1
00:00:00,000 --> 00:00:11,200

2
00:00:11,200 --> 00:00:12,580
>> DAVID Malan: haki wote, kuwakaribisha nyuma.

3
00:00:12,580 --> 00:00:13,290
Hii ni CS50.

4
00:00:13,290 --> 00:00:15,130
Huu ni mwanzo wa wiki saba.

5
00:00:15,130 --> 00:00:18,890
Hivyo imekuwa ni ya muda, hivyo nimeona tunatarajia
kuchukua ziara ya kimbunga ambapo sisi

6
00:00:18,890 --> 00:00:20,760
kushoto mbali na ambapo sisi ni sasa kwenda.

7
00:00:20,760 --> 00:00:23,310
>> Hivyo jambo hili hapa ili kuwa
imesababisha baadhi ya Angst saa ya kwanza.

8
00:00:23,310 --> 00:00:27,680
Lakini pengine, wewe ni mwanzo
acclimate kwa nini hii inaashiria hapa -

9
00:00:27,680 --> 00:00:32,670
nyota anayewakilisha pointer, ambayo ni
kile tu, katika suala layman zaidi?

10
00:00:32,670 --> 00:00:33,400
Hivyo ni anwani.

11
00:00:33,400 --> 00:00:35,490
>> Hivyo ni anwani ya
kitu katika kumbukumbu.

12
00:00:35,490 --> 00:00:38,260
Na sisi kuanza peel nyuma tabaka
michache ya wiki iliyopita, mambo kama

13
00:00:38,260 --> 00:00:41,800
GetString na wengine vile kazi
muda wote huu wamekuwa kurudi

14
00:00:41,800 --> 00:00:46,010
anwani ya mambo katika kumbukumbu, kama
anuani ya tabia ya kwanza katika

15
00:00:46,010 --> 00:00:46,990
baadhi ya mlolongo.

16
00:00:46,990 --> 00:00:50,360
>> Hivyo sisi pia ilianzisha Valgrind, ambayo
itabidi kuanza kutumia kwa ajili ya tatizo hili

17
00:00:50,360 --> 00:00:53,380
kuweka, hasa kwa ajili ya pili
tatizo kuweka pia.

18
00:00:53,380 --> 00:00:54,980
Na Valgrind anafanya nini kwa ajili yetu?

19
00:00:54,980 --> 00:00:57,520

20
00:00:57,520 --> 00:01:01,020
Ni hundi kwa uvujaji kumbukumbu, na
pia hundi kwa ajili ya matumizi mabaya ya kumbukumbu.

21
00:01:01,020 --> 00:01:05,890
>> Inaweza, pamoja na uwezekano baadhi, kuchunguza kama
kanuni yako ni kwenda kwa kugusa kumbukumbu

22
00:01:05,890 --> 00:01:07,100
kwamba tu hawapaswi.

23
00:01:07,100 --> 00:01:10,410
Hivyo si lazima leak, lakini kama wewe
kwenda zaidi ya mipaka ya baadhi ya

24
00:01:10,410 --> 00:01:14,730
safu, na wewe kweli kuendesha Valgrind
na kushawishi kwamba tabia wakati

25
00:01:14,730 --> 00:01:17,870
Valgrind ni mbio katika mpango wako ni
mbio ndani yake, utapata

26
00:01:17,870 --> 00:01:21,460
ujumbe kama hii - "batili kuandika ya
ukubwa 4, "ambayo, kukumbuka michache ya

27
00:01:21,460 --> 00:01:25,880
wiki iliyopita na maana kwamba mimi alikuwa na ajali
kama kwenye int moja mbali mno

28
00:01:25,880 --> 00:01:27,250
zaidi ya mipaka ya safu.

29
00:01:27,250 --> 00:01:30,790
Na hivyo ukubwa 4 maana hapa ukubwa
ya kwamba int fulani.

30
00:01:30,790 --> 00:01:35,260
>> Hivyo kuchukua uhakika katika ukweli kwamba
pato Valgrind ya, muundo wa hayo,

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ni mauaji.

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00:01:36,170 --> 00:01:40,180
Ni kweli ni vigumu kuona kwa kupitia fujo
kwa habari ya kuvutia.

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00:01:40,180 --> 00:01:42,910
Hivyo kile ambacho tumefanya hapa ni Excerpt
baadhi ya wanandoa wa zaidi

34
00:01:42,910 --> 00:01:43,850
kuvutia mistari.

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00:01:43,850 --> 00:01:46,760
Lakini kutambua kwamba 80% ya wa Valgrind
pato ni kwenda kuwa kidogo ya

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ovyo.

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00:01:47,650 --> 00:01:52,820
>> Kuangalia tu kwa chati kama haya -
batili kulia, batili kusoma, ka 40

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00:01:52,820 --> 00:01:56,690
na baadhi ya idadi ya vitalu ni dhahiri
waliopotea, maneno kama hayo.

39
00:01:56,690 --> 00:02:01,920
Na nini wewe utakuwa hopefully kuona ni baadhi
aina ya kuwaeleza ya nini kazi

40
00:02:01,920 --> 00:02:03,340
kosa ni kweli in

41
00:02:03,340 --> 00:02:07,195
Katika kesi hii hapa, katika kile mstari wa
kanuni yangu ilikuwa inaonekana makosa?

42
00:02:07,195 --> 00:02:09,729

43
00:02:09,729 --> 00:02:14,130
>> 26 katika faili inayoitwa memory.c, ambayo ilikuwa
mfano sisi walikuwa kucheza na

44
00:02:14,130 --> 00:02:14,890
kwa wakati.

45
00:02:14,890 --> 00:02:16,460
Hivyo pengine si katika malloc.

46
00:02:16,460 --> 00:02:18,630
Ilikuwa pengine katika kanuni yangu badala yake.

47
00:02:18,630 --> 00:02:20,910
Hivyo tutaweza kuona hili tena
na tena kabla ya muda mrefu.

48
00:02:20,910 --> 00:02:24,080
>> Hivyo scanf, hii walifika katika
michache ya aina hivi sasa.

49
00:02:24,080 --> 00:02:26,410
Tuliona sscanf ufupi.

50
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Ni kitu ya simu ya
wewe dived katika katika yako

51
00:02:28,330 --> 00:02:29,535
maandalizi ya chemsha bongo.

52
00:02:29,535 --> 00:02:33,130
Na scanf ni kweli nini CS50
maktaba imekuwa kutumia chini ya

53
00:02:33,130 --> 00:02:36,560
Hood kwa muda ili baadhi kabisa
kupata mawazo kutoka kwa mtumiaji.

54
00:02:36,560 --> 00:02:40,420
>> Kwa mfano, kama mimi hoja juu ya CS50
appliance hapa, napenda kufungua

55
00:02:40,420 --> 00:02:45,315
mfano leo kwamba wito scanf-0.c
Na ni super rahisi.

56
00:02:45,315 --> 00:02:46,590
Ni tu mistari michache ya kificho.

57
00:02:46,590 --> 00:02:50,880
Lakini inaonyesha kweli jinsi GetInt
imekuwa ikifanya kazi yote ya wakati huu.

58
00:02:50,880 --> 00:02:54,710
>> Katika mpango huu hapa, katika mstari wa 16
, Taarifa kwamba mimi kutangaza int.

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00:02:54,710 --> 00:02:57,270
Hivyo hakuna kuyatumia, kitu kichawi
huko, tu int.

60
00:02:57,270 --> 00:03:00,330
Kisha katika mstari 17, mimi haraka
mtumiaji kwa ajili ya simu, tafadhali.

61
00:03:00,330 --> 00:03:02,930
Kisha katika 18 marehemu, mimi kutumia scanf hapa.

62
00:03:02,930 --> 00:03:06,910
Na mimi maalum, aina ya kama printf,
kwamba mimi nina wanatarajia quote

63
00:03:06,910 --> 00:03:08,110
unquote asilimia i.

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00:03:08,110 --> 00:03:10,920
>> Hivyo asilimia i, bila shaka,
inaashiria int.

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00:03:10,920 --> 00:03:14,580
Lakini taarifa ya nini pili
hoja ya scanf ni.

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00:03:14,580 --> 00:03:17,350
Jinsi gani unaweza kuelezea pili
Hoja baada ya koma?

67
00:03:17,350 --> 00:03:19,450
Hiyo ni nini?

68
00:03:19,450 --> 00:03:20,670
>> Ni anuani ya x.

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00:03:20,670 --> 00:03:25,490
Hivyo hii ni muhimu kwa sababu kwa kutoa
scanf na anuani ya x, ni nini

70
00:03:25,490 --> 00:03:29,560
kwamba kuwawezesha kuwa kazi ya kufanya?

71
00:03:29,560 --> 00:03:33,010
Si tu kwenda huko, lakini pia kufanya nini?

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00:03:33,010 --> 00:03:34,060
>> Kufanya mabadiliko hayo.

73
00:03:34,060 --> 00:03:38,080
Kwa sababu unaweza kwenda huko, ni aina ya
kama ramani ya eneo katika kumbukumbu.

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00:03:38,080 --> 00:03:41,900
Na hivyo muda mrefu kama wewe kutoa scanf, au
kazi yoyote na ramani, vile kwamba

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00:03:41,900 --> 00:03:45,840
kazi inaweza kwenda huko, na si tu
kuangalia thamani, lakini unaweza pia

76
00:03:45,840 --> 00:03:49,670
mabadiliko ya kwamba thamani, ambayo ni muhimu kama
kusudi katika maisha ya scanf ni

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00:03:49,670 --> 00:03:53,060
Scan pembejeo kutoka kwa mtumiaji, hasa
kutoka keyboard.

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00:03:53,060 --> 00:03:57,830
Na f inaashiria mpangilio tu kama
printf, f inaashiria mpangilio

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00:03:57,830 --> 00:03:58,930
kamba kwamba unataka magazeti.

80
00:03:58,930 --> 00:04:04,430
>> Hivyo katika muda mfupi, hii 18 mstari tu anasema,
kujaribu kusoma int kutoka user

81
00:04:04,430 --> 00:04:10,420
keyboard na kuhifadhi ndani ya x, saa
chochote anuani x hutokea kuishi katika.

82
00:04:10,420 --> 00:04:14,860
Na kisha mwishowe, mstari 19 tu anasema,
shukrani kwa ajili ya int, katika kesi hii.

83
00:04:14,860 --> 00:04:15,940
>> Hivyo basi mimi kwenda mbele na kufanya hii.

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00:04:15,940 --> 00:04:18,570
Hivyo kufanya scanf 0.

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00:04:18,570 --> 00:04:20,130
Hebu kwenda mbele na zoom in

86
00:04:20,130 --> 00:04:22,960
Nitakwenda na kukimbia hii na
dots kufyeka scanf 0.

87
00:04:22,960 --> 00:04:24,020
Simu, tafadhali?

88
00:04:24,020 --> 00:04:24,720
50.

89
00:04:24,720 --> 00:04:25,730
Shukrani kwa ajili ya 50.

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00:04:25,730 --> 00:04:27,270
Hivyo ni rahisi sana.

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00:04:27,270 --> 00:04:28,160
>> Sasa ni nini si kufanya?

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00:04:28,160 --> 00:04:29,940
Siyo kufanya rundo zima
ya kuangalia makosa.

93
00:04:29,940 --> 00:04:33,000
Kwa mfano, kama mimi si kushirikiana,
na mimi si aina katika idadi, lakini

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00:04:33,000 --> 00:04:37,860
badala mimi kuandika kitu kama "hello,"
hiyo ni aina tu ya ajabu.

95
00:04:37,860 --> 00:04:41,130
Na hivyo moja ya mambo CS50
maktaba amekuwa akifanya kwa ajili yetu kwa baadhi ya

96
00:04:41,130 --> 00:04:43,440
muda ni kwamba reprompting
na reprompting.

97
00:04:43,440 --> 00:04:49,320
>> Jaribu tena maneno kukumbuka ilikuwa katika cs50.c,
na kwamba ni sababu ya kwamba GetInt katika

98
00:04:49,320 --> 00:04:51,670
Maktaba CS50 ni kweli nzima
rundo la mistari ya muda mrefu, kwa sababu tuko

99
00:04:51,670 --> 00:04:53,190
kuangalia kwa mambo ya kijinga kama hii.

100
00:04:53,190 --> 00:04:55,730
Je, si kutoa mtumiaji
yetu, kwa kweli, int?

101
00:04:55,730 --> 00:04:57,910
Je, yeye au kutupa kitu
kama barua ya herufi?

102
00:04:57,910 --> 00:05:01,410
Kama ni hivyo, tunataka kuchunguza
kwamba na yell katika wao.

103
00:05:01,410 --> 00:05:03,915
>> Lakini mambo kupata zaidi ya kuvutia
katika mfano huu unaofuata.

104
00:05:03,915 --> 00:05:09,840
Kama mimi kwenda scanf-1.c, kile ni moja
kitu kwamba ni kimsingi iliyopita katika

105
00:05:09,840 --> 00:05:11,135
mfano huu ijayo?

106
00:05:11,135 --> 00:05:13,690

107
00:05:13,690 --> 00:05:16,010
Mimi nina kutumia * Char, bila shaka,
badala ya int.

108
00:05:16,010 --> 00:05:19,210
>> Hivyo hii ni ya kuvutia, kwa sababu Char *,
kukumbuka, ni kweli tu

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00:05:19,210 --> 00:05:20,190
kitu kimoja kama kamba.

110
00:05:20,190 --> 00:05:23,840
Hivyo anahisi kama labda hii ni super
rahisi ya utekelezaji wa GetString.

111
00:05:23,840 --> 00:05:26,010
Lakini nimepata peeled nyuma ya safu
ya maktaba CS50, hivyo mimi nina

112
00:05:26,010 --> 00:05:27,550
wito huu * Char sasa.

113
00:05:27,550 --> 00:05:30,070
Basi hebu angalia ambapo, kama mahali popote,
sisi kwenda vibaya.

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00:05:30,070 --> 00:05:30,840
>> Mstari 17 -

115
00:05:30,840 --> 00:05:33,950
Mimi tena kusema, tafadhali nipe kitu,
katika kesi hii, kamba.

116
00:05:33,950 --> 00:05:37,940
Na kisha katika mstari wa pili, mimi wito scanf,
tena, kutoa ni kanuni ya muundo,

117
00:05:37,940 --> 00:05:39,310
lakini hii asilimia muda s.

118
00:05:39,310 --> 00:05:41,900
Na kisha wakati huu, mimi nina
kutoa ni buffer.

119
00:05:41,900 --> 00:05:43,550
>> Sasa taarifa, mimi si kutumia
Ampersand.

120
00:05:43,550 --> 00:05:47,120
Lakini kwa nini ni kwamba pengine OK hapa?

121
00:05:47,120 --> 00:05:49,760
Sababu kile ni buffer tayari?

122
00:05:49,760 --> 00:05:50,770
Ni tayari pointer.

123
00:05:50,770 --> 00:05:51,650
Ni tayari anwani.

124
00:05:51,650 --> 00:05:54,510
>> Na hebu neno hili "kuwachanganya," basi mimi
tu kuiita s, kwa mfano, kwa

125
00:05:54,510 --> 00:05:55,050
unyenyekevu.

126
00:05:55,050 --> 00:05:58,250
Lakini nimepata kuitwa ni buffer kwa sababu katika
ujumla, katika programu, kama una

127
00:05:58,250 --> 00:06:02,130
chunk ya kumbukumbu, ambayo string kweli
tu ni, unaweza kuiita buffer.

128
00:06:02,130 --> 00:06:04,460
Ni mahali pa kuhifadhi habari.

129
00:06:04,460 --> 00:06:07,400
>> Sawa na mambo kama YouTube, wakati
wao ni buffering, hivyo kusema, kwamba

130
00:06:07,400 --> 00:06:10,270
tu ina maana ni kushusha bits kutoka
internet na kuzihifadhi katika

131
00:06:10,270 --> 00:06:14,160
mitaa safu, chunk mitaa ya kumbukumbu ili
kwamba unaweza kuangalia ni baadaye bila

132
00:06:14,160 --> 00:06:16,830
ni kuruka au kunyongwa
wewe wakati kucheza nyuma.

133
00:06:16,830 --> 00:06:20,930
>> Hivyo kuna tatizo hapa ingawa,
kwa sababu mimi nina kuwaambia scanf, wanatarajia

134
00:06:20,930 --> 00:06:22,320
kamba kutoka mtumiaji.

135
00:06:22,320 --> 00:06:24,410
Hapa ni anwani ya
chunk ya kumbukumbu.

136
00:06:24,410 --> 00:06:26,180
Kuweka kwamba kamba huko.

137
00:06:26,180 --> 00:06:31,230
Kwa nini ni kwamba amefungwa kutoa
sisi shida, ingawa?

138
00:06:31,230 --> 00:06:33,490
>> Nini hiyo?

139
00:06:33,490 --> 00:06:35,510
Naruhusiwa kupata
kuwa sehemu ya kumbukumbu?

140
00:06:35,510 --> 00:06:36,250
Unajua, mimi sijui.

141
00:06:36,250 --> 00:06:39,210
Kwa sababu ina buffer wamekuwa initialized
na kitu chochote?

142
00:06:39,210 --> 00:06:39,820
Si kweli.

143
00:06:39,820 --> 00:06:43,090
Na hivyo ni nini tumekuwa wito
thamani taka, ambayo

144
00:06:43,090 --> 00:06:44,040
si neno rasmi.

145
00:06:44,040 --> 00:06:49,200
Ni tu ina maana hatuna wazo nini bits
ni ndani ya ka nne ambazo

146
00:06:49,200 --> 00:06:51,240
Mimi zilizotengwa kama kinga.

147
00:06:51,240 --> 00:06:52,450
>> Mimi si kuitwa malloc.

148
00:06:52,450 --> 00:06:53,940
Nimekuwa dhahiri si kuitwa GetString.

149
00:06:53,940 --> 00:06:56,380
Hivyo ambaye anajua nini ni kweli
ndani ya buffer?

150
00:06:56,380 --> 00:07:00,550
Na bado kuwaambia scanf upofu, kwenda huko
na kuweka chochote mtumiaji typed.

151
00:07:00,550 --> 00:07:04,460
>> Kwa hiyo kile ni uwezekano wa kusababisha
katika kanuni zetu kama sisi kukimbia?

152
00:07:04,460 --> 00:07:05,700
Pengine segfault.

153
00:07:05,700 --> 00:07:07,970
Labda si, lakini pengine segfault.

154
00:07:07,970 --> 00:07:10,620
Na mimi kusema labda si kwa sababu wakati mwingine
kufanya, wakati mwingine

155
00:07:10,620 --> 00:07:11,380
huwezi kupata segfault.

156
00:07:11,380 --> 00:07:14,280
Wakati mwingine wewe tu kupata bahati, lakini
hata hivyo ni kwenda kuwa

157
00:07:14,280 --> 00:07:15,340
mdudu katika programu yetu.

158
00:07:15,340 --> 00:07:17,060
>> Hivyo basi mimi kwenda mbele na kukusanya hii.

159
00:07:17,060 --> 00:07:18,280
Mimi naenda kufanya hivyo umri wa shule ya njia.

160
00:07:18,280 --> 00:07:23,825
Hivyo Clang dash 0, scanf-1,
scanf-1.c, kuingia.

161
00:07:23,825 --> 00:07:24,720
Lo, mzee sana shule.

162
00:07:24,720 --> 00:07:26,550
Hebu angalia.

163
00:07:26,550 --> 00:07:28,440
Wapi mimi kwenda?

164
00:07:28,440 --> 00:07:29,700
Oh, char * buffer.

165
00:07:29,700 --> 00:07:33,595

166
00:07:33,595 --> 00:07:35,130
Oh, asante -

167
00:07:35,130 --> 00:07:36,930
Ila, OK -

168
00:07:36,930 --> 00:07:37,690
zamani sana shule.

169
00:07:37,690 --> 00:07:38,900
Haki ya wote, imekuwa ni muda.

170
00:07:38,900 --> 00:07:41,720
>> Hivyo nimekuwa tu baada ya kuokolewa faili
maamuzi kwamba muda

171
00:07:41,720 --> 00:07:42,700
mabadiliko ya wakati iliyopita.

172
00:07:42,700 --> 00:07:46,090
Na sasa mimi ni compiled
manually na Clang.

173
00:07:46,090 --> 00:07:49,500
Na sasa mimi nina kwenda mbele
na kukimbia scanf-1, kuingia.

174
00:07:49,500 --> 00:07:50,290
Kamba tafadhali.

175
00:07:50,290 --> 00:07:51,600
Mimi itabidi aina katika "hello."

176
00:07:51,600 --> 00:07:54,070
>> Na sasa, hapa ambapo, kusema ukweli, printf
unaweza ni kidogo annoying.

177
00:07:54,070 --> 00:07:56,020
Siyo kweli kwenda
segfault katika kesi hii.

178
00:07:56,020 --> 00:07:59,860
Printf ni kidogo maalum kwa sababu
hivyo ni super kawaida kutumika kwamba

179
00:07:59,860 --> 00:08:03,570
kimsingi printf ni kufanya
sisi neema na kutambua,

180
00:08:03,570 --> 00:08:04,830
si kwamba pointer halali.

181
00:08:04,830 --> 00:08:09,080
Napenda kuchukua juu ya mwenyewe tu magazeti
nje katika null mabano, hata

182
00:08:09,080 --> 00:08:13,340
ingawa ni lazima si kile
sisi wenyewe ilivyotarajiwa.

183
00:08:13,340 --> 00:08:16,940
>> Hivyo hatuwezi kweli urahisi kushawishi
segfault na hili, lakini ni wazi hii

184
00:08:16,940 --> 00:08:18,600
si tabia nilitaka.

185
00:08:18,600 --> 00:08:19,800
Basi nini ufumbuzi rahisi?

186
00:08:19,800 --> 00:08:25,650
Naam, katika scanf-2, napenda kupendekeza kwamba
badala ya kweli tu kugawa

187
00:08:25,650 --> 00:08:30,100
* Char, basi mimi kuwa ni kidogo nadhifu kuhusu
hii, na napenda kutenga buffer

188
00:08:30,100 --> 00:08:32,940
kama mlolongo wa chars 16.

189
00:08:32,940 --> 00:08:34,200
>> Hivyo naweza kufanya hivyo katika michache ya njia.

190
00:08:34,200 --> 00:08:35,610
Mimi naweza kabisa kutumia malloc.

191
00:08:35,610 --> 00:08:38,980
Lakini siwezi kwenda nyuma ya wiki mbili wakati
Mimi tu inahitajika rundo zima la

192
00:08:38,980 --> 00:08:39,620
wahusika.

193
00:08:39,620 --> 00:08:40,860
Hiyo tu safu.

194
00:08:40,860 --> 00:08:44,870
Hivyo basi mimi badala redefine buffer
kuwa safu ya wahusika 16.

195
00:08:44,870 --> 00:08:47,340
>> Na sasa, wakati mimi kupita buffer katika -

196
00:08:47,340 --> 00:08:49,940
na hii ni kitu hatukuwa
majadiliano juu katika wiki mbili -

197
00:08:49,940 --> 00:08:53,730
lakini unaweza kutibu safu kama
ingawa ni anwani.

198
00:08:53,730 --> 00:08:56,390
Kitaalam, kama tumeona, wao ni
tofauti kidogo.

199
00:08:56,390 --> 00:09:01,290
Lakini scanf si akili kama wewe kupita
jina la safu, kwa sababu kile

200
00:09:01,290 --> 00:09:05,030
Clang kufanya kwa sisi kimsingi ni
kutibu jina la safu kwamba kama

201
00:09:05,030 --> 00:09:08,280
anuani ya chunk ya ka 16.

202
00:09:08,280 --> 00:09:09,550
>> Hivyo hii ni bora.

203
00:09:09,550 --> 00:09:12,110
Hii ina maana kwamba sasa naweza hopefully
kufanya yafuatayo.

204
00:09:12,110 --> 00:09:16,800
Hebu zoom nje kwa muda na
kufanya kufanya scanf-2, ulioandaliwa OK.

205
00:09:16,800 --> 00:09:19,390
Sasa basi mimi wala got kufyeka scanf-2.

206
00:09:19,390 --> 00:09:22,430
Kamba tafadhali. "Hello." Na ni
walionekana kazi wakati huu.

207
00:09:22,430 --> 00:09:26,020
>> Lakini mtu anaweza kupendekeza mazingira
ambayo wanaweza bado kazi?

208
00:09:26,020 --> 00:09:28,550
Yeah?

209
00:09:28,550 --> 00:09:30,640
Kitu zaidi ya wahusika 16.

210
00:09:30,640 --> 00:09:32,020
Na kwa kweli, tunaweza kuwa na
kidogo sahihi zaidi.

211
00:09:32,020 --> 00:09:36,540
Kitu tena basi 15 wahusika,
kwa sababu kwa kweli tunahitaji kukumbuka

212
00:09:36,540 --> 00:09:39,920
kwamba tunahitaji kuwa backslash sifuri
inamuunga mwisho wa kamba,

213
00:09:39,920 --> 00:09:42,950
ambayo ni scanf kando mapenzi kawaida
utunzaji wa kwetu.

214
00:09:42,950 --> 00:09:46,210
>> Hivyo basi mimi kufanya kitu kama -

215
00:09:46,210 --> 00:09:48,040
wakati mwingine tunaweza tu
kuondoka ni kama hiyo.

216
00:09:48,040 --> 00:09:50,630
OK, hivyo tumekuwa sasa ikiwa
segmentation wetu kosa.

217
00:09:50,630 --> 00:09:51,000
Kwa nini?

218
00:09:51,000 --> 00:09:54,940
Kwa sababu mimi niliandika kwa zaidi ya 15
wahusika, na hivyo tumekuwa kweli

219
00:09:54,940 --> 00:09:58,280
kuguswa kumbukumbu kwamba mimi kwa kweli
unapaswa kuwa.

220
00:09:58,280 --> 00:10:00,180
>> Basi nini ufumbuzi kweli hapa?

221
00:10:00,180 --> 00:10:02,210
Naam, nini kama tunahitaji kamba tena?

222
00:10:02,210 --> 00:10:03,960
Naam, sisi kufanya hivyo labda 32 ka.

223
00:10:03,960 --> 00:10:05,160
Naam, ni nini kama si kwamba muda wa kutosha?

224
00:10:05,160 --> 00:10:06,040
Vipi kuhusu 64 ka?

225
00:10:06,040 --> 00:10:07,080
Nini kama si kwamba muda wa kutosha?

226
00:10:07,080 --> 00:10:09,640
Vipi kuhusu 128 au 200 ka?

227
00:10:09,640 --> 00:10:12,660
Kile kwa kweli ni ufumbuzi hapa katika
kesi ujumla, kama hatujui katika

228
00:10:12,660 --> 00:10:14,460
kuendeleza kile user kinaendelea na aina?

229
00:10:14,460 --> 00:10:20,000

230
00:10:20,000 --> 00:10:23,050
>> Ni tu aina ya maumivu kubwa katika punda,
kuwa waaminifu, ambayo ni kwa nini

231
00:10:23,050 --> 00:10:29,050
CS50 maktaba ina mistari kadhaa chache ya
kificho kwamba pamoja kutekeleza

232
00:10:29,050 --> 00:10:32,390
GetString kamba katika njia kwamba hatuna
kujua mapema kile

233
00:10:32,390 --> 00:10:33,430
user ni kwenda aina.

234
00:10:33,430 --> 00:10:37,370
Hasa, kama wewe kuangalia nyuma katika
cs50.c kutoka wiki mbili zilizopita, utaona

235
00:10:37,370 --> 00:10:40,480
GetString kwamba kweli haina
si kutumia scanf kwa njia hii.

236
00:10:40,480 --> 00:10:43,720
Badala yake, anasoma moja tabia
kwa wakati.

237
00:10:43,720 --> 00:10:46,010
>> Sababu moja nzuri kitu kuhusu
kusoma tabia moja ni tunaweza

238
00:10:46,010 --> 00:10:48,490
kuhakikisha wenyewe daima
angalau moja Char.

239
00:10:48,490 --> 00:10:51,740
Naweza tu kutangaza Char, na kisha kuchukua
hatua hizi kweli mtoto tu

240
00:10:51,740 --> 00:10:54,380
kusoma tabia moja katika saa
wakati kutoka keyboard.

241
00:10:54,380 --> 00:10:58,240
Na kisha, nini utaona GetString
gani ni kila wakati anaendesha nje ya,

242
00:10:58,240 --> 00:11:02,280
kusema, ka 16 ya kumbukumbu, inatumia
malloc, au binamu yake, kwa

243
00:11:02,280 --> 00:11:06,810
kutenga zaidi ya kumbukumbu, kuiga kale
kumbukumbu katika kutambaa mpya, na kisha

244
00:11:06,810 --> 00:11:09,900
pamoja, kupata tabia moja kwa wakati,
na wakati anaendesha nje ya kwamba

245
00:11:09,900 --> 00:11:13,370
chunk ya kumbukumbu, kumtupia mbali, grabs
chunk kubwa ya kumbukumbu, nakala ya zamani

246
00:11:13,370 --> 00:11:14,750
katika mpya, na kurudia.

247
00:11:14,750 --> 00:11:18,480
Na ni kweli maumivu ya kweli
kutekeleza kitu rahisi kama

248
00:11:18,480 --> 00:11:19,710
kupata pembejeo kutoka kwa mtumiaji.

249
00:11:19,710 --> 00:11:21,090
>> Hivyo unaweza kutumia scanf.

250
00:11:21,090 --> 00:11:22,430
Unaweza kutumia kazi nyingine kama hiyo.

251
00:11:22,430 --> 00:11:25,420
Na mengi ya vitabu vya kiada na online
mifano kufanya, lakini wao ni wote

252
00:11:25,420 --> 00:11:27,210
mazingira magumu na matatizo kama hii.

253
00:11:27,210 --> 00:11:29,550
Na hatimaye, kupata segfault
ni aina ya annoying.

254
00:11:29,550 --> 00:11:30,680
Ni si nzuri kwa ajili ya mtumiaji.

255
00:11:30,680 --> 00:11:33,560
>> Lakini katika hali mbaya zaidi, ni nini
kimsingi ni kuweka yako

256
00:11:33,560 --> 00:11:37,160
kanuni katika hatari ya?

257
00:11:37,160 --> 00:11:39,250
Baadhi ya aina ya mashambulizi, uwezekano.

258
00:11:39,250 --> 00:11:41,680
Kuongelea mashambulizi moja vile -
wingi stack.

259
00:11:41,680 --> 00:11:44,660
Lakini kwa ujumla, kama wewe ni kuruhusiwa
kufurika buffer, kama tulivyofanya

260
00:11:44,660 --> 00:11:48,070
michache ya wiki iliyopita, na kuandika tu
zaidi ya "hello" juu ya stack, unaweza

261
00:11:48,070 --> 00:11:52,330
unaweza kweli kuchukua, uwezekano,
kompyuta, au angalau kupata saa data kwamba

262
00:11:52,330 --> 00:11:53,510
siyo wewe.

263
00:11:53,510 --> 00:11:55,970
>> Hivyo katika muda mfupi, hii ni kwa nini tuna
magurudumu mafunzo hayo.

264
00:11:55,970 --> 00:11:59,090
Lakini sasa, sisi kuanza kuchukua mbali,
kama mipango yetu hakuna haja tena,

265
00:11:59,090 --> 00:12:00,610
lazima, pembejeo kutoka kwa mtumiaji.

266
00:12:00,610 --> 00:12:03,960
Lakini katika kesi ya tatizo kuweka sita,
mchango wako watakuja kutoka kubwa

267
00:12:03,960 --> 00:12:07,520
kamusi faili na baadhi ya 150
isiyo ya kawaida maneno elfu.

268
00:12:07,520 --> 00:12:10,330
>> Hivyo huwezi kuwa na wasiwasi kuhusu
mtumiaji holela pembejeo.

269
00:12:10,330 --> 00:12:13,720
Sisi nitakupa baadhi ya mawazo
kuhusu faili hilo.

270
00:12:13,720 --> 00:12:20,340
Maswali yoyote juu ya kuyatumia au scanf
au mtumiaji pembejeo kwa ujumla?

271
00:12:20,340 --> 00:12:24,450
>> Haki ya wote, hivyo kuangalia haraka kisha saa moja
trailing mada kutoka wiki mbili zilizopita.

272
00:12:24,450 --> 00:12:28,590
Na kwamba alikuwa wazo hili la struct.

273
00:12:28,590 --> 00:12:34,180
Si kwamba - wazo hili la
Struct, ambayo ilikuwa nini?

274
00:12:34,180 --> 00:12:35,430
Nini struct kufanya kwa ajili yetu?

275
00:12:35,430 --> 00:12:39,280

276
00:12:39,280 --> 00:12:39,860
>> Kufafanua -

277
00:12:39,860 --> 00:12:41,710
pole?

278
00:12:41,710 --> 00:12:42,820
Kufafanua aina ya kutofautiana.

279
00:12:42,820 --> 00:12:44,410
Hivyo aina ya.

280
00:12:44,410 --> 00:12:46,180
Sisi ni kweli kuchanganya mada mbili.

281
00:12:46,180 --> 00:12:49,510
Hivyo, pamoja na typedef, kukumbuka kwamba tunaweza
kutangaza aina ya yetu wenyewe, kama

282
00:12:49,510 --> 00:12:51,500
kisawe, kama kamba kwa ajili ya * Char.

283
00:12:51,500 --> 00:12:56,200
Lakini kwa kutumia typedef na struct, tunaweza
kujenga kweli wetu data mwenyewe miundo.

284
00:12:56,200 --> 00:12:59,600
>> Kwa mfano, kama mimi kurejea katika gedit
hapa kwa muda tu, na mimi kwenda mbele

285
00:12:59,600 --> 00:13:08,230
na kufanya kitu kama, napenda kuokoa
hii kama, hebu sema, structs.c

286
00:13:08,230 --> 00:13:10,840
muda, Mimi tu kwenda
kwa kwenda mbele na ni pamoja na

287
00:13:10,840 --> 00:13:14,360
standardio.h, int kuu utupu.

288
00:13:14,360 --> 00:13:18,960
Na kisha katika hapa, tuseme kwamba mimi nataka
kuandika mpango kwamba maduka

289
00:13:18,960 --> 00:13:21,840
nyingi wanafunzi kutoka nyingi
nyumba, kwa mfano.

290
00:13:21,840 --> 00:13:24,430
Hivyo ni kama registrarial
database ya aina fulani.

291
00:13:24,430 --> 00:13:29,550
>> Hivyo kama nahitaji jina mwanafunzi mmoja, mimi
anaweza kufanya kitu kama jina Char *,

292
00:13:29,550 --> 00:13:31,570
na mimi itabidi kufanya kitu kama -

293
00:13:31,570 --> 00:13:34,410
kweli, hebu kutumia maktaba CS50
kwa muda tu kufanya hii

294
00:13:34,410 --> 00:13:38,380
kidogo rahisi, ili tuweze kukopa
wale kadhaa ya mistari ya kificho.

295
00:13:38,380 --> 00:13:39,340
Na wacha tu kuitunza rahisi.

296
00:13:39,340 --> 00:13:42,610
Tutaweza kushika ni kamba,
na sasa GetString.

297
00:13:42,610 --> 00:13:47,420
>> Hivyo mimi sasa wanadai kwamba nimepata kuhifadhiwa jina
baadhi ya mwanafunzi, na nyumba ya

298
00:13:47,420 --> 00:13:50,240
baadhi ya mwanafunzi, kifupi kwa kutumia vigezo
kama tulivyofanya na katika wiki moja.

299
00:13:50,240 --> 00:13:52,370
Lakini nadhani sasa wanataka kusaidia
mbalimbali ya wanafunzi.

300
00:13:52,370 --> 00:13:58,460
Haki ya wote, hivyo silika yangu ni kufanya
kamba NAME2, anapata GetString, kamba

301
00:13:58,460 --> 00:14:01,370
house2 anapata GetString.

302
00:14:01,370 --> 00:14:05,850
Na kisha mwanafunzi wetu wa tatu,
hebu kufanya name3 GetString.

303
00:14:05,850 --> 00:14:09,170
>> Haki wote, hivyo hii ni hopefully fora
wewe kama aina ya kijinga,

304
00:14:09,170 --> 00:14:11,580
kwa sababu mchakato huu ni kweli kamwe
kwenda mwisho, na ni kwenda tu

305
00:14:11,580 --> 00:14:13,130
kufanya code yangu kuangalia mbaya
na mbaya zaidi na zaidi.

306
00:14:13,130 --> 00:14:14,810
Lakini sisi kutatuliwa hilo pia katika wiki mbili.

307
00:14:14,810 --> 00:14:19,450
Ni ufumbuzi gani wetu kiasi safi
wakati tulikuwa na vigezo mbalimbali ya

308
00:14:19,450 --> 00:14:23,580
huo data aina kuwa ni wote kuhusiana, lakini
sisi hakutaka hii fujo mauaji

309
00:14:23,580 --> 00:14:26,870
ya vigezo vile vile jina lake?

310
00:14:26,870 --> 00:14:30,060
Nini sisi nini badala yake?

311
00:14:30,060 --> 00:14:31,260
>> Hivyo nadhani nikasikia maeneo machache.

312
00:14:31,260 --> 00:14:32,590
Tulikuwa safu.

313
00:14:32,590 --> 00:14:37,110
Kama unataka matukio mbalimbali ya
kitu, kwa nini sio sisi safi hii kila

314
00:14:37,110 --> 00:14:39,540
juu na kusema tu, nipe
safu kuitwa majina?

315
00:14:39,540 --> 00:14:41,640
>> Na kwa sasa, hebu ngumu kanuni 3.

316
00:14:41,640 --> 00:14:44,450
Na kisha nipe mwingine safu
kuitwa nyumba, na napenda kwa

317
00:14:44,450 --> 00:14:45,800
sasa kwa bidii kanuni 3.

318
00:14:45,800 --> 00:14:49,220
Na nimekuwa massively alisafisha
fujo kwamba mimi tu kuundwa.

319
00:14:49,220 --> 00:14:52,400
Sasa, nimekuwa bado ngumu coded 3, lakini hata
3 inaweza dynamically kuja kutoka

320
00:14:52,400 --> 00:14:54,350
mtumiaji, au argv, au kama.

321
00:14:54,350 --> 00:14:55,720
Hivyo hii ni tayari safi.

322
00:14:55,720 --> 00:15:00,100
>> Lakini nini annoying kuhusu hili ni kwamba
sasa, hata kama jina ni namna fulani

323
00:15:00,100 --> 00:15:02,280
Kimsingi wanaohusishwa na
mwanafunzi nyumba -

324
00:15:02,280 --> 00:15:04,720
ni mwanafunzi wa kwamba mimi kwa kweli
wanataka kuwakilisha -

325
00:15:04,720 --> 00:15:08,080
Mimi sasa na arrays mbili ambazo ni sambamba
kwa maana ya kwamba wao ni

326
00:15:08,080 --> 00:15:13,930
ukubwa huo, na majina ya mabano 0
labda ramani ya nyumba mabano 0,

327
00:15:13,930 --> 00:15:16,600
na majina mabano 1 ramani
na nyumba mabano 1.

328
00:15:16,600 --> 00:15:19,280
Kwa maneno mengine, mwanafunzi kwamba maisha katika
kwamba nyumba, na kwamba mwanafunzi mwingine

329
00:15:19,280 --> 00:15:20,530
maisha katika nyumba nyingine.

330
00:15:20,530 --> 00:15:23,720
Lakini hakika hii inaweza kuwa
kufanyika hata zaidi cleanly.

331
00:15:23,720 --> 00:15:24,990
>> Vizuri, inaweza, kwa kweli.

332
00:15:24,990 --> 00:15:28,730
Na napenda kwenda mbele na kufungua
hadi structs.h, na utasikia

333
00:15:28,730 --> 00:15:31,130
kuona wazo hili hapa.

334
00:15:31,130 --> 00:15:34,905
Taarifa kwamba nimekuwa kutumika typedef, kama wewe
alluded wakati iliyopita kutangaza wetu

335
00:15:34,905 --> 00:15:35,570
mwenyewe data aina.

336
00:15:35,570 --> 00:15:39,660
Lakini nina pia kutumia Keyword nyingine
kuitwa struct ambayo inatoa mimi mpya

337
00:15:39,660 --> 00:15:40,790
data muundo.

338
00:15:40,790 --> 00:15:43,980
>> Na muundo huu data mimi kudai ni kwenda
kuwa na mambo mawili ndani ya

339
00:15:43,980 --> 00:15:47,060
yake - string kuitwa jina, na
string kuitwa nyumba.

340
00:15:47,060 --> 00:15:49,820
Na jina Mimi naenda kuwapa
muundo huu data ni kwenda

341
00:15:49,820 --> 00:15:51,005
kuitwa mwanafunzi.

342
00:15:51,005 --> 00:15:54,030
Mimi naweza kuiita kitu nataka,
lakini hii semantically kufanya

343
00:15:54,030 --> 00:15:55,810
kuhisi na mimi katika mawazo yangu.

344
00:15:55,810 --> 00:15:59,160
>> Hivyo sasa, kama mimi kufungua toleo bora
ya mpango Nilianza kuandika

345
00:15:59,160 --> 00:16:00,390
huko, basi mimi kitabu juu.

346
00:16:00,390 --> 00:16:03,190
Na kuna baadhi ya zaidi ya mistari ya kanuni
hapa, lakini napenda kuzingatia kwa

347
00:16:03,190 --> 00:16:04,160
sasa juu ya mmoja.

348
00:16:04,160 --> 00:16:07,790
Nimekuwa alitangaza mara kwa mara wanafunzi kinachoitwa
na ngumu coded 3 kwa sasa.

349
00:16:07,790 --> 00:16:11,110
Lakini sasa, taarifa jinsi safi
kanuni yangu huanza kupata.

350
00:16:11,110 --> 00:16:15,030
>> Katika mstari wa 22, mimi kutangaza
safu ya wanafunzi.

351
00:16:15,030 --> 00:16:18,760
Na taarifa kwamba mwanafunzi ni inaonekana
sasa aina data.

352
00:16:18,760 --> 00:16:23,360
Kwa sababu saa ya juu ya faili hili, taarifa
Nimekuwa pamoja na kwamba faili header

353
00:16:23,360 --> 00:16:24,820
kwamba mimi vunjwa juu tu wakati iliyopita.

354
00:16:24,820 --> 00:16:28,820
Na kwamba faili header kabisa tu alikuwa
ufafanuzi huu wa mwanafunzi.

355
00:16:28,820 --> 00:16:32,470
>> Hivyo sasa, nimekuwa kuundwa data yangu mwenyewe desturi
aina ya kwamba waandishi wa miaka C

356
00:16:32,470 --> 00:16:33,890
iliyopita hakufikiri wa mapema.

357
00:16:33,890 --> 00:16:34,570
Lakini hakuna tatizo.

358
00:16:34,570 --> 00:16:35,870
Siwezi kufanya hivyo mwenyewe.

359
00:16:35,870 --> 00:16:39,050
Hivyo hii ni safu kuitwa wanafunzi,
kila mmoja wa wanachama ambao

360
00:16:39,050 --> 00:16:41,100
ni muundo wa mwanafunzi.

361
00:16:41,100 --> 00:16:44,270
Na mimi nataka tatu ya wale
katika safu.

362
00:16:44,270 --> 00:16:46,030
>> Na sasa, je, wengine
ya mpango huu kufanya?

363
00:16:46,030 --> 00:16:47,550
Mimi zinahitajika kitu kidogo holela.

364
00:16:47,550 --> 00:16:51,450
Hivyo kutokana na kuendelea online 24,
Mimi iterate 0-3.

365
00:16:51,450 --> 00:16:54,000
Mimi kisha kuuliza mtumiaji kwa ajili ya
mwanafunzi jina.

366
00:16:54,000 --> 00:16:56,110
Na kisha mimi kutumia GetString kama kabla.

367
00:16:56,110 --> 00:16:59,410
Basi mimi kuuliza kwa ajili ya nyumba ya mwanafunzi,
na mimi kutumia GetString kama kabla.

368
00:16:59,410 --> 00:17:01,780
>> Lakini ilani - kidogo mpya
kipande cha syntax -

369
00:17:01,780 --> 00:17:07,010
Mimi bado unaweza index kwa mwanafunzi i-th,
lakini jinsi gani mimi kupata saa data maalum

370
00:17:07,010 --> 00:17:08,354
shamba ndani ya struct?

371
00:17:08,354 --> 00:17:11,770
Vizuri, nini inaonekana
mpya kipande cha syntax?

372
00:17:11,770 --> 00:17:13,339
Ni tu operator dot.

373
00:17:13,339 --> 00:17:14,510
>> Tumekuwa si kweli kuona hii kabla.

374
00:17:14,510 --> 00:17:17,819
Ve kuonekana katika pset tano kama wameweza
dived katika tayari kwa files bitmap.

375
00:17:17,819 --> 00:17:22,372
Lakini dot tu ina maana ndani ya hii
struct au mashamba mbalimbali, kutoa dot

376
00:17:22,372 --> 00:17:24,510
jina, au nipe dot nyumba.

377
00:17:24,510 --> 00:17:28,690
Hiyo ina maana kwenda ndani ya struct
na kupata mashamba hayo hasa.

378
00:17:28,690 --> 00:17:30,200
>> Nini wengine wa mpango hii nini?

379
00:17:30,200 --> 00:17:31,190
Siyo sexy kwamba wote.

380
00:17:31,190 --> 00:17:34,640
Taarifa kwamba mimi iterate 0-3 tena,
na mimi tu kujenga Kiingereza

381
00:17:34,640 --> 00:17:40,500
maneno kama hivyo na hivyo ni katika vile na
nyumba hiyo, kupita katika jina dot kutoka

382
00:17:40,500 --> 00:17:43,320
mwanafunzi i-th na wao
nyumba pia.

383
00:17:43,320 --> 00:17:47,560
>> Na kisha mwisho, sasa tutaweza kuanza kupata
anal kuhusu hili, sasa kwamba sisi ni

384
00:17:47,560 --> 00:17:49,580
ukoo na nini malloc na
kazi nyingine wamekuwa

385
00:17:49,580 --> 00:17:50,570
kufanya wakati huu wote.

386
00:17:50,570 --> 00:17:54,220
Kwa nini nina huru wawili jina
na nyumba, hata mimi

387
00:17:54,220 --> 00:17:56,960
hakuwa na wito malloc?

388
00:17:56,960 --> 00:17:58,020
>> GetString alivyofanya.

389
00:17:58,020 --> 00:18:00,930
Na kwamba ilikuwa chafu kidogo siri kwa
wiki kadhaa, lakini ana GetString

390
00:18:00,930 --> 00:18:03,530
imekuwa kinachovuja kumbukumbu yote juu ya
mahali yote ya muhula wa hivi sasa.

391
00:18:03,530 --> 00:18:05,990
Na valgrand mapenzi hatimaye
yatangaza hii kwetu.

392
00:18:05,990 --> 00:18:10,730
>> Lakini si kubwa mpango huo, kwa sababu ninajua
kwamba naweza tu huru jina

393
00:18:10,730 --> 00:18:15,750
na nyumba, ingawa kitaalam, kwa
kuwa super, super salama, nitakuwa

394
00:18:15,750 --> 00:18:17,890
kufanya baadhi ya makosa ya kuangalia hapa.

395
00:18:17,890 --> 00:18:19,040
Je, ni silika yako nakuambia?

396
00:18:19,040 --> 00:18:22,480
Nini anatakiwa kuwa na kuangalia kwa
kabla mimi huru ni nini

397
00:18:22,480 --> 00:18:25,470
kamba, aka ambayo * Char?

398
00:18:25,470 --> 00:18:33,460
>> Mimi lazima kweli kuwa na kuangalia kama wanafunzi
bracket i dot jina haina

399
00:18:33,460 --> 00:18:34,840
sawa null.

400
00:18:34,840 --> 00:18:40,400
Basi utakuwa ni sawa na kwenda mbele na bure
kwamba pointer, na moja au nyingine

401
00:18:40,400 --> 00:18:41,160
moja pia.

402
00:18:41,160 --> 00:18:46,860
Kama wanafunzi mabano i dot nyumba si
sawa na null, hii sasa kulinda

403
00:18:46,860 --> 00:18:52,520
dhidi ya kesi ya kona ambayo
GetString anarudi kitu kama null.

404
00:18:52,520 --> 00:18:57,310
Na tuliona wakati iliyopita, printf mapenzi
kulinda sisi hapa juu na kusema tu

405
00:18:57,310 --> 00:18:58,990
null, ambayo ni kwenda kuangalia weird.

406
00:18:58,990 --> 00:19:02,340
Lakini angalau itakuwa si segfault,
kama tulivyoona.

407
00:19:02,340 --> 00:19:05,990
>> Vizuri, basi mimi kufanya jambo moja nyingine hapa.
structs-0 ni aina ya mpango wa kijinga

408
00:19:05,990 --> 00:19:09,700
kwa sababu mimi kuingia hii data zote, na kisha
ni kupotea mara moja mpango wa mwisho.

409
00:19:09,700 --> 00:19:10,940
Lakini napenda kwenda mbele na kufanya hili.

410
00:19:10,940 --> 00:19:12,830
Napenda kufanya terminal
dirisha kubwa kidogo.

411
00:19:12,830 --> 00:19:17,000
Napenda kufanya structs-1, ambayo
ni toleo jipya la hii.

412
00:19:17,000 --> 00:19:18,520
>> Mimi itabidi kuvuta kidogo.

413
00:19:18,520 --> 00:19:21,620
Na sasa basi mimi kukimbia dot
kufyeka structs-1.

414
00:19:21,620 --> 00:19:22,590
Jina ya mwanafunzi -

415
00:19:22,590 --> 00:19:31,500
Daudi Mather, hebu kufanya Rob Kirkland,
hebu kufanya Lauren LEVERETT.

416
00:19:31,500 --> 00:19:33,650
Nini kuvutia sasa ni taarifa -

417
00:19:33,650 --> 00:19:35,540
na mimi tu najua hili kwa sababu
Niliandika mpango -

418
00:19:35,540 --> 00:19:38,930
kuna faili sasa sasa yangu
saraka ya kuitwa students.csv.

419
00:19:38,930 --> 00:19:40,420
Baadhi ya unaweza kuwa na kuonekana
hizi katika ulimwengu wa kweli.

420
00:19:40,420 --> 00:19:42,980
>> Nini faili CSV?

421
00:19:42,980 --> 00:19:44,170
Koma maadili.

422
00:19:44,170 --> 00:19:46,670
Ni aina ya kama maskini wa mtu
toleo la faili Excel.

423
00:19:46,670 --> 00:19:50,580
Ni meza ya safu na nguzo kwamba
unaweza kufungua katika mpango kama Excel,

424
00:19:50,580 --> 00:19:51,800
Hesabu au juu ya Mac.

425
00:19:51,800 --> 00:19:55,180
>> Na kama mimi kufungua faili hii hapa gedit,
ilani - na idadi si huko.

426
00:19:55,180 --> 00:19:57,360
Hiyo tu gedit kuwaambia
mimi line namba.

427
00:19:57,360 --> 00:19:59,740
Taarifa juu ya line ya kwanza ya hii
faili ni Daudi na Mather.

428
00:19:59,740 --> 00:20:01,450
mstari wa pili ni Rob comma Kirkland.

429
00:20:01,450 --> 00:20:04,170
Na mstari wa tatu ni Lauren
comma LEVERETT.

430
00:20:04,170 --> 00:20:05,480
>> Hivyo kile mimi umba?

431
00:20:05,480 --> 00:20:09,580
Nimepata sasa imeandikwa mpango C kwamba
ufanisi inaweza kuzalisha Spreadsheets

432
00:20:09,580 --> 00:20:11,840
kwamba anaweza kufunguliwa katika
mpango kama Excel.

433
00:20:11,840 --> 00:20:15,520
Si kulazimisha kwamba wote kuweka data, lakini
kama una chunks kubwa ya

434
00:20:15,520 --> 00:20:18,440
data kwamba kweli wanataka
kuendesha na kufanya grafu ya na

435
00:20:18,440 --> 00:20:21,260
kama, hii labda ni moja
njia ya kujenga data hizo.

436
00:20:21,260 --> 00:20:25,370
Aidha, ni kweli CSVs super kawaida
tu kwa ajili ya kuhifadhi data rahisi -

437
00:20:25,370 --> 00:20:28,940
Yahoo Fedha, kwa mfano, kama kupata
hisa quotes kupitia yao kinachojulikana

438
00:20:28,940 --> 00:20:33,180
API, huduma ya bure ambayo inakuwezesha
kupata sasa up-to-ya-tarehe hisa

439
00:20:33,180 --> 00:20:35,650
quotes kwa ajili ya makampuni, wao
kutoa data nyuma katika

440
00:20:35,650 --> 00:20:37,800
super rahisi CSV format.

441
00:20:37,800 --> 00:20:39,380
>> Hivyo ni jinsi gani sisi kufanya hivyo?

442
00:20:39,380 --> 00:20:42,530
Vizuri taarifa, zaidi ya hii ya mpango
karibu sawa.

443
00:20:42,530 --> 00:20:46,870
Lakini taarifa chini hapa, badala ya magazeti
wanafunzi nje, juu ya mstari 35

444
00:20:46,870 --> 00:20:51,040
kuendelea, mimi kudai kwamba mimi nina kuokoa
wanafunzi kwa disk, hivyo kuokoa faili.

445
00:20:51,040 --> 00:20:53,630
>> Hivyo taarifa mimi nina kutangaza JALADA * -

446
00:20:53,630 --> 00:20:57,260
sasa, hii ni aina ya makosa katika C.
Kwa sababu yoyote, JALADA ni kila kofia,

447
00:20:57,260 --> 00:21:00,690
ambayo si kama aina nyingine ya data
katika C. Lakini hii ni kujengwa katika

448
00:21:00,690 --> 00:21:02,320
data aina, JALADA *.

449
00:21:02,320 --> 00:21:05,900
Na mimi nina kutangaza pointer faili,
ni jinsi gani unaweza kufikiri ya kwamba.

450
00:21:05,900 --> 00:21:08,070
>> fopen maana faili wazi.

451
00:21:08,070 --> 00:21:09,470
Nini faili unataka wazi?

452
00:21:09,470 --> 00:21:12,620
Nataka kufungua faili kwamba mimi
kiholela kuwaita students.csv.

453
00:21:12,620 --> 00:21:14,480
Mimi naweza kuita kwamba kitu nataka.

454
00:21:14,480 --> 00:21:15,200
>> Na kisha kuchukua nadhani.

455
00:21:15,200 --> 00:21:18,960
Ni nini hoja ya pili
kwa fopen pengine maana?

456
00:21:18,960 --> 00:21:21,480
Haki, w kwa kuandika, inaweza
kuwa r kwa ajili ya kusoma.

457
00:21:21,480 --> 00:21:24,120
Kuna kwa append kama wewe
unataka kuongeza mistari na si

458
00:21:24,120 --> 00:21:25,200
overwrite jambo zima.

459
00:21:25,200 --> 00:21:28,005
>> Lakini mimi tu wanataka kujenga faili hii
mara moja, hivyo mimi itabidi kutumia quote unquote w.

460
00:21:28,005 --> 00:21:31,880
Na najua kwamba tu kutoka baada ya kusoma
nyaraka, au ukurasa mtu.

461
00:21:31,880 --> 00:21:35,100
Kama faili si null - kwa maneno mengine,
kama hakuna kitu potoka huko -

462
00:21:35,100 --> 00:21:37,820
basi mimi iterate juu ya
wanafunzi 0-3.

463
00:21:37,820 --> 00:21:40,410
>> Na sasa taarifa kuna kitu
milele hivyo tofauti kidogo

464
00:21:40,410 --> 00:21:42,110
kuhusu line 41 hapa.

465
00:21:42,110 --> 00:21:42,960
Siyo printf.

466
00:21:42,960 --> 00:21:46,530
Ni kwa ajili ya faili fprintf printf.

467
00:21:46,530 --> 00:21:47,790
Hivyo ni kwenda kuandika na faili.

468
00:21:47,790 --> 00:21:48,860
Ambayo faili?

469
00:21:48,860 --> 00:21:53,630
mtu ambaye pointer bayana
kama hoja ya kwanza.

470
00:21:53,630 --> 00:21:55,940
>> Kisha sisi bayana kamba format.

471
00:21:55,940 --> 00:21:59,660
Kisha sisi bayana nini kamba tunataka
kuziba katika s kwanza kwa asilimia, na

472
00:21:59,660 --> 00:22:04,320
kisha mwingine kutofautiana au
pili asilimia s.

473
00:22:04,320 --> 00:22:06,760
Kisha sisi karibu faili na fclose.

474
00:22:06,760 --> 00:22:09,380
Kuliko mimi huru kumbukumbu kama kabla, ingawa
Mimi lazima kurudi nyuma katika na kuongeza

475
00:22:09,380 --> 00:22:10,540
baadhi ya hundi kwa null.

476
00:22:10,540 --> 00:22:12,090
>> Na hiyo ni yake.

477
00:22:12,090 --> 00:22:16,960
fopen, fprintf, fclose anitiaye
uwezo wa kujenga files maandishi.

478
00:22:16,960 --> 00:22:19,640
Sasa, utaona katika tatizo kuweka tano,
ambayo inahusisha picha, wewe utakuwa kutumia

479
00:22:19,640 --> 00:22:20,990
binary files badala yake.

480
00:22:20,990 --> 00:22:24,200
Lakini kimsingi, wazo ni sawa,
hata ingawa kazi utasikia

481
00:22:24,200 --> 00:22:28,710
kuona ni tofauti kidogo.

482
00:22:28,710 --> 00:22:32,580
>> Hivyo kimbunga ziara, lakini utapata
wote pia familiar na faili I/O--

483
00:22:32,580 --> 00:22:34,960
pembejeo na pato - na pset tano.

484
00:22:34,960 --> 00:22:38,607
Na maswali yoyote kuhusu
awali misingi hapa?

485
00:22:38,607 --> 00:22:39,857
Yeah?

486
00:22:39,857 --> 00:22:41,880

487
00:22:41,880 --> 00:22:43,710
>> Nini kama wewe kujaribu bure thamani null?

488
00:22:43,710 --> 00:22:48,880
Naamini, isipokuwa bure imenipatia
kidogo zaidi user-kirafiki, unaweza

489
00:22:48,880 --> 00:22:49,890
uwezekano segfault.

490
00:22:49,890 --> 00:22:54,160
Kupita null ni mbaya kwa sababu mimi si
kuamini bure bothers kuangalia kwa ajili yenu,

491
00:22:54,160 --> 00:22:57,330
sababu ingekuwa uwezekano kuwa taka
ya muda kwa ajili yake kufanya yenyewe kwa ajili ya

492
00:22:57,330 --> 00:22:59,022
kila mtu katika ulimwengu.

493
00:22:59,022 --> 00:23:00,590
Nzuri swali, ingawa.

494
00:23:00,590 --> 00:23:04,300
>> Haki ya wote, hivyo aina hii ya anapata
sisi mada ya kuvutia.

495
00:23:04,300 --> 00:23:07,010
mandhari ya kuweka tatizo
tano ni forensics.

496
00:23:07,010 --> 00:23:08,420
Angalau hiyo ni sehemu
ya kuweka tatizo.

497
00:23:08,420 --> 00:23:12,030
Forensics kwa ujumla inahusu
ahueni wa habari kwamba wanaweza au

498
00:23:12,030 --> 00:23:14,110
inaweza kuwa imefutwa
makusudi.

499
00:23:14,110 --> 00:23:18,680
Na hivyo mimi mawazo ningependa kukupa haraka
ladha ya kile ni kweli kinachoendelea kila

500
00:23:18,680 --> 00:23:21,230
wakati huu chini ya
kofia ya kompyuta yako.

501
00:23:21,230 --> 00:23:23,960
>> Kwa mfano, kama una yako ndani ya
mbali au desktop yako kompyuta

502
00:23:23,960 --> 00:23:28,040
gari ngumu, ni aidha mitambo
kifaa kwamba kweli spins -

503
00:23:28,040 --> 00:23:31,650
kuna mviringo mambo kuitwa platters
kwamba kuangalia kabisa kama kile

504
00:23:31,650 --> 00:23:34,540
tu alikuwa juu ya screen hapa, ingawa
hii ni inazidi umri wa shule.

505
00:23:34,540 --> 00:23:37,370
Hii ni mitatu na nusu-inch
gari ngumu.

506
00:23:37,370 --> 00:23:40,070
Na tatu na nusu inchi inahusu ya
na wa kitu wakati wa kufunga ni

507
00:23:40,070 --> 00:23:40,890
katika kompyuta.

508
00:23:40,890 --> 00:23:44,890
>> Wengi wenu guys katika Laptops yako sasa
kuwa anatoa imara-hali, au SSDs,

509
00:23:44,890 --> 00:23:46,260
ambayo hakuna kusonga sehemu.

510
00:23:46,260 --> 00:23:49,170
Wao ni zaidi kama RAM na chini kama
haya vifaa mitambo.

511
00:23:49,170 --> 00:23:51,450
Lakini mawazo bado ni sawa,
hakika kama wao kuhusiana

512
00:23:51,450 --> 00:23:52,790
kwa tatizo kuweka tano.

513
00:23:52,790 --> 00:23:57,400
>> Na kama unadhani kuhusu sasa gari ngumu
inawakilisha kuwa mduara, ambayo

514
00:23:57,400 --> 00:23:58,930
Mimi itabidi kuteka kama hii hapa.

515
00:23:58,930 --> 00:24:02,290
Wakati kujenga faili kwenye kompyuta yako,
kama ni SSD, au katika

516
00:24:02,290 --> 00:24:06,610
kesi hii, wakubwa shule ngumu kuendesha gari,
faili ambayo inajumuisha bits nyingi.

517
00:24:06,610 --> 00:24:10,510
Hebu kusema kwamba ni hii 0 na 1,
kundi zima la sekunde 0 na 1s.

518
00:24:10,510 --> 00:24:11,660
Hivyo hii ni ngumu wangu wote gari.

519
00:24:11,660 --> 00:24:13,225
Hii ni inaonekana faili pretty kubwa.

520
00:24:13,225 --> 00:24:18,080
Na ni kwa kutumia hadi sekunde 0 na 1s saa kwamba
sehemu ya sahani ya kimwili.

521
00:24:18,080 --> 00:24:19,750
>> Naam, kile ni kwamba sehemu ya kimwili?

522
00:24:19,750 --> 00:24:25,310
Naam, zinageuka kuwa kwenye gari ngumu,
angalau ya aina hii, kuna

523
00:24:25,310 --> 00:24:27,340
haya kidogo kidogo magnetic chembe.

524
00:24:27,340 --> 00:24:32,630
Na wao kimsingi kuwa na kaskazini na
kusini fito kwa wao, ili kwamba kama wewe

525
00:24:32,630 --> 00:24:35,710
kurejea moja ya chembe wale magnetic
njia hii, unaweza kusema kwamba ni

526
00:24:35,710 --> 00:24:36,720
anayewakilisha 1.

527
00:24:36,720 --> 00:24:39,340
Na kama ni kichwa chini kusini
kaskazini, unaweza kusema kwamba ni

528
00:24:39,340 --> 00:24:40,390
anayewakilisha 0.

529
00:24:40,390 --> 00:24:43,660
>> Hivyo katika ulimwengu halisi ya kimwili, hiyo ni
jinsi gani unaweza kuwakilisha kitu katika

530
00:24:43,660 --> 00:24:45,670
binary hali ya 0 na 1.

531
00:24:45,670 --> 00:24:46,720
Hivyo kwamba ni faili wote ni.

532
00:24:46,720 --> 00:24:49,300
Kuna rundo zima la magnetic
chembe kuwa ni yao kwa njia hii au

533
00:24:49,300 --> 00:24:51,920
njia hii, kujenga chati
ya sekunde 0 na 1s.

534
00:24:51,920 --> 00:24:56,760
>> Lakini zinageuka wakati wewe ila faili,
baadhi ya habari ni kuokolewa tofauti.

535
00:24:56,760 --> 00:25:00,000
Hivyo hii ni meza kidogo,
directory, hivyo kusema.

536
00:25:00,000 --> 00:25:05,810
Na Mimi nitakuita jina hili safu, na
Mimi nitakuita hii eneo safu.

537
00:25:05,810 --> 00:25:08,850
>> Na mimi nina kwenda kusema, tuseme
hii ni resume yangu.

538
00:25:08,850 --> 00:25:14,050
Resume.doc yangu ni kuhifadhiwa katika
mahali, hebu sema 123.

539
00:25:14,050 --> 00:25:15,390
Mimi daima kwenda kwa idadi hiyo.

540
00:25:15,390 --> 00:25:18,810
Lakini inatosha kusema kwamba kama tu
katika RAM, unaweza kuchukua gari ngumu

541
00:25:18,810 --> 00:25:22,350
hiyo ni gigabytes gigabyte au 200
au terabyte, na unaweza

542
00:25:22,350 --> 00:25:23,750
idadi yote ya ka.

543
00:25:23,750 --> 00:25:26,480
Unaweza kuzihesabu chunks wote wa bits 8.

544
00:25:26,480 --> 00:25:29,030
>> Hivyo tutaweza kusema kwamba hii
ni eneo 123.

545
00:25:29,030 --> 00:25:32,070
Hivyo hii ndani ya saraka ya uendeshaji yangu
mfumo anakumbuka kwamba yangu

546
00:25:32,070 --> 00:25:34,250
resume ni katika eneo 123.

547
00:25:34,250 --> 00:25:36,850
Lakini anapata kuvutia wakati
kufuta faili.

548
00:25:36,850 --> 00:25:37,820
>> Hivyo kwa mfano -

549
00:25:37,820 --> 00:25:40,790
na nashiriki, wengi wa dunia ina
hawakupata kwenye hii - kile kinachotokea wakati

550
00:25:40,790 --> 00:25:45,040
Drag faili takataka yako Mac OS
au Windows yako Recycle Bin?

551
00:25:45,040 --> 00:25:48,290

552
00:25:48,290 --> 00:25:50,510
Nini madhumuni ya kufanya hivyo?

553
00:25:50,510 --> 00:25:53,860
Ni wazi kujikwamua faili,
lakini nini kitendo cha akawatoa na

554
00:25:53,860 --> 00:25:57,550
kuacha katika takataka yako au yako
Recycle Bin kufanya kwenye kompyuta?

555
00:25:57,550 --> 00:25:59,230
>> Kabisa kitu, kwa kweli.

556
00:25:59,230 --> 00:26:00,320
Ni kama tu folder.

557
00:26:00,320 --> 00:26:01,800
Ni folder maalum, kuwa na uhakika.

558
00:26:01,800 --> 00:26:04,460
Lakini je, ni kweli kufuta faili?

559
00:26:04,460 --> 00:26:06,780
>> Naam, hapana, kwa sababu baadhi yenu pengine
wamekuwa kama, oh damn, wewe si

560
00:26:06,780 --> 00:26:07,420
maana kwa kufanya hivyo.

561
00:26:07,420 --> 00:26:09,130
Hivyo bonyeza mara mbili
Takataka au Recycle Bin.

562
00:26:09,130 --> 00:26:11,630
Umefanya poked karibu na umefanya zinalipwa
faili tu na akawatoa ni

563
00:26:11,630 --> 00:26:12,110
nje ya hapo.

564
00:26:12,110 --> 00:26:14,420
Hivyo ni wazi, siyo lazima
kufuta yake.

565
00:26:14,420 --> 00:26:15,990
>> OK, wewe ni nadhifu zaidi ya hiyo.

566
00:26:15,990 --> 00:26:18,860
Unajua kwamba tu akawatoa ndani
Takataka au Recycle Bin haina maana

567
00:26:18,860 --> 00:26:19,930
wewe ni kuondoa takataka.

568
00:26:19,930 --> 00:26:24,110
Hivyo kwenda hadi orodha, na kusema
Tupu takataka au Tupu Recycle Bin.

569
00:26:24,110 --> 00:26:25,360
Kisha nini kitatokea?

570
00:26:25,360 --> 00:26:29,070

571
00:26:29,070 --> 00:26:32,530
>> Yeah, hivyo ni ilifutwa zaidi ya hivyo.

572
00:26:32,530 --> 00:26:37,660
Lakini yote ambayo hufanyika ni hii.

573
00:26:37,660 --> 00:26:45,350
kompyuta anasahau ambapo
resume.doc mara.

574
00:26:45,350 --> 00:26:47,400
>> Lakini nini haujabadilika inaonekana
kwenye picha?

575
00:26:47,400 --> 00:26:51,390

576
00:26:51,390 --> 00:26:55,570
bits, sekunde 0 na 1s kwamba mimi kudai ni
kwenye tovuti ya nyanja baadhi ya kimwili ya

577
00:26:55,570 --> 00:26:56,280
vifaa.

578
00:26:56,280 --> 00:26:57,110
Bado wapo.

579
00:26:57,110 --> 00:26:58,930
Ni tu kompyuta ina
wamesahau nini hao.

580
00:26:58,930 --> 00:27:03,160
>> Hivyo ni kimsingi huru faili
bits ili waweze kutumika tena.

581
00:27:03,160 --> 00:27:06,940
Lakini si mpaka kujenga files zaidi,
na zaidi files, na zaidi files mapenzi

582
00:27:06,940 --> 00:27:12,150
probabilistically, wale sekunde 0 na 1s,
chembe wale magnetic, kupata kutumika tena,

583
00:27:12,150 --> 00:27:16,220
kichwa au upande wa kulia juu, kwa
nyingine files, sekunde 0 na 1s.

584
00:27:16,220 --> 00:27:17,980
>> Hivyo kuwa na dirisha hili la wakati.

585
00:27:17,980 --> 00:27:19,860
Na si wa kutabirika
urefu, kwa kweli.

586
00:27:19,860 --> 00:27:22,240
Inategemea na ukubwa wa bidii yako
gari na jinsi wengi files una na

587
00:27:22,240 --> 00:27:23,490
jinsi ya haraka ya kufanya ndio mpya.

588
00:27:23,490 --> 00:27:27,050
Lakini kuna hii dirisha la muda wakati
ambayo faili kwamba ni bado kikamilifu

589
00:27:27,050 --> 00:27:27,770
recoverable.

590
00:27:27,770 --> 00:27:31,050
>> Hivyo kama wewe milele kutumia programu kama McAfee
au Norton kujaribu kuokoa

591
00:27:31,050 --> 00:27:35,680
data, kila unachokifanya ni kujaribu
kupona saraka hii kinachojulikana kwa

592
00:27:35,680 --> 00:27:37,340
kufikiri ambapo faili yako mara.

593
00:27:37,340 --> 00:27:40,605
Na wakati mwingine Norton na kusema,
faili ni 93% recoverable.

594
00:27:40,605 --> 00:27:42,020
Naam, hiyo ina maana gani?

595
00:27:42,020 --> 00:27:45,690
Kwamba tu ina maana kwamba baadhi ya faili nyingine
bahati kuishia kutumia, kusema,

596
00:27:45,690 --> 00:27:48,920
wale bits nje ya faili yako ya awali.

597
00:27:48,920 --> 00:27:51,950
>> Hivyo kile ni kweli kushiriki
katika kurejesha data?

598
00:27:51,950 --> 00:27:55,720
Naam, kama huna kitu kama
Norton kabla ya imewekwa kwenye kompyuta yako,

599
00:27:55,720 --> 00:27:59,510
bora unaweza wakati mwingine kufanya ni kuangalia
saa nzima gari ngumu kuangalia kwa

600
00:27:59,510 --> 00:28:00,510
chati ya bits.

601
00:28:00,510 --> 00:28:05,350
Na moja ya mandhari ya kuweka tatizo
tano ni kwamba utakuwa kutafuta

602
00:28:05,350 --> 00:28:09,570
sawa ya gari ngumu, kuchunguza mauaji
mfano wa kadi Compact flash kutoka

603
00:28:09,570 --> 00:28:13,660
kamera ya digital, kwa ajili ya kutafuta sekunde 0
na 1s kwamba kwa kawaida, na high

604
00:28:13,660 --> 00:28:16,720
uwezekano, kuwakilisha
kuanza wa picha JPEG.

605
00:28:16,720 --> 00:28:21,120
>> Na wewe guys anaweza kupona picha hizo na
kuchukua, kama mimi kuona muundo huu wa

606
00:28:21,120 --> 00:28:24,380
bits juu ya picha kuchunguza mauaji, na
juu ya uwezekano, kwamba alama

607
00:28:24,380 --> 00:28:25,650
mwanzo wa JPEG.

608
00:28:25,650 --> 00:28:29,520
Na kama mimi kuona mfano huo tena,
kwamba pengine ni mwanzo wa

609
00:28:29,520 --> 00:28:32,440
mwingine JPEG, na mwingine
JPEG, na mwingine JPEG.

610
00:28:32,440 --> 00:28:34,970
Na hii ni kawaida jinsi
data ahueni itakuwa kazi.

611
00:28:34,970 --> 00:28:37,870
Nini ni nzuri kuhusu JPEGs ni hata ingawa
aina ya faili yenyewe ni kiasi fulani

612
00:28:37,870 --> 00:28:44,400
tata, mwanzo wa kila vile
faili ni kweli haki zinazotambulika

613
00:28:44,400 --> 00:28:47,370
na rahisi, kama utaona,
kama wameweza si tayari.

614
00:28:47,370 --> 00:28:50,270
>> Basi hebu kuangalia kwa karibu chini ya
kofia kama na hasa nini imekuwa

615
00:28:50,270 --> 00:28:53,360
kinachoendelea, na nini hawa sekunde 0 na 1s
ni, kukupa zaidi kidogo ya

616
00:28:53,360 --> 00:28:55,330
mazingira kwa ajili ya changamoto hii hasa.

617
00:28:55,330 --> 00:28:55,510
>> [Video avspelning]

618
00:28:55,510 --> 00:28:58,700
>> -Wapi PC yako maduka zaidi
ya data yake ya kudumu.

619
00:28:58,700 --> 00:29:03,390
Kufanya hivyo, data husafiri kutoka RAM
pamoja na programu ishara kwamba kuwaambia

620
00:29:03,390 --> 00:29:06,110
gari ngumu jinsi ya kuhifadhi data hizo.

621
00:29:06,110 --> 00:29:09,410
ngumu kuendesha nyaya kutafsiri
wale ishara katika voltage

622
00:29:09,410 --> 00:29:10,870
kushuka kwa thamani.

623
00:29:10,870 --> 00:29:14,970
Hizi, kwa upande wake, kudhibiti gari ngumu ya
kuhamia sehemu, baadhi ya wachache

624
00:29:14,970 --> 00:29:17,910
kuhamia maeneo kushoto katika
kisasa ya kompyuta.

625
00:29:17,910 --> 00:29:22,130
>> Baadhi ya ishara ya kudhibiti motor
ambayo spins platters chuma-coated.

626
00:29:22,130 --> 00:29:25,470
Data zako ni kweli kuhifadhiwa
juu ya haya platters.

627
00:29:25,470 --> 00:29:28,610
Ishara nyingine hoja ya kusoma / kuandika
vichwa kusoma au

628
00:29:28,610 --> 00:29:30,710
kuandika data kwenye sahani.

629
00:29:30,710 --> 00:29:35,450
Hii mitambo hivyo sahihi kwamba binadamu
nywele hakuweza hata kupita kati ya

630
00:29:35,450 --> 00:29:37,280
vichwa na platters inazunguka.

631
00:29:37,280 --> 00:29:40,316
Hata hivyo, kila kazi kwa kasi kali.

632
00:29:40,316 --> 00:29:40,660
>> [MWISHO video avspelning]

633
00:29:40,660 --> 00:29:42,190
>> DAVID Malan: Zoom katika kidogo
undani sasa saa nini

634
00:29:42,190 --> 00:29:44,360
kweli juu platters hayo.

635
00:29:44,360 --> 00:29:44,720
>> [Video avspelning]

636
00:29:44,720 --> 00:29:47,660
>> -Hebu kuangalia nini sisi tu
aliona katika mwendo wa polepole.

637
00:29:47,660 --> 00:29:51,710
Wakati mapigo mafupi ya umeme ni
kutumwa kwa kichwa kusoma / kuandika, kama flips

638
00:29:51,710 --> 00:29:54,650
juu ya sumakuumeme vidogo kwa ajili ya
sehemu ya pili.

639
00:29:54,650 --> 00:29:58,970
sumaku inajenga uwanja, ambayo
mabadiliko polarity ya vidogo, vidogo

640
00:29:58,970 --> 00:30:02,850
sehemu ya chembe chuma ambayo
kanzu kila uso sahani.

641
00:30:02,850 --> 00:30:05,940
>> mfululizo mfano wa haya vidogo,
kushtakiwa-up maeneo ya rekodi

642
00:30:05,940 --> 00:30:08,470
inawakilisha kidogo moja ya
data katika idadi binary

643
00:30:08,470 --> 00:30:10,530
mfumo kutumiwa na kompyuta.

644
00:30:10,530 --> 00:30:13,775
Sasa, kama sasa ni kutumwa kwa njia moja
kupitia kusoma / kuandika kichwa, eneo

645
00:30:13,775 --> 00:30:15,970
ni polarized katika mwelekeo mmoja.

646
00:30:15,970 --> 00:30:17,950
Kama sasa ni alimtuma katika
kinyume mwelekeo,

647
00:30:17,950 --> 00:30:19,930
ubaguzi ni kuachwa.

648
00:30:19,930 --> 00:30:22,370
>> Jinsi ya kupata data mbali disk ngumu?

649
00:30:22,370 --> 00:30:24,090
Tu kubadili mchakato.

650
00:30:24,090 --> 00:30:26,550
Hivyo ni chembe ya rekodi
kwamba kupata sasa katika

651
00:30:26,550 --> 00:30:27,960
kusoma / kuandika kichwa kusonga mbele.

652
00:30:27,960 --> 00:30:30,700
Kuweka pamoja mamilioni ya hizi
sumaku makundi, na

653
00:30:30,700 --> 00:30:32,160
nimepata faili.

654
00:30:32,160 --> 00:30:36,060
>> Sasa, vipande vya faili moja huenda
watatawanyika wote juu ya gari

655
00:30:36,060 --> 00:30:39,970
platters, aina ya kama fujo
karatasi ya dawati yako.

656
00:30:39,970 --> 00:30:43,500
Hivyo maalum faili ziada anaendelea kufuatilia
ya ambapo kila kitu.

657
00:30:43,500 --> 00:30:45,985
Je, si unataka wewe alikuwa
kitu kama hicho?

658
00:30:45,985 --> 00:30:46,470
>> [MWISHO video avspelning]

659
00:30:46,470 --> 00:30:47,820
>> DAVID Malan: OK, pengine si.

660
00:30:47,820 --> 00:30:52,070
Hivyo ni jinsi wengi wenu guys
ikakua na haya?

661
00:30:52,070 --> 00:30:53,970
OK, hivyo ni chache na chache
mikono kila mwaka.

662
00:30:53,970 --> 00:30:56,550
Lakini mimi nina furaha uko angalau ukoo
pamoja nao, kwa sababu hii na yetu wenyewe

663
00:30:56,550 --> 00:31:00,520
kitabu demo, cha kusikitisha, wanakufa sana
kupunguza vifo hapa ya kufahamiana.

664
00:31:00,520 --> 00:31:04,010
>> Lakini hii ni nini mimi, angalau, nyuma katika
shule ya sekondari, kutumika kwa ajili ya matumizi ya Hifadhi.

665
00:31:04,010 --> 00:31:08,110
Na ilikuwa ni ajabu, kwa sababu wewe
inaweza kuhifadhi megabaiti 1.4 juu ya

666
00:31:08,110 --> 00:31:08,930
hii disk fulani.

667
00:31:08,930 --> 00:31:12,260
Na hii ilikuwa high wiani toleo,
kama unahitajika kwa HD, ambayo ina

668
00:31:12,260 --> 00:31:14,240
maana kabla ya video ya leo HD.

669
00:31:14,240 --> 00:31:16,400
>> Wiani kiwango mara 800 kilobytes.

670
00:31:16,400 --> 00:31:18,640
Na kabla ya kuwa, kulikuwa na
400-KiloByte disks.

671
00:31:18,640 --> 00:31:23,120
Na kabla ya kuwa, kulikuwa na 5 na 1/4
inch disks, ambayo yalikuwa kweli floppy,

672
00:31:23,120 --> 00:31:25,680
na pana kidogo na mirefu
kuliko haya mambo hapa.

673
00:31:25,680 --> 00:31:29,150
Lakini unaweza kweli kuona kinachojulikana
floppy disks nyanja ya haya.

674
00:31:29,150 --> 00:31:32,630
>> Na functionally, wao ni kweli
pretty sawa na anatoa ngumu ya saa

675
00:31:32,630 --> 00:31:33,570
angalau aina hii.

676
00:31:33,570 --> 00:31:37,270
Tena, SSDs katika kompyuta ya karibu zaidi
kazi tofauti kidogo.

677
00:31:37,270 --> 00:31:41,530
Lakini kama wewe hoja kwamba kidogo chuma tab,
unaweza kweli kuona alama ya cookie kidogo,

678
00:31:41,530 --> 00:31:42,560
au ulio.

679
00:31:42,560 --> 00:31:43,830
>> Siyo chuma kama hii moja.

680
00:31:43,830 --> 00:31:46,000
Moja hii ni kweli baadhi ya bei nafuu
plastiki nyenzo.

681
00:31:46,000 --> 00:31:46,750
Na unaweza aina ya wiggle yake.

682
00:31:46,750 --> 00:31:50,310
Na umefanya trully tu wiped off baadhi
idadi ya bits au chembe magnetic

683
00:31:50,310 --> 00:31:51,220
kutoka disk hii.

684
00:31:51,220 --> 00:31:52,710
>> Hivyo nashiriki, kuna kitu juu yake.

685
00:31:52,710 --> 00:31:55,790
Kama jambo hilo katika njia - na kufunika
macho yako na wale wa jirani yako -

686
00:31:55,790 --> 00:31:58,865
unaweza tu aina ya kuvuta hii
nzima ala mbali kama hiyo.

687
00:31:58,865 --> 00:32:01,900
Lakini kuna spring kidogo, hivyo kuwa na
kufahamu kwamba kwa macho yako.

688
00:32:01,900 --> 00:32:03,620
Hivyo sasa una kweli disketi.

689
00:32:03,620 --> 00:32:07,090
>> Na nini ajabu kuhusu hili
ni kwamba katika kiasi kama hii ni

690
00:32:07,090 --> 00:32:10,830
wadogo wadogo kubwa ya uwakilishi wa
gari ngumu, mambo haya ni super,

691
00:32:10,830 --> 00:32:11,590
super rahisi.

692
00:32:11,590 --> 00:32:15,170
Kama wewe Bana chini yake, sasa kwamba
kwamba jambo chuma ni mbali, na peel

693
00:32:15,170 --> 00:32:20,990
yao wazi, kila kuna ni vipande viwili vya
waliona na kinachojulikana floppy disk

694
00:32:20,990 --> 00:32:22,930
na kipande cha chuma ya ndani.

695
00:32:22,930 --> 00:32:25,990
>> Na huenda kuna nusu ya
disk yangu yaliyomo.

696
00:32:25,990 --> 00:32:27,540
Huenda kuna mwingine nusu yao.

697
00:32:27,540 --> 00:32:31,375
Lakini hiyo yote ilikuwa inazunguka ndani
ya kompyuta yako katika yesteryear.

698
00:32:31,375 --> 00:32:35,220

699
00:32:35,220 --> 00:32:38,310
>> Na tena, kwa kuweka hii katika mtazamo,
jinsi kubwa ni zaidi ya yako

700
00:32:38,310 --> 00:32:39,560
ngumu anatoa siku hizi?

701
00:32:39,560 --> 00:32:41,960

702
00:32:41,960 --> 00:32:46,230
500 gigabytes, terabyte, labda katika
desktop kompyuta, terabytes 2, 3

703
00:32:46,230 --> 00:32:47,630
terabytes, terabytes 4, haki?

704
00:32:47,630 --> 00:32:52,480
Hii ni moja megabyte, kutoa au kuchukua,
ambayo hawezi hata fit MP3 kawaida

705
00:32:52,480 --> 00:32:55,310
tena siku hizi, au baadhi ya
sawa muziki faili.

706
00:32:55,310 --> 00:32:59,500
>> Hivyo souvenir kidogo kwa ajili yenu leo, na
pia kusaidia contextualize nini

707
00:32:59,500 --> 00:33:03,570
tutaweza kuwa na kuchukua kwa nafasi
sasa katika tatizo kuweka tano.

708
00:33:03,570 --> 00:33:04,820
Hivyo wale ni yako ya kutunza.

709
00:33:04,820 --> 00:33:07,340

710
00:33:07,340 --> 00:33:13,370
Hivyo basi mimi mpito ambapo itakuwa
matumizi pset ijayo pia.

711
00:33:13,370 --> 00:33:18,470
Hivyo tumekuwa sasa kuweka ukurasa huu kwa ajili - oh,
michache ya matangazo ya haraka.

712
00:33:18,470 --> 00:33:21,730
>> Ijumaa hii, kama ungependa kujiunga CS50
kwa chakula cha mchana, kwenda mahali kawaida,

713
00:33:21,730 --> 00:33:23,610
cs50.net/rsvp.

714
00:33:23,610 --> 00:33:25,100
Na ya mwisho ya mradi -

715
00:33:25,100 --> 00:33:28,520
hivyo kwa mtaala, tumekuwa posted
mwisho wa mradi vipimo tayari.

716
00:33:28,520 --> 00:33:31,410
Kutambua kwamba haina maana kwamba
ni kutokana hasa hivi karibuni.

717
00:33:31,410 --> 00:33:33,990
Ni posted, kwa kweli, tu kupata
guys kufikiri juu yake.

718
00:33:33,990 --> 00:33:37,620
Na kwa kweli, muhimu super
asilimia ya utakuwa kukabiliana na

719
00:33:37,620 --> 00:33:40,780
mwisho miradi juu ya vifaa kwamba sisi
si hata wamezipata kwa darasani,

720
00:33:40,780 --> 00:33:42,730
bali mapenzi mapema wiki ijayo.

721
00:33:42,730 --> 00:33:45,530
>> Ilani, ingawa, kwamba spec wito kwa
vipengele kadhaa tofauti ya

722
00:33:45,530 --> 00:33:46,190
mwisho wa mradi.

723
00:33:46,190 --> 00:33:49,590
kwanza, katika wiki chache, ni
kabla ya pendekezo, email pretty kawaida na

724
00:33:49,590 --> 00:33:52,760
TF wako kumwambia au nini wewe
kufikiri juu kwa ajili ya mradi wako, na

725
00:33:52,760 --> 00:33:53,650
hakuna kujitoa.

726
00:33:53,650 --> 00:33:56,710
Pendekezo itakuwa hasa yako
ahadi, akisema, hapa, hii ni nini

727
00:33:56,710 --> 00:33:57,770
Ningependa kufanya kwa ajili ya mradi wangu.

728
00:33:57,770 --> 00:33:58,250
Unafikiri nini?

729
00:33:58,250 --> 00:33:58,650
Kubwa mno?

730
00:33:58,650 --> 00:33:59,145
Ndogo mno?

731
00:33:59,145 --> 00:34:00,330
Je, ni manageable?

732
00:34:00,330 --> 00:34:02,230
Na unaweza kuona spec kwa maelezo zaidi.

733
00:34:02,230 --> 00:34:05,060
>> Wiki kadhaa baada ya kuwa ni hali ya
Ripoti hiyo, ambayo ni vile vile

734
00:34:05,060 --> 00:34:08,260
kawaida email TF yako ya kusema tu jinsi
mbali nyuma wewe ni katika fainali yako

735
00:34:08,260 --> 00:34:12,360
utekelezaji wa mradi, ikifuatiwa na
Hackathon CS50 ambayo kila mtu

736
00:34:12,360 --> 00:34:17,520
ni waalikwa, ambayo itakuwa ya tukio kutoka
20:00 jioni kwenye moja mpaka 07:00

737
00:34:17,520 --> 00:34:19,150
Asubuhi asubuhi.

738
00:34:19,150 --> 00:34:22,560
Pizza, kama nipate kuwa zilizotajwa katika wiki
sifuri, Wil kuwa aliwahi saa 9:00,

739
00:34:22,560 --> 00:34:24,120
Kichina chakula saa 1:00 asubuhi.

740
00:34:24,120 --> 00:34:27,929
Na kama wewe ni bado macho saa 5:00 asubuhi,
tutaweza kuchukua wewe IHOP kwa kifungua kinywa.

741
00:34:27,929 --> 00:34:31,310
>> Hivyo hackathon ni moja ya zaidi
kukumbukwa uzoefu katika darasa.

742
00:34:31,310 --> 00:34:35,290
Kisha utekelezaji ni kutokana na
kisha climactic CS50 Fair.

743
00:34:35,290 --> 00:34:38,070
Maelezo zaidi juu ya yote haya
katika wiki ijayo.

744
00:34:38,070 --> 00:34:40,739
>> Lakini hebu kwenda nyuma ya kitu
umri wa shule -

745
00:34:40,739 --> 00:34:41,920
tena, safu.

746
00:34:41,920 --> 00:34:45,040
Hivyo safu ilikuwa nzuri, kwa sababu ni kutatua
matatizo kama tuliona tu

747
00:34:45,040 --> 00:34:49,290
wakati iliyopita na miundo ya mwanafunzi
kupata nje kidogo ya kudhibiti kama sisi

748
00:34:49,290 --> 00:34:52,405
wanataka kuwa na mwanafunzi mmoja, mwanafunzi mbili,
mwanafunzi wa tatu, mwanafunzi dot dot dot,

749
00:34:52,405 --> 00:34:54,400
baadhi ya idadi holela wa wanafunzi.

750
00:34:54,400 --> 00:34:58,850
>> Hivyo arrays, wiki chache zilizopita, swooped katika
na kutatuliwa matatizo yote ya yetu ya si

751
00:34:58,850 --> 00:35:03,340
kujua mapema jinsi mambo mengi
ya aina fulani sisi kutaka.

752
00:35:03,340 --> 00:35:07,390
Na tumeona kwamba structs unaweza kutusaidia
zaidi kuandaa kanuni wetu na kuendelea

753
00:35:07,390 --> 00:35:11,660
conceptually sawa vigezo, kama
jina na nyumba, pamoja, hivyo kwamba sisi

754
00:35:11,660 --> 00:35:15,570
wanaweza kutibu yao kama moja chombo, ndani ya
ya ambayo kuna vipande vidogo.

755
00:35:15,570 --> 00:35:17,810
>> Lakini arrays na baadhi hasara.

756
00:35:17,810 --> 00:35:19,780
Ni nini baadhi ya hasara
tumekuwa wamekutana

757
00:35:19,780 --> 00:35:22,320
na arrays hivi sasa?

758
00:35:22,320 --> 00:35:23,450
Nini hiyo?

759
00:35:23,450 --> 00:35:28,130
Fasta ukubwa - hivyo hata kama wewe ili
kuwa na uwezo wa kutenga kumbukumbu kwa

760
00:35:28,130 --> 00:35:32,310
safu, mara tu kujua jinsi wanafunzi wengi
una ngapi wahusika una

761
00:35:32,310 --> 00:35:35,460
kutoka kwa mtumiaji, mara moja umefanya zilizotengwa
safu, umefanya aina ya walijenga

762
00:35:35,460 --> 00:35:36,740
mwenyewe katika kona.

763
00:35:36,740 --> 00:35:40,600
>> Sababu huwezi kuingiza vipengele mpya
ndani ya katikati ya safu.

764
00:35:40,600 --> 00:35:43,660
Huwezi kuingiza mambo zaidi
mwisho wa safu.

765
00:35:43,660 --> 00:35:47,750
Kweli, una ya mapumziko kwa kujenga
nzima mwezi safu, kama tumekuwa kujadiliwa,

766
00:35:47,750 --> 00:35:49,320
kuiga zamani katika mpya.

767
00:35:49,320 --> 00:35:52,610
Na tena, kwamba ni kichwa kwamba
GetString inahusika na kwa ajili yenu.

768
00:35:52,610 --> 00:35:56,170
>> Lakini tena, unaweza hata kuingiza
kitu ndani ya katikati ya safu

769
00:35:56,170 --> 00:35:58,200
ikiwa ni kiwango cha si kabisa kujazwa.

770
00:35:58,200 --> 00:36:03,010
Kwa mfano, kama hii safu ya ukubwa hapa
sita tu ana mambo matano katika hayo,

771
00:36:03,010 --> 00:36:06,080
vizuri, unaweza tu tack
kitu kwenye mwisho.

772
00:36:06,080 --> 00:36:08,200
Lakini nini kama unataka kuingiza kitu
ndani ya katikati ya

773
00:36:08,200 --> 00:36:11,280
safu, hata ingawa inaweza kuwa
watano kati ya vitu sita katika hilo?

774
00:36:11,280 --> 00:36:14,250
>> Vizuri, nini cha kufanya wakati tulikuwa wote
ya kujitolea yetu ya kibinadamu onstage katika

775
00:36:14,250 --> 00:36:15,110
wiki iliyopita?

776
00:36:15,110 --> 00:36:18,710
Kama sisi alitaka kuweka mtu hapa, ama
hawa watu jinsi ya hoja hii

777
00:36:18,710 --> 00:36:22,540
njia, au watu hawa jinsi ya hoja hii
njia, na kwamba akawa ghali.

778
00:36:22,540 --> 00:36:26,950
shifting ya watu ndani ya
safu kuishia na kuongeza hadi na kugharimu

779
00:36:26,950 --> 00:36:31,240
sisi wakati, hivyo mengi ya squared wetu n
mbio mara kama aina kuingizwa, kwa ajili ya

780
00:36:31,240 --> 00:36:32,550
mfano, katika kesi mbaya.

781
00:36:32,550 --> 00:36:36,520
Hivyo arrays ni kubwa, lakini una
kujua mapema jinsi kubwa unataka yao.

782
00:36:36,520 --> 00:36:38,030
>> OK hivyo, hapa ufumbuzi.

783
00:36:38,030 --> 00:36:43,860
Kama mimi si kujua mapema ngapi
wanafunzi nipate kuwa, na mimi kujua mara moja

784
00:36:43,860 --> 00:36:47,870
Mimi kuamua, ingawa, mimi nina kukwama na kwamba
wanafunzi wengi, kwa nini sio mimi tu daima

785
00:36:47,870 --> 00:36:51,740
kutenga mara mbili kama vile nafasi
kama mimi ili nadhani wanahitaji?

786
00:36:51,740 --> 00:36:54,450
Ni kwamba si suluhisho busara?

787
00:36:54,450 --> 00:36:58,240
>> Realistically, sidhani kwamba sisi ni
kwenda haja inafaa zaidi ya 50

788
00:36:58,240 --> 00:37:02,190
katika safu kwa ajili ya darasa kati-kawaida,
hivyo hebu tu pande zote juu.

789
00:37:02,190 --> 00:37:07,040
Mimi itabidi kufanya inafaa 100 katika safu yangu, tu
ili tuweze dhahiri kupata

790
00:37:07,040 --> 00:37:10,330
idadi ya wanafunzi mimi kutarajia
kuwa katika baadhi ya tabaka la kati-size.

791
00:37:10,330 --> 00:37:14,320
Hivyo kwa nini siyo tu pande zote juu na kutenga
zaidi ya kumbukumbu, kwa kawaida, kwa ajili ya safu

792
00:37:14,320 --> 00:37:16,290
kuliko unafikiri unaweza hata haja?

793
00:37:16,290 --> 00:37:20,190
Nini hii pushback rahisi
na wazo hilo?

794
00:37:20,190 --> 00:37:21,440
>> Wewe tu kupoteza kumbukumbu.

795
00:37:21,440 --> 00:37:25,350
Literally kila mpango kuandika basi
labda ni kwa kutumia mara mbili kama vile kumbukumbu kama

796
00:37:25,350 --> 00:37:26,680
haja kweli.

797
00:37:26,680 --> 00:37:28,990
Na kwamba tu haina kujisikia kama
hasa kifahari ufumbuzi.

798
00:37:28,990 --> 00:37:31,990
Aidha, ni tu itapungua
uwezekano wa tatizo.

799
00:37:31,990 --> 00:37:35,300
Kama kutokea kwa kuwa na shaka maarufu
moja muhula na una 101

800
00:37:35,300 --> 00:37:39,610
wanafunzi, mpango wako bado ni
kimsingi yanayowakabili suala hilo hilo.

801
00:37:39,610 --> 00:37:44,280
>> Hivyo nashiriki, kuna ufumbuzi kwa
ad hii matatizo yetu yote katika fomu

802
00:37:44,280 --> 00:37:46,790
ya data miundo ambayo ni
ngumu zaidi kuliko wale

803
00:37:46,790 --> 00:37:47,970
tumeona hivi sasa.

804
00:37:47,970 --> 00:37:50,530
Hii, mimi kudai, ni orodha zinazoungwa.

805
00:37:50,530 --> 00:37:51,920
Hii ni orodha ya idadi -

806
00:37:51,920 --> 00:37:54,970
9, 17, 22, 26, na 34 -

807
00:37:54,970 --> 00:38:00,120
ambayo yamekuwa wanaohusishwa pamoja kwa njia
ya nini nimekuwa inayotolewa kama mishale.

808
00:38:00,120 --> 00:38:03,580
>> Kwa maneno mengine, kama alitaka kuwakilisha
safu, mimi naweza kufanya

809
00:38:03,580 --> 00:38:04,910
kitu kama hiki.

810
00:38:04,910 --> 00:38:07,310
Na mimi itabidi kuweka hii juu ya uendeshaji
katika muda tu.

811
00:38:07,310 --> 00:38:09,970
Mimi naweza kufanya -

812
00:38:09,970 --> 00:38:12,520
hello, wote haki.

813
00:38:12,520 --> 00:38:14,470
Kusimama kwa.

814
00:38:14,470 --> 00:38:17,360
Mpya ya kompyuta hapa, wazi -

815
00:38:17,360 --> 00:38:18,090
wote haki.

816
00:38:18,090 --> 00:38:21,730
>> Hivyo kama nina namba hizi katika safu -

817
00:38:21,730 --> 00:38:28,880
9, 17, 22, 26, 24 -

818
00:38:28,880 --> 00:38:30,530
si lazima wadogo.

819
00:38:30,530 --> 00:38:33,730
Haki ya wote, hivyo hapa ni safu yangu -

820
00:38:33,730 --> 00:38:34,980
oh mungu wangu.

821
00:38:34,980 --> 00:38:38,700

822
00:38:38,700 --> 00:38:40,395
Haki ya wote, hivyo hapa ni safu yangu.

823
00:38:40,395 --> 00:38:44,110

824
00:38:44,110 --> 00:38:45,050
Oh mungu wangu.

825
00:38:45,050 --> 00:38:48,820
>> [Kicheko]

826
00:38:48,820 --> 00:38:49,440
>> DAVID Malan: kujifanya.

827
00:38:49,440 --> 00:38:52,330
Ni sana juhudi ya kwenda nyuma
na kurekebisha kwamba, hivyo kuna -

828
00:38:52,330 --> 00:38:54,290
26.

829
00:38:54,290 --> 00:38:57,650
Hivyo tuna hii safu ya
9, 17, 22, 26, na 34.

830
00:38:57,650 --> 00:39:00,260
Kwa wale wa wewe unaweza kuona
kosa aibu mimi tu alifanya,

831
00:39:00,260 --> 00:39:00,830
huko ni.

832
00:39:00,830 --> 00:39:04,490
>> Hivyo mimi kudai kwamba hii ni
ufanisi sana ufumbuzi.

833
00:39:04,490 --> 00:39:07,310
Nimekuwa zilizotengwa kama ints wengi kama
Nahitaji - moja, mbili, tatu,

834
00:39:07,310 --> 00:39:09,100
nne, tano, au sita -

835
00:39:09,100 --> 00:39:11,660
na nimekuwa kisha kuhifadhiwa idadi
ndani ya safu hii.

836
00:39:11,660 --> 00:39:15,220
Lakini tuseme, basi, nataka kuingiza
thamani kama idadi ya 8?

837
00:39:15,220 --> 00:39:16,100
Naam, yanakwenda wapi?

838
00:39:16,100 --> 00:39:18,530
Tuseme nataka kuingiza
idadi kama 20.

839
00:39:18,530 --> 00:39:19,790
Naam, yanakwenda wapi?

840
00:39:19,790 --> 00:39:23,160
Mahali fulani pale katikati,
au namba 35 ina kwenda

841
00:39:23,160 --> 00:39:24,010
mahali fulani mwishoni.

842
00:39:24,010 --> 00:39:25,320
Lakini mimi nina wote nje ya nafasi.

843
00:39:25,320 --> 00:39:29,120
>> Na hivyo hii ni changamoto za msingi
ya arrays kwamba hana ni ufumbuzi.

844
00:39:29,120 --> 00:39:32,280
Mimi alidai wakati iliyopita, GetString
kutatua tatizo hili.

845
00:39:32,280 --> 00:39:37,380
Kama unataka kuingiza idadi ya sita
ndani ya safu hii, ni nini angalau moja

846
00:39:37,380 --> 00:39:40,090
ufumbuzi unaweza kuanguka nyuma kwa hakika,
tu kama sisi kufanya na GetString?

847
00:39:40,090 --> 00:39:44,340

848
00:39:44,340 --> 00:39:46,030
Nini hiyo?

849
00:39:46,030 --> 00:39:48,190
>> Vizuri, kufanya hivyo ni kubwa
rahisi kusema kuliko kutenda.

850
00:39:48,190 --> 00:39:52,810
Tunaweza si lazima kufanya safu
kubwa, lakini tunaweza kufanya nini?

851
00:39:52,810 --> 00:39:56,570
Kufanya safu mpya kwamba ni kubwa zaidi, ya kawaida
6, au labda kawaida 10, kama tunataka

852
00:39:56,570 --> 00:40:00,490
kupata mbele ya mambo, na kisha nakala
safu ya zamani katika mpya, na kisha

853
00:40:00,490 --> 00:40:01,680
huru safu ya zamani.

854
00:40:01,680 --> 00:40:05,770
>> Lakini nini wakati mbio
sasa ya mchakato huo?

855
00:40:05,770 --> 00:40:09,870
Ni kubwa O ya n, kwa sababu ya kuiga
ni kwenda gharama vitengo baadhi ya

856
00:40:09,870 --> 00:40:13,480
wakati, hivyo si hivyo bora kama tuna
kutenga safu mpya, ambayo ni kwenda

857
00:40:13,480 --> 00:40:15,610
kuwaondoa mara mbili kama vile
kumbukumbu kwa muda.

858
00:40:15,610 --> 00:40:16,660
Nakala ya zamani katika mpya -

859
00:40:16,660 --> 00:40:18,800
I mean, ni tu maumivu ya kichwa, ambayo
ni, tena, kwa nini sisi aliandika

860
00:40:18,800 --> 00:40:19,920
GetString kwa ajili yenu.

861
00:40:19,920 --> 00:40:21,380
>> Basi nini ili sisi nini badala yake?

862
00:40:21,380 --> 00:40:25,000
Vizuri, nini kama yetu data muundo
kweli ina mapungufu katika hivyo?

863
00:40:25,000 --> 00:40:30,790
Tuseme kwamba mimi kupumzika lengo langu la kuwa na
contiguous chunks ya kumbukumbu, ambapo 9

864
00:40:30,790 --> 00:40:34,500
ni haki ya karibu na 17, ambayo ni
haki ya karibu na 22, na kadhalika.

865
00:40:34,500 --> 00:40:39,570
>> Na tuseme kwamba 9 inaweza kuwa zaidi ya hapa katika
RAM, na 17 inaweza kuwa zaidi ya hapa katika RAM,

866
00:40:39,570 --> 00:40:40,990
na 22 inaweza kuwa zaidi ya hapa katika RAM.

867
00:40:40,990 --> 00:40:43,610
Kwa maneno mengine, mimi hawana haja nao
hata nyuma kwa nyuma tena.

868
00:40:43,610 --> 00:40:47,850
Mimi tu na kwa namna fulani thread sindano
kupitia katika kila namba hizi, au kila

869
00:40:47,850 --> 00:40:51,010
ya nodi hiyo, kama tutaweza kuwaita
mistatili kama nimekuwa inayotolewa yao, ili

870
00:40:51,010 --> 00:40:55,670
kumbuka jinsi ya kupata mwisho
vile nodi kutoka kwanza.

871
00:40:55,670 --> 00:40:59,940
>> Kwa hiyo kile ni kujenga programu
tumeona kabisa hivi karibuni na ambayo mimi

872
00:40:59,940 --> 00:41:03,030
inaweza kutekeleza kwamba thread, au
inayotolewa hapa, na ambayo naweza

873
00:41:03,030 --> 00:41:05,430
kutekeleza mishale hizo?

874
00:41:05,430 --> 00:41:06,500
Hivyo kuyatumia, haki?

875
00:41:06,500 --> 00:41:09,560
Kama mimi kutenga si tu
int, lakini nodi - na kwa

876
00:41:09,560 --> 00:41:10,810
nodi, mimi tu maana chombo.

877
00:41:10,810 --> 00:41:12,900
Na kuibua, I mean mstatili.

878
00:41:12,900 --> 00:41:16,420
Hivyo nodi inaonekana mahitaji
vyenye maadili mbili -

879
00:41:16,420 --> 00:41:21,490
int yenyewe, na kisha, kama alisema kwa
nusu ya chini ya Mstatili,

880
00:41:21,490 --> 00:41:23,010
nafasi ya kutosha kwa int.

881
00:41:23,010 --> 00:41:26,130
>> Hivyo tu kufikiri mbele hapa,
jinsi kubwa ni nodi hii, hii

882
00:41:26,130 --> 00:41:27,170
chombo katika swali?

883
00:41:27,170 --> 00:41:29,250
Ngapi ka kwa int?

884
00:41:29,250 --> 00:41:31,310
Takribani 4, ikiwa ni
sawa kama kawaida.

885
00:41:31,310 --> 00:41:33,270
Na kisha ngapi ka
kwa pointer?

886
00:41:33,270 --> 00:41:33,650
4.

887
00:41:33,650 --> 00:41:37,940
Hivyo hii chombo, au hii nodi, ni
kwenda kuwa muundo wa 8-Byte.

888
00:41:37,940 --> 00:41:41,760
Oh, na kwamba ni bahati mbaya furaha kwamba
sisi tu ilianzisha wazo hili la

889
00:41:41,760 --> 00:41:44,400
struct, au muundo C.

890
00:41:44,400 --> 00:41:48,890
>> Hivyo mimi kudai kwamba nataka kuchukua hatua
kuelekea hii ya kisasa zaidi

891
00:41:48,890 --> 00:41:52,560
utekelezaji wa orodha ya idadi,
wanaohusishwa orodha ya idadi, mimi haja ya kufanya

892
00:41:52,560 --> 00:41:56,920
zaidi kidogo kufikiri hadi mbele na
kutangaza si tu int, lakini struct

893
00:41:56,920 --> 00:41:58,620
kwamba Mimi nitakuita, conventionally
hapa, nodi.

894
00:41:58,620 --> 00:42:01,630
Tunaweza kuiita kitu tunataka, lakini
nodi ni kwenda kuwa mada katika mengi

895
00:42:01,630 --> 00:42:03,560
ya mambo ya sisi kuanza kuangalia sasa.

896
00:42:03,560 --> 00:42:06,480
>> Ndani ya nodi kwamba ni n int.

897
00:42:06,480 --> 00:42:09,350
Na kisha hii syntax, kidogo
weird katika mtazamo wa kwanza -

898
00:42:09,350 --> 00:42:12,960
struct nodi * ijayo.

899
00:42:12,960 --> 00:42:16,900
Vizuri pictorially, hiyo ni nini?

900
00:42:16,900 --> 00:42:21,000
Hiyo ni nusu ya chini ya
Mstatili kuwa tuliona

901
00:42:21,000 --> 00:42:22,730
muda tu iliyopita.

902
00:42:22,730 --> 00:42:27,600
>> Lakini kwa nini mimi kusema struct nodi *
kinyume na * tu nodi?

903
00:42:27,600 --> 00:42:31,370
Kwa sababu kama pointer kwamba ni akizungumzia
kwenye nodi mwingine, ni tu

904
00:42:31,370 --> 00:42:32,760
anuani ya nodi.

905
00:42:32,760 --> 00:42:35,630
Hiyo ni thabiti na nini tumekuwa
kujadiliwa kuhusu kuyatumia hivi sasa.

906
00:42:35,630 --> 00:42:39,690
Lakini kwa nini, kama mimi kudai muundo huu ni
kuitwa nodi, wala mimi kusema struct

907
00:42:39,690 --> 00:42:42,660
nodi ndani ya hapa?

908
00:42:42,660 --> 00:42:43,190
>> Hasa.

909
00:42:43,190 --> 00:42:46,490
Ni aina ya hali halisi ya kijinga ya C.
typedef, hivyo kusema, hana

910
00:42:46,490 --> 00:42:47,220
kilichotokea bado.

911
00:42:47,220 --> 00:42:48,510
C ni super halisi.

912
00:42:48,510 --> 00:42:51,050
Anasoma kanuni yako ya juu kwa
chini, kushoto na kulia.

913
00:42:51,050 --> 00:42:54,930
Na mpaka hits kwamba semicolon juu ya
bottom line, nadhani nini haina

914
00:42:54,930 --> 00:42:57,590
kuwepo kama aina data?

915
00:42:57,590 --> 00:42:59,060
Nodi, quote unquote nodi.

916
00:42:59,060 --> 00:43:03,050
>> Lakini kwa sababu ya verbose zaidi
tamko mimi juu ya mstari wa kwanza -

917
00:43:03,050 --> 00:43:05,340
typedef struct nodi -

918
00:43:05,340 --> 00:43:08,790
kwa sababu kwamba alikuja kwanza, kabla ya
curly braces, hiyo ni aina ya kama

919
00:43:08,790 --> 00:43:11,800
kabla ya kuelimisha Clang kwamba, wewe
kujua nini, nipe struct

920
00:43:11,800 --> 00:43:13,570
kuitwa struct nodi.

921
00:43:13,570 --> 00:43:16,270
Kusema ukweli, sijui kama mambo wito
struct nodi, struct nodi kila

922
00:43:16,270 --> 00:43:17,090
katika kanuni yangu.

923
00:43:17,090 --> 00:43:20,660
Lakini mimi itabidi kuitumia tu mara moja, tu ndani,
ili niweze ufanisi

924
00:43:20,660 --> 00:43:25,010
kuunda aina ya kumbukumbu ya mviringo, si
pointer mwenyewe per se, lakini

925
00:43:25,010 --> 00:43:29,400
pointer mwingine wa
aina kufanana.

926
00:43:29,400 --> 00:43:32,330
>> Hivyo zinageuka kuwa juu ya muundo wa data
kama hii, kuna wachache

927
00:43:32,330 --> 00:43:34,470
shughuli ambayo inaweza kuwa
wa maslahi na sisi.

928
00:43:34,470 --> 00:43:37,460
Sisi kutaka kuingiza
katika orodha kama hii.

929
00:43:37,460 --> 00:43:39,850
Sisi kutaka kufuta
kutoka kwenye orodha kama hii.

930
00:43:39,850 --> 00:43:43,490
Sisi kutaka kutafuta orodha ya
thamani, au zaidi kwa ujumla, tindanga.

931
00:43:43,490 --> 00:43:46,410
Na tindanga ni njia tu ya dhana ya
akisema kuanza saa kushoto na hoja zote

932
00:43:46,410 --> 00:43:47,650
njia ya haki.

933
00:43:47,650 --> 00:43:52,640
>> Na notisi, hata na hii zaidi kidogo
kisasa data muundo, basi

934
00:43:52,640 --> 00:43:56,510
mimi kupendekeza kwamba tunaweza kukopa baadhi ya
mawazo ya wiki mbili zilizopita na

935
00:43:56,510 --> 00:43:58,410
kutekeleza kazi kuitwa
kutafuta kama hii.

936
00:43:58,410 --> 00:44:01,360
Ni kwenda na kurudi kweli au
uongo, kuonyesha, au ndiyo

937
00:44:01,360 --> 00:44:03,390
hakuna, n ni katika orodha.

938
00:44:03,390 --> 00:44:05,960
Hoja yake ya pili ni pointer
kwa orodha yenyewe, hivyo

939
00:44:05,960 --> 00:44:07,920
pointer nodi.

940
00:44:07,920 --> 00:44:10,350
>> Kila nitakacho kisha kufanya ni kutangaza
kutofautiana ya muda mfupi.

941
00:44:10,350 --> 00:44:12,730
Tutaweza kuiita PTR kwa mkataba,
kwa pointer.

942
00:44:12,730 --> 00:44:15,220
Na mimi hawawajui ni sawa na
mwanzo wa orodha.

943
00:44:15,220 --> 00:44:16,680
>> Na sasa taarifa kitanzi wakati.

944
00:44:16,680 --> 00:44:20,640
Hivyo muda mrefu kama pointer si sawa
kwa null, mimi nina kwenda kuangalia.

945
00:44:20,640 --> 00:44:24,520
Ni pointer mshale n sawa na
n kwamba ilipitishwa katika?

946
00:44:24,520 --> 00:44:26,410
Na kusubiri dakika - mpya
kipande cha syntax.

947
00:44:26,410 --> 00:44:29,324
Kile ni mshale wote wa ghafla?

948
00:44:29,324 --> 00:44:30,574
Yeah?

949
00:44:30,574 --> 00:44:34,200

950
00:44:34,200 --> 00:44:34,810
>> Hasa.

951
00:44:34,810 --> 00:44:38,860
Hivyo ambapo dakika chache zilizopita, sisi kutumika
nukta nukuu kupata kitu

952
00:44:38,860 --> 00:44:43,080
ndani ya struct, kama variable
wewe si struct

953
00:44:43,080 --> 00:44:47,420
yenyewe, lakini pointer struct,
nashiriki, kipande cha syntax kwamba

954
00:44:47,420 --> 00:44:48,620
hatimaye hufanya akili angavu.

955
00:44:48,620 --> 00:44:52,360
mshale maana yake kufuata pointer,
kama mishale yetu kawaida maana

956
00:44:52,360 --> 00:44:56,570
pictorially, na kwenda katika
shamba data ndani.

957
00:44:56,570 --> 00:44:59,700
Hivyo mshale ni kitu sawa kama nukta, lakini
wewe kutumia wakati una pointer.

958
00:44:59,700 --> 00:45:05,270
>> Hivyo tu kwa kurejea basi, kama n shamba
ndani ya struct kuitwa pointer

959
00:45:05,270 --> 00:45:07,760
sawa sawa n, kurudi kweli.

960
00:45:07,760 --> 00:45:11,970
Vinginevyo, line hii hapa - pointer
sawa pointer ijayo.

961
00:45:11,970 --> 00:45:17,540
Basi nini hii ni kufanya, ilani, ni kama mimi
am sasa akionyesha struct

962
00:45:17,540 --> 00:45:21,430
zenye 9, na 9 ni si idadi
Mimi nina kuangalia kwa - nadhani nina kuangalia

963
00:45:21,430 --> 00:45:22,830
kwa ajili ya n sawa na 50 -

964
00:45:22,830 --> 00:45:25,930
Mimi nina kwenda update pointer yangu muda
na si kumweka kwenye nodi hii

965
00:45:25,930 --> 00:45:31,190
tena, lakini pointer mshale ijayo, ambayo
ni kwenda kuweka me up hapa.

966
00:45:31,190 --> 00:45:34,270
>> Sasa, mimi barabara ni kimbunga
utangulizi.

967
00:45:34,270 --> 00:45:37,380
Siku ya Jumatano, tutaweza kweli kufanya hii
pamoja na baadhi ya binadamu na kwa baadhi ya zaidi

968
00:45:37,380 --> 00:45:38,900
kanuni kwa kasi ndogo.

969
00:45:38,900 --> 00:45:42,990
Lakini kutambua, sisi ni sasa kufanya takwimu zetu
miundo ngumu zaidi ili wetu

970
00:45:42,990 --> 00:45:45,780
algorithms wanaweza kupata ufanisi zaidi, ambayo
ni kwenda kuwa zinazohitajika kwa

971
00:45:45,780 --> 00:45:50,500
pset sita, wakati sisi mzigo katika, tena, wale
150,000 maneno, lakini haja ya kufanya hivyo

972
00:45:50,500 --> 00:45:55,650
ufanisi, na walau, kujenga
mpango kwamba anaendesha kwa watumiaji wetu si katika

973
00:45:55,650 --> 00:46:00,460
linear, si katika n squared, lakini katika
mara kwa mara wakati, katika bora.

974
00:46:00,460 --> 00:46:02,300
>> Tutaweza kuona juu ya Jumatano.

975
00:46:02,300 --> 00:46:07,240
>> SPIKA: Katika CS50 ijayo, Daudi
anasahau wigo wake kesi.

976
00:46:07,240 --> 00:46:12,770
>> DAVID Malan: Na kwamba ni jinsi ya kutuma
Nakala ujumbe na C. Nini -

977
00:46:12,770 --> 00:46:14,020
>> [MBALIMBALI TEXT UJUMBE
Taarifa Sauti]

978
00:46:14,020 --> 00:46:19,734