1
00:00:00,000 --> 00:00:12,040
>> [Daqq ta mużika]

2
00:00:12,040 --> 00:00:16,460
>> SPEAKER 1: Kull dritt, dan huwa CS50,
u dan huwa l-bidu ta 'erba' ġimgħat,

3
00:00:16,460 --> 00:00:20,420
u kif inti tista smajt jew
aqra, id-dinja kienet jispiċċa.

4
00:00:20,420 --> 00:00:23,520
Going kollha madwar l-internet
għandha Kien għarfien u l-kuxjenza

5
00:00:23,520 --> 00:00:27,100
ta 'bug fi programm, a
lingwa ta 'programmar imsejħa Bash.

6
00:00:27,100 --> 00:00:32,729
Dan ġie wonderfully marka
bħala Shellshock, jew il-bieb Bash,

7
00:00:32,729 --> 00:00:35,485
imma artikoli bħal dawn
ma ġewx komuni.

8
00:00:35,485 --> 00:00:38,807
U fil-fatt, ħafna minnhom iġġib
memorji lura ta Heartbleed,

9
00:00:38,807 --> 00:00:41,640
li jista 'jkollok ndunat fil-
agħfas lura din ir-rebbiegħa passat, li

10
00:00:41,640 --> 00:00:43,980
kien similarment pjuttost drammatika.

11
00:00:43,980 --> 00:00:47,110
Issa ta 'dawk minnkom hawn
illum, kemm għandek,

12
00:00:47,110 --> 00:00:50,330
anki jekk inti ma jifhmux dak
dan kollu dwar, semgħu Shellshock?

13
00:00:50,330 --> 00:00:51,370

14
00:00:51,370 --> 00:00:54,245
Kull dritt, u kif ħafna minnkom
jkollhom kompjuters li huma vulnerabbli?

15
00:00:54,245 --> 00:00:55,680

16
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OK, għandu jkun hemm ħafna, ferm aktar hands
up dritt issa, għal raġunijiet ser naraw.

17
00:01:00,250 --> 00:01:02,580
>> Ejja tagħti ħarsa lejn x'hemm
ilu għaddej fil-midja

18
00:01:02,580 --> 00:01:05,304
u mbagħad jispjegaw daqsxejn
hawn għalina teknikament.

19
00:01:05,304 --> 00:01:07,670

20
00:01:07,670 --> 00:01:11,250
>> SPEAKER 2: Esperti tas-Sigurtà ikollhom
wissa li difett serju jkunu jistgħu

21
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jkun ta 'madwar li jaffettwaw mijiet ta'
miljuni ta 'utenti tal-web-dinja.

22
00:01:15,650 --> 00:01:20,600
Allura x'inhi eżattament l-bug li kien
iddabbjati Shellshock, u dak ma tagħmel?

23
00:01:20,600 --> 00:01:23,720

24
00:01:23,720 --> 00:01:28,910
Ukoll, Shellshock hija magħrufa wkoll bħala l-
Bug Bash, is-software li hu jisfrutta.

25
00:01:28,910 --> 00:01:33,230
Hackers jużaw il-virus li scan vulnerabbli
sistemi running Linux u Unix

26
00:01:33,230 --> 00:01:36,300
sistemi operattivi u mbagħad jinfettaw lilhom.

27
00:01:36,300 --> 00:01:38,730
Bash huwa qoxra kmand tal-linja.

28
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Dan tikri utenti kwistjoni jikkmanda biex tniedi
programmi u l-karatteristiċi fi ħdan software

29
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billi tittajpja test.

30
00:01:45,250 --> 00:01:49,980
Huwa tipikament użati mill-programmers, u
m'għandhiex tkun miftuħa għal dinja usa ',

31
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għalkemm Shellshock bidliet li.

32
00:01:51,590 --> 00:01:54,160

33
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>> Ukoll, worringly, xi analisti
twissi din tista 'tkun ta' theddida akbar,

34
00:01:57,910 --> 00:02:01,580
minħabba Shellshock tippermetti kompluta
kontroll ta 'magna infettati,

35
00:02:01,580 --> 00:02:06,030
billi Heartbleed permess biss
hackers biex spy fuq il-kompjuters.

36
00:02:06,030 --> 00:02:09,130
Huwa tant serja, huwa
ġiet stmata għal 10 minn 10

37
00:02:09,130 --> 00:02:11,900
għas-severità mill-Awtorità Nazzjonali
Database Vulnerabbiltà.

38
00:02:11,900 --> 00:02:15,530

39
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2/3 ta 'servers kollha web huma fi
riskju, inklużi xi kompjuters Mac.

40
00:02:20,015 --> 00:02:22,760

41
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Ukoll, aċċerta ruħek li
garża sistemi tiegħek issa.

42
00:02:25,600 --> 00:02:29,330
Kulħadd tospita websajt running
is-sistemi operattivi affettwati

43
00:02:29,330 --> 00:02:31,800
għandha tieħu azzjoni kemm jista 'jkun malajr.

44
00:02:31,800 --> 00:02:35,390
Kulħadd li jistgħu jaffordjaw li għandu look
għall-monitoraġġ u l-web-applikazzjoni tagħhom

45
00:02:35,390 --> 00:02:37,355
firewalls li għandek toqgħod attent għal xi attakki.

46
00:02:37,355 --> 00:02:39,979

47
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SPEAKER 3: ħaġa Agħar
li jista 'jiġri huwa

48
00:02:41,770 --> 00:02:45,080
li xi ħadd se jikteb kodiċi li
awtomatikament imorru u scan

49
00:02:45,080 --> 00:02:48,280
l-internet u jaffettwa b'mod
kollha ta 'dawn il-kompjuters.

50
00:02:48,280 --> 00:02:50,710
U ladarba dawn jagħmlu dan, ukoll,
l-agħar ħaġa li tista 'tagħmel

51
00:02:50,710 --> 00:02:53,300
huwa biss ħassar kollox,
jew shut-siti isfel.

52
00:02:53,300 --> 00:02:55,360
Allura nistgħu naraw ħsara
minn dak il-lat,

53
00:02:55,360 --> 00:02:58,300
fejn aħna se jkollu nies malizzjużi
li sempliċiment jiddeċiedu li jikkawżaw havoc

54
00:02:58,300 --> 00:03:02,534
minn sistemi jġibu isfel jew tħassir
fajls, u affarijiet bħal dik.

55
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SPEAKER 2: Xi wħud jgħidu li dan huwa wieħed
mill-aktar diffiċli biex jitkejjel

56
00:03:05,200 --> 00:03:08,080
bugs fis-snin, u dan
jista 'jieħu ġimgħat jew saħansitra

57
00:03:08,080 --> 00:03:10,820
xhur biex tiddetermina l-impatt aħħari tagħha.

58
00:03:10,820 --> 00:03:12,180

59
00:03:12,180 --> 00:03:15,560
>> SPEAKER 1: Allura kollha ta 'dan huwa veru,
imma l-ħaġa umoristiċi hija, kważi kollha

60
00:03:15,560 --> 00:03:18,330
tal-xbihat inti biss raw,
ħlief għall forsi l-keyboard,

61
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għandha x'taqsam xejn mal-
l-bug tkun xi tkun.

62
00:03:20,930 --> 00:03:23,960
Servers u wajers u ibqa 'sejjer hekk,
huwa relatat tip ta tanġenzjali,

63
00:03:23,960 --> 00:03:27,410
iżda fil-qalba huwa attwalment pretty
familjari x'inhu għaddej hawn.

64
00:03:27,410 --> 00:03:30,050
Fil-fatt, let me go fis
appliance CS50 tagħna.

65
00:03:30,050 --> 00:03:32,910
Let me imorru quddiem u timmassimizza
-tieqa terminal hawn.

66
00:03:32,910 --> 00:03:36,020
U inti guys kienu qegħdin jużaw dan,
jew il-verżjoni integrati tiegħu,

67
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fil gedit sabiex jiktbu programmi,
tip jikkmanda, u oħrajn,

68
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u dan huwa fil-fatt, u għandu
ilha għal ġimgħat, Bash, B-A-S-H.

69
00:03:43,690 --> 00:03:46,890
Dan huwa l-Bourne-ġdid qoxra,
li huwa biss mod fancy ta 'tgħid,

70
00:03:46,890 --> 00:03:50,220
dan huwa programm li għandu
Teptip fil-pront, b'mod effettiv,

71
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li tpoġġi hemm stennija
għal input għalik.

72
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U huwa l-kmand
interface on-line permezz tagħhom

73
00:03:53,920 --> 00:03:57,650
inti guys ġew running jikkmanda u
finalment kompilazzjoni u mbagħad running

74
00:03:57,650 --> 00:03:58,400
programmi.

75
00:03:58,400 --> 00:04:01,320
>> Iżda Bash huwa wkoll l-ipprogrammar
lingwa fis-sens li ġejja.

76
00:04:01,320 --> 00:04:05,460
Inti taf li hemm jikkmanda bħal
cd u ls u wkoll clang u oħrajn,

77
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imma int tista 'tiddefinixxi jikkmanda tiegħek stess
billi l-implimentazzjoni tagħhom fl Bash.

78
00:04:09,580 --> 00:04:11,420
Issa aħna mhux qed tmur biex
mur fid-dettal ħafna

79
00:04:11,420 --> 00:04:16,089
bħala li bash l-lingwa ta 'programmar, iżda
taf, per eżempju, li fil-mument,

80
00:04:16,089 --> 00:04:17,607
hemm l-ebda kmand imsejħa "bonjour."

81
00:04:17,607 --> 00:04:19,440
Allura li jista 'jinstab fil-
wieħed minn dawn il-pakketti.

82
00:04:19,440 --> 00:04:20,856
Mhuwiex installat fil-kompjuter tiegħi.

83
00:04:20,856 --> 00:04:21,870
Staqsi amministratur tiegħek.

84
00:04:21,870 --> 00:04:26,030
Imma jekk jien tixtieq li jkun hemm programm
imsejħa "bonjour" fil Bash jew fuq pront tiegħi,

85
00:04:26,030 --> 00:04:30,810
I jistgħu attwalment jużaw sintassi thats
pjuttost simili C. Huwa pjuttost mhux l-istess,

86
00:04:30,810 --> 00:04:35,020
iżda jistenna pretty simili għal
funzjoni, għalkemm nieqsa xi dettalji.

87
00:04:35,020 --> 00:04:38,090
Xejn jidher li jiġri,
imma issa jekk I tip "hello,"

88
00:04:38,090 --> 00:04:40,960
inti tista 'attwalment jiktbu
programm, mhux fis-C, mhux fl Java,

89
00:04:40,960 --> 00:04:44,280
mhux fl-ipprogrammar ieħor
lingwa, iżda Bash innifsu.

90
00:04:44,280 --> 00:04:47,630
>> Issa l-prinċipali hawnhekk hija li I kiteb l-
isem I riedu jagħtu dan il-kmand ġdid,

91
00:04:47,630 --> 00:04:50,820
u l-parentesi huma wkoll
simboliku ta 'dan huwa funzjoni.

92
00:04:50,820 --> 00:04:54,010
Bħala twarrib, inti tista 'ukoll tagħmel gost
affarijiet, u fil-fatt, anke fuq OS Mac,

93
00:04:54,010 --> 00:04:55,620
dan huwa programm imsejjaħ Terminal.

94
00:04:55,620 --> 00:04:58,800
Jidħol mibnija fis tal ħadd
kompjuter li għandu Mac f'din il-kamra,

95
00:04:58,800 --> 00:05:03,640
u inti tista 'tagħmel affarijiet simili fl Mac
OS, imma int tista 'tmur aktar lil hinn minn dak.

96
00:05:03,640 --> 00:05:07,110
U dan huwa ftit tanġenzjali,
imma hija tip ta 'gost.

97
00:05:07,110 --> 00:05:09,715
I kien fakkar dalgħodu,
meta ħsieb dan permezz,

98
00:05:09,715 --> 00:05:13,279
ta 'logħba ftit I użati biex jilagħbu
ma 'waħda mill TFS preċedenti CS50 tal

99
00:05:13,279 --> 00:05:16,570
li bih kwalunkwe żmien li kien ikun walk away minn
keyboard tiegħu bl-iskrin tiegħu jinfetaħ,

100
00:05:16,570 --> 00:05:23,611
Nixtieq tesegwixxi kmand
bħal this-- "jgħidu bonjour."

101
00:05:23,611 --> 00:05:26,610
U issa xi darba hu daħal lura tiegħu
keyboard wara I kklerjat l-iskrin

102
00:05:26,610 --> 00:05:27,985
u li kieku joqogħdu bilqegħda,
jipprova jagħmel xi xogħol,

103
00:05:27,985 --> 00:05:29,250
lista tal-kontenut ta 'directory-- tiegħu

104
00:05:29,250 --> 00:05:29,510
>> [AUDIO Daqq]

105
00:05:29,510 --> 00:05:30,010
>> -Hello.

106
00:05:30,010 --> 00:05:31,621

107
00:05:31,621 --> 00:05:32,120
Hello.

108
00:05:32,120 --> 00:05:35,030
>> SPEAKER 1: Allura, fl-ekwità,
ma kienx fil-fatt "bonjour."

109
00:05:35,030 --> 00:05:36,894
Kien normalment xi ħaġa
aktar viċin għall that--

110
00:05:36,894 --> 00:05:37,560
[AUDIO Daqq]

111
00:05:37,560 --> 00:05:37,750
-Beep.

112
00:05:37,750 --> 00:05:39,320
SPEAKER 1: --that I would--
hekk kompjuter tiegħu kieku

113
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naħlef fi lilu kwalunkwe ħin hu attwalment
sib stabbiliti fuq tastiera tiegħu.

114
00:05:42,170 --> 00:05:46,265
U malajr ħafna hu dehret
ma jħallu l-iskrin tiegħu jinfetaħ.

115
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Iżda dan jissuġġerixxi t-tip
ta 'gost stupid li inti

116
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jista 'jkollha ma' xi ħaġa bħal Bash.

117
00:05:50,210 --> 00:05:52,770
Iżda huwa ftit aktar
serja, biex tkun ċert, minn dak.

118
00:05:52,770 --> 00:05:57,235
U fil-fatt, dan huwa wieħed mill-
aktar bugs perikolużi u fit-tul

119
00:05:57,235 --> 00:05:58,860
li tkun verament laqat il-dinja globalment.

120
00:05:58,860 --> 00:06:02,060
Dan bug kien madwar
għal xi 20 sena,

121
00:06:02,060 --> 00:06:05,780
u tkun taf tkun laqat fi ftit
mument mill-sempliċità relattiva tiegħu.

122
00:06:05,780 --> 00:06:07,990
>> Allura dan huwa rappreżentattiv
kmand li jekk inti

123
00:06:07,990 --> 00:06:10,448
stess a Mac, litteralment dritt issa
meta jkollok għatu tiegħek miftuħa,

124
00:06:10,448 --> 00:06:12,940
inti tista 'tipprova ittajpjar f'dak
programm imsejjaħ Terminal.

125
00:06:12,940 --> 00:06:15,410
Terminal huwa taħt
Applikazzjonijiet Utilities--

126
00:06:15,410 --> 00:06:18,790
għal darba, Windows utenti ma jkollhom
joqogħdu jinkwetaw dwar dan threat-- partikolari

127
00:06:18,790 --> 00:06:22,310
iżda dawk tal inti ma MACs tista tip
dan fi tieqa bħal I ser nagħmlu hawnhekk,

128
00:06:22,310 --> 00:06:24,210
u jekk inti tip
li fis dan il-programm

129
00:06:24,210 --> 00:06:28,830
imsejħa Terminal, bħal I ser tagħmel issa,
jekk tara l-kelma "vulnerabbli,"

130
00:06:28,830 --> 00:06:32,200
kompjuter tiegħek huwa
vulnerabbli għall-isfruttament.

131
00:06:32,200 --> 00:06:33,850
>> Issa dak li ma attwalment jfisser?

132
00:06:33,850 --> 00:06:35,870
U dan huwa ċertament
xi sintassi pretty crazy,

133
00:06:35,870 --> 00:06:39,050
imma ejja mill-inqas jiġbed out
xi wħud mill-aspetti interessanti.

134
00:06:39,050 --> 00:06:42,567
Allura hemm xi sintassi li jistenna
ftit familjari, mill-inqas minn C

135
00:06:42,567 --> 00:06:43,950
u l-ipprogrammar aktar ġenerali.

136
00:06:43,950 --> 00:06:47,550
I tara xi parentesi,
semicolons, braces kaboċċi, u bħal dawn,

137
00:06:47,550 --> 00:06:50,820
iżda jirriżulta li dan
Ħaġa stupid hawn isfar

138
00:06:50,820 --> 00:06:53,580
huwa essenzjalment funzjoni
li ma xejn.

139
00:06:53,580 --> 00:06:57,840
Il-mezzi kolon ma tagħmel xejn, u l-
virgola ifisser tieqaf tagħmel xejn.

140
00:06:57,840 --> 00:07:00,250
Allura ġewwa minn dawn
braces kaboċċi, il-fatt

141
00:07:00,250 --> 00:07:02,440
li għandi ugwali
jiffirmaw għall-xellug, din

142
00:07:02,440 --> 00:07:05,500
huwa essenzjalment ħolqien
kmand, jew varjabbli,

143
00:07:05,500 --> 00:07:09,520
imsejħa x, u assenjazzjoni tiegħu
li ftit isfar tal-kodiċi hemmhekk.

144
00:07:09,520 --> 00:07:14,040
Dan jista 'jkun xi ħaġa bħal "eku
bonjour "jew" jgħidu ħoss "jew xi ħaġa

145
00:07:14,040 --> 00:07:15,120
simili għal dak.

146
00:07:15,120 --> 00:07:17,780
Iżda avviż jekk l-għajnejn tiegħek
wander aktar lejn il-lemin,

147
00:07:17,780 --> 00:07:22,150
hemm aktar din il-linja minn
biss it-tmiem ta 'dak il virgola.

148
00:07:22,150 --> 00:07:25,160
"Echo vulnerabbli," u mbagħad
lil hinn minn dak hemm anke aktar.

149
00:07:25,160 --> 00:07:26,530
Punto virgola, -C Ieħor bash :.

150
00:07:26,530 --> 00:07:28,120

151
00:07:28,120 --> 00:07:34,050
>> Allura qasir storja twila,
din il-linja tal-kodiċi hija

152
00:07:34,050 --> 00:07:36,660
biżżejjed għall konvinċenti
kompjuter li l-

153
00:07:36,660 --> 00:07:39,830
vulnerabbli li jagħmlu xi ħaġa
li inti tixtieq li tagħmel,

154
00:07:39,830 --> 00:07:44,290
għaliex hemm bug fil biha Bash
anki jekk Bash kien suppost biex tieqaf

155
00:07:44,290 --> 00:07:48,980
linji qari ta 'dritt kmand
hemm wara t-test isfar,

156
00:07:48,980 --> 00:07:52,520
għal sena 20-plus bug qodma,
Bash ikun attwalment ġie qari

157
00:07:52,520 --> 00:07:56,780
lil hinn minn dik virgola u pretty
ħafna jagħmlu dak li huwa qal.

158
00:07:56,780 --> 00:07:59,070
>> Allura x'inhu l-implikazzjoni
ta 'dik finalment?

159
00:07:59,070 --> 00:08:01,340
I biss qal "eku bonjour"
jew "eku vulnerabbli,"

160
00:08:01,340 --> 00:08:05,449
imma dak jekk inti għamilt xi ħaġa
attwalment malizzjużi, bħal rm -rf *,

161
00:08:05,449 --> 00:08:07,240
li inti tista 'ma
qatt ittajpjat qabel,

162
00:08:07,240 --> 00:08:08,920
u franchement inti probabilment
m'għandhomx wisq malajr,

163
00:08:08,920 --> 00:08:10,700
għaliex inti tista 'tagħmel
ħafna ħsara magħha.

164
00:08:10,700 --> 00:08:11,210
Għaliex?

165
00:08:11,210 --> 00:08:12,990
rm ma dak, tal-kors?

166
00:08:12,990 --> 00:08:14,270
Ineħħi.

167
00:08:14,270 --> 00:08:15,930
* Ifisser liema?

168
00:08:15,930 --> 00:08:16,430
Kollha.

169
00:08:16,430 --> 00:08:18,180
Allura huwa l-hekk imsejħa
wild card, hekk dan ifisser

170
00:08:18,180 --> 00:08:20,410
ħassar kollox fil
l-direttorju kurrenti.

171
00:08:20,410 --> 00:08:23,379
-r jiġri li jfisser rikursivi,
li jfisser li jekk dak li qed jitħassru

172
00:08:23,379 --> 00:08:26,420
huwa direttorju, u ġewwa ta 'hemmhekk
hija fajls oħra u direttorji oħra,

173
00:08:26,420 --> 00:08:28,950
recursively adsa fis hemmhekk
u ħassar kollha ta 'dak.

174
00:08:28,950 --> 00:08:31,040
U -f huwa l-agħar minnhom kollha.

175
00:08:31,040 --> 00:08:32,580
Xi ħadd jaf liema -f jfisser hawn?

176
00:08:32,580 --> 00:08:33,690

177
00:08:33,690 --> 00:08:34,360
Forza.

178
00:08:34,360 --> 00:08:37,830
Allura seħħ tfisser, anke
jekk din hija idea ħażina,

179
00:08:37,830 --> 00:08:40,939
tagħmel dan mingħajr suġġeriment me
Għal konferma aktar.

180
00:08:40,939 --> 00:08:43,230
Allura, inti taf, aħna tidħaq
dan, imma franchement, I probabbilment

181
00:08:43,230 --> 00:08:44,972
din it-tip ħinijiet multipli
kuljum, għaliex ir-realtà

182
00:08:44,972 --> 00:08:47,210
huwa huwa l-aktar mod li
tħassar mazz sħiħ ta 'għalf.

183
00:08:47,210 --> 00:08:48,590
Iżda anke I għamlu xi ħsara.

184
00:08:48,590 --> 00:08:53,100
>> Imma jekk ġejt biex trick kompjuter
fis tiddefinixxi xi varjabbli stupid

185
00:08:53,100 --> 00:08:56,810
jew funzjoni msejħa x, iżda mbagħad
tricking l-kompjuter fis eżekuzzjoni

186
00:08:56,810 --> 00:09:00,030
lil hinn mill-konfini ta 'dik
funzjoni, lil hinn minn dak virgola,

187
00:09:00,030 --> 00:09:04,430
inti tista 'tabilħaqq trick kompjuter
fis eżekuzzjoni xi ħaġa bħal rm -rf

188
00:09:04,430 --> 00:09:07,810
jew l-kmand Email
jew l-kmand Kopja.

189
00:09:07,810 --> 00:09:11,400
Xejn litteralment inti tista 'tagħmel ma' l-
kompjuter, kemm jekk huwa tħassar files,

190
00:09:11,400 --> 00:09:15,350
ħolqien ta 'fajls, spamming ħadd,
jattakkaw xi server remot,

191
00:09:15,350 --> 00:09:17,190
jekk inti tista 'tesprimi lilha
bi kmand, inti

192
00:09:17,190 --> 00:09:19,120
jista trick kompjuter fis tagħmel dan.

193
00:09:19,120 --> 00:09:21,510
>> Issa x'hemm eżempju ta '
kif inti tista 'tagħmel dan?

194
00:09:21,510 --> 00:09:24,300
Ukoll, hemm ħafna ta 'kompjuters
fuq l-Bash internet running.

195
00:09:24,300 --> 00:09:26,390
Kollha ta 'l-utenti minna Mac huma bejniethom.

196
00:09:26,390 --> 00:09:30,390
A lott ta 'servers Linux huma fost
lilhom ukoll, u servers Unix.

197
00:09:30,390 --> 00:09:32,630
Windows darb'oħra gets
relattivament off-ganċ

198
00:09:32,630 --> 00:09:34,590
sakemm inti ħadthom installati
software speċjali.

199
00:09:34,590 --> 00:09:37,130
Issa ħafna ta 'servers, għal
Pereżempju, servers mill-web run,

200
00:09:37,130 --> 00:09:39,840
u fil-fatt Linux hija forsi l-
aktar sistema operattiva popolari

201
00:09:39,840 --> 00:09:43,060
li jimxu fuq kompjuters fuq l-internet
li huma jservu up paġni web.

202
00:09:43,060 --> 00:09:44,910
Issa kif Ser naraw aktar tard
fil-semestru, meta

203
00:09:44,910 --> 00:09:48,470
inti tibgħat talba minn
Chrome browser-- tiegħek,

204
00:09:48,470 --> 00:09:50,790
Internet Explorer, whatever--
ma 'server remot,

205
00:09:50,790 --> 00:09:53,730
jirriżulta li anki jekk
inti biss ittajpjat www.example.com,

206
00:09:53,730 --> 00:09:59,590
browser tiegħek hija li jibgħat messaġġ
thats ftit aktar arcane, bħal dan.

207
00:09:59,590 --> 00:10:01,239
>> Imma tinnota ftit xi ħaġa stramba.

208
00:10:01,239 --> 00:10:03,030
L-ewwel żewġ linji
Stajt qatt qabel,

209
00:10:03,030 --> 00:10:04,904
iżda dawn ma tfittex
partikolarment theddida.

210
00:10:04,904 --> 00:10:08,030
Imma avviż dak li stajt misruqa
għat-tielet linja hawnhekk.

211
00:10:08,030 --> 00:10:13,390
Jekk Guy ħażina kienu li jibgħat messaġġ
bħal din mill-kompjuter tiegħu jew tagħha

212
00:10:13,390 --> 00:10:17,270
għal Mac vulnerabbli jew
server Linux vulnerabbli,

213
00:10:17,270 --> 00:10:21,580
il-ħaġa umoristiċi hija li Bash,
li sempliċi kmand ftit pront,

214
00:10:21,580 --> 00:10:27,450
huwa omnipreżenti u huwa spiss
użati biex tesegwixxi essenzjalment

215
00:10:27,450 --> 00:10:30,020
il-kontenut ta '
messaġġ li hija tirċievi.

216
00:10:30,020 --> 00:10:33,490
U billi li l-loġika, inti tista '
trick web server, għalhekk,

217
00:10:33,490 --> 00:10:36,370
billi jibgħat xi ħaġa simili
User-aġent, li normalment

218
00:10:36,370 --> 00:10:38,300
huwa suppost li jgħidu l-
isem tal-browser tiegħek.

219
00:10:38,300 --> 00:10:42,420
User-aġent Chrome, User-aġent Internet
Explorer, User-aġent Firefox, dan

220
00:10:42,420 --> 00:10:44,590
huwa biss browser tiegħek
mod ta 'identifikazzjoni ta innifsu.

221
00:10:44,590 --> 00:10:46,605
Imma jekk Guy ħażina ħafna
cleverly jgħid, mm mm, jien

222
00:10:46,605 --> 00:10:47,930
mhux ser jgħidlek
dak browser tiegħi huwa,

223
00:10:47,930 --> 00:10:50,888
Jien minflok ser inti tibgħat dan
cryptic li tħares ħaġa ma '-rf rm

224
00:10:50,888 --> 00:10:55,840
* Fiha, inti tista litteralment trick
web server vulnerabbli fuq l-internet

225
00:10:55,840 --> 00:10:59,055
fis eżekuzzjoni eżattament dak fl
hemm għal tħassir kollha tal-fajls.

226
00:10:59,055 --> 00:11:00,930
U franchement, li mhux
anke l-agħar ta 'dan.

227
00:11:00,930 --> 00:11:01,763
Tista 'tagħmel xejn.

228
00:11:01,763 --> 00:11:04,480
Inti tista 'tibda mqassma
ċaħda ta 'attakk servizz

229
00:11:04,480 --> 00:11:07,030
jekk inti mibgħut dan il-messaġġ lil
għenieqed sħaħ ta 'servers mill-web

230
00:11:07,030 --> 00:11:10,256
u mbagħad kellhom lilhom kollha jinżlu, għal
Pereżempju, fuq servers Harvard.edu,

231
00:11:10,256 --> 00:11:12,130
u inti tista sort ta bang
l-Heck barra minnhom

232
00:11:12,130 --> 00:11:15,490
minn netwerk tat-traffiku li kien
triggered mod ieħor minn dan Guy ħażina.

233
00:11:15,490 --> 00:11:18,760
>> Allura, storja twila fil-qosor, kważi
kulħadd f'din il-kamra li tipposjedi Mac

234
00:11:18,760 --> 00:11:20,240
hija vulnerabbli għal dan.

235
00:11:20,240 --> 00:11:24,100
Il-kisja tal-fidda huwa li sakemm int
tmexxija ta 'web server fuq laptop tiegħek,

236
00:11:24,100 --> 00:11:27,780
u sakemm inti ħadthom attwalment konfigurati
biex jippermetti li xi ħaġa bħal SSH fis dan,

237
00:11:27,780 --> 00:11:28,670
int attwalment sikur.

238
00:11:28,670 --> 00:11:31,710
Huwa vulnerabbli, iżda hemm ebda
wieħed tipprova tikseb fis-laptop tiegħek,

239
00:11:31,710 --> 00:11:33,290
sabiex inti tista 'tip ta' mistrieħ assigurat.

240
00:11:33,290 --> 00:11:36,210
Madankollu, Apple dalwaqt
jkun aġġornament jiffissaw għal dan.

241
00:11:36,210 --> 00:11:39,660
Id-dinja tal-Linux diġà rilaxxati
numru ta 'jiffissa għall Fedora u Ubuntu

242
00:11:39,660 --> 00:11:43,790
u verżjonijiet l-oħra tal-Linux, u tabilħaqq
jekk inti tmexxi aġġornament 50 fl-appliance,

243
00:11:43,790 --> 00:11:45,930
anki li wisq se tkun
aġġornati u korretti.

244
00:11:45,930 --> 00:11:47,764
Iżda li wisq ma jkunx
ġie verament vulnerabbli,

245
00:11:47,764 --> 00:11:49,804
għaliex sakemm inti stajt
tinkered mal-appliance

246
00:11:49,804 --> 00:11:52,770
u magħmula laptop tiegħek pubblikament
aċċessibbli fuq l-internet, li mhuwiex

247
00:11:52,770 --> 00:11:54,910
kontumaċja, inti stajt
attwalment ġiet multa minħabba

248
00:11:54,910 --> 00:11:56,890
ta firewalling u tekniki oħra.

249
00:11:56,890 --> 00:12:01,000
>> Imma hija eżempju estrem ta 'bug
li aħna ve għexet għal ta litteralment 20

250
00:12:01,000 --> 00:12:04,050
snin, u li jaf jekk xi ħadd
dan il-ħin ikun magħruf dwar dan?

251
00:12:04,050 --> 00:12:06,300
U fil-fatt, dan huwa wieħed ta '
l-isfidi fundamentali

252
00:12:06,300 --> 00:12:08,690
li aħna ser tara aktar tard fil-
semestru dwar is-sigurtà,

253
00:12:08,690 --> 00:12:13,020
li huwa biss bħal fid-dinja reali,
l-guys tajba huma fil-iżvantaġġ.

254
00:12:13,020 --> 00:12:16,500
Biex iżommu l-guys ħżiena out, għandna biex
kun żgur li kull bieb ikun imsakkar,

255
00:12:16,500 --> 00:12:20,340
li kull tieqa hija sigura, li
kull punt ta 'dħul fis-dar

256
00:12:20,340 --> 00:12:21,980
huwa sikur biex iżommu l-guys ħżiena out.

257
00:12:21,980 --> 00:12:26,870
Imma dak ma l-Guy ħażina jkollu
tagħmel biex attwalment kompromess dar tiegħek

258
00:12:26,870 --> 00:12:28,200
u steal mill inti?

259
00:12:28,200 --> 00:12:32,574
Hu jew hi biss trid li ssib wieħed imsakkar
bieb, tieqa waħda miksur, jew xi ħaġa

260
00:12:32,574 --> 00:12:35,240
flimkien dawk il-linji, u huwa l-
istess ħaġa fil sigurtà tal-kompjuter.

261
00:12:35,240 --> 00:12:37,660
Nistgħu jiktbu miljuni ta '
linji ta 'kodiċi ta' programmazzjoni

262
00:12:37,660 --> 00:12:40,570
u jonfqu mijiet jew eluf
ta 'sigħat tipprova tikseb dan korretta,

263
00:12:40,570 --> 00:12:43,370
imma jekk inti tagħmel wieħed biss
żball fl korrettezza,

264
00:12:43,370 --> 00:12:47,030
inti tista 'tpoġġi s-sistema kollha u
tabilħaqq f'dan il-każ, l-internet kollu

265
00:12:47,030 --> 00:12:48,660
u fid-dinja f'riskju.

266
00:12:48,660 --> 00:12:51,950
>> Mela jekk inti tixtieq titgħallem aktar
dwar dan, mur dan il-URL hawn.

267
00:12:51,950 --> 00:12:54,450
M'hemm l-ebda ħtieġa għal azzjoni
tonight sakemm int

268
00:12:54,450 --> 00:12:57,116
fost dawk aktar komdu li
ġew running web tiegħek stess

269
00:12:57,116 --> 00:12:59,810
server, f'liema każ inti għandek,
fil-fatt, taġġorna software tiegħek.

270
00:12:59,810 --> 00:13:03,244
>> U dan ukoll huwa t-titlu ta '
diskors, u issa karta,

271
00:13:03,244 --> 00:13:05,410
li konna marbuta fuq il-
websajt kors għall-lum.

272
00:13:05,410 --> 00:13:07,600
Kien minn sħabi
jismu Ken Thompson, li

273
00:13:07,600 --> 00:13:10,120
kien jaċċetta famużi ħafna
għoti fix-xjenza tal-kompjuter,

274
00:13:10,120 --> 00:13:13,495
u hu taw dan id-diskors xi snin
ilu, essenzjalment fuq dan l-istess suġġett.

275
00:13:13,495 --> 00:13:18,250

276
00:13:18,250 --> 00:13:20,520
Tistaqsi folks il-kwistjoni,
Jekk You verament

277
00:13:20,520 --> 00:13:23,480
fiduċja, finalment, il-
software inti ħadthom ġiet mogħtija?

278
00:13:23,480 --> 00:13:26,100
Per eżempju, ilkoll għandna
ġie kitba programmi,

279
00:13:26,100 --> 00:13:27,820
u konna qegħdin jiġbru
bl Clang.

280
00:13:27,820 --> 00:13:31,830
U biex l-għarfien tiegħek, qatt bil-miktub
xi programmi għall CS50 fejn hemm l-

281
00:13:31,830 --> 00:13:35,310
bieb lura ta 'tipi, hemm mod
li Guy ħażina, jekk running program tiegħek,

282
00:13:35,310 --> 00:13:37,410
setgħet tieħu f'idejha l-kompjuter tiegħek?

283
00:13:37,410 --> 00:13:38,310
Probabbilment le, id-dritt?

284
00:13:38,310 --> 00:13:40,180
Mario, u greedy, u Credit.

285
00:13:40,180 --> 00:13:41,680
Dawn huma programmi kollha pretty żgħar.

286
00:13:41,680 --> 00:13:43,910
Youd għandek tkun pretty
ħażina jekk inti fil-fatt

287
00:13:43,910 --> 00:13:47,310
magħmula sħiħa tal-kompjuter tiegħek vulnerabbli
wara bil-miktub 10 jew 20 linji ta 'kodiċi,

288
00:13:47,310 --> 00:13:49,690
jew għall-inqas konxji ta 'xi wħud
ta 'l-implikazzjonijiet ta' sigurtà.

289
00:13:49,690 --> 00:13:52,023
Now I ngħid li facetiously,
imma aħna qed tmur biex tara llum

290
00:13:52,023 --> 00:13:54,600
u din il-ġimgħa huwa attwalment
tassew, tassew faċli

291
00:13:54,600 --> 00:13:57,980
li jkun ħażin u tagħmel anke
programmi qosra vulnerabbli.

292
00:13:57,980 --> 00:14:02,880
>> Iżda għal issa, mill-inqas, tirrealizza
li l-kwistjoni qed jintalbu hawn

293
00:14:02,880 --> 00:14:04,850
huwa dwar Clang fil kompilatur.

294
00:14:04,850 --> 00:14:08,360
Għaliex aħna ġew fidu Clang
għall-aħħar żewġ jew tliet ġimgħat?

295
00:14:08,360 --> 00:14:12,650
Min hu ngħid li kull min kiteb Clang
ma kellux "jekk" kundizzjoni fil hemm

296
00:14:12,650 --> 00:14:17,680
li essenzjalment injettat xi żerijiet
u dawk fis-kull programm jikkompila

297
00:14:17,680 --> 00:14:21,180
li let lilu jew lilha aċċess
kompjuter tiegħek meta int rieqed

298
00:14:21,180 --> 00:14:23,580
u għatu laptop tiegħek hija miftuħa
u l-kompjuter tiegħek tkun qed taħdem?

299
00:14:23,580 --> 00:14:24,080
Right?

300
00:14:24,080 --> 00:14:28,350
Għandna din it-tip tad-dritt sistema unur
issa fejn aħna fiduċja li Clang huwa leġittimu.

301
00:14:28,350 --> 00:14:30,000
Inti fiduċja li l-appliance huwa leġittimu.

302
00:14:30,000 --> 00:14:34,430
Inti fiduċja li litteralment kull programm
fuq Mac tiegħek jew PC hija affidabbli.

303
00:14:34,430 --> 00:14:37,510
U kif tissuġġerixxi din bug sempliċi,
anki jekk mhuwiex malizzjużi,

304
00:14:37,510 --> 00:14:40,580
li assolutament ma
probabbli li jkun il-każ.

305
00:14:40,580 --> 00:14:42,350
>> Allura inti għandek tkun jibża bħala infern.

306
00:14:42,350 --> 00:14:45,560
Franchement, hemm ebda sempliċi
soluzzjoni għal din ieħor

307
00:14:45,560 --> 00:14:48,185
minn tip ta 'kuxjenza tas-soċjetà
tal-kumplessità dejjem tiżdied

308
00:14:48,185 --> 00:14:50,310
li aħna qed tibni fuq nett
ta 'sistemi tal-kompjuter tagħna,

309
00:14:50,310 --> 00:14:53,740
u kif dejjem aktar vulnerabbli
nistgħu tajjeb ħafna 'jkun.

310
00:14:53,740 --> 00:14:55,570
>> Issa ma 'dak imsemmi, tbegħid.

311
00:14:55,570 --> 00:14:59,889
Allura tbegħid huwa problema stabbiliti tlieta, u
Tbegħid hija logħba mill-imgħoddi

312
00:14:59,889 --> 00:15:02,180
li inti tista 'recall, iżda
għalina fil-problema sett tlieta,

313
00:15:02,180 --> 00:15:04,450
dan jippermetti li tieħu
affarijiet back up a talja

314
00:15:04,450 --> 00:15:08,880
b'tali mod li meta aħna bil-miktub programmi,
anki fil-tieqa Terminal bħal dan,

315
00:15:08,880 --> 00:15:14,670
nistgħu tmexxi effettivament, finalment,
programmi grafika mhux

316
00:15:14,670 --> 00:15:17,800
b'differenza ta 'dawk kellna
aċċess fil Scratch.

317
00:15:17,800 --> 00:15:20,910
Allura dan huwa l-tal-persunal
implimentazzjoni ta 'tbegħid,

318
00:15:20,910 --> 00:15:23,930
li huwa biss dan l-briks-tkissir
logħba, li inti timxi jaqdfu tiegħek lura

319
00:15:23,930 --> 00:15:27,590
u lura, u inti laqat il-ballun
kontra dawk briks kkulurita top up.

320
00:15:27,590 --> 00:15:30,020
Allura dan huwa li jġibu us
tip ta 'lura lejn fejn

321
00:15:30,020 --> 00:15:33,180
konna kapaċi li jkunu malajr ħafna
ma Scratch, u issa ma 'C,

322
00:15:33,180 --> 00:15:35,800
implimentazzjoni tagħna stess
interfaces għall-utenti grafika.

323
00:15:35,800 --> 00:15:38,960
>> Iżda aktar minn dan, din
sett problema tirrappreżenta l-ewwel

324
00:15:38,960 --> 00:15:41,000
li aħna qed tagħti
inti mazz ta 'kodiċi.

325
00:15:41,000 --> 00:15:43,940
U fil-fatt, I iġibu espliċita
attenzjoni għal dan, għaliex speċjalment

326
00:15:43,940 --> 00:15:47,090
għal dawk inqas komdi, dan
problema stabbiliti, mill-inqas fl-ewwel daqqa t'għajn,

327
00:15:47,090 --> 00:15:49,170
huwa se jħossu bħal
aħna ħadt it up a talja.

328
00:15:49,170 --> 00:15:51,540
Għaliex aħna ve tak,
għal xi wħud mill-tfittxija

329
00:15:51,540 --> 00:15:54,930
u l-għażla l-problemi fil-pset,
mazz ta 'kodiċi li aħna kiteb,

330
00:15:54,930 --> 00:15:56,680
u l-koppja ta 'kummenti
li jgħidu "li tagħmel,"

331
00:15:56,680 --> 00:15:58,221
fejn inti għandek timla l-vojt.

332
00:15:58,221 --> 00:16:00,020
Allura mhux wisq scary, iżda
huwa l-ewwel darba

333
00:16:00,020 --> 00:16:03,370
aħna qed għoti inti kodiċi li għandek bżonn biex
ewwel taqra, tifhem, u mbagħad żid sa

334
00:16:03,370 --> 00:16:04,290
u titlesta.

335
00:16:04,290 --> 00:16:05,940
>> U mbagħad mal tbegħid,
aħna qed tmur biex jagħmlu l-istess,

336
00:16:05,940 --> 00:16:08,740
giving you tużżana ftit aktar linji
tal-kodiċi li, franchement, jagħtik

337
00:16:08,740 --> 00:16:11,490
lott tal-qafas għall-
il-logħba imma waqfa qasira

338
00:16:11,490 --> 00:16:14,304
tal-implimentazzjoni tal-briks
u l-ballun u l-jaqdfu,

339
00:16:14,304 --> 00:16:15,970
iżda nagħmlu jimplimentaw xi karatteristiċi oħra.

340
00:16:15,970 --> 00:16:18,280
U anki li ewwel daqqa t'għajn, għal darb'oħra,
speċjalment jekk inqas komdi,

341
00:16:18,280 --> 00:16:21,480
jista 'jidher partikolarment kbar u
taħseb li hemm funzjonijiet ġodda tant

342
00:16:21,480 --> 00:16:24,070
għandek bżonn biex nagħlaq moħħ tiegħek
madwar, u dan huwa veru.

343
00:16:24,070 --> 00:16:26,281
Iżda jżomm f'moħħu, huwa
pjuttost simili Scratch.

344
00:16:26,281 --> 00:16:28,780
Odds huma inti ma tuża kollha ta '
il-biċċiet puzzle fil Scratch.

345
00:16:28,780 --> 00:16:31,120
Odds huma inti ma 'kura biex nagħlaq
moħħok madwar kull wieħed minnhom

346
00:16:31,120 --> 00:16:33,617
minħabba li kull ma ħadet kien
t'għajn malajr biex jifhmu, oh,

347
00:16:33,617 --> 00:16:35,450
dan huwa dak I tista 'tagħmel
ma dik il-biċċa puzzle.

348
00:16:35,450 --> 00:16:38,260
U fil-fatt, fil-problema sett
3 spec, aħna ser punt inti

349
00:16:38,260 --> 00:16:41,370
fil-dokumentazzjoni li se
jintroduċu inti għal xi funzjonijiet ġodda,

350
00:16:41,370 --> 00:16:43,570
u finalment l-ipprogrammar
constructs tuża.

351
00:16:43,570 --> 00:16:47,610
Kundizzjonijiet, loops,
varjabbli, u funzjonijiet

352
00:16:47,610 --> 00:16:50,720
se jkun identiku għal
dak li aħna stajt tidher s'issa.

353
00:16:50,720 --> 00:16:53,560
>> Allura fil-fatt, dak li aħna ser jagħtuk
inti xi kodiċi tal-kampjun li

354
00:16:53,560 --> 00:16:56,110
ihallik toħloq tieqa
li jistenna ma b'differenza dan,

355
00:16:56,110 --> 00:16:59,540
u finalment jibdluh
xi ħaġa pjuttost bħal dan.

356
00:16:59,540 --> 00:17:02,250
Sabiex jieħdu vantaġġ ta 'CS50,
jiddiskutu ħinijiet tal-uffiċċju u aktar,

357
00:17:02,250 --> 00:17:05,290
u jieħdu l-kumdità fil-fatt li
l-ammont tal-kodiċi inti ghandek tikteb

358
00:17:05,290 --> 00:17:06,760
huwa attwalment mhux kollha li ħafna.

359
00:17:06,760 --> 00:17:10,359
L-ewwel sfida hija biss biex aklimatizza
lilek innifsek biex xi kodiċi konna bil-miktub.

360
00:17:10,359 --> 00:17:11,450

361
00:17:11,450 --> 00:17:15,810
>> Kwalunkwe mistoqsijiet dwar pset3,
Shellshock, jew inkella?

362
00:17:15,810 --> 00:17:19,226
>> UDJENZA: Huwa dehret qisha
għaddejjin ma tbegħid

363
00:17:19,226 --> 00:17:22,154
li l-kodiċi huwa kważi
stil oġġett orjentati lejn,

364
00:17:22,154 --> 00:17:24,675
imma ħsibt C kien
programm oġġett orjentati lejn.

365
00:17:24,675 --> 00:17:26,050
SPEAKER 1: An kwistjoni eċċellenti.

366
00:17:26,050 --> 00:17:28,258
Allura meta tħares permezz tal-
kodiċi ta 'distribuzzjoni, il-kodiċi

367
00:17:28,258 --> 00:17:30,180
aħna kiteb għall pset3,
għal dawk familjari, huwa

368
00:17:30,180 --> 00:17:32,230
qisu huwa
ftit oġġett orjentati lejn.

369
00:17:32,230 --> 00:17:33,800
Risposta qasira hija, huwa.

370
00:17:33,800 --> 00:17:38,130
Huwa ta 'approssimazzjoni ta' kif inti
tista 'tagħmel kodiċi oġġett orjentati lejn użu

371
00:17:38,130 --> 00:17:41,850
lingwa bħal C, iżda huwa
xorta finalment proċedurali.

372
00:17:41,850 --> 00:17:44,900
M'hemm l-ebda metodi ġewwa ta
il-varjabbli, kif tkun taf tara.

373
00:17:44,900 --> 00:17:46,180
Iżda huwa reminixxenti ta 'dak.

374
00:17:46,180 --> 00:17:48,780
U aħna ser tara li karatteristika darb'oħra
meta nikbru biex PHP u JavaScript

375
00:17:48,780 --> 00:17:49,946
lejn l-aħħar tal-semestru.

376
00:17:49,946 --> 00:17:53,667
Iżda għal issa, jaħsbu li bħala
ħjiel ta 'dak li ġejjin.

377
00:17:53,667 --> 00:17:54,250
Mistoqsija tajba.

378
00:17:54,250 --> 00:17:56,051

379
00:17:56,051 --> 00:17:56,550
Kull dritt.

380
00:17:56,550 --> 00:17:59,730
Allura jingħaqdu sort kien kif aħna
affarijiet xellug aħħar darba.

381
00:17:59,730 --> 00:18:03,250
U jingħaqdu sort kien jibred fil-
sens li kien tant ħafna aktar mgħaġġla,

382
00:18:03,250 --> 00:18:07,100
mill-inqas ibbażat fuq it-testijiet ta 'malajr
għamilna aħħar ġimgħa, minn, ngħidu aħna, bubble

383
00:18:07,100 --> 00:18:08,710
sort, sort għażla, sort inserzjoni.

384
00:18:08,710 --> 00:18:11,780
U dak kien pulita wisq huwa biss
kif konċiż u nadif

385
00:18:11,780 --> 00:18:12,810
inti tista 'tesprimi lilha.

386
00:18:12,810 --> 00:18:15,840
U dak ma ngħidu li kien ta 'fuq
marbuta fuq il-running time ta jingħaqdu

387
00:18:15,840 --> 00:18:16,340
sort?

388
00:18:16,340 --> 00:18:17,633

389
00:18:17,633 --> 00:18:18,495
Yeah?

390
00:18:18,495 --> 00:18:19,360
>> UDJENZA: n log n?

391
00:18:19,360 --> 00:18:20,819
>> SPEAKER 1: n log n, id-dritt. n log n.

392
00:18:20,819 --> 00:18:23,776
U aħna ser terga 'lura għal dak li
verament ifisser jew fejn dik ġejja minn,

393
00:18:23,776 --> 00:18:25,570
iżda dan kien aħjar
minn dak iż-żmien running

394
00:18:25,570 --> 00:18:28,440
li rajna għal bubble
għażla u sort inserzjoni?

395
00:18:28,440 --> 00:18:30,610
Allura n kwadrat. n kwadrat
hija akbar minn dan,

396
00:18:30,610 --> 00:18:34,650
u anki jekk mhuwiex pjuttost ovvju,
jafu li log n huwa iżgħar minn n,

397
00:18:34,650 --> 00:18:36,910
hekk jekk inti tagħmel n darbiet
xi ħaġa iżgħar minn n,

398
00:18:36,910 --> 00:18:38,680
li għaddej biex tkun inqas minn n kwadrat.

399
00:18:38,680 --> 00:18:40,130
Huwa daqsxejn ta intwizzjoni hemmhekk.

400
00:18:40,130 --> 00:18:42,190
Iżda aħna mħallsa prezz għal dan.

401
00:18:42,190 --> 00:18:47,000
Kien aktar mgħaġġel, iżda tema li beda
jitfaċċaw aħħar ġimgħa kien dan tradeoff.

402
00:18:47,000 --> 00:18:49,804
I ltqajna prestazzjoni aħjar
ħin għaqli, imma dak

403
00:18:49,804 --> 00:18:52,470
ma I jkollu jonfoq fuq l-oħra
idejn, sabiex jintlaħaq dak?

404
00:18:52,470 --> 00:18:53,591
>> UDJENZA: Memorja.

405
00:18:53,591 --> 00:18:54,465
SPEAKER 1: Say mill-ġdid?

406
00:18:54,465 --> 00:18:55,173
UDJENZA: Memorja.

407
00:18:55,173 --> 00:18:57,040
SPEAKER 1: Memorja, jew
spazju aktar ġenerali.

408
00:18:57,040 --> 00:18:59,040
U ma kienx super
ovvja mal-bnedmin tagħna,

409
00:18:59,040 --> 00:19:02,240
iżda tfakkar li l-voluntiera tagħna
kienu żżid l quddiem u t-tisħiħ

410
00:19:02,240 --> 00:19:04,780
lura bħallikieku hemm firxa
hawn, u bħala għalkemm hemm

411
00:19:04,780 --> 00:19:07,130
tieni firxa hawnhekk li
huma jistgħu jużaw, għaliex aħna

412
00:19:07,130 --> 00:19:09,080
someplace meħtieġa li jingħaqdu dawk folks.

413
00:19:09,080 --> 00:19:11,480
Aħna ma setgħux biss tpartit lilhom fil-post.

414
00:19:11,480 --> 00:19:13,800
Allura jingħaqdu leverage sort
huwa aktar spazju, li

415
00:19:13,800 --> 00:19:15,620
aħna ma bżonn ma
l-algoritmi oħra,

416
00:19:15,620 --> 00:19:17,410
iżda l-rasu hija li huwa ħafna aktar mgħaġġla.

417
00:19:17,410 --> 00:19:20,780
U franchement, fl-ispazju dinja reali
dawn RAM days--, disk hard space--

418
00:19:20,780 --> 00:19:25,030
huwa relattivament irħis, u b'tali mod li
mhux bilfors ħaġa ħażina.

419
00:19:25,030 --> 00:19:28,320
>> Mela ejja tagħti ħarsa, ftit
aktar metodiku, fuq dak li għamilna

420
00:19:28,320 --> 00:19:30,220
u għaliex aħna qal li kien n log n.

421
00:19:30,220 --> 00:19:33,260
Allura hawn huma l-tmien numri u l-
tmien voluntiera kellna aħħar darba.

422
00:19:33,260 --> 00:19:35,718
U l-ewwel ħaġa li Merge
Sort qalulna li tagħmel kien dak?

423
00:19:35,718 --> 00:19:37,010

424
00:19:37,010 --> 00:19:38,010
UDJENZA: Divide fi tnejn.

425
00:19:38,010 --> 00:19:38,663
SPEAKER 1: Say mill-ġdid?

426
00:19:38,663 --> 00:19:39,650
UDJENZA: Divide fi tnejn.

427
00:19:39,650 --> 00:19:40,610
SPEAKER 1: Iddividi fi tnejn, id-dritt.

428
00:19:40,610 --> 00:19:42,818
Dan huwa ħafna reminixxenti ta '
il-ktieb tat-telefon, tal-firda

429
00:19:42,818 --> 00:19:44,220
u conquer aktar ġenerali.

430
00:19:44,220 --> 00:19:45,640
Allura ħarisna lejn in-nofs xellugi.

431
00:19:45,640 --> 00:19:48,700
U mbagħad darba għidna, sort
in-nofs xellugi tal-elementi,

432
00:19:48,700 --> 00:19:49,690
dak li aħna ma jmiss ngħidu?

433
00:19:49,690 --> 00:19:51,210

434
00:19:51,210 --> 00:19:54,860
Sort in-nofs xellugi tal-xellug
nofs, li ħallietna nsiru,

435
00:19:54,860 --> 00:19:57,570
wara diviż fi tnejn,
tiffoka fuq erba 'u tnejn.

436
00:19:57,570 --> 00:20:01,280
>> Kif inti sort lista issa, fl
isfar, ta 'daqs tnejn, uża Jingħaqdu Sort?

437
00:20:01,280 --> 00:20:02,330

438
00:20:02,330 --> 00:20:04,580
Ukoll jaqsam min-nofs,
u sort l-nofs tax-xellug.

439
00:20:04,580 --> 00:20:07,100
U dan kien fejn l-affarijiet
ltqajna qosor stupid ftit.

440
00:20:07,100 --> 00:20:10,720
Kif inti sort lista li l-ta
daqs wieħed, bħal dan in-numru erbgħa hawn?

441
00:20:10,720 --> 00:20:12,330

442
00:20:12,330 --> 00:20:13,210
Huwa magħżula.

443
00:20:13,210 --> 00:20:14,200
Inti qed isir.

444
00:20:14,200 --> 00:20:17,300
>> Imma allura kif taħseb sort lista ta '
daqs wieħed meta huwa n-numru tnejn?

445
00:20:17,300 --> 00:20:21,640
Ukoll, l-istess ħaġa, iżda issa dak li kien l-
tielet u l-pass ewlieni fil Sort Merge?

446
00:20:21,640 --> 00:20:24,020
You kellhom jingħaqdu ix-xellug
nofs u l-nofs tal-lemin.

447
00:20:24,020 --> 00:20:26,580
U ladarba għamilna li, ħarisna
għal erbgħa, ħarisna lejn tnejn.

448
00:20:26,580 --> 00:20:28,750
Aħna iddeċieda id-dritt,
ovvjament tnejn jiġi l-ewwel,

449
00:20:28,750 --> 00:20:31,840
hekk aħna tpoġġi tnejn fil tagħha
post, segwit minn erbgħa.

450
00:20:31,840 --> 00:20:35,010
U issa inti għandek tip ta 'kontrina,
u dan huwa tip ta 'karatteristika

451
00:20:35,010 --> 00:20:37,570
ta 'algoriżmu bħal Merge
Sort, kontrina fil-memorja.

452
00:20:37,570 --> 00:20:40,240
Liema kienet l-linja li jmiss tal-istorja?

453
00:20:40,240 --> 00:20:41,780
X'għandi I jkun qed jiffoka fuq li jmiss?

454
00:20:41,780 --> 00:20:43,110

455
00:20:43,110 --> 00:20:47,350
Id-nofs tal-lemin tal-xellug
nofs, Liema hija sitta u tmienja.

456
00:20:47,350 --> 00:20:50,320
>> So let me biss pass permezz ta 'dan
mingħajr belaboring il-punt wisq.

457
00:20:50,320 --> 00:20:53,330
Sitta u tmienja, allura sitta hija
magħżula, tmienja huwa magħżul.

458
00:20:53,330 --> 00:20:57,190
Jingħaqdu flimkien bħal dik,
u issa l-pass kbir li jmiss

459
00:20:57,190 --> 00:21:00,990
huwa, naturalment, isolvi l-nofs tal-lemin minn
l-ewwel pass ta 'din algoritmu.

460
00:21:00,990 --> 00:21:02,870
Allura aħna niffukaw fuq waħda, tlieta, seba ', ħamsa.

461
00:21:02,870 --> 00:21:04,540
Aħna mbagħad tiffoka fuq in-nofs xellugi.

462
00:21:04,540 --> 00:21:09,400
Il-half-xellug ta 'dik, l-nofs tal-lemin tal-
li, u mbagħad jingħaqdu f'waħda u tlieta.

463
00:21:09,400 --> 00:21:13,100
Imbagħad il-nofs tal-lemin, mbagħad titħalla nofs
ta 'dan, allura l-nofs tal-lemin ta' dan.

464
00:21:13,100 --> 00:21:15,985
Jingħaqdu fil, u issa liema pass jibqa?

465
00:21:15,985 --> 00:21:18,040

466
00:21:18,040 --> 00:21:22,460
Jingħaqdu in-nofs xellugi kbar u l-big
nofs tal-lemin, sabiex wieħed jinżel hemmhekk,

467
00:21:22,460 --> 00:21:27,330
imbagħad tnejn, imbagħad tlieta, imbagħad erba, allura
ħames, allura sitta, allura seba ', imbagħad tmienja.

468
00:21:27,330 --> 00:21:31,990
>> Allura issa għaliex dan huwa finalment tiżvela,
speċjalment jekk nu logaritmi aktar

469
00:21:31,990 --> 00:21:35,487
ġeneralment pjuttost jaħarbu inti,
inqas fil-memorja riċenti?

470
00:21:35,487 --> 00:21:37,070
Ukoll, avviż l-għoli ta 'dan il-ħaġa.

471
00:21:37,070 --> 00:21:41,230
Kellna tmien elementi, u aħna
maqsuma lilha mill tnejn, minn tnejn, bi tnejn.

472
00:21:41,230 --> 00:21:44,590
Allura log bażi tnejn tmienja tagħtina tlieta.

473
00:21:44,590 --> 00:21:45,640

474
00:21:45,640 --> 00:21:48,540
U trust me fuq li jekk
a imċajpra ftit fuq dak.

475
00:21:48,540 --> 00:21:54,710
Iżda log bażi tnejn ta 'tmienja hija tlieta,
hekk aħna ghamilt tliet saffi ta 'amalgamazzjoni.

476
00:21:54,710 --> 00:21:57,170
U meta aħna magħquda
elementi, kif ħafna elementi

477
00:21:57,170 --> 00:21:58,950
ma nħarsu lejn fuq kull waħda minn dawk il-ringieli?

478
00:21:58,950 --> 00:22:00,212

479
00:22:00,212 --> 00:22:01,437
A total ta n, id-dritt?

480
00:22:01,437 --> 00:22:04,020
Minħabba li jingħaqdu l-filliera ta 'fuq,
anke jekk aħna ma kien frammentat,

481
00:22:04,020 --> 00:22:05,990
aħna finalment mimsus kull numru darba.

482
00:22:05,990 --> 00:22:09,054
U fit-tieni ringiela, biex
jingħaqdu dawn il-listi ta 'daqs tnejn,

483
00:22:09,054 --> 00:22:10,470
kellna tmissx kull element darba.

484
00:22:10,470 --> 00:22:12,690
U allura hawnhekk verament
b'mod ċar fl-aħħar ringiela,

485
00:22:12,690 --> 00:22:15,430
kellna tmissx kull wieħed minn dawk
Elementi darba, imma darba biss,

486
00:22:15,430 --> 00:22:18,400
hekk hawnhekk tinsab, allura, log n tagħna n.

487
00:22:18,400 --> 00:22:21,780
>> U issa biss biex jagħmlu l-affarijiet ftit
aktar formali għal ftit mument, jekk inti

488
00:22:21,780 --> 00:22:24,260
kellhom issa tanalizza din
fuq tip ta 'livell ogħla

489
00:22:24,260 --> 00:22:28,340
u jippruvaw biex jiddeċiedu, sew kif
jista inti tmur dwar jesprimu

490
00:22:28,340 --> 00:22:31,780
l-running time ta 'dan algoritmu
biss billi tħares lejn dan u mhux

491
00:22:31,780 --> 00:22:33,590
bl-użu ta 'eżempju artifiċjali?

492
00:22:33,590 --> 00:22:36,590
Well, kemm ħin inti tgħid a
pass bħal dan bl-isfar se tieħu,

493
00:22:36,590 --> 00:22:37,173
jekk n <2 ritorn?

494
00:22:37,173 --> 00:22:38,840

495
00:22:38,840 --> 00:22:39,830
Li l-O kbira ta 'dak?

496
00:22:39,830 --> 00:22:41,450

497
00:22:41,450 --> 00:22:44,540
So jien jaraw wieħed, hekk pass wieħed,
forsi żewġ passi għaliex dan huwa jekk

498
00:22:44,540 --> 00:22:47,110
u mbagħad jirritornaw, imma hija
ħin kostanti, id-dritt?

499
00:22:47,110 --> 00:22:49,960
Allura aħna qal O (1), u li l-
kif I ser jesprimu dan.

500
00:22:49,960 --> 00:22:51,480
T, jkun biss running time.

501
00:22:51,480 --> 00:22:54,150
n huwa d-daqs ta 'l-input,
hekk T (n), biss mod fancy

502
00:22:54,150 --> 00:22:56,330
ta 'tgħid it-tmexxija
ħin input mogħti d-daqs n

503
00:22:56,330 --> 00:23:00,220
se tkun fuq l-ordni
ta 'żmien kostanti, fil O (1).

504
00:23:00,220 --> 00:23:01,970
>> Iżda altrimenti, dak dwar dan?

505
00:23:01,970 --> 00:23:05,660
Kif inti tesprimi l-
żmien ta 'din il-linja isfar running?

506
00:23:05,660 --> 00:23:06,250
T ta 'dak?

507
00:23:06,250 --> 00:23:09,440

508
00:23:09,440 --> 00:23:12,665
Tista 'tip ta' iqarrqu hawn u
iwieġeb il-mistoqsija tiegħi ċiklikament.

509
00:23:12,665 --> 00:23:14,770

510
00:23:14,770 --> 00:23:17,900
Allura jekk il-ħin jibda fil
ġenerali aħna biss ngħid huwa T (n).

511
00:23:17,900 --> 00:23:18,950

512
00:23:18,950 --> 00:23:22,490
U issa int tip ta 'punting hawn u
qal, ukoll, biss issolvi in-nofs xellugi,

513
00:23:22,490 --> 00:23:23,920
u mbagħad issolvi l-nofs tal-lemin.

514
00:23:23,920 --> 00:23:27,520
Kif tista aħna simbolikament jirrappreżentaw
l-running time ta 'din il-linja isfar?

515
00:23:27,520 --> 00:23:28,020
T ta 'dak?

516
00:23:28,020 --> 00:23:29,360
X'hemm-daqs tal-input?

517
00:23:29,360 --> 00:23:30,510

518
00:23:30,510 --> 00:23:31,057
n matul tnejn.

519
00:23:31,057 --> 00:23:32,140
Għaliex ma I biss jgħidu li?

520
00:23:32,140 --> 00:23:36,449
U allura dan hu T ieħor (n / 2) u mbagħad
darb'oħra, jekk I jingħaqdu żewġ nofsijiet magħżula,

521
00:23:36,449 --> 00:23:38,615
kemm elementi ħafna jien ser
li jkollhom tmissx total?

522
00:23:38,615 --> 00:23:39,780

523
00:23:39,780 --> 00:23:40,320
n.

524
00:23:40,320 --> 00:23:42,790
So I tista 'tesprimi dan,
biss sabiex ikunu tip ta 'fancy,

525
00:23:42,790 --> 00:23:44,430
bħala l-running time b'mod ġenerali.

526
00:23:44,430 --> 00:23:51,140
T (n) huwa biss il-ħin running ta 'T (n / 2),
plus T (n / 2), ħalla nofs u nofs tal-lemin,

527
00:23:51,140 --> 00:23:55,360
plus O (n), li huwa probabbilment n passi,
imma forsi, jekk jien jużaw żewġ swaba,

528
00:23:55,360 --> 00:23:57,960
huwa darbtejn daqs
passi, imma hija lineari.

529
00:23:57,960 --> 00:24:00,440
Huwa xi numru ta 'passi
li l-fattur ta 'n,

530
00:24:00,440 --> 00:24:02,270
hekk aħna jistgħu jifformulaw dan bħala dan.

531
00:24:02,270 --> 00:24:05,550
U dan huwa fejn issa aħna ser Punt għall-
lura l-iskola għolja matematika textbook tagħna

532
00:24:05,550 --> 00:24:10,290
aħna qed li rikorrenza finalment
jispiċċa daqs dan, n drabi log n,

533
00:24:10,290 --> 00:24:12,530
jekk inti fil-fatt tagħmel out
l-matematika b'mod aktar formali.

534
00:24:12,530 --> 00:24:13,950
>> Allura dak biss żewġ perspettivi.

535
00:24:13,950 --> 00:24:17,500
Wieħed numerikament bi
hard-kodifikati eżempju rappreżentattiv

536
00:24:17,500 --> 00:24:21,140
jużaw tmien numri, u aktar
ħarsa ġenerali lejn kif sirna hemmhekk.

537
00:24:21,140 --> 00:24:25,670
Imma x'hemm verament interessanti hawn
hija, għal darb'oħra, dan il-kunċett ta 'ċikliżmu.

538
00:24:25,670 --> 00:24:26,900
Jien ma jużaw għall loops.

539
00:24:26,900 --> 00:24:29,860
Jien tip ta 'tiddefinixxi
xi ħaġa f'termini ta nnifisha,

540
00:24:29,860 --> 00:24:31,950
mhux biss ma 'dan
funzjoni matematika,

541
00:24:31,950 --> 00:24:34,860
iżda wkoll f'termini ta 'dan il-kodiċi psewdo.

542
00:24:34,860 --> 00:24:38,260
Dan il-kodiċi psewdo huwa rikursivi
f'dak tnejn ta 'linji tagħha

543
00:24:38,260 --> 00:24:42,310
huwa essenzjalment javżak li tmur
jużaw ruħha li ssolvi iżgħar

544
00:24:42,310 --> 00:24:45,400
problema ta 'daqs iżgħar,
u mbagħad għal darb'oħra u għal darb'oħra

545
00:24:45,400 --> 00:24:48,820
u għal darb'oħra sakemm aħna Whittle dan
stabbiliti għal din l-hekk imsejħa każ bażi.

546
00:24:48,820 --> 00:24:52,810
>> Mela ejja attwalment jiġbed aktar konvinċenti
take-away minn dan kif ġej.

547
00:24:52,810 --> 00:24:58,420
Let me go fis gedit u tieħu
nħarsu lejn uħud mill-kodiċi sors tal-lum,

548
00:24:58,420 --> 00:24:59,930
b'mod partikolari f'dan l-eżempju hawn.

549
00:24:59,930 --> 00:25:03,709
Sigma 0, li apparentement żżid
in-numri wieħed permezz n.

550
00:25:03,709 --> 00:25:05,750
Mela ejja ara x'hemm familjari
u mhux familjari hawn.

551
00:25:05,750 --> 00:25:08,690
L-ewwel għandna koppja ta '
jinkludi, b'hekk m'hemm xejn ġdid.

552
00:25:08,690 --> 00:25:09,190
Prototip.

553
00:25:09,190 --> 00:25:11,370
Jien imċajpra ftit fuq
dan wara ftit jiem,

554
00:25:11,370 --> 00:25:13,790
imma dak li ma aħna ngħidu
prototip ta 'funzjoni hu?

555
00:25:13,790 --> 00:25:15,099

556
00:25:15,099 --> 00:25:16,015
UDJENZA: [inaudible].

557
00:25:16,015 --> 00:25:16,905
SPEAKER 1: X'hemm li?

558
00:25:16,905 --> 00:25:17,800
UDJENZA: Aħna jħabbar dan.

559
00:25:17,800 --> 00:25:18,883
SPEAKER 1: Aħna jħabbar dan.

560
00:25:18,883 --> 00:25:22,290
Allura inti qed jgħallmu Clang, ħej,
mhux attwalment timplimenta dan għadu,

561
00:25:22,290 --> 00:25:25,740
iżda x'imkien fil dan il-fajl, preżumibbilment,
se tkun funzjoni msejħa liema?

562
00:25:25,740 --> 00:25:26,930

563
00:25:26,930 --> 00:25:27,540
Sigma.

564
00:25:27,540 --> 00:25:30,540
U dan huwa biss wegħda li
li għaddej biex teżamina bħal dan.

565
00:25:30,540 --> 00:25:33,720
Huwa ser jieħu integer bħala
input-- u I tista 'tkun aktar espliċita

566
00:25:33,720 --> 00:25:36,570
u jgħidu int n --and huwa
ser jirritorna l int,

567
00:25:36,570 --> 00:25:39,900
iżda mezzi punto virgola, mm, jien ser tikseb madwar
biex jiġi implimentat dan ftit aktar tard.

568
00:25:39,900 --> 00:25:40,989
Għal darb'oħra, Clang huwa dumb.

569
00:25:40,989 --> 00:25:43,280
Huwa biss ser tkun taf liema
inti tgħid li fuq għal isfel,

570
00:25:43,280 --> 00:25:45,765
għalhekk għandna bżonn biex tagħti mill-inqas
huwa ħjiel ta 'dak li ġejjin.

571
00:25:45,765 --> 00:25:47,330
>> Issa ejja nħarsu lejn prinċipali hawnhekk.

572
00:25:47,330 --> 00:25:50,040
Ejja iscroll hawn u
ara dak prinċipali qed tagħmel.

573
00:25:50,040 --> 00:25:53,780
Mhuwiex dak twil ta 'funzjoni, u
fil-fatt il tibni hawnhekk huwa familjari.

574
00:25:53,780 --> 00:25:57,590
Niddikjara n varjabbli, u mbagħad
I jiffittaw bis-utent mill-ġdid u għal darb'oħra

575
00:25:57,590 --> 00:26:01,880
għal numru sħiħ pożittiv jużaw getInt,
u biss ħruġ minn dan loop

576
00:26:01,880 --> 00:26:03,280
ladarba l-utent ikun ikkonforma.

577
00:26:03,280 --> 00:26:05,670
Do Filwaqt, konna użati biex
jiffittaw bis-utent b'dan il-mod.

578
00:26:05,670 --> 00:26:06,670
Issa dan huwa interessanti.

579
00:26:06,670 --> 00:26:08,510
Niddikjara li int imsejħa "risposta."

580
00:26:08,510 --> 00:26:11,420
I tassenja din il-valur tar-ritorn
ta 'funzjoni msejħa "sigma."

581
00:26:11,420 --> 00:26:15,200
I do not know dak li ma s'issa, iżda
I remember tiddikjarah mument ilu.

582
00:26:15,200 --> 00:26:18,310
U mbagħad jien tgħaddi fil-
valur li l-utent ittajpjat fil, n,

583
00:26:18,310 --> 00:26:20,420
u mbagħad I tirrapporta l-risposta.

584
00:26:20,420 --> 00:26:22,260
Well ejja iscroll lura
għal ftit mument.

585
00:26:22,260 --> 00:26:28,620
Ejja imorru quddiem fis dan id-direttorju, jagħmlu
sigma 0, u fil-fatt imexxu dan il-programm

586
00:26:28,620 --> 00:26:30,490
u tara x'jiġri.

587
00:26:30,490 --> 00:26:35,930
Mela jekk jien aqbad u run
dan il-programm, ./sigma-0,

588
00:26:35,930 --> 00:26:40,139
u I tip fil pożittiva
integer bħall tnejn, Sigma,

589
00:26:40,139 --> 00:26:43,180
bħala s-simbolu Grieg jimplika, huwa biss
ser jammontaw-numri kollha mill-

590
00:26:43,180 --> 00:26:44,320
żero fuq sa tnejn.

591
00:26:44,320 --> 00:26:46,560
Allura 0 plus 1 plus 2.

592
00:26:46,560 --> 00:26:48,830
Allura dan għandu nisperaw tagħti me 3.

593
00:26:48,830 --> 00:26:49,750
Li kollox huwa qed jagħmel.

594
00:26:49,750 --> 00:26:52,690
U bl-istess mod, jekk I run dan jerġa
u I tagħtiha n-numru tlieta,

595
00:26:52,690 --> 00:26:56,721
li għamilhom 3 plus 2, b'tali mod li
5, flimkien ma '1 għandu jagħti me 6.

596
00:26:56,721 --> 00:26:59,470
U mbagħad jekk niġi verament crazy u
tibda ittajpjar f'numri akbar,

597
00:26:59,470 --> 00:27:01,290
hija għandha tagħti me
somom akbar u akbar.

598
00:27:01,290 --> 00:27:02,250
Allura li kollox.

599
00:27:02,250 --> 00:27:04,010
>> Allura dak li ma sigma look like?

600
00:27:04,010 --> 00:27:05,430
Ukoll, huwa pjuttost sempliċi.

601
00:27:05,430 --> 00:27:08,940
Huwa mod kif aħna jista 'jkollha implimentati
dan għall-aħħar ftit ġimgħat.

602
00:27:08,940 --> 00:27:11,120
"Int" se jkun it-tip ta 'ritorn.

603
00:27:11,120 --> 00:27:14,330
Sigma huwa l-isem, u li tieħu
m varjabbli minflok n.

604
00:27:14,330 --> 00:27:15,940
I ser bidla li top up.

605
00:27:15,940 --> 00:27:17,340
Imbagħad din hija biss check sanità.

606
00:27:17,340 --> 00:27:18,430

607
00:27:18,430 --> 00:27:19,950
Aħna ser tara għaliex fil-mument.

608
00:27:19,950 --> 00:27:24,220
Issa Niddikjara varjabbli ieħor,
somma, initialize għal żero.

609
00:27:24,220 --> 00:27:28,140
Imbagħad I jkollhom din Għal loop
mtennija, apparentement għaċ-ċarezza,

610
00:27:28,140 --> 00:27:33,810
mill-i = 1 fuq sa = m, li huwa
ikun x'ikun l-utent ittajpjat fil, u mbagħad I

611
00:27:33,810 --> 00:27:35,690
inkrement-somma bħal dan.

612
00:27:35,690 --> 00:27:37,360
U mbagħad jirritornaw is-somma.

613
00:27:37,360 --> 00:27:38,440
>> Allura koppja ta 'mistoqsijiet.

614
00:27:38,440 --> 00:27:42,370
Wieħed, I jitolbu fil-kummenti tiegħi li dan
jevita riskju ta 'loop infinita.

615
00:27:42,370 --> 00:27:45,620
Għaliex kieku tgħaddi f'numru negattiv
jinduċu, potenzjalment, loop infinita?

616
00:27:45,620 --> 00:27:49,396

617
00:27:49,396 --> 00:27:51,290
>> UDJENZA: Inti qatt ma ser ikollok jilħqu m.

618
00:27:51,290 --> 00:27:52,880
>> SPEAKER 1: Qatt jilħqu m.

619
00:27:52,880 --> 00:27:55,880
Iżda m huwa mgħoddi fil, so ejja
jikkunsidraw eżempju sempliċi.

620
00:27:55,880 --> 00:27:58,510
Jekk m huwa mgħoddi fil mill-
utent bħala wieħed negattiv.

621
00:27:58,510 --> 00:28:00,059
Irrispettivament ta 'prinċipali.

622
00:28:00,059 --> 00:28:01,850
Main jipproteġi lilna minn
dan ukoll, hekk jien biss

623
00:28:01,850 --> 00:28:04,680
tkun verament anali ma '
sigma li wkoll tagħmel żgur

624
00:28:04,680 --> 00:28:06,540
li l-input ma tistax tkun negattiva.

625
00:28:06,540 --> 00:28:10,130
Mela jekk m huwa negattiv,
xi ħaġa bħal waħda negattiva.

626
00:28:10,130 --> 00:28:11,930
X'hemm jiġri?

627
00:28:11,930 --> 00:28:14,390
Well, I se
nikseb initialized għal wieħed,

628
00:28:14,390 --> 00:28:19,060
u mbagħad i se tkun
inqas minn jew ugwali għal m?

629
00:28:19,060 --> 00:28:24,130

630
00:28:24,130 --> 00:28:24,765
>> Stand by.

631
00:28:24,765 --> 00:28:26,930

632
00:28:26,930 --> 00:28:29,370
Li was-- ejja ma,
ejja nix din l-istorja.

633
00:28:29,370 --> 00:28:32,780
I ma jistaqsu din il-kwistjoni, minħabba
ir-riskju li jiena jalludi għal

634
00:28:32,780 --> 00:28:38,360
huwa ma jiġri għaliex i huwa
dejjem se jkun OK than-- akbar,

635
00:28:38,360 --> 00:28:39,871
I tinġibed din id-domanda.

636
00:28:39,871 --> 00:28:40,370
OK.

637
00:28:40,370 --> 00:28:42,030
Ejja tiffoka biss fuq din il-parti hawn.

638
00:28:42,030 --> 00:28:44,210

639
00:28:44,210 --> 00:28:48,830
Għaliex ma Niddikjara xi
barra tal-linja?

640
00:28:48,830 --> 00:28:52,010
Avviż fuq il-linja 49 stajt
ddikjarat i ġewwa tal-loop,

641
00:28:52,010 --> 00:28:54,950
imma online 48 stajt
ddikjaraw madwar barra.

642
00:28:54,950 --> 00:28:55,695
Yeah.

643
00:28:55,695 --> 00:28:56,611
UDJENZA: [inaudible].

644
00:28:56,611 --> 00:28:58,734

645
00:28:58,734 --> 00:28:59,400
SPEAKER 1: Sure.

646
00:28:59,400 --> 00:29:03,360
Allura l-ewwel u qabel kollox I ċertament ma
tixtieq li tiddikjara u initialize somma

647
00:29:03,360 --> 00:29:06,130
għal żero ġewwa tal-
loop fuq kull iterazzjoni,

648
00:29:06,130 --> 00:29:09,370
minħabba li dan itellef b'mod ċar l-
għan tal jingħaddu up-numri.

649
00:29:09,370 --> 00:29:11,770
Nixtieq iżommu jinbidlu
il-valur lura għal żero.

650
00:29:11,770 --> 00:29:17,992
U wkoll, x'hemm ieħor aktar arcane
raġuni għal dik l-istess deċiżjoni disinn?

651
00:29:17,992 --> 00:29:18,954
Yeah.

652
00:29:18,954 --> 00:29:20,279
>> UDJENZA: [inaudible].

653
00:29:20,279 --> 00:29:21,070
SPEAKER 1: Eżattament.

654
00:29:21,070 --> 00:29:24,060
Irrid li jkollhom aċċess għaliha barra
tal-linja wisq fuq dak line?

655
00:29:24,060 --> 00:29:25,390

656
00:29:25,390 --> 00:29:26,400
Fuq 53.

657
00:29:26,400 --> 00:29:29,910
U bbażat fuq ir-regola tagħna ta 'thumb
minn koppja ta 'lectures ilu,

658
00:29:29,910 --> 00:29:33,680
varjabbli huma scoped, verament, l-
braces kaboċċi li jinkludu lilhom.

659
00:29:33,680 --> 00:29:38,190
Mela jekk jien ma jiddikjarawx somma ġewwa
ta 'dawn ċingi kaboċċi ta' barra,

660
00:29:38,190 --> 00:29:40,250
I ma tistax tużah fil-linja 53.

661
00:29:40,250 --> 00:29:43,160
Fi kliem ieħor, jekk I ddikjarat
somma hawn, jew saħansitra fi ħdan il-

662
00:29:43,160 --> 00:29:45,410
Għal loop, I ma setax aċċess għaliha fi 53.

663
00:29:45,410 --> 00:29:47,150
Il-varjabbli tkun marret effettiv.

664
00:29:47,150 --> 00:29:48,579
Allura ftit ta 'raġunijiet hemmhekk.

665
00:29:48,579 --> 00:29:50,370
Imma issa ejja mmorru lura
u tara x'jiġri.

666
00:29:50,370 --> 00:29:51,730
Allura sigma gets imsejħa.

667
00:29:51,730 --> 00:29:55,640
Hija żżid up 1 plus 2, jew 1 plus 2
plus 3, u mbagħad lura l-valur,

668
00:29:55,640 --> 00:29:59,660
taħżnu fil-tweġiba, u printf hawn
huwa għaliex jien jaraw fuq l-iskrin.

669
00:29:59,660 --> 00:30:03,079
Allura dan huwa dak li aħna ser sejħa ta 'iterattiv
approċċ, fejn iterazzjoni biss

670
00:30:03,079 --> 00:30:03,870
tfisser li tuża loop.

671
00:30:03,870 --> 00:30:06,900
A Għal loop, linja Filwaqt, Do Filwaqt
loop, biss tagħmel xi ħaġa mill-ġdid

672
00:30:06,900 --> 00:30:08,380
u għal darb'oħra u għal darb'oħra.

673
00:30:08,380 --> 00:30:13,505
>> Iżda sigma huwa tip ta 'funzjoni pulita fil
li I jista 'jimplimenta b'mod differenti.

674
00:30:13,505 --> 00:30:14,620

675
00:30:14,620 --> 00:30:19,120
What dwar dan, li
biss sabiex ikunu tip ta 'kessaħ,

676
00:30:19,120 --> 00:30:21,880
let me verament jeħles
ta 'lott ta' distrazzjoni

677
00:30:21,880 --> 00:30:24,380
għaliex din il-funzjoni
huwa verament pjuttost sempliċi.

678
00:30:24,380 --> 00:30:27,780
Ejja Whittle l-isfel biss
għal-linji ewlenin tagħha erba

679
00:30:27,780 --> 00:30:30,410
u jeħles l-
kummenti u braces kaboċċi.

680
00:30:30,410 --> 00:30:34,334
Dan huwa tip ta 'mind-blowing
implimentazzjoni alternattiva.

681
00:30:34,334 --> 00:30:37,250
Kull dritt, forsi mhux nfiħ mind-,
imma hija tip ta 'sexier, id-dritt,

682
00:30:37,250 --> 00:30:39,920
li tħares lejn dan tant aktar konċiż.

683
00:30:39,920 --> 00:30:43,120
Bil biss erba 'linji ta' kodiċi,
I l-ewwel ikollhom dan il-kontroll sanità.

684
00:30:43,120 --> 00:30:45,732
Jekk m hija inqas minn jew ugwali għal
żero, sigma jagħmel ebda sens.

685
00:30:45,732 --> 00:30:48,190
Huwa biss suppost li jkun
F'dan il-każ għal numri pożittivi,

686
00:30:48,190 --> 00:30:50,340
hekk jien biss se
ritorn żero arbitrarjament

687
00:30:50,340 --> 00:30:53,210
sabiex inkunu inqas ikollhom
xi hekk imsejħa każ bażi.

688
00:30:53,210 --> 00:30:54,430
>> Iżda hawn l-sbuħija.

689
00:30:54,430 --> 00:30:59,930
Il-intier ta 'din l-idea, li żżid l-
b'numri minn 1 sa n, jew m f'dan il-każ,

690
00:30:59,930 --> 00:31:02,630
jista 'jsir billi tip ta' tgħaddi l-Buck.

691
00:31:02,630 --> 00:31:04,947
Ukoll, dak li huwa s-somma ta '1 sa m?

692
00:31:04,947 --> 00:31:05,780
Well, inti taf liema?

693
00:31:05,780 --> 00:31:11,949
Huwa l-istess bħala s-somma ta 'm
flimkien mat-total ta '1 sa m minus 1.

694
00:31:11,949 --> 00:31:12,740
Well inti taf liema?

695
00:31:12,740 --> 00:31:13,940
X'hemm sigma ta m minus 1?

696
00:31:13,940 --> 00:31:17,860
Ukoll, jekk inti tip ta 'ssegwi dan
loġikament, huwa l-istess bħal m minus 1

697
00:31:17,860 --> 00:31:21,415
plus sigma tat m minus 2.

698
00:31:21,415 --> 00:31:22,480

699
00:31:22,480 --> 00:31:26,012
Allura inti tista 'tip ta' just--
dan huwa simili, jekk int biss

700
00:31:26,012 --> 00:31:28,220
jippruvaw idejqu xi ħabib
u dawn nistaqsik mistoqsija,

701
00:31:28,220 --> 00:31:31,344
inti tip ta jirrispondu bil-kwistjoni,
inti tista 'tip ta' jżomm tgħaddi l-Buck.

702
00:31:31,344 --> 00:31:34,560
Imma x'hemm importanti hu li jekk inti żżomm
jagħmlu l-kwistjoni iżgħar

703
00:31:34,560 --> 00:31:36,910
u iżgħar, int
ma tistaqsi x'hemm sigma

704
00:31:36,910 --> 00:31:39,116
ta n, x'hemm sigma ta
n, x'hemm sigma ta n?

705
00:31:39,116 --> 00:31:40,990
Inti qed tistaqsi x'inhu
sigma ta n, x'hemm sigma

706
00:31:40,990 --> 00:31:42,839
ta n minus 1, x'hemm sigma tal minus 2 n?

707
00:31:42,839 --> 00:31:44,880
Eventwalment mistoqsija tiegħek
se ssir liema?

708
00:31:44,880 --> 00:31:50,250
X'inhu sigma ta 'wieħed jew
żero, xi valur żgħir ħafna,

709
00:31:50,250 --> 00:31:52,220
u hekk kif inti
nikseb li, ħabib tiegħek,

710
00:31:52,220 --> 00:31:54,350
inti mhux ser jistaqsu
l-istess kwistjoni mill-ġdid,

711
00:31:54,350 --> 00:31:55,975
int biss se ngħid, oh huwa żero.

712
00:31:55,975 --> 00:31:58,490
We qed isir playing dan it-tip
ta 'logħba ċiklika stupid.

713
00:31:58,490 --> 00:32:02,950
>> Allura recursion huwa l-att fil-programmazzjoni
ta 'funzjoni ssejjaħ lilha nnifisha.

714
00:32:02,950 --> 00:32:06,630
Dan il-programm, meta miġbura u run, huwa
ser jaġixxu eżattament l-istess mod,

715
00:32:06,630 --> 00:32:09,620
imma x'hemm importanti hija li fi ħdan
ta 'funzjoni msejħa sigma,

716
00:32:09,620 --> 00:32:13,150
hemm linja ta 'kodiċi wherein
aħna qed ssejjaħ lilna nfusna,

717
00:32:13,150 --> 00:32:14,980
li normalment jkun ħażin.

718
00:32:14,980 --> 00:32:21,160
Per eżempju, jekk dak I-ewwel
kkompilata dan, sabiex tagħmel sigma--

719
00:32:21,160 --> 00:32:22,710
jagħmlu sigma 1 ./sigma-1.

720
00:32:22,710 --> 00:32:25,050

721
00:32:25,050 --> 00:32:27,690
Numru sħiħ pożittiv, jekk jogħġbok, 50 1275.

722
00:32:27,690 --> 00:32:30,810
Allura dak li l-funzjoni jidher li
jkun, ibbażata fuq test wieħed, korretta.

723
00:32:30,810 --> 00:32:34,917
Imma x'jiġri jekk I jiksbu ftit perikolużi
u ħassar l-hekk imsejħa każ bażi,

724
00:32:34,917 --> 00:32:37,750
u biss jgħidu, ukoll jien biss tagħmel
dan aktar ikkumplikat milli hi.

725
00:32:37,750 --> 00:32:42,450
Ejja biss kkalkulata l-sigma
billi mu mbagħad jiżdied

726
00:32:42,450 --> 00:32:44,564
fil sigma ta 'wieħed m nieqes?

727
00:32:44,564 --> 00:32:45,980
Ukoll, dak li jiġri hawn?

728
00:32:45,980 --> 00:32:47,140
Ejja zoom out.

729
00:32:47,140 --> 00:32:52,920
Ejja recompile-programm,
isalvawh, recompile-programm,

730
00:32:52,920 --> 00:33:00,450
u mbagħad lesti ./sigma 1 zooming,
jidħol numru sħiħ pożittiv jekk jogħġbok, 50.

731
00:33:00,450 --> 00:33:02,180

732
00:33:02,180 --> 00:33:04,430
Kemm inti lest
li fess li jaraw li?

733
00:33:04,430 --> 00:33:04,950
>> OK.

734
00:33:04,950 --> 00:33:06,690
Allura dan jista 'jiġri għal
numru ta 'raġunijiet,

735
00:33:06,690 --> 00:33:09,148
u franchement din il-ġimgħa aħna qed
waslet biex jagħtuk aktar minnhom.

736
00:33:09,148 --> 00:33:11,780
Iżda f'dan il-każ, ipprova
għal raġuni lura

737
00:33:11,780 --> 00:33:14,430
x'seta 'ġara hawn?

738
00:33:14,430 --> 00:33:17,400
Tort Segmentazzjoni, għidna aħħar
żmien, jirreferi għal segment ta 'memorja.

739
00:33:17,400 --> 00:33:18,690
Xi ħaġa ħażina ġara.

740
00:33:18,690 --> 00:33:21,550
Imma dak ma kien
mekkanikament li marru awry

741
00:33:21,550 --> 00:33:25,000
hawnhekk għaliex ta 'tneħħija tiegħi
ta 'dik hekk imsejħa każ bażi,

742
00:33:25,000 --> 00:33:26,870
fejn I lura valur hard-coded?

743
00:33:26,870 --> 00:33:28,970

744
00:33:28,970 --> 00:33:30,460
What do you think marret ħażin?

745
00:33:30,460 --> 00:33:31,219
Yeah.

746
00:33:31,219 --> 00:33:32,135
>> UDJENZA: [inaudible].

747
00:33:32,135 --> 00:33:36,387

748
00:33:36,387 --> 00:33:36,970
SPEAKER 1: Ah.

749
00:33:36,970 --> 00:33:37,550
Mistoqsija tajba.

750
00:33:37,550 --> 00:33:39,508
Allura l-daqs tan-numru
li kien I jingħaddu up

751
00:33:39,508 --> 00:33:41,920
ltqajna daqshekk kbira li jinqabeż
id-daqs tal-ispazju memorja.

752
00:33:41,920 --> 00:33:44,640
Idea tajba, iżda mhux fundamentalment
se jikkawżaw crash.

753
00:33:44,640 --> 00:33:48,230
Li jista 'jikkawża overflow numru sħiħ,
fejn il-bits ftit flip fuq

754
00:33:48,230 --> 00:33:51,760
u allura aħna żball verament kbir
numru simili għal numru negattiv,

755
00:33:51,760 --> 00:33:53,260
iżda li hi stess mhux se jikkawża crash.

756
00:33:53,260 --> 00:33:55,509
Minħabba fl-aħħar tal-
jum ta int għadu 32 bits.

757
00:33:55,509 --> 00:33:57,640
Int mhux ser
aċċidentalment steal daqsxejn 33.

758
00:33:57,640 --> 00:33:58,431
Iżda riflessjoni tajba.

759
00:33:58,431 --> 00:33:58,984
Yeah.

760
00:33:58,984 --> 00:33:59,900
>> UDJENZA: [inaudible].

761
00:33:59,900 --> 00:34:00,551

762
00:34:00,551 --> 00:34:02,300
SPEAKER 1: Il-metodu
qatt tieqaf taħdem,

763
00:34:02,300 --> 00:34:06,658
u tabilħaqq hija ssejjaħ lilha nnifisha mill-ġdid
u għal darb'oħra u għal darb'oħra u għal darb'oħra

764
00:34:06,658 --> 00:34:08,449
u għal darb'oħra, u ħadd minn
dawk il-funzjonijiet qatt

765
00:34:08,449 --> 00:34:13,310
finitura minħabba linja unika tagħhom ta '
kodiċi jitlob themself ġdid u għal darb'oħra

766
00:34:13,310 --> 00:34:14,219
u għal darb'oħra.

767
00:34:14,219 --> 00:34:16,080
U x'hemm verament
jiġri hawn, u issa aħna

768
00:34:16,080 --> 00:34:18,100
tista tip ta 'tiġbed dan pictorially.

769
00:34:18,100 --> 00:34:20,899
Let me go fuq għal
stampa għal ftit mument.

770
00:34:20,899 --> 00:34:22,940
Din hija stampa, li
eventwalment se tlaħħam

771
00:34:22,940 --> 00:34:26,336
f'aktar dettall, ta 'x'inhu għaddej
ġewwa tal-memorja tal-kompjuter tiegħek.

772
00:34:26,336 --> 00:34:28,460
U jirriżulta li fuq
il-qiegħ ta 'din l-istampa

773
00:34:28,460 --> 00:34:29,709
hija xi ħaġa imsejjaħ il-munzell.

774
00:34:29,709 --> 00:34:31,920
Din hija blokki ta '
memorja, blokki ta 'RAM,

775
00:34:31,920 --> 00:34:33,920
li jinsab biss jintuża kwalunkwe ħin
funzjoni huwa msejjaħ.

776
00:34:33,920 --> 00:34:36,239
Kwalunkwe ħin li inti, programmer,
sejħa funzjoni,

777
00:34:36,239 --> 00:34:38,860
is-sistema operattiva, bħal
Mac OS, Windows, jew Linux,

778
00:34:38,860 --> 00:34:41,920
grabs mazz ta 'bytes, forsi
ftit kilobytes, forsi ftit megabytes

779
00:34:41,920 --> 00:34:44,590
tal-memorja, idejn minnhom
lilek, u mbagħad tikri

780
00:34:44,590 --> 00:34:47,650
inti tmexxi funzjoni tiegħek billi tuża
kwalunkwe varjabbli għandek bżonn.

781
00:34:47,650 --> 00:34:50,699
U jekk inti mbagħad sejħa ieħor
funzjoni u funzjoni oħra,

782
00:34:50,699 --> 00:34:53,590
ikollok porzjon ieħor ta 'memorja
u porzjon ieħor ta 'memorja.

783
00:34:53,590 --> 00:34:57,090
>> U tabilħaqq, jekk dawn trejs aħdar
minn Annenberg jirrappreżentaw li l-memorja,

784
00:34:57,090 --> 00:34:59,870
hawn hu dak li jiġri l-ewwel
ħin inti sejħa sigma funzjoni.

785
00:34:59,870 --> 00:35:04,510
Huwa simili tqegħid trej bħal dan
fuq x'hemm inizjalment munzell vojta.

786
00:35:04,510 --> 00:35:07,142
Iżda mbagħad jekk dik trej
jitlob huwa stess, biex ngħidu hekk,

787
00:35:07,142 --> 00:35:08,850
ssejjaħ eżempju ieħor
ta sigma, li l-

788
00:35:08,850 --> 00:35:11,640
simili tistaqsi s-sistema operattiva,
ooh, jeħtieġ memorja ftit aktar,

789
00:35:11,640 --> 00:35:12,520
jagħtu me li.

790
00:35:12,520 --> 00:35:14,840
U allura jiġrilha piled fuq fuq nett.

791
00:35:14,840 --> 00:35:18,030
Imma x'hemm prinċipali hawnhekk hija li
l-ewwel trej għadha hemm,

792
00:35:18,030 --> 00:35:20,620
minħabba li hu invokat din it-tieni trej.

793
00:35:20,620 --> 00:35:23,500
Issa sadanittant, sigma sejħa sigma,
thats simili tistaqsi għall-memorja aktar.

794
00:35:23,500 --> 00:35:25,830
Gets piled fuq matul hawn.

795
00:35:25,830 --> 00:35:29,350
sigma sejħa sigma, li l-ieħor
trej li gets piled fuq hawn.

796
00:35:29,350 --> 00:35:32,942
U jekk inti żżomm tagħmel dan,
eventwalment, it-tip ta 'Mappa Dan viżwali

797
00:35:32,942 --> 00:35:35,525
għal dak chart, dak li għaddej biex
jiġri bil-munzell ta 'dixxijiet?

798
00:35:35,525 --> 00:35:37,480

799
00:35:37,480 --> 00:35:41,160
Huwa ser jaqbeż l-ammont
tal-memorja tal-kompjuter tiegħek.

800
00:35:41,160 --> 00:35:45,790
U hekk kif dan trej aħdar
jaqbeż il-linja orizzontali

801
00:35:45,790 --> 00:35:49,410
hawn fuq munzell u fuq din il-kelma borġ,
li aħna ser terga 'lura għal fil-futur,

802
00:35:49,410 --> 00:35:50,410
li hija ħaġa ħażina.

803
00:35:50,410 --> 00:35:52,810
Il borġ huwa differenti
segment ta 'memorja,

804
00:35:52,810 --> 00:35:55,190
u jekk inti let dawn
trejs pile u pile fuq,

805
00:35:55,190 --> 00:35:57,800
int ser taqbeż
segment tiegħek stess ta 'memorja,

806
00:35:57,800 --> 00:36:00,420
u programm huwa tabilħaqq se crash.

807
00:36:00,420 --> 00:36:02,930
>> Issa bħala twarrib, din l-idea
ta recursion, għalhekk,

808
00:36:02,930 --> 00:36:06,500
b'mod ċar jista 'jwassal għal problemi, iżda
mhuwiex neċessarjament ħaġa ħażina.

809
00:36:06,500 --> 00:36:08,840
Minħabba tikkunsidra, wara
kollha, how-- u forsi

810
00:36:08,840 --> 00:36:11,700
dan jieħu xi jkollna użati
li --how eleganti jew kif sempliċi

811
00:36:11,700 --> 00:36:14,890
li l-implimentazzjoni tal sigma kien.

812
00:36:14,890 --> 00:36:17,440
U aħna ma tkunx qed tmur għall-użu
recursion kollha li ħafna fl CS50,

813
00:36:17,440 --> 00:36:20,780
iżda fil CS51, u verament xi klassi
fejn inti jimmanipulaw data strutturi

814
00:36:20,780 --> 00:36:23,640
bħal siġar, jew siġar tal-familja,
li għandhom xi ġerarkija,

815
00:36:23,640 --> 00:36:26,000
huwa super, super utli.

816
00:36:26,000 --> 00:36:29,750
Issa, bħala twarrib, sabiex inti
bħala jaspiraw xjenzjati tal-kompjuter

817
00:36:29,750 --> 00:36:33,180
huma familjari ma 'wħud mill-Google
ċajt ġewwa, jekk inti tmur biex Google

818
00:36:33,180 --> 00:36:36,345
u inti tfittex up dak huwa l-
definizzjoni ta ', ngħidu aħna, recursion, jidħol.

819
00:36:36,345 --> 00:36:40,208

820
00:36:40,208 --> 00:36:41,110
Uh-huh.

821
00:36:41,110 --> 00:36:42,670
Bħala twarrib, I jinġibed up ftit.

822
00:36:42,670 --> 00:36:45,470
Dan kien simili 10 minuta ta '
procrastination dalgħodu.

823
00:36:45,470 --> 00:36:52,890
Jekk inti wkoll Google "askew," avviż
bl-inklinar ras tiegħek slightly--

824
00:36:52,890 --> 00:36:55,120
u allura dan huwa wieħed forsi
aktar atroċi ta 'kulħadd

825
00:36:55,120 --> 00:36:57,286
peress xi ħadd jintefqu bħal
ġurnata tagħhom jimplimentaw din

826
00:36:57,286 --> 00:36:59,880
xi snin ago-- come fuq.

827
00:36:59,880 --> 00:37:01,140

828
00:37:01,140 --> 00:37:04,540
Oh, wait-- thats bug.

829
00:37:04,540 --> 00:37:08,410

830
00:37:08,410 --> 00:37:11,410
>> Allura taħdem fuq waħda mill-
websajts akbar fid-dinja

831
00:37:11,410 --> 00:37:13,510
huma dawn il-bajd tal-Għid stupid ftit.

832
00:37:13,510 --> 00:37:16,690
Huma probabbilment jikkunsmaw
numru nontrivial ta 'linji ta' kodiċi

833
00:37:16,690 --> 00:37:19,280
biss hekk li jista 'jkollna
affarijiet gost ftit bħal dik.

834
00:37:19,280 --> 00:37:22,140
Imma l-anqas issa ikollok
xi wħud minn dawk ċajt ġewwa.

835
00:37:22,140 --> 00:37:28,330
>> Issa ejja tagħti ħarsa lejn uħud mill-
abjad tinsab konna kienu javżak ta tard,

836
00:37:28,330 --> 00:37:30,707
u tibda titqaxxar lura
wħud mis-saffi teknikament

837
00:37:30,707 --> 00:37:32,790
sabiex inti verament jifhmu
dak li kien għaddej

838
00:37:32,790 --> 00:37:34,860
u inti tista 'tifhem
xi wħud mill-theddidiet,

839
00:37:34,860 --> 00:37:38,060
bħal Shellshock, li
issa bdew isiru

840
00:37:38,060 --> 00:37:41,110
fuq quddiemnett ta 'l kulħadd
attenzjoni, għall-inqas fil-midja.

841
00:37:41,110 --> 00:37:45,810
Allura hawnhekk hija funzjoni sempliċi ħafna
li jirritorna xejn, bla effett.

842
00:37:45,810 --> 00:37:46,790
Isem tagħha huwa swap.

843
00:37:46,790 --> 00:37:50,880
Huwa jieħu f'żewġ varjabbli
u dan jirritorna xejn.

844
00:37:50,880 --> 00:37:52,260
Jieħu fil au b.

845
00:37:52,260 --> 00:37:53,337
Allura dimostrazzjoni ta 'malajr.

846
00:37:53,337 --> 00:37:54,170
Aħna miġjuba dawn il-up.

847
00:37:54,170 --> 00:37:56,100
Aħna tista 'ukoll tieħu ftit
break hawn għal ftit mument

848
00:37:56,100 --> 00:37:57,250
u jkollhom ftit xi ħaġa li tixrob.

849
00:37:57,250 --> 00:38:00,120
Jekk xi ħadd ma mind tgħaqqad
me up hawn għal ftit mument.

850
00:38:00,120 --> 00:38:01,830
Kif dwarek fil-shirt maroon?

851
00:38:01,830 --> 00:38:02,335
Come fuq up.

852
00:38:02,335 --> 00:38:04,060

853
00:38:04,060 --> 00:38:05,260
Just l-waħda llum.

854
00:38:05,260 --> 00:38:06,251
Grazzi, għalkemm.

855
00:38:06,251 --> 00:38:08,000
Kull dritt, u għandna
ġejjin up li hawn?

856
00:38:08,000 --> 00:38:08,660
X'hemm isem tiegħek?

857
00:38:08,660 --> 00:38:09,360
>> SPEAKER 4: Laura.

858
00:38:09,360 --> 00:38:09,740
>> SPEAKER 1: Laura.

859
00:38:09,740 --> 00:38:10,370
Come fuq up.

860
00:38:10,370 --> 00:38:11,460

861
00:38:11,460 --> 00:38:13,850
Allura Laura, sfida sempliċi ħafna llum.

862
00:38:13,850 --> 00:38:14,704

863
00:38:14,704 --> 00:38:15,370
Nizza li jissodisfaw yo.

864
00:38:15,370 --> 00:38:16,410

865
00:38:16,410 --> 00:38:16,910
Kull dritt.

866
00:38:16,910 --> 00:38:21,179
Allura aħna għandna xi ħalib matul hawn u
għandna xi meraq tal-larinġ hawn fuq

867
00:38:21,179 --> 00:38:23,345
u xi tazzi li aħna
misluf mill Annenberg llum.

868
00:38:23,345 --> 00:38:24,178
>> SPEAKER 4: Mislufa.

869
00:38:24,178 --> 00:38:27,240
SPEAKER 1: U se jimxi 'l quddiem
u jagħtuk nofs tazza ta 'dan.

870
00:38:27,240 --> 00:38:28,250

871
00:38:28,250 --> 00:38:28,800
Kull dritt.

872
00:38:28,800 --> 00:38:30,750
U aħna ser jagħtuk nofs
ħġieġ tal-ħalib.

873
00:38:30,750 --> 00:38:31,905

874
00:38:31,905 --> 00:38:35,890
Oh, u biss sabiex inti tista '
ftakar dak li dan kien simili,

875
00:38:35,890 --> 00:38:38,860
I mfakkar li jġibu
dan up u fuq llum.

876
00:38:38,860 --> 00:38:42,030

877
00:38:42,030 --> 00:38:42,530
Okay.

878
00:38:42,530 --> 00:38:45,470
Jekk inti ma mind, ejja ara, irridu
tista 'tpoġġihom fuq nuċċalijiet tiegħek stess

879
00:38:45,470 --> 00:38:46,560
jekk inti tixtieq.

880
00:38:46,560 --> 00:38:48,710
Dan ser ikun id-dinja mill-għajnejn Laura.

881
00:38:48,710 --> 00:38:49,210
Kull dritt.

882
00:38:49,210 --> 00:38:53,820
Allura mira tiegħek, jingħataw żewġ tazzi tal-
likwidu hawn, ħalib u meraq tal-larinġ,

883
00:38:53,820 --> 00:38:58,370
hija tpartit iż-żewġ kontenuti hekk li l-
meraq tal-larinġ tmur fil-tazza tal-ħalib

884
00:38:58,370 --> 00:39:00,710
u l-ħalib tmur fis
l-tazza meraq tal-larinġ.

885
00:39:00,710 --> 00:39:02,359
>> SPEAKER 4: Do I nikseb tazza ieħor?

886
00:39:02,359 --> 00:39:05,650
SPEAKER 1: Jien ferħan inti tlabt, għalkemm
kien ikun footage ħafna aħjar

887
00:39:05,650 --> 00:39:06,710
jekk inti ma kinux mitluba.

888
00:39:06,710 --> 00:39:10,620
Iżda iva, nistgħu noffrulek terz
tazza li l-vojta, tal-kors.

889
00:39:10,620 --> 00:39:11,120
Kull dritt.

890
00:39:11,120 --> 00:39:12,300
Allura tpartit l-kontenut hemmhekk.

891
00:39:12,300 --> 00:39:16,100

892
00:39:16,100 --> 00:39:17,050
Sbieħ ħafna.

893
00:39:17,050 --> 00:39:20,390

894
00:39:20,390 --> 00:39:21,305
Tajjeb ħafna.

895
00:39:21,305 --> 00:39:23,121

896
00:39:23,121 --> 00:39:24,745
Inti qed tagħmel dan rimarkabbilment b'attenzjoni.

897
00:39:24,745 --> 00:39:26,970

898
00:39:26,970 --> 00:39:28,655
U pass tlieta.

899
00:39:28,655 --> 00:39:30,390

900
00:39:30,390 --> 00:39:31,350
Kull dritt.

901
00:39:31,350 --> 00:39:31,930
Eċċellenti.

902
00:39:31,930 --> 00:39:33,930
A round kbir ta 'applause
ikun tajjeb għall Laura.

903
00:39:33,930 --> 00:39:36,500

904
00:39:36,500 --> 00:39:37,000
Kull dritt.

905
00:39:37,000 --> 00:39:40,790
Għandna rigal firda ftit
għalik, iżda let me jieħdu dawn.

906
00:39:40,790 --> 00:39:42,620
Grazzi tant.

907
00:39:42,620 --> 00:39:46,170
Allura eżempju sempliċi, għalkemm,
biex turi li jekk inti tagħmel

908
00:39:46,170 --> 00:39:48,300
tixtieq li tpartit l-kontenut
ta 'żewġ kontenituri,

909
00:39:48,300 --> 00:39:52,360
jew ejja jsejħulhom varjabbli,
għandek bżonn xi ħażna temporanja

910
00:39:52,360 --> 00:39:56,710
għal stadju wieħed tal-kontenuti fil-każ
li inti tista 'attwalment jagħmlu l-swap.

911
00:39:56,710 --> 00:40:01,790
Allura fil-fatt, dan is-sors kodiċi up here fl
C huwa rappreżentattiv tal eżattament dak.

912
00:40:01,790 --> 00:40:06,340
Jekk il-meraq tal-larinġ kien u l-ħalib
kien b, u ridna li tpartit it-tnejn,

913
00:40:06,340 --> 00:40:08,990
inti tista 'tipprova xi ħaġa kreattiva
billi tferra wieħed fil-oħra,

914
00:40:08,990 --> 00:40:11,031
iżda li probabbilment ma
jispiċċaw partikolarment tajjeb.

915
00:40:11,031 --> 00:40:15,260
U hekk aħna jużaw tazza terz, call
dan TMP, T-M-P b'konvenzjoni,

916
00:40:15,260 --> 00:40:19,370
u tpoġġi l-kontenut tal-
ĠU f'dak, allura tpartit tazza waħda,

917
00:40:19,370 --> 00:40:22,610
allura tpoġġi l-ĠU fil-
tazza oriġinali, b'hekk

918
00:40:22,610 --> 00:40:25,320
kisba, eżattament kif
Laura għamlet, l-swap.

919
00:40:25,320 --> 00:40:26,850
>> Mela ejja do eżattament dan.

920
00:40:26,850 --> 00:40:30,110
Let me imorru quddiem u tiftaħ
up eżempju li l-

921
00:40:30,110 --> 00:40:32,720
attwalment imsejħa "l-ebda
tpartit, "għaliex din m'hijiex

922
00:40:32,720 --> 00:40:36,180
kif sempliċement isir kif inti tista 'taħseb.

923
00:40:36,180 --> 00:40:41,190
Allura f'dan il-programm, avviż li
Jien jużaw stdio.h, ħabib antik tagħna.

924
00:40:41,190 --> 00:40:43,130
Għandi l-prototip
għall swap up hemm, li

925
00:40:43,130 --> 00:40:45,450
tfisser l-implimentazzjoni tagħha
probabbilment stabbiliti hawn taħt,

926
00:40:45,450 --> 00:40:48,050
u ejja ara dak dan prinċipali
programm għaddej biex tagħmel għalija.

927
00:40:48,050 --> 00:40:52,020
I ewwel niddikjara int x gets
wieħed, u int y gets tnejn.

928
00:40:52,020 --> 00:40:54,930
Allura taħseb ta 'dawk bħala ĠU
u ħalib, rispettivament.

929
00:40:54,930 --> 00:40:57,100
U mbagħad I biss ikollhom
printf qal x hija din

930
00:40:57,100 --> 00:41:00,120
u y huwa dan, biss hekk I tista '
viżwalment tara x'inhu għaddej.

931
00:41:00,120 --> 00:41:03,810
Imbagħad I printf titlob
li jien iskambji it-tnejn,

932
00:41:03,810 --> 00:41:07,100
u mbagħad I jistampa
jsostnu li dawn qed biddlu,

933
00:41:07,100 --> 00:41:09,300
u I jistampa xuy darb'oħra.

934
00:41:09,300 --> 00:41:13,010
Allura stabbiliti hawn fl swap hija
eżattament dak Laura għamlet,

935
00:41:13,010 --> 00:41:16,240
u eżattament dak li rajna fuq
l-iskrin mument ilu.

936
00:41:16,240 --> 00:41:19,380
>> Mela ejja imorru quddiem u
jkun sorely diżappuntat.

937
00:41:19,380 --> 00:41:24,690
Jagħmlu l-ebda tpartit, u run ebda swap,
zooming fl fuq l-output hawn.

938
00:41:24,690 --> 00:41:28,320
Ikteb x hija l-1, y huwa 2, jagħmlu skambju skambjat.

939
00:41:28,320 --> 00:41:32,700
x għadu 1, u y għadu 2.

940
00:41:32,700 --> 00:41:37,630
Allura anke jekk, franchement, dan jistenna
eżattament simili, għalkemm aktar teknikament,

941
00:41:37,630 --> 00:41:40,730
dak Laura għamilt, ma jidhirx li jaħdmu.

942
00:41:40,730 --> 00:41:42,130
Allura għaliex huwa li?

943
00:41:42,130 --> 00:41:46,630
Ukoll, jirriżulta li meta
aħna tikteb programm bħal dan

944
00:41:46,630 --> 00:41:51,590
li tkun kemm prinċipali, enfasizzat hawnhekk,
u mbagħad funzjoni oħra, bħal tpartit,

945
00:41:51,590 --> 00:41:54,230
enfasizzat hawnhekk, li
jitlob, id-dinja

946
00:41:54,230 --> 00:41:57,030
jistenna ftit xi ħaġa bħal
dawn trejs mument ilu.

947
00:41:57,030 --> 00:42:00,440
Meta prinċipali ewwel gets imsejħa,
thats simili tistaqsi sistema operattiva

948
00:42:00,440 --> 00:42:04,030
għal daqsxejn ta 'memorja għal kwalunkwe lokali
varjabbli bħall x u y li għandu prinċipali,

949
00:42:04,030 --> 00:42:05,660
u jispiċċaw hemm dritt.

950
00:42:05,660 --> 00:42:10,920
Imma jekk jitlob ewlenin tpartit, u prinċipali
jgħaddi tpartit żewġ argumenti, A u B,

951
00:42:10,920 --> 00:42:16,410
meraq tal-larinġ u l-ħalib, mhuwiex simili
għoti-meraq tal-larinġ u l-ħalib

952
00:42:16,410 --> 00:42:17,500
għall Laura.

953
00:42:17,500 --> 00:42:21,300
What a kompjuter ma, huwa
tgħaddi kopji tal-meraq tal-larinġ

954
00:42:21,300 --> 00:42:27,110
u kopji tal-ħalib li Laura, b'tali mod li
x'hemm finalment ġewwa ta 'dan trej

955
00:42:27,110 --> 00:42:32,510
huwa l-waħda valur u tnejn, jew ĀU
u tal-ħalib, iżda kopji tagħhom,

956
00:42:32,510 --> 00:42:34,790
hekk li f'dan il-punt
fl-istorja, hemm

957
00:42:34,790 --> 00:42:36,930
huwa ĠU u ħalib f'kull wieħed minn dawn dixxijiet.

958
00:42:36,930 --> 00:42:39,260
Hemm wieħed u tnejn
f'kull wieħed minn dawn dixxijiet,

959
00:42:39,260 --> 00:42:41,720
u l-funzjoni tpartit tabilħaqq taħdem.

960
00:42:41,720 --> 00:42:46,090
Huwa iskambji minnhom ġewwa
tat-trej tieni topmost,

961
00:42:46,090 --> 00:42:48,147
iżda li iskambji m'għandha l-ebda impatt.

962
00:42:48,147 --> 00:42:49,980
U bbażata fuq ftit biss
prinċipju bażiku konna

963
00:42:49,980 --> 00:42:52,970
tkellmu dwar qabel, u tabilħaqq
ftit minuti ilu, liema

964
00:42:52,970 --> 00:42:58,770
jista 'jispjega għaliex qed jinbidlu
au b ġewwa ta 'swap

965
00:42:58,770 --> 00:43:05,560
m'għandha l-ebda effett fuq xu y, anki jekk
I għadda xuy għall-funzjoni tpartit.

966
00:43:05,560 --> 00:43:08,750
X'hemm-kelma ewlenija hawnhekk li
jista simplistikament jispjegaw?

967
00:43:08,750 --> 00:43:11,250

968
00:43:11,250 --> 00:43:12,627
I think I smajt li hawn?

969
00:43:12,627 --> 00:43:13,335
UDJENZA: Ritorn.

970
00:43:13,335 --> 00:43:14,085
SPEAKER 1: Ritorn?

971
00:43:14,085 --> 00:43:14,590
Mhux ritorn.

972
00:43:14,590 --> 00:43:15,895
Ejja jmorru ma waħda oħra.

973
00:43:15,895 --> 00:43:16,395
X'hemm li?

974
00:43:16,395 --> 00:43:17,080
>> UDJENZA: [inaudible].

975
00:43:17,080 --> 00:43:20,000
>> SPEAKER 1: OK, hekk return-- nistgħu
jagħmlu x-xogħol tar-ritorn fl-istorja,

976
00:43:20,000 --> 00:43:21,914
iżda hemm spjegazzjoni saħansitra aktar sempliċi.

977
00:43:21,914 --> 00:43:22,580
UDJENZA: Ambitu.

978
00:43:22,580 --> 00:43:23,288
SPEAKER 1: Ambitu.

979
00:43:23,288 --> 00:43:24,300
I ser tieħu ambitu.

980
00:43:24,300 --> 00:43:27,290
Allura ambitu, ftakar fejn
x tagħna uy iddikjarat.

981
00:43:27,290 --> 00:43:30,840
Huma qed iddikjarata ġewwa
tad ewlenija dritt up here.

982
00:43:30,840 --> 00:43:33,200
au b, sadanittant, huma
ddikjarat b'mod effettiv

983
00:43:33,200 --> 00:43:35,930
ġewwa tal tpartit, pjuttost mhux fil
l-braces kaboċċi iżda xorta

984
00:43:35,930 --> 00:43:37,690
fil-qasam ġenerali ta 'swap.

985
00:43:37,690 --> 00:43:40,560
U għalhekk tabilħaqq, au b
jeżistu biss fi ħdan dan trej

986
00:43:40,560 --> 00:43:44,850
minn Annenberg, dan
tieni blokki ta 'kodiċi.

987
00:43:44,850 --> 00:43:49,500
Allura aħna qed tabilħaqq jinbidlu l-kopja, iżda
li mhux verament dak kollu li utli.

988
00:43:49,500 --> 00:43:52,190
>> Mela ejja tagħti ħarsa lejn
dan il-livell ftit iktar baxx.

989
00:43:52,190 --> 00:43:55,430
Jien se jmorru lura fis
il Sors Directory,

990
00:43:55,430 --> 00:43:58,330
u jien ser ewwel
zoom fil hawn, u biss

991
00:43:58,330 --> 00:44:02,290
biex tikkonferma li jien f'dan
tieqa terminal akbar,

992
00:44:02,290 --> 00:44:04,430
il-programm għadu iġib ruħu bħal dik.

993
00:44:04,430 --> 00:44:06,840
Ejja ngħidu issa li din
mhuwiex intenzjonat.

994
00:44:06,840 --> 00:44:10,090
Ovvjament jien ridt swap biex
xogħol, u għalhekk iħoss bħal bug.

995
00:44:10,090 --> 00:44:12,780
Now I tista 'tibda żżid
lott ta 'printf lejn kodiċi tiegħi,

996
00:44:12,780 --> 00:44:16,010
stampar x hawn fuq, y fuq
Hawnhekk, hawn, b hawn fuq.

997
00:44:16,010 --> 00:44:18,220
Iżda franchement, dan huwa probabbilment dak
inti kont qed tagħmel għal ftit ġimgħat

998
00:44:18,220 --> 00:44:20,190
issa, fil-ħinijiet tal-uffiċċju
u fid-dar meta jkunu qed jaħdmu

999
00:44:20,190 --> 00:44:22,150
fuq psets jippruvaw isibu xi bugs.

1000
00:44:22,150 --> 00:44:25,560
Imma int ser tara, jekk inti ma jkunux diġà,
dik il-problema sett tlieta tintroduċi inti

1001
00:44:25,560 --> 00:44:31,630
għal kmand imsejħa GDB,
fejn GDB, debugger GNU,

1002
00:44:31,630 --> 00:44:34,040
nnifisha jkollha mazz sħiħ ta '
karatteristiċi li jistgħu attwalment

1003
00:44:34,040 --> 00:44:38,160
ejjew nifhmu sitwazzjonijiet
bħal dan, iżda aktar compellingly,

1004
00:44:38,160 --> 00:44:39,940
isolvu problemi u jsibu bugs.

1005
00:44:39,940 --> 00:44:40,940
So jien ser jagħmlu dan.

1006
00:44:40,940 --> 00:44:44,770
Minflok ./noswap, jien minflok
tmur jiddekorri ./noswap GDB.

1007
00:44:44,770 --> 00:44:47,410

1008
00:44:47,410 --> 00:44:51,200
Fi kliem ieħor, jien ser jimxu tiegħi
programm mhux Bash, ħabib ġdid tagħna

1009
00:44:51,200 --> 00:44:51,850
llum.

1010
00:44:51,850 --> 00:44:53,970
Jien ser jimxu tiegħi
noswap programm ġewwa

1011
00:44:53,970 --> 00:44:56,900
ta 'dan il-programm l-oħra msejħa
GDB, li huwa debugger, li

1012
00:44:56,900 --> 00:45:01,035
huwa programm li, imfassla biex tgħin
inti bnedmin isibu u neħħi bugs.

1013
00:45:01,035 --> 00:45:03,410
Mela jekk jien hit Run hawn, hemm
ammont atroċi tat-test

1014
00:45:03,410 --> 00:45:04,868
li int verament qatt ma għandek taqra.

1015
00:45:04,868 --> 00:45:07,290
Huwa essenzjalment distrazzjoni
mill-pront, li

1016
00:45:07,290 --> 00:45:10,030
Jien ser hit Control-L
biex tikseb up fil-quċċata hemmhekk.

1017
00:45:10,030 --> 00:45:11,800
Dan huwa l-GDB pront.

1018
00:45:11,800 --> 00:45:15,550
Jekk I tixtieq li tmexxi dan il-programm issa,
kif dan iqarrqu folja ftit fuq illum

1019
00:45:15,550 --> 00:45:21,860
slide jissuġġerixxi, Run hija l-ewwel
jikkmanda li aħna fisser li tintroduċi.

1020
00:45:21,860 --> 00:45:25,150
U jien biss ser tip
run up here ġewwa tal GDB,

1021
00:45:25,150 --> 00:45:26,811
u tabilħaqq dam programm tiegħi.

1022
00:45:26,811 --> 00:45:29,310
Issa hemm xi addizzjonali
riżultati tal-iskrin bħal dan,

1023
00:45:29,310 --> 00:45:31,910
iżda li GDB sempliċement anali
u tgħidilna x'inhu għaddej.

1024
00:45:31,910 --> 00:45:34,451
Inti ma verament ikollhom għalfejn tinkwieta
dwar dawn id-dettalji dritt issa.

1025
00:45:34,451 --> 00:45:36,890
Imma x'hemm verament jibred dwar
GDB, jekk nagħmel dan again--

1026
00:45:36,890 --> 00:45:42,100
Kontroll-L ikklerja l screen-- let me go
quddiem u tip "break prinċipali," u b'hekk,

1027
00:45:42,100 --> 00:45:45,743
meta I hit Ikteb, iffissar x'hemm
tissejjaħ punt tal-qasma fil noswap.c,

1028
00:45:45,743 --> 00:45:51,270
linja 16, li huwa fejn GDB
dehret-programm tiegħi attwalment

1029
00:45:51,270 --> 00:45:53,070
huwa, funzjoni tiegħi fil-fatt hu.

1030
00:45:53,070 --> 00:45:55,070
Dan aħna ser ninjoraw għal issa
iżda li l-indirizz

1031
00:45:55,070 --> 00:45:57,310
fil-memorja speċifikament ta 'din il-funzjoni.

1032
00:45:57,310 --> 00:46:00,240
Allura issa meta I tip run,
Avviż x'hemm jibred hawn.

1033
00:46:00,240 --> 00:46:05,650
Programm My waqfiet fil-linja I
qal GDB li nieqaf eżekuzzjoni fi.

1034
00:46:05,650 --> 00:46:09,850
So I ma jkollhomx biex issa bidla kodiċi tiegħi,
żid xi tal printf, recompile dan, terġa 'ssir

1035
00:46:09,850 --> 00:46:13,300
dan, bidla, żid ftit tal printf,
isalvawh, recompile dan, run.

1036
00:46:13,300 --> 00:46:18,100
I tista 'biss walk permezz tal-programm tiegħi
pass pass pass fil-veloċità tal-bniedem,

1037
00:46:18,100 --> 00:46:20,880
mhux fil-tip Intel-ġewwa ta 'veloċità.

1038
00:46:20,880 --> 00:46:24,580
>> Allura issa avviż din il-linja
jidher hawn, u jekk immur lura

1039
00:46:24,580 --> 00:46:27,800
program tiegħi fil gedit,
avviż li dan huwa attwalment

1040
00:46:27,800 --> 00:46:29,280
l-ewwel linja tal-kodiċi.

1041
00:46:29,280 --> 00:46:31,240
Hemm linja 16 gedit.

1042
00:46:31,240 --> 00:46:34,610
Hemm linja 16 fi ħdan GDB, u anki
għalkemm dan interface iswed u abjad

1043
00:46:34,610 --> 00:46:37,760
mhuwiex kważi bħala utent
friendly, dan ifisser

1044
00:46:37,760 --> 00:46:41,680
dik il-linja 16 ma tkunx ġiet esegwita
s'issa, iżda huwa dwar li jkun.

1045
00:46:41,680 --> 00:46:46,220
So tabilħaqq jekk I tip print
x, mhux printf, biss print x,

1046
00:46:46,220 --> 00:46:50,730
I nikseb xi valur fittizji hemmhekk ta 'żero,
minħabba x ma ġiex initialized s'issa.

1047
00:46:50,730 --> 00:46:54,760
So jien ser tip li jmiss, jew, jekk inti
tixtieq li tkun fancy, biss N għal li jmiss.

1048
00:46:54,760 --> 00:46:59,090
Imma meta I tip li jmiss tidħol, issa
Avviż timxi fuq linja 17.

1049
00:46:59,090 --> 00:47:02,840
Allura loġikament, jekk stajt esegwiti
linja 16 u I issa tip print x,

1050
00:47:02,840 --> 00:47:03,640
x'għandi tara I?

1051
00:47:03,640 --> 00:47:04,970

1052
00:47:04,970 --> 00:47:05,520
Wieħed.

1053
00:47:05,520 --> 00:47:07,820
>> U issa dan huwa ċertament konfuża.

1054
00:47:07,820 --> 00:47:11,260
$ 2 huwa biss mod fancy ta ', jekk inti
tixtieq li jirreferu għal dak il-valur aktar tard,

1055
00:47:11,260 --> 00:47:12,510
inti tista 'tgħid "dollaru sinjal tnejn."

1056
00:47:12,510 --> 00:47:13,480
Huwa simili referenza lura.

1057
00:47:13,480 --> 00:47:14,570
Iżda għal issa, biss jinjoraha.

1058
00:47:14,570 --> 00:47:17,070
X'hemm interessanti hija x'hemm
dwar id-dritt tas-sinjal ugwali.

1059
00:47:17,070 --> 00:47:21,000
U issa jekk jien tip li jmiss darb'oħra
u y print, I għandha tara 2.

1060
00:47:21,000 --> 00:47:23,870
I tista 'wkoll issa jistampaw
x darb'oħra, u franchement,

1061
00:47:23,870 --> 00:47:27,130
jekk jien jkollna ftit konfuż dwar
fejn I am, I tista 'tip-lista għall-lista

1062
00:47:27,130 --> 00:47:30,590
u biss tara xi kuntest madwar
il-punt jien attwalment fi.

1063
00:47:30,590 --> 00:47:35,180
U issa I tista tip
jmiss, u hemm x hija l-1.

1064
00:47:35,180 --> 00:47:36,300
Now I tip li jmiss.

1065
00:47:36,300 --> 00:47:37,710
Oh, y hija 2.

1066
00:47:37,710 --> 00:47:40,750
U għal darb'oħra, huwa konfużjoni,
minħabba output GDB tal

1067
00:47:40,750 --> 00:47:43,044
qed jiġi mħalltin ma output tiegħi stess.

1068
00:47:43,044 --> 00:47:45,710
Imma jekk inti żżomm f'moħħu, billi
glancing quddiem u lura fil-kodiċi tiegħek

1069
00:47:45,710 --> 00:47:47,740
jew li out ġenb
ġenb forsi, inti ser

1070
00:47:47,740 --> 00:47:51,020
tara li verament jien biss
titjib permezz tal-programm tiegħi.

1071
00:47:51,020 --> 00:47:54,620
>> Imma avviż x'jiġri li jmiss, litteralment.

1072
00:47:54,620 --> 00:47:56,380
Hawn linja 22.

1073
00:47:56,380 --> 00:48:01,315
Let me go fuqha, u b'hekk miexja fuq
sa 23, u jekk I jistampaw x issa, xorta waħda.

1074
00:48:01,315 --> 00:48:03,890
U jekk I jistampaw y issa, xorta waħda.

1075
00:48:03,890 --> 00:48:05,820
Allura din mhix eżerċizzju utli.

1076
00:48:05,820 --> 00:48:07,450
Mela ejja jerġa 'jagħmel dan.

1077
00:48:07,450 --> 00:48:10,069
Let me jmorru lura sa l-
top u t-tip run darb'oħra.

1078
00:48:10,069 --> 00:48:12,110
U huwa qal il-programm
thats qed debugged

1079
00:48:12,110 --> 00:48:14,109
bdiet diġà,
beda mill-bidu.

1080
00:48:14,109 --> 00:48:15,420
Iva, ejja tagħmel dan mill-ġdid.

1081
00:48:15,420 --> 00:48:22,000
U din id-darba ejja do jmiss,
jmiss, li jmiss, li jmiss, li jmiss,

1082
00:48:22,000 --> 00:48:24,180
iżda issa l-affarijiet nikseb interessanti.

1083
00:48:24,180 --> 00:48:27,760
Issa nixtieq li pass lejn
tpartit, so I ma tip li jmiss.

1084
00:48:27,760 --> 00:48:34,380
I tip pass, u issa jindunax bih
qabża me għal-linja noswap.c 33.

1085
00:48:34,380 --> 00:48:37,240
Jekk immur lura għal gedit, x'hemm linja 33?

1086
00:48:37,240 --> 00:48:40,500
Dik hija l-ewwel reali
linja tal-kodiċi ġewwa ta 'swap.

1087
00:48:40,500 --> 00:48:44,150
Liema huwa sbieħ, għaliex issa nista
tip ta 'poke madwar u nikseb kurjużi

1088
00:48:44,150 --> 00:48:46,052
dwar x'inhu għaddej verament fil hemmhekk.

1089
00:48:46,052 --> 00:48:46,760
Let me jistampaw TMP.

1090
00:48:46,760 --> 00:48:47,770

1091
00:48:47,770 --> 00:48:48,800
Whoa.

1092
00:48:48,800 --> 00:48:51,438
Għaliex ma TMP għandhom xi
crazy, valur żibel fittizji?

1093
00:48:51,438 --> 00:48:54,579

1094
00:48:54,579 --> 00:48:56,120
UDJENZA: Ma ġiex initialized.

1095
00:48:56,120 --> 00:48:57,150
SPEAKER 1: Ma ġiex initialized.

1096
00:48:57,150 --> 00:49:00,270
U fil-fatt, meta inti tmexxi programm,
int tingħata mazz sħiħ ta 'memorja

1097
00:49:00,270 --> 00:49:03,392
mis-sistema operattiva, imma int
ma initialized xi valuri,

1098
00:49:03,392 --> 00:49:05,600
sabiex ikun x'ikun bits int
jaraw hawn, anke jekk huwa

1099
00:49:05,600 --> 00:49:07,770
dan negattiv big crazy
numru, ifisser biss

1100
00:49:07,770 --> 00:49:10,750
li dawk huma l-fdalijiet mill-
xi użu qabel ta 'dak RAM,

1101
00:49:10,750 --> 00:49:13,050
anki jekk I ma jkunux
myself meħtieġa encore.

1102
00:49:13,050 --> 00:49:17,086
Allura issa jien ser jimxi 'l quddiem u t-tip
jmiss, u jekk I issa tip TMP print,

1103
00:49:17,086 --> 00:49:17,835
x'għandi tara I?

1104
00:49:17,835 --> 00:49:19,570

1105
00:49:19,570 --> 00:49:23,360
Tkun xi tkun il-valur ta 'kien,
a huwa l-ewwel argument, biss

1106
00:49:23,360 --> 00:49:25,550
bħall x kienet l-ewwel
Ħaġa jiġu mgħoddija fi,

1107
00:49:25,550 --> 00:49:30,450
hekk u x għandu jkun l-istess,
hekk jistampaw TMP għandhom jistampaw me wieħed.

1108
00:49:30,450 --> 00:49:36,360
>> Allura dak li inti ser tara fil sett problema
tliet huwa tutorja ta 'tipi fuq GDB,

1109
00:49:36,360 --> 00:49:40,020
iżda jirrealizzaw li dan huwa l-bidu
ta ħarsa lejn għodda li se attwalment

1110
00:49:40,020 --> 00:49:42,774
jgħinuk issolvi l-problemi
għalhekk ħafna aktar effettiv.

1111
00:49:42,774 --> 00:49:44,690
Dak li aħna qed finalment
se jagħmlu l-Erbgħa

1112
00:49:44,690 --> 00:49:48,180
hija tibda titqaxxar lura ftit saffi
u neħħi xi roti ta 'taħriġ.

1113
00:49:48,180 --> 00:49:50,496
Li ħaġa imsejħa string li
konna użati għal xi żmien,

1114
00:49:50,496 --> 00:49:53,370
aħna qed tmur biex bil-mod jieħdu dik l bogħod
minn int u jibda jitkellem dwar

1115
00:49:53,370 --> 00:49:55,725
xi ħaġa aktar esoterically
magħrufa bħala char *,

1116
00:49:55,725 --> 00:49:59,550
imma aħna qed tmur biex tagħmel dan sbieħ u
b'ġentilezza fl-ewwel, anke jekk pointers,

1117
00:49:59,550 --> 00:50:02,730
kif dawn qed jissejjaħ, tista 'tagħmel xi
affarijiet ħżiena ħafna jekk abbużati,

1118
00:50:02,730 --> 00:50:06,040
billi tħares lejn claymation ftit minn
ħabib tagħna Nick Parlante minn Stanford

1119
00:50:06,040 --> 00:50:09,670
University, professur fil-kompjuter
xjenza li tpoġġi flimkien dan preview

1120
00:50:09,670 --> 00:50:11,075
ta dak li ġejjin dan l-Erbgħa.

1121
00:50:11,075 --> 00:50:12,196

1122
00:50:12,196 --> 00:50:13,400
>> [Daqq ta 'video]

1123
00:50:13,400 --> 00:50:13,900
-Hey, Binky.

1124
00:50:13,900 --> 00:50:14,930

1125
00:50:14,930 --> 00:50:15,780
Wake up.

1126
00:50:15,780 --> 00:50:17,240
Wasal iż-żmien għall-gost pointer.

1127
00:50:17,240 --> 00:50:18,260

1128
00:50:18,260 --> 00:50:19,350
>> Liema-li?

1129
00:50:19,350 --> 00:50:21,150
Tgħallem dwar pointers?

1130
00:50:21,150 --> 00:50:22,050
Oh, Goody!

1131
00:50:22,050 --> 00:50:22,897

1132
00:50:22,897 --> 00:50:23,730
[END daqq ta 'video]

1133
00:50:23,730 --> 00:50:25,396
SPEAKER 1: Li jistenna inti nhar l-Erbgħa.

1134
00:50:25,396 --> 00:50:26,440
Aħna ser tara int imbagħad.

1135
00:50:26,440 --> 00:50:27,106
[Daqq ta 'video]

1136
00:50:27,106 --> 00:50:30,420
-U Issa, Ħsibijiet Deep,
billi Daven Farnham.

1137
00:50:30,420 --> 00:50:33,980

1138
00:50:33,980 --> 00:50:35,900
>> -Għaliex Aħna jitgħallmu C?

1139
00:50:35,900 --> 00:50:36,785
Għaliex ma A +?

1140
00:50:36,785 --> 00:50:38,550

1141
00:50:38,550 --> 00:50:40,910
>> [Rires]

1142
00:50:40,910 --> 00:50:42,160
>> [END daqq ta 'video]