 00:30:52,354
Yah, kita benar-benar akan
melemparkan dua switch sekarang setidaknya

710
00:30:52,354 --> 00:30:53,794
versus negara ini,
kita harus menukar

711
00:30:53,794 --> 00:30:56,004
dalam medan kedua itu
mematikan yang medan

712
00:30:56,284 --> 00:30:59,644
dan sekarang kami mempunyai nilai
satu di medan berpasangan.

713
00:30:59,644 --> 00:31:01,384
Jadi, itulah jumlah keseluruhan
nilai dua.

714
00:31:01,704 --> 00:31:04,034
Sekarang, latihan mental cepat;
apa yang akan terjadi

715
00:31:04,034 --> 00:31:05,024
dengan urutan seterusnya?

716
00:31:05,024 --> 00:31:06,524
Bagaimana saya mempresentasikan
nombor tiga?

717
00:31:06,824 --> 00:31:08,364
Yah, aku butuh satu
dari medan berpasangan,

718
00:31:08,364 --> 00:31:10,324
salah satu daripada bertiga
medan dan ha ah.

719
00:31:10,324 --> 00:31:11,964
Jadi, sekarang aku sudah bertambah
yang satu.

720
00:31:12,174 --> 00:31:13,824
Dan sekarang, ini sama
dasar pola berulang.

721
00:31:13,824 --> 00:31:14,774
Apa nombor empat?

722
00:31:14,874 --> 00:31:17,014
Yah mari kita lihat, saya hanya perlu
pertama dalam medan merangkak

723
00:31:17,014 --> 00:31:18,864
dan kemudian sifar di
yang berpasangan dan yang.

724
00:31:19,234 --> 00:31:21,134
Jadi, terus seperti itu.

725
00:31:21,134 --> 00:31:22,524
Dan, itu hanya ini
urutan langkah.

726
00:31:22,714 --> 00:31:25,864
Dan dalam pengertian binari
benar-benar tidak semua yang rumit.

727
00:31:25,864 --> 00:31:27,484
Di atas sana kita
mempunyai lapan sifar.

728
00:31:27,854 --> 00:31:29,874
Berikut yang telah kami
tujuh sifar dan satu.

729
00:31:30,114 --> 00:31:32,214
Berikut yang telah kami
enam sifar, satu,

730
00:31:32,494 --> 00:31:34,204
dan sifar dan itu binari.

731
00:31:34,454 --> 00:31:38,164
Sekarang, untungnya, kami komputer
saintis, pengaturcara kami

732
00:31:38,164 --> 00:31:41,674
oleh keperluan akhir tidak akan
sering menulis dalam binari,

733
00:31:41,674 --> 00:31:43,694
bertutur dalam binari,
berfikir dalam binari

734
00:31:43,894 --> 00:31:47,204
kerana kami telah membina banyak lapisan
dari traksi di atas itu.

735
00:31:47,204 --> 00:31:49,434
Bahkan, orang jarang
berbicara tentang bit kecuali

736
00:31:49,434 --> 00:31:51,344
dalam konteks rangkaian
mereka berbicara tentang bait

737
00:31:51,404 --> 00:31:53,144
kerana sedikit pun,
tidak berguna,

738
00:31:53,354 --> 00:31:55,444
lapan bit hari ini
masih tidak berguna,

739
00:31:55,444 --> 00:31:56,484
tapi setidaknya lapan bit,

740
00:31:56,484 --> 00:31:59,914
satu bait setidaknya mendapatkan
kita ke arah lebih bermanfaat unit

741
00:31:59,914 --> 00:32:00,484
saiz.

742
00:32:00,764 --> 00:32:02,734
Tapi, ketika kita mula mencari
bawah kap mobil,

743
00:32:02,814 --> 00:32:05,324
ketika kita masalah-masalah tertentu
seperti melihat gambar

744
00:32:05,324 --> 00:32:06,764
dan mungkin melihat
lalu lintas rangkaian,

745
00:32:07,014 --> 00:32:08,304
itu akan menjadi menarik

746
00:32:08,304 --> 00:32:10,844
untuk mengetahui bagaimana anda mewakili
data kerana anda akan

747
00:32:10,844 --> 00:32:13,774
harus mencari cara untuk
memaparkan bahawa maklumat yang sama.

748
00:32:13,774 --> 00:32:16,954
Dan, pada kenyataannya, kita, jika kita
hanya memiliki sifar dan yang,

749
00:32:17,164 --> 00:32:21,744
bagaimana kita menjalani mewakili,
mengatakan huruf abjad?

750
00:32:21,744 --> 00:32:23,994
Yah, kita akan
harus mempunyai beberapa pemetaan

751
00:32:24,104 --> 00:32:25,774
antara binari dan huruf.

752
00:32:25,824 --> 00:32:27,564
Tapi itu seperti yang belum jelas.

753
00:32:27,564 --> 00:32:30,464
Tapi untuk saat ini palu
rumah dan memberikan saya berehat

754
00:32:30,464 --> 00:32:33,614
dari berbicara di, saya pikir
Aku berhenti sejenak dan melihat

755
00:32:33,614 --> 00:32:35,774
jika kita tidak boleh merekrut
lapan relawan,

756
00:32:36,134 --> 00:32:37,344
satu bait lapan orang.

757
00:32:37,674 --> 00:32:41,224
Bolehkah saya mendapatkan lapan orang untuk
yang tidak terlalu canggung

758
00:32:41,224 --> 00:32:41,754
datang ke atas.

759
00:32:41,804 --> 00:32:45,384
baik, baik satu, dua, tiga,
empat, lima, enam, tujuh,

760
00:32:45,384 --> 00:32:48,464
sangat antusias lapan
lapan, datang ke bawah.

761
00:32:49,024 --> 00:32:51,584
Jadi, kamu semua, untuk hanya
saat di sini, oh dan anda mempunyai

762
00:32:51,644 --> 00:32:53,914
harus bersedia untuk tidak berada di
internet kerana ada

763
00:32:53,914 --> 00:32:55,294
sebenarnya kamera di
bahagian belakang bilik ini.

764
00:32:55,634 --> 00:32:58,114
Jadi, kembali sekarang jika anda
tidak mahu berada di,

765
00:32:58,374 --> 00:33:00,314
halo ibu, untuk selama-lamanya.

766
00:33:01,134 --> 00:33:05,084
Jadi, mari kita lihat, anda di sini
akan menjadi medan 128.

767
00:33:05,344 --> 00:33:08,504
Dan biarkan aku meminta anda
hanya terus ini sebelum anda.

768
00:33:08,504 --> 00:33:10,124
Dan sebenarnya, jika anda boleh
scooch cara ini hanya sedikit

769
00:33:10,124 --> 00:33:12,484
sedikit, maka saya akan
menyingkir anda.

770
00:33:12,484 --> 00:33:14,174
Anda akan medan 64's,

771
00:33:15,074 --> 00:33:18,164
Anda akan menjadi 32's
medan dan 16's.

772
00:33:18,424 --> 00:33:25,444
32's, 16, 8, 4's,
2's dan 1's.

773
00:33:25,444 --> 00:33:26,134
Baik.

774
00:33:26,134 --> 00:33:28,414
Jadi sempurna berbaris dengan
pemegang tempat dari sebelumnya,

775
00:33:28,574 --> 00:33:30,614
tapi kita perlu sedikit
pemetaan, sehingga set up cepat.

776
00:33:30,844 --> 00:33:34,754
Kita hanya perlu cara sewenang-wenangnya
pemetaan nombor binari,

777
00:33:34,754 --> 00:33:37,314
yang benar-benar dapat dikonversi
sangat mudah untuk nombor perpuluhan.

778
00:33:37,314 --> 00:33:39,734
Jadi kita perlu cara
menukar nombor bagi huruf

779
00:33:39,804 --> 00:33:42,524
jika komputer kita benar-benar
akan menunjukkan kepada kita email

780
00:33:42,794 --> 00:33:46,604
atau taip URL atau sebenarnya
memaparkan maklumat bukan numerik.

781
00:33:46,764 --> 00:33:49,934
Dan, dalam kenyataannya, ada suatu sistem
untuk itu, itu namanya ASCII,

782
00:33:50,204 --> 00:33:53,044
akronim yang maknanya tidak

783
00:33:53,044 --> 00:33:56,354
begitu menarik, tapi
yang utiliti.

784
00:33:56,554 --> 00:33:58,984
Ini hanya pemetaan
dari huruf ke angka

785
00:33:58,984 --> 00:34:00,984
dan sebenarnya ada banyak
lebih nombor di paparan,

786
00:34:00,984 --> 00:34:02,484
dan kalian, tidak
bimbang, tidak akan memiliki

787
00:34:02,524 --> 00:34:04,174
untuk menguji dirimu dengan
ini hanya dalam beberapa saat.

788
00:34:04,424 --> 00:34:06,324
Tapi ada pemetaan
antara nombor dan huruf

789
00:34:06,324 --> 00:34:07,884
dan aku hanya akan mendapatkan
kami mulai dengan menunjuk

790
00:34:07,884 --> 00:34:08,664
keluar beberapa ini.

791
00:34:08,954 --> 00:34:12,284
Jumlah bunga
sekarang akan menjadi,

792
00:34:12,284 --> 00:34:14,084
whoops, akan menjadi ini.

793
00:34:14,854 --> 00:34:17,434
Whoops. Jadi, dalam medan ini
di sini, aku tidak bisa untuk memperbesar

794
00:34:17,434 --> 00:34:19,124
di secara bersamaan,
kami telah perpuluhan.

795
00:34:19,194 --> 00:34:19,964
Disember untuk perpuluhan.

796
00:34:20,134 --> 00:34:22,384
Dan kemudian kita aksara
di sebelah kanan.

797
00:34:22,614 --> 00:34:25,084
Jadi jika aku melompat lebih ke ini
medan, pikir itu agak kecil

798
00:34:25,084 --> 00:34:28,834
pada paparan, jumlah
65 mewakili surat apa?

799
00:34:30,024 --> 00:34:32,484
Modal A. Dan jumlah 97?

800
00:34:33,134 --> 00:34:35,714
A. huruf kecil Baiklah.

801
00:34:35,714 --> 00:34:38,644
Jadi dua saja, ke kanan,
jadi jangan pulang dan cuba

802
00:34:38,644 --> 00:34:39,854
mengingati grafik ASCII.

803
00:34:39,854 --> 00:34:42,164
Ayo masa kuis, jangan cuba
menghafal sebuah jadual ASCII.

804
00:34:42,374 --> 00:34:45,864
Menghafal dua, 65 adalah modal
A dan 97 adalah huruf kecil A.

805
00:34:46,044 --> 00:34:47,884
Dan dari sana anda boleh
Bootstrap diri anda untuk semua

806
00:34:47,884 --> 00:34:49,184
yang lain abjad
aksara.

807
00:34:49,404 --> 00:34:51,534
Tapi semua jadual ini berkata, dan
Aku hanya turun jadual ini

808
00:34:51,534 --> 00:34:54,084
dari ASCIItable.com, ini
adalah standard yang telah

809
00:34:54,084 --> 00:34:55,544
sekitar bagi banyak orang,
banyak, banyak tahun,

810
00:34:55,684 --> 00:34:57,224
tapi kebanyakan komputer masih menggunakannya.

811
00:34:57,394 --> 00:34:58,784
Apa yang sekarang kita miliki adalah sarana

812
00:34:58,784 --> 00:35:02,194
pengekodan abjad
maklumat dengan menggunakan apa yang

813
00:35:02,194 --> 00:35:03,184
akhirnya berangka.

814
00:35:03,184 --> 00:35:05,814
Jadi, jika orang-orang ini hanya
suis, bola lampu,

815
00:35:06,064 --> 00:35:08,614
komputer, kita dapat
benar-benar menyampaikan mesej.

816
00:35:08,904 --> 00:35:10,974
Jadi anda masing-masing telah
beberapa penggunaan di bahagian belakang.

817
00:35:11,364 --> 00:35:13,574
Kita akan mempunyai tiga pusingan
di sini di mana orang-orang ini akan

818
00:35:13,574 --> 00:35:15,884
mengeja dalam bahasa Inggeris,
dalam ASCII,

819
00:35:16,104 --> 00:35:18,014
mesej yang sangat singkat,
Perkataan surat tiga.

820
00:35:18,754 --> 00:35:21,364
Ini akan melibatkan mereka
baik mengangkat tangan mereka,

821
00:35:21,364 --> 00:35:24,274
dengan demikian mewakili satu atau
hanya berdiri kikuk,

822
00:35:24,274 --> 00:35:25,994
dengan demikian mewakili sifar.

823
00:35:26,484 --> 00:35:28,754
Jadi mengapa kita tidak meneruskan
segera dengan pusingan pertama

824
00:35:28,904 --> 00:35:31,014
dan anda dapat meningkatkan
atau tidak mengangkat tangan anda.

825
00:35:31,704 --> 00:35:35,064
Jadi penonton tidak
melepaskan dr kesukaran.

826
00:35:35,104 --> 00:35:37,964
Nombor berapa yang mereka
saat ini mewakili?

827
00:35:39,174 --> 00:35:39,954
66. Benar.

828
00:35:39,954 --> 00:35:42,864
Tidak sulit kerana kami mempunyai satu satu,
tangan di medan 64s,

829
00:35:42,864 --> 00:35:44,214
tangan di medan 2's.

830
00:35:44,214 --> 00:35:47,094
64 kali satu ditambah
dua kali pertama 66.

831
00:35:47,124 --> 00:35:48,254
Mereka mewakili
nombor 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
[Tertawa]

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
[Tepuk tangan]

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
[Diam]

869
00:37:23,664 ---> 00:37:25,344
It's slowly spreading, yes?

870
00:37:25,479 ---> 00:37:27,479
[Tertawa]

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
[Musik]

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
[Musik]

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
[Tertawa]

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
[Tertawa]

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
[Tertawa]

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
[Tertawa]

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
[Tertawa]

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
[Tepuk tangan]