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[MUSIC KUCHEZA]

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>> DAVID J. Malan: All wa kulia.

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00:00:12,640 --> 00:00:14,525
Hii ni CS50.

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00:00:14,525 --> 00:00:16,009
Na hii ni mwanzo wa wiki 5.

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Na kama unaweza kuwa niliona,
baadhi ya vifaa

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00:00:18,050 --> 00:00:21,050
ni kupata kidogo zaidi
tata, denser kidogo.

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>> Na ni rahisi sana, hasa kama
tumekuwa katika tabia kwa muda fulani,

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kuwa anajaribu mpapuro chini zaidi
chochote cha kufanya, sisi ni kusema katika darasa.

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Lakini kutambua, kwamba ni si labda
mbinu bora za ufundishaji

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kujifunza aina hii ya vifaa,
na vifaa zaidi kwa ujumla.

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Na hivyo sisi ni radhi kwa
kutangaza kwamba CS50 ya mwenyewe Gheng

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Gong imeanza kuandaa
kisheria seti ya maelezo

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kwa ajili ya kozi, tumaini la
ambayo ni kwamba, mmoja, haya

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si tu kutumika kama
kumbukumbu na rasilimali

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kwa kupitia upya nyenzo na kwenda
nyuma kwa njia ya vifaa kwamba wanaweza kuwa na

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alitoroka mara ya kwanza kote, lakini
pia hivyo vichwa yako inaweza kuwa zaidi

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up kuliko chini, wakati
inakuja wakati kwa hotuba,

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00:00:53,740 --> 00:00:56,960
hivyo kwamba unaweza kushiriki
zaidi kwa kufikiri, kama

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kinyume na zaidi scribbly.

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>> Kwa kuwa alisema, ni nini utapata juu ya
tovuti ni hati kama huu.

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Na taarifa, juu kushoto, kuna
si tu meza ya yaliyomo,

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lakini pia codes huo
mara moja kuruka wewe

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kwa sehemu sahihi
katika video online.

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Na nini Chang hapa amefanya
ni, kimsingi, kumbukumbu

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kile kilichotokea katika hii
hasa hotuba.

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Na wengi wa mihadhara ni
tayari online sasa na URL hii.

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Na tutaweza kuendelea baada ya salio
ya wale mwishoni mwa wiki hii,

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hivyo kuchukua faida ya rasilimali hiyo.

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>> Hivyo bila wasiwasi zaidi,
sisi kuanza peel nyuma

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safu ambayo imekuwa
kamba kwa muda fulani.

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Na nini sisi kusema kamba
kweli ni wiki iliyopita?

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Hivyo char nyota.

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Na char nyota, vizuri, nini
gani kwamba kweli maana?

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Naam, muda wote huu, kama tumekuwa
wamekuwa wakitoa wito kazi,

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kama GetString, na hifadhi
kinachojulikana kurudi

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thamani ya GetString katika
variable-- ni kuitwa

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s aina string-- sisi tumekuwa kuandika
mstari wa kanuni up huko juu.

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Na ni tu wakati mimi kuona yangu
handwriting kujitukuza hapa

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kufanya mimi kutambua jinsi mauaji hii ni.

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>> Hata hivyo, hebu kudhani kwamba,
juu ya upande wa kulia

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ni, hata hivyo, busara
picha ya nini

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kinachoendelea haya yote
muda na GetString.

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GetString, bila shaka, anapata kamba.

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Lakini ni nini kwamba kweli maana yake nini?

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Ina maana anapata chunk ya
kumbukumbu kutoka mfumo wa uendeshaji

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na wito kazi, iitwayo malloc.

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Lakini zaidi juu ya kwamba baadaye.

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Na kisha populates
kwamba chunk ya kumbukumbu

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pamoja na barua user ina
typed katika, ikifuatiwa na, bila shaka,

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null tabia, au backslash
zero mwishoni sana.

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>> Wakati huo huo, upande wa mkono wa kushoto
ya hadithi hii, muda wote huu,

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tumekuwa kutangaza variable, kama s.

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Na kwamba variable ni nini sasa
kuanza wito pointer.

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Siyo sanduku ndani ya ambayo
sisi kuweka kamba, Daven, per se,

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lakini badala ya sisi kuweka katika kwamba mraba
sanduku upande wa kushoto nini hasa?

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00:02:32,550 --> 00:02:34,890

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Yeah?

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>> Watazamaji: pepe ya
ambapo ni iko katika kumbukumbu.

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>> DAVID J. Malan: Hasa.

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pepe ya ambapo Daven
iko katika kumbukumbu.

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Na si ambapo wote wa Daven iko,
per se, lakini hasa anwani

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ya nini?

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Yeah?

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>> Watazamaji: tabia ya kwanza.

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>> DAVID J. Malan: tabia ya kwanza
katika Daven, ambayo, katika kesi hii,

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Mimi mapendekezo mara kiholela
na kubadili pesa 1, OX1,

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ambayo ina maana ya
hexadecimal ya simu ya 1.

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Lakini pengine ni kwenda
kuwa idadi kubwa sana

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ili tupate kuteka
kwa 0x kama kiambishi awali,

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anayewakilisha tabia ya hexadecimal.

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Na kwa sababu hatuna haja ya kujua wapi
mapumziko ya wahusika wa Daven

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ni kwa sababu ya yale kubuni rahisi
uamuzi huo ulifanywa miaka mingi iliyopita?

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Yeah?

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>> Watazamaji: Backslash 0.

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DAVID J. Malan: Yeah, kwa uhakika.

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backslash 0 utapata, angalau katika
wakati linear, traverse kamba,

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kutembea kutoka kushoto kwenda kulia,
na kwa kitanzi, au wakati wa

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kitanzi, au kitu kama
kwamba, na kuamua, oh, hapa

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ni mwisho wa kamba fulani.

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Hivyo, pamoja na tu anwani katika
mwanzo wa kamba,

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tuweze kupata ukamilifu wa
yake, kwa sababu wakati wote huu,

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kamba imekuwa tu nyota Char.

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>> Hivyo ni hakika faini kuendelea kutumia
Maktaba CS50 na kufikirika hii,

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hivyo kusema, lakini tutaweza
kuanza kuona hasa

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nini imekuwa kinachoendelea
chini ya wakati huu kwa ujumla.

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Hivyo unaweza kukumbuka mfano huu,
pia, kutoka wakati wa mwisho, kulinganisha 0,

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ambao hawakuwa kweli kulinganisha.

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Lakini sisi alianza kutatua hili.

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>> Lakini kama labda rejea,
natakiwa maslahi mtu

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katika pink tembo leo,
pia yaliyotolewa na Chang?

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Vipi kuhusu wewe mbele? [Inaudible].

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Kuja juu juu.

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>> Na wakati huo huo,
kama wewe kuja, hebu

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kufikiria kwa muda tu kile
kanuni hii kwa kweli alikuwa akifanya.

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Ni kutangaza vigezo mbili hadi
juu, s na t, na wito GetString.

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Hii si sana user-kirafiki mpango,
kwa sababu haina kukuambia nini cha kufanya.

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Lakini hebu kudhani tu tuko
kulenga sehemu Juicy.

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Na kisha sisi kufanya, kama s ni sawa na
sawa na t, ni lazima kusema printf,

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typed kitu kimoja.

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Hello.

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Nini jina lako?

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>> Janelle: Janelle.

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DAVID J. Malan: Janelle,
vyema kukutana na wewe.

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Hivyo changamoto yako katika
mkono kwa ajili ya tembo hii

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ni kuteka us kwanza picha ya nini
kuwakilishwa katika wale wawili wa kwanza

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mistari.

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Hivyo s na t inaweza kuwa
kuwakilishwa jinsi ya screen?

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Na unaweza tu kuteka ni pamoja na
kidole yako juu ya screen hii kubwa.

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>> Hivyo kuna nusu mbili kwa
kila upande wa kwamba equation.

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Hivyo kuna s upande wa kushoto, na
kisha GetString juu ya haki.

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Na kisha kuna t upande wa kushoto,
na kisha GetString juu ya haki.

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Hivyo jinsi gani tunaanza
kuchora picha kwamba

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inawakilisha nini kinaendelea
hapa katika kumbukumbu, unaweza kusema?

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Na napenda basi wewe kueleza
nini unafanya kama wewe kwenda.

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>> Janelle: OK.

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Naam, kwanza, itakuwa kuuliza
kupata string pembejeo.

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Na itakuwa store-- oh, sorry.

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DAVID J. Malan: OK.

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Good.

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Na hii inaitwa nini?

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Oh, OK.

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Kuendelea.

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Sikuwa na maana kwa kupinga.

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Janelle: Sorry.

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Hivyo ingekuwa pembejeo katika
anwani of-- si uhakika.

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Siwezi hasa kumbuka ya simu,
lakini naamini ilikuwa ni kwa kuanzia na 0.

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>> DAVID J. Malan: Hiyo ni haki ya wote,
kwa sababu mimi alifanya namba up,

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hivyo hakuna jibu sahihi.

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>> Janelle: Kuanzia na 0 arc.

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>> DAVID J. Malan: Sawa, hivyo kipengele 0.

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Uhakika.

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>> Janelle: Na kisha kama alikuwa
kama wawili tu-letter--

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>> DAVID J. Malan: Sawa, nyuma yenu.

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>> Janelle: Hivyo kipengele 0, na
basi kipengele 1 au kipengele 2.

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DAVID J. Malan: Na ambayo kipande cha
picha ni wewe kuchora sasa hivi?

140
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wito kwa GetString?

141
00:05:37,690 --> 00:05:38,830
Au tamko la s?

142
00:05:38,830 --> 00:05:42,890
>> Janelle: tamko
ya s, naamini.

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00:05:42,890 --> 00:05:45,980
Oh, GetString, kwa sababu ingekuwa
kuwa inputted katika kila [? eneo hilo. ?]

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>> DAVID J. Malan: Good.

145
00:05:46,510 --> 00:05:47,051
Hasa.

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00:05:47,051 --> 00:05:49,300
Hata ingawa hii kwa ufanisi
anarudi safu, kukumbuka,

147
00:05:49,300 --> 00:05:53,300
wakati sisi kupata nyuma kamba, tunaweza
index ndani ya kwamba string kutumia 01 na 2.

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Kitaalam, hizi ni pengine
kuwakilishwa na anwani ya mtu binafsi,

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lakini hiyo ni faini.

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>> Hivyo tuseme, kama naweza tu kufunga
mbele kwa ambapo sisi kushoto mbali

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00:06:00,170 --> 00:06:04,320
mara ya mwisho, kama moja ya
masharti mara g b e,

152
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backslash 0, na hivyo anayewakilisha Gabe ya
pembejeo, jinsi gani sisi kuwakilisha s sasa?

153
00:06:10,337 --> 00:06:12,670
Kama hii ni kumbukumbu hiyo ni
wamekuwa akarudi na GetString?

154
00:06:12,670 --> 00:06:14,415

155
00:06:14,415 --> 00:06:17,610
>> Janelle: Je, ni kuwa
kuwakilishwa na arc?

156
00:06:17,610 --> 00:06:18,750
>> DAVID J. Malan: Kwa arc?

157
00:06:18,750 --> 00:06:19,130
Naam, hakuna.

158
00:06:19,130 --> 00:06:21,171
Hebu tu kusema, pictorially,
basi mimi tu kwenda mbele

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00:06:21,171 --> 00:06:25,710
na kupendekeza kwamba, kama hii ni s, hii
ni thamani ya kurudi kwa GetString.

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Na ve inayotolewa hii kama 0, 1, 2, ambayo
ni kikamilifu busara, kwa sababu sisi

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unaweza index ndani ya kamba, kama vile.

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00:06:30,940 --> 00:06:33,340
Lakini tu kuwa thabiti na
mara ya mwisho, basi mimi kwenda mbele

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na kiholela kupendekeza kwamba hii
ni mahali 1, hii ni mahali 2,

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00:06:37,310 --> 00:06:39,597
hii ni anwani 3, na kadhalika.

165
00:06:39,597 --> 00:06:41,430
Na hivyo, tu kuwa super
wazi, nini kinaendelea

166
00:06:41,430 --> 00:06:44,580
kwenda katika s kama matokeo ya
mstari wa kwanza wa code, ungeweza kusema?

167
00:06:44,580 --> 00:06:45,420
>> Janelle: 1 mitaani?

168
00:06:45,420 --> 00:06:46,420
>> DAVID J. Malan: Hasa.

169
00:06:46,420 --> 00:06:47,190
Hivyo kushughulikia 0x1.

170
00:06:47,190 --> 00:06:48,220

171
00:06:48,220 --> 00:06:51,230
Na wakati huo huo, napenda kwenda mbele na
duplicate mengi ya nini umefanya kosa

172
00:06:51,230 --> 00:06:52,740
na kuongeza t yangu mwenyewe hapa.

173
00:06:52,740 --> 00:06:56,340
Kama ningekuwa na aina katika Gabe
tena mara ya pili,

174
00:06:56,340 --> 00:07:01,530
wakati wakiongozwa na GetString, ambapo,
bila shaka, ni Gabe kwenda?

175
00:07:01,530 --> 00:07:02,280
Naam, presumably--

176
00:07:02,280 --> 00:07:04,935

177
00:07:04,935 --> 00:07:05,975
>> Janelle: Kama ilivyokuwa katika hapa?

178
00:07:05,975 --> 00:07:06,850
DAVID J. Malan: Yeah.

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00:07:06,850 --> 00:07:08,516
Janelle: Au ni pia katika masanduku sawa?

180
00:07:08,516 --> 00:07:11,940
DAVID J. Malan: Hebu kupendekeza, yeah,
hasa, hivyo katika masanduku haya ya ziada.

181
00:07:11,940 --> 00:07:15,230
Lakini nini muhimu sasa ni kwamba, hata
ingawa nimekuwa inayotolewa haya pretty karibu

182
00:07:15,230 --> 00:07:18,650
together-- 0x1, hii
ni 0x2-- katika hali halisi,

183
00:07:18,650 --> 00:07:25,750
hii sasa inaweza kuwa anwani 0x10,
kwa mfano, na 0x11, na 0x12,

184
00:07:25,750 --> 00:07:26,870
na kadhalika.

185
00:07:26,870 --> 00:07:29,955
Na hivyo, kama hiyo kesi,
nini kinaendelea na kuishia hapa katika t?

186
00:07:29,955 --> 00:07:30,830
>> Janelle: 0x10?

187
00:07:30,830 --> 00:07:31,830
DAVID J. Malan: Hasa.

188
00:07:31,830 --> 00:07:33,180
Hivyo 0x10.

189
00:07:33,180 --> 00:07:34,570
Na hivyo sasa, swali la mwisho.

190
00:07:34,570 --> 00:07:37,510
Una, kwa mbali, alikuwa na kazi
gumu kwa tembo hivi sasa.

191
00:07:37,510 --> 00:07:42,650
Kwa sasa, kama mimi kuvuta up code
tena, wakati mimi kufanya, katika line tatu,

192
00:07:42,650 --> 00:07:47,630
kama s ni sawa na ni sawa na t, nini ni mimi kwa kweli
kulinganisha kwamba tumekuwa inayotolewa hapa?

193
00:07:47,630 --> 00:07:49,271
>> Janelle: anwani mbili?

194
00:07:49,271 --> 00:07:50,270
DAVID J. Malan: Hasa.

195
00:07:50,270 --> 00:07:53,350
Hivyo mimi nina kusema ni s sawa sawa na t?

196
00:07:53,350 --> 00:07:56,210
Kwa maneno mengine, ni sawa sawa na 1 10?

197
00:07:56,210 --> 00:07:59,710
Na bila shaka,
Jibu la wazi sasa ni, hakuna.

198
00:07:59,710 --> 00:08:02,920
Na hivyo mpango huu ni hatimaye
kwenda magazeti nini, unaweza kusema?

199
00:08:02,920 --> 00:08:05,770

200
00:08:05,770 --> 00:08:08,405
>> Janelle: Je, ni kuwa,
typed kitu kimoja?

201
00:08:08,405 --> 00:08:11,446
>> DAVID J. Malan: Hivyo kama
s ni 1 na t ni 10?

202
00:08:11,446 --> 00:08:13,320
>> Janelle: You typed mambo mbalimbali.

203
00:08:13,320 --> 00:08:13,570
>> DAVID J. Malan: Hasa.

204
00:08:13,570 --> 00:08:14,480
Typed mambo mbalimbali.

205
00:08:14,480 --> 00:08:14,850
Wote haki.

206
00:08:14,850 --> 00:08:16,714
Hivyo duru ya applause,
kama tunaweza, hapa.

207
00:08:16,714 --> 00:08:17,214
[Makofi]

208
00:08:17,214 --> 00:08:17,708
Hiyo ilikuwa chungu.

209
00:08:17,708 --> 00:08:18,208
Mimi najua.

210
00:08:18,208 --> 00:08:19,684
Nicely kufanyika.

211
00:08:19,684 --> 00:08:24,690
Hivyo sasa hebu angalia kama hatuwezi
tease mbali nini fix mara.

212
00:08:24,690 --> 00:08:28,040
Na bila shaka, wakati sisi fasta Haya
ambayo mimi itabidi sasa ya kuwakilisha katika green--

213
00:08:28,040 --> 00:08:29,690
sisi alifanya michache ya nyongeza hapa.

214
00:08:29,690 --> 00:08:32,409
Kwanza, tu kama sanity
kuangalia, mimi nina kuangalia kwanza

215
00:08:32,409 --> 00:08:35,110
kama s ni sawa na batili na t sawa na null.

216
00:08:35,110 --> 00:08:39,440
Na tu kuwa wazi, wakati anaweza
s au t kuwa null katika code kama hii?

217
00:08:39,440 --> 00:08:43,140

218
00:08:43,140 --> 00:08:44,490
Wakati wanaweza s au t kuwa null.

219
00:08:44,490 --> 00:08:44,990
Yeah?

220
00:08:44,990 --> 00:08:45,990
>> Watazamaji: [inaudible].

221
00:08:45,990 --> 00:08:49,490

222
00:08:49,490 --> 00:08:50,510
>> DAVID J. Malan: Hasa.

223
00:08:50,510 --> 00:08:52,840
Kama string kwamba mtumiaji
typed katika ni njia ya muda mrefu pia

224
00:08:52,840 --> 00:08:56,140
walionao katika kumbukumbu, au baadhi
weird kona kesi kama hiyo,

225
00:08:56,140 --> 00:08:59,010
GetString, kama tutaweza kuona, literally
leo, katika nyaraka zake,

226
00:08:59,010 --> 00:09:02,330
anasema atarudi null kama
thamani maalum sentinel,

227
00:09:02,330 --> 00:09:05,417
au tu aina ya ishara maalum
hiyo ina maana kitu potoka.

228
00:09:05,417 --> 00:09:07,500
Hivyo tunataka kuangalia kwa
kwamba, kwa sababu ni zamu nje

229
00:09:07,500 --> 00:09:09,720
kwamba null ni thamani ya hatari sana.

230
00:09:09,720 --> 00:09:14,250
>> Mara nyingi, kama wewe jaribu kufanya kitu kwa
null kuwashirikisha function-- kupita

231
00:09:14,250 --> 00:09:17,470
kama pembejeo, kwa instance-- kazi ambayo
wanaweza sana itakuwa ajali na, pamoja na hayo,

232
00:09:17,470 --> 00:09:19,090
kuchukua chini ya mpango yako yote.

233
00:09:19,090 --> 00:09:22,570
Hivyo line hii ya tatu sasa ni tu sanity
kuangalia, kuangalia makosa, kama wewe.

234
00:09:22,570 --> 00:09:25,450
Hiyo ni tabia nzuri sasa kwa
sisi kupata katika wakati wowote sisi

235
00:09:25,450 --> 00:09:28,050
kujaribu kutumia thamani kwamba
inaweza, uwezekano, kuwa null.

236
00:09:28,050 --> 00:09:32,000
>> Sasa, katika mstari wa nne hapa,
"Kama strcmp (s, t)," vizuri,

237
00:09:32,000 --> 00:09:33,180
nini kuwa akimaanisha?

238
00:09:33,180 --> 00:09:36,750
Naam, sisi alisema hii ilikuwa kwa ufupi sana
aitwaye kazi kwa kamba kulinganisha.

239
00:09:36,750 --> 00:09:40,370
Na madhumuni yake katika maisha ni kulinganisha
hoja yake ya kwanza dhidi yake ya pili,

240
00:09:40,370 --> 00:09:44,640
lakini si katika suala la anwani zao,
kama tulivyofanya bila kukusudia wakati

241
00:09:44,640 --> 00:09:48,270
iliyopita na kanuni nyekundu, lakini
badala ya kulinganisha hizo mbili

242
00:09:48,270 --> 00:09:53,210
masharti katika humanly Intuitive
njia kwa kulinganisha hili, juu ya hii,

243
00:09:53,210 --> 00:09:56,690
dhidi ya hili, juu ya hili, na
kisha kuacha ikiwa na wakati moja

244
00:09:56,690 --> 00:09:59,590
au wote wawili wa vidole yangu
hits backslash 0.

245
00:09:59,590 --> 00:10:04,530
Hivyo mtu miaka iliyopita kutekelezwa strcmp
kutekeleza kwa us utendaji

246
00:10:04,530 --> 00:10:08,890
kwamba sisi matumaini sisi ingekuwa Gotten
na tu kulinganisha maadili mbili rahisi.

247
00:10:08,890 --> 00:10:14,929
>> Sasa kusema ukweli, mimi kuweka kuchora
yote ya namba hizi mbalimbali.

248
00:10:14,929 --> 00:10:17,470
Lakini ukweli ni, nimekuwa
kufanya haya juu wakati wote.

249
00:10:17,470 --> 00:10:19,580
Na hivyo basi mimi tu kwenda mbele
na mpapuro hizi nje

250
00:10:19,580 --> 00:10:23,100
kufanya hatua hiyo, mwishoni mwa
wa siku na kusonga mbele,

251
00:10:23,100 --> 00:10:30,160
sisi siyo kweli kwenda huduma ya juu
nini anwani mambo ni kweli

252
00:10:30,160 --> 00:10:30,790
katika kumbukumbu.

253
00:10:30,790 --> 00:10:34,320
Hivyo mimi nina si kwenda kuteka haya
aina ya namba sana tena,

254
00:10:34,320 --> 00:10:38,970
Mimi tu abstract hii mbali
kidogo zaidi ya kirafiki na mishale tu.

255
00:10:38,970 --> 00:10:42,060
>> Kwa maneno mengine, kama s ni pointer,
vizuri, hebu tu kuteka ni, literally,

256
00:10:42,060 --> 00:10:45,430
kama pointer, arrow akizungumzia
kutoka yenyewe kwa kitu kingine,

257
00:10:45,430 --> 00:10:48,280
na si wasiwasi sana zaidi kuhusu
minutia ya anwani hizi

258
00:10:48,280 --> 00:10:49,910
ambayo, tena, mimi alifanya juu anyway.

259
00:10:49,910 --> 00:10:52,680
Lakini tutaweza kuona wale anwani,
wakati mwingine, wakati debugging code.

260
00:10:52,680 --> 00:10:56,450
>> Sasa wakati huo huo, mpango huu
up hapa fixes, bila shaka,

261
00:10:56,450 --> 00:10:58,720
kwamba tatizo kwa kulinganisha
wale masharti mawili.

262
00:10:58,720 --> 00:11:00,260
Lakini sisi mbio katika tatizo jingine.

263
00:11:00,260 --> 00:11:03,180
Hii ilikuwa na nakala
mpango mara ya mwisho,

264
00:11:03,180 --> 00:11:06,880
ambapo, mimi alikuwa anajaribu capitalize
tu tabia ya kwanza katika kamba.

265
00:11:06,880 --> 00:11:09,620
Lakini ilikuwa ni nini dalili
tuliona mara ya mwisho wakati

266
00:11:09,620 --> 00:11:14,150
user typed katika thamani, kama
Gabe katika lowercase, kwa s,

267
00:11:14,150 --> 00:11:19,310
kisha sisi kwa ajili s katika t,
kama katika mstari wa tatu huko,

268
00:11:19,310 --> 00:11:22,900
na kisha mimi alijaribu
capitalize t bracket 0?

269
00:11:22,900 --> 00:11:25,950
Mara ya athari za nini
kubadilisha t bracket 0 hapa?

270
00:11:25,950 --> 00:11:27,150
>> Watazamaji: Ni iliyopita s.

271
00:11:27,150 --> 00:11:29,360
>> DAVID J. Malan: Yeah,
Mimi iliyopita s, kama vile.

272
00:11:29,360 --> 00:11:31,050
Kwa sababu kile kweli kinachoendelea?

273
00:11:31,050 --> 00:11:34,130
Naam, napenda kuona kama naweza safi
up picha hii, kama ifuatavyo.

274
00:11:34,130 --> 00:11:41,390
>> Kama s ni, tena, neno g,
a, b, e, backslash, 0, na s

275
00:11:41,390 --> 00:11:44,084
tutaweza kuendelea kuchora kama sanduku
hapa, lakini hakuna zaidi ya anwani.

276
00:11:44,084 --> 00:11:45,250
Hebu kuacha kufanya mambo up.

277
00:11:45,250 --> 00:11:47,510
Hebu tu kuteka picha
kurahisisha dunia.

278
00:11:47,510 --> 00:11:52,640
>> Wakati mimi kutangaza t kwa kamba t,
ambayo inajenga kwamba chunk ya kumbukumbu.

279
00:11:52,640 --> 00:11:55,850
Square hutokea kwa kuwa 32
bits katika kompyuta nyingi.

280
00:11:55,850 --> 00:11:59,530
Kwa kweli, kama wameweza milele habari za
kompyuta kuwa na 32-bit usanifu,

281
00:11:59,530 --> 00:12:03,000
kweli dhana-kusema, kwamba tu
ina maana inatumia anwani 32-bit.

282
00:12:03,000 --> 00:12:05,370
Na kama kiufundi kando,
kama wameweza umewahi kujiuliza

283
00:12:05,370 --> 00:12:09,630
kwa nini kompyuta wakubwa, kama kweli
alijaribu supu yao juu na kura ya RAM,

284
00:12:09,630 --> 00:12:12,360
inaweza tu kuwa na upeo
ya gigabytes nne ya RAM,

285
00:12:12,360 --> 00:12:14,860
vizuri kwamba ni kwa sababu, literally,
kompyuta yako ya zamani inaweza tu

286
00:12:14,860 --> 00:12:17,250
kuhesabu kama juu kama 4
bilioni, bilioni 4 ka,

287
00:12:17,250 --> 00:12:20,590
kwa sababu ilikuwa kutumia 32-bit
namba kwa anwani.

288
00:12:20,590 --> 00:12:23,260
>> Lakini katika hali yoyote, katika hii
mfano, hadithi ya rahisi sana.

289
00:12:23,260 --> 00:12:27,250
t ni mwingine tu pointer, au
kweli nyota char, kamba aka.

290
00:12:27,250 --> 00:12:30,860
Na jinsi gani mimi wanataka update picha hii
sasa na kwamba mstari wa pili wa kanuni,

291
00:12:30,860 --> 00:12:31,950
baada ya dot, dot, dot?

292
00:12:31,950 --> 00:12:35,845
Wakati mimi kufanya string t sawa na s semicolon,
jinsi gani picha hii kubadilika?

293
00:12:35,845 --> 00:12:37,500

294
00:12:37,500 --> 00:12:38,000
Yeah?

295
00:12:38,000 --> 00:12:38,916
>> Watazamaji: [inaudible].

296
00:12:38,916 --> 00:12:41,087

297
00:12:41,087 --> 00:12:42,020
>> DAVID J. Malan: Yeah.

298
00:12:42,020 --> 00:12:42,600
Hasa.

299
00:12:42,600 --> 00:12:45,620
Mimi tu ya kuweka mshale kutoka
t sanduku kwa anwani huo,

300
00:12:45,620 --> 00:12:47,570
ile ile ya kwanza ya mbili katika alitoa.

301
00:12:47,570 --> 00:12:50,850
Au kitaalam, kama hii
guy bado walikuwa katika 0x1,

302
00:12:50,850 --> 00:12:53,052
ni kama nilikuwa ingawa
0x1 hapa na 0x1 hapa.

303
00:12:53,052 --> 00:12:54,760
Lakini tena, anayejali
kuhusu anwani?

304
00:12:54,760 --> 00:12:56,345
Ni wazo tu kwamba sasa mambo.

305
00:12:56,345 --> 00:12:57,720
Hivyo hii ni nini kinatokea hapa.

306
00:12:57,720 --> 00:13:02,690
Hivyo bila shaka, kama wewe kufanya t bracket
0, ambayo ni safu nukuu,

307
00:13:02,690 --> 00:13:05,650
ya course-- na kusema ukweli, inaonekana
kama kuna safu zaidi ya hapa,

308
00:13:05,650 --> 00:13:07,340
lakini sasa kuna jambo hili weird.

309
00:13:07,340 --> 00:13:11,160
Kujua kwamba lugha ya programu,
C, inatoa kipengele hiki,

310
00:13:11,160 --> 00:13:14,650
ambapo, hata kama t ni
pointer, au s ni pointer,

311
00:13:14,650 --> 00:13:18,050
bado unaweza kutumia utambuzi,
starehe za mraba bracket

312
00:13:18,050 --> 00:13:22,520
nukuu kwenda kipengele kwanza,
au kipengele pili, au yoyote ya kipengele

313
00:13:22,520 --> 00:13:26,130
kwamba pointer ni akizungumzia
kwa sababu, labda, ni

314
00:13:26,130 --> 00:13:29,410
ni, kama katika kesi hii,
akionyesha baadhi safu.

315
00:13:29,410 --> 00:13:30,340
>> Hivyo ni jinsi gani sisi kurekebisha hili?

316
00:13:30,340 --> 00:13:33,660
Kwa kweli, hii ni mahali ambapo got
kidogo mno katika mtazamo wa kwanza.

317
00:13:33,660 --> 00:13:35,340
Lakini hapa ni toleo mpya na kuboreshwa.

318
00:13:35,340 --> 00:13:37,460
>> Hivyo kwanza, mimi nina kupata
kuondoa maktaba CS50,

319
00:13:37,460 --> 00:13:41,170
tu kuwaonyesha kwamba s ni kweli
nyota Char, tu kisawe.

320
00:13:41,170 --> 00:13:43,540
Na t ni pia nyota Char.

321
00:13:43,540 --> 00:13:48,290
Lakini ni nini kinaendelea juu ya
mkono wa kulia upande wa kwamba line

322
00:13:48,290 --> 00:13:49,970
ambapo t ni kwa ajili thamani?

323
00:13:49,970 --> 00:13:50,790
>> Malloc ni nini?

324
00:13:50,790 --> 00:13:51,630
Nini ni strlen?

325
00:13:51,630 --> 00:13:52,547
Sizeof (Char) ni nini?

326
00:13:52,547 --> 00:13:54,380
Kwa nini heck gani hii
line kuangalia hivyo tata?

327
00:13:54,380 --> 00:13:55,713
Nini ni kufanya katika ngazi ya juu?

328
00:13:55,713 --> 00:13:56,482

329
00:13:56,482 --> 00:13:57,440
Nini ni kuhifadhi katika t?

330
00:13:57,440 --> 00:13:58,646
Yeah?

331
00:13:58,646 --> 00:14:01,104
Watazamaji: Ni kugawa
kiasi fulani cha kumbukumbu nafasi.

332
00:14:01,104 --> 00:14:03,032
Ni kuhifadhi, mimi nadhani,
barua [inaudible].

333
00:14:03,032 --> 00:14:04,032
>> DAVID J. Malan: Perfect.

334
00:14:04,032 --> 00:14:04,540
Perfect.

335
00:14:04,540 --> 00:14:06,650
Ni kugawa baadhi ya
kiasi cha kumbukumbu nafasi

336
00:14:06,650 --> 00:14:08,940
kuhifadhi, labda, barua siku zijazo.

337
00:14:08,940 --> 00:14:11,310
Na hasa, malloc
hiyo ni kurudi nini?

338
00:14:11,310 --> 00:14:13,114

339
00:14:13,114 --> 00:14:14,851
>> Watazamaji: Kurudi [inaudible]?

340
00:14:14,851 --> 00:14:15,850
DAVID J. Malan: Hasa.

341
00:14:15,850 --> 00:14:18,850
Kurudi pepe ya kwamba kumbukumbu,
ambayo ni njia dhana ya kusema,

342
00:14:18,850 --> 00:14:21,640
anarudi pepe ya
Byte kwanza ya kwamba kumbukumbu.

343
00:14:21,640 --> 00:14:25,460
Wajibu ni juu yangu kukumbuka
kiasi gani kumbukumbu mimi kwa kweli

344
00:14:25,460 --> 00:14:27,140
zilizotengwa au aliuliza malloc kwa.

345
00:14:27,140 --> 00:14:28,384
>> Sasa ni kiasi gani ni kwamba?

346
00:14:28,384 --> 00:14:30,550
Vizuri, hata kama kuna
mengi ya mabano hapa,

347
00:14:30,550 --> 00:14:32,970
malloc inachukua tu hoja moja.

348
00:14:32,970 --> 00:14:37,250
Na mimi nina kubainisha strlen ya s, hivyo kutoa
me ka kama wengi kama kuna katika s,

349
00:14:37,250 --> 00:14:37,800
lakini kuongeza moja.

350
00:14:37,800 --> 00:14:38,300
Kwa nini?

351
00:14:38,300 --> 00:14:39,030

352
00:14:39,030 --> 00:14:39,530
Yeah?

353
00:14:39,530 --> 00:14:40,840
>> Watazamaji: backslash 0.

354
00:14:40,840 --> 00:14:41,840
DAVID J. Malan: Hasa.

355
00:14:41,840 --> 00:14:43,423
Sisi nimepata kufanya housekeeping kidogo.

356
00:14:43,423 --> 00:14:45,970
Hivyo kwa sababu kuna backslash
0, tunatarajia bora kukumbuka kwamba.

357
00:14:45,970 --> 00:14:47,310
Vinginevyo, tunakwenda
kujenga string kwamba

358
00:14:47,310 --> 00:14:49,170
hana kwamba Terminator maalum.

359
00:14:49,170 --> 00:14:52,640
>> Wakati huo huo, tu kuwa super
anal, nina sizeof (Char),

360
00:14:52,640 --> 00:14:55,730
tu katika kesi ya mtu anaendesha yangu
code si juu ya CS50 appliance,

361
00:14:55,730 --> 00:14:58,220
lakini labda kompyuta tofauti
kabisa ambapo chars

362
00:14:58,220 --> 00:15:01,470
ni byte moja, kwa mkataba huo, lakini mbili
ka, au jambo kubwa kuliko hiyo.

363
00:15:01,470 --> 00:15:04,490
Ni tu kuwa super,
super mnaichukia makosa.

364
00:15:04,490 --> 00:15:06,940
Hata ingawa, katika hali halisi, ni
zaidi uwezekano wa kwenda kuwa 1.

365
00:15:06,940 --> 00:15:11,490
>> Sasa, wakati huo huo, mimi kwenda mbele na nakala
kamba, t bracket i sawa na t bracket s.

366
00:15:11,490 --> 00:15:14,962
Nami kuahirisha kwa wiki iliyopita
chanzo code kuona nini kinaendelea.

367
00:15:14,962 --> 00:15:17,670
Lakini takeaway muhimu, na
sababu mimi kuweka code sasa katika kijani,

368
00:15:17,670 --> 00:15:22,520
ni kwa sababu kwamba mstari wa mwisho sana,
t bracket 0 sawa na toupper,

369
00:15:22,520 --> 00:15:25,230
ina athari ya
kuyafanyia ambayo kamba?

370
00:15:25,230 --> 00:15:26,960
t na / au s?

371
00:15:26,960 --> 00:15:29,280

372
00:15:29,280 --> 00:15:30,580
Hiyo mstari wa mwisho wa kanuni.

373
00:15:30,580 --> 00:15:32,930

374
00:15:32,930 --> 00:15:35,560
>> Tu t, kwa sababu nini
kilichotokea wakati huu,

375
00:15:35,560 --> 00:15:41,500
kama mimi kidogo kutengua hatua hiyo ya mwisho,
nini kilichotokea, ambapo mimi wito malloc,

376
00:15:41,500 --> 00:15:45,380
Mimi kimsingi kupata chunk ya kumbukumbu
kwamba ni kawaida sawa kama awali,

377
00:15:45,380 --> 00:15:47,020
kwa sababu hiyo ni hesabu mimi alivyofanya.

378
00:15:47,020 --> 00:15:50,920
Mimi nina kuhifadhi katika t anwani
ya kwamba chunk ya kumbukumbu.

379
00:15:50,920 --> 00:15:53,370
Hata ingawa hii inaonekana nzuri
na pretty, nzuri na tupu,

380
00:15:53,370 --> 00:15:56,882
ukweli ni kuna, nini tutaweza
kuweka wito, maadili takataka katika hapa.

381
00:15:56,882 --> 00:15:59,340
Hiyo chunk ya kumbukumbu nguvu sana
vizuri na zimetumika kabla,

382
00:15:59,340 --> 00:16:00,940
sekunde chache, dakika chache zilizopita.

383
00:16:00,940 --> 00:16:04,410
Hivyo kuna inaweza kabisa kuwa namba
au barua huko, tu kwa ajali.

384
00:16:04,410 --> 00:16:08,580
Lakini wao ni si halali, hata mimi
mwenyewe na idadi ya chunk hii ya kumbukumbu

385
00:16:08,580 --> 00:16:12,510
na chars halisi, kama mimi
kufanya katika kwamba kwa kitanzi huko.

386
00:16:12,510 --> 00:16:13,180
Wote haki?

387
00:16:13,180 --> 00:16:16,180
>> Hivyo sasa, kilele cha
mifano hizi tatu

388
00:16:16,180 --> 00:16:20,730
kwamba walikuwa inaonekana kuvunjwa mara ya mwisho,
hii Swap mfano, kazi hii

389
00:16:20,730 --> 00:16:23,670
kazi katika akili
kuwa ni swapped a na b.

390
00:16:23,670 --> 00:16:25,620
Lakini haikuwa kazi kwa namna gani nyingine?

391
00:16:25,620 --> 00:16:27,616

392
00:16:27,616 --> 00:16:28,614
Yeah?

393
00:16:28,614 --> 00:16:29,612
>> Watazamaji: [inaudible].

394
00:16:29,612 --> 00:16:35,600

395
00:16:35,600 --> 00:16:36,700
>> DAVID J. Malan: Hasa.

396
00:16:36,700 --> 00:16:39,530
Kama ningekuwa kuwaita kazi hii
kutoka another-- kwa mfano,

397
00:16:39,530 --> 00:16:42,870
kutokana na kazi kama kuu, ambapo
Nina variable, x na y, kama mimi

398
00:16:42,870 --> 00:16:46,160
alifanya wiki iliyopita, kanuni na huo,
na mimi kupita katika x na y

399
00:16:46,160 --> 00:16:49,860
kwa Byta, na kisha kuwaita Swap-- hii,
bila shaka, ni toleo sahihi

400
00:16:49,860 --> 00:16:52,220
ni nini sisi ni juu ya
see-- haikuwa kazi.

401
00:16:52,220 --> 00:16:53,770
Kwa hiyo kile ni fix?

402
00:16:53,770 --> 00:16:56,850
>> Naam, hivyo tu kuwa
wazi, basi mimi kwenda mbele

403
00:16:56,850 --> 00:17:05,450
and-- nipe moja ya pili hapa, na kuona
kama naweza kuonyesha moja ya mwisho, ambayo

404
00:17:05,450 --> 00:17:12,464
itakuwa in-- hebu angalia kama naweza kupata
hii fast-- OK halisi, [inaudible].

405
00:17:12,464 --> 00:17:18,440

406
00:17:18,440 --> 00:17:19,240
OK, huko ni.

407
00:17:19,240 --> 00:17:21,000
Hivyo kupuuza amri mimi nina tu kuandika.

408
00:17:21,000 --> 00:17:23,780
Mimi nataka retrieve katika
dakika ya mwisho mfano

409
00:17:23,780 --> 00:17:27,960
kutoka wakati wa mwisho, ambayo
sasa inaitwa hakuna Swap.

410
00:17:27,960 --> 00:17:30,200
>> Hivyo hakuna Swap ni ambapo
sisi kushoto mbali wakati wa mwisho,

411
00:17:30,200 --> 00:17:32,930
ambapo, mimi initialized
x kwa 1 na y kwa 2.

412
00:17:32,930 --> 00:17:35,840
Mimi kisha kuwaita Swap, kupita katika 1 na 2.

413
00:17:35,840 --> 00:17:37,930
Na kisha kazi hii
kazi katika baadhi ya hisia,

414
00:17:37,930 --> 00:17:40,750
lakini hakuwa na kudumu
athari juu ya x na y.

415
00:17:40,750 --> 00:17:45,430
Hivyo swali katika mkono ni jinsi sasa
je, sisi kweli kurekebisha tatizo hili?

416
00:17:45,430 --> 00:17:47,820
Ni ufumbuzi katika mkono ni nini?

417
00:17:47,820 --> 00:17:53,150
>> Naam, katika swap.c, ambayo ni mpya leo,
taarifa wanandoa wa tofauti.

418
00:17:53,150 --> 00:17:54,700
x na y ni sawa.

419
00:17:54,700 --> 00:17:57,250
Lakini nini ni wazi
tofauti juu ya line 25?

420
00:17:57,250 --> 00:17:58,880

421
00:17:58,880 --> 00:18:01,715
Nini mpya huko, kama unakumbuka
nini inaonekana kama pili iliyopita?

422
00:18:01,715 --> 00:18:02,565
>> Watazamaji: [inaudible].

423
00:18:02,565 --> 00:18:03,440
>> DAVID J. Malan: Yeah.

424
00:18:03,440 --> 00:18:06,680
Hivyo ampersands ni kipande mpya
ya syntax si tu katika mpango huu,

425
00:18:06,680 --> 00:18:08,560
lakini pia kwa ujumla zaidi katika CS50.

426
00:18:08,560 --> 00:18:10,680
Hadi sasa, sidhani
tumeona mifano yoyote

427
00:18:10,680 --> 00:18:14,070
au kweli aliyesema kuhusu wao katika yoyote
undani, zaidi ya, labda, preemptively

428
00:18:14,070 --> 00:18:16,467
katika sehemu, Ampersand kama hii.

429
00:18:16,467 --> 00:18:19,300
Naam, ni zamu nje Ampersand ni moja
ya vipande ya mwisho ya syntax mpya

430
00:18:19,300 --> 00:18:20,174
tunakwenda kujifunza.

431
00:18:20,174 --> 00:18:23,500
All maana ni
pepe ya baadhi kutofautiana.

432
00:18:23,500 --> 00:18:25,070
Kwa nini anwani haina x kuishi?

433
00:18:25,070 --> 00:18:26,510
Lakini nini anwani haina y kuishi?

434
00:18:26,510 --> 00:18:28,700
Kwa sababu kama
tatizo la msingi kabla ya

435
00:18:28,700 --> 00:18:32,970
ilikuwa kwamba x na y walikuwa kuwa kupita
kama nakala, nini sisi kweli wanataka kufanya

436
00:18:32,970 --> 00:18:38,780
ni kutoa Swap na kama ilivyo kwa hazina
ramani ambayo inaongoza kwa ambapo x na y kweli

437
00:18:38,780 --> 00:18:41,910
ni katika RAM, ili
Swap unaweza kufuata ramani kwamba

438
00:18:41,910 --> 00:18:47,760
na kwenda popote x au y alama doa
na mabadiliko ya maadili halisi ya 1 na 2

439
00:18:47,760 --> 00:18:48,270
huko.

440
00:18:48,270 --> 00:18:50,710
>> Hivyo Swap inahitaji mabadiliko kidogo sana.

441
00:18:50,710 --> 00:18:53,760
Na katika mtazamo wa kwanza, hii nguvu
kuonekana kidogo sawa na char nyota.

442
00:18:53,760 --> 00:18:54,850
Na hakika ni.

443
00:18:54,850 --> 00:18:59,635
Hivyo ni pointer kwa nini aina ya data,
misingi ya sehemu hii yalionyesha?

444
00:18:59,635 --> 00:19:00,810

445
00:19:00,810 --> 00:19:01,620
Hivyo ni int.

446
00:19:01,620 --> 00:19:04,880
>> Hivyo ni tena int,
ni pepe ya int.

447
00:19:04,880 --> 00:19:07,910
Na vile vile, b sasa ni kwenda
kuwa pepe ya int.

448
00:19:07,910 --> 00:19:12,470
Hivyo wakati mimi sasa wito Swap kutoka Kuu,
Mimi si kwenda kutoa Swap 1 na 2.

449
00:19:12,470 --> 00:19:15,540
Mimi nina kwenda kuwapa kama
Ng'ombe-kitu na ng'ombe-kitu,

450
00:19:15,540 --> 00:19:19,820
anwani mbili ambayo itasababisha
Swap na maeneo yao halisi

451
00:19:19,820 --> 00:19:21,310
katika kumbukumbu ya kompyuta yangu.

452
00:19:21,310 --> 00:19:25,580
>> Hivyo sasa, utekelezaji yangu iliyobaki
inahitaji mabadiliko tad.

453
00:19:25,580 --> 00:19:28,650
Nini ni wazi tofauti na sasa
katika mistari haya matatu ya kanuni?

454
00:19:28,650 --> 00:19:31,350
Kuna nyota hizi damn wote
juu ya mahali pa, wote haki?

455
00:19:31,350 --> 00:19:33,014
Hivyo nini kinaendelea hapa?

456
00:19:33,014 --> 00:19:33,514
Yeah?

457
00:19:33,514 --> 00:19:35,055
>> Watazamaji: Ni wazi [inaudible].

458
00:19:35,055 --> 00:19:36,832

459
00:19:36,832 --> 00:19:37,990
>> DAVID J. Malan: Hasa.

460
00:19:37,990 --> 00:19:41,560
Hivyo katika context-- hii na hii ilikuwa si
bora uamuzi wa kubuni, admittedly,

461
00:19:41,560 --> 00:19:42,530
miaka iliyopita.

462
00:19:42,530 --> 00:19:45,110
Katika hali hii, ambapo
wewe tu na nyota,

463
00:19:45,110 --> 00:19:48,240
na huna kuwa na aina data,
kama int, mara moja kwa upande wa kushoto,

464
00:19:48,240 --> 00:19:53,146
badala una ishara sawa, kwa uwazi,
kwa mantiki hii, wakati wewe kusema nyota,

465
00:19:53,146 --> 00:19:56,980
hiyo ina maana kwenda
anwani hiyo ni katika.

466
00:19:56,980 --> 00:19:58,870
Kufuata ramani hazina, hivyo kusema.

467
00:19:58,870 --> 00:20:01,720
>> Na wakati huo huo, katika line 37,
ina maana kitu kimoja.

468
00:20:01,720 --> 00:20:05,460
Kwenda mahali a, na kuweka kile huko?

469
00:20:05,460 --> 00:20:09,520
Chochote ni saa
eneo hilo b bayana.

470
00:20:09,520 --> 00:20:10,980
Kwa maneno mengine, kwenda b.

471
00:20:10,980 --> 00:20:12,130
Kupata thamani hiyo.

472
00:20:12,130 --> 00:20:15,620
Kwenda na, kwa sawa
saini, zoezi operator,

473
00:20:15,620 --> 00:20:17,010
kuweka thamani kwamba kuna.

474
00:20:17,010 --> 00:20:19,272
>> Vile vile, int temp ni tu int.

475
00:20:19,272 --> 00:20:20,730
Hakuna inahitaji mabadiliko kuhusu temp.

476
00:20:20,730 --> 00:20:24,810
Ni tu kioo vipuri kutoka Annenberg
kwa baadhi ya maziwa au juisi ya machungwa.

477
00:20:24,810 --> 00:20:27,630
Lakini mimi haja ya kusema, kwenda b.

478
00:20:27,630 --> 00:20:31,449
Kwenda kwamba marudio na
kuweka thamani katika temp huko.

479
00:20:31,449 --> 00:20:32,490
Hivyo nini kinatokea, basi?

480
00:20:32,490 --> 00:20:36,540
Wakati mimi kwa kweli kuwaita Byta wakati huu, kama
tray hii ya kwanza hapa inawakilisha Kuu,

481
00:20:36,540 --> 00:20:42,270
tray hii ya pili inawakilisha Swap, wakati
Mimi kupita Ampersand x na y Ampersand

482
00:20:42,270 --> 00:20:47,150
kutoka Kuu kwa Byta, tu kuwa wazi,
ni kitu gani stack frame kupokea?

483
00:20:47,150 --> 00:20:48,700

484
00:20:48,700 --> 00:20:49,200
Yeah?

485
00:20:49,200 --> 00:20:50,180
>> Watazamaji: [inaudible].

486
00:20:50,180 --> 00:20:51,180
DAVID J. Malan: Hasa.

487
00:20:51,180 --> 00:20:53,129
pepe ya x na anwani ya y.

488
00:20:53,129 --> 00:20:55,170
Na unaweza kufikiria haya
kama anwani ya posta.

489
00:20:55,170 --> 00:20:58,772
33 Oxford Street na 35
Oxford Street, na wewe

490
00:20:58,772 --> 00:21:01,230
wanataka kuhamia majengo mawili
kwamba ni katika maeneo hayo.

491
00:21:01,230 --> 00:21:04,680
>> Ni aina ya wazo ujinga,
lakini hiyo yote maana sisi na mahali.

492
00:21:04,680 --> 00:21:07,000
Ambapo katika dunia unaweza
wewe kupata wale ints mbili?

493
00:21:07,000 --> 00:21:09,470
Ambapo katika dunia unaweza
kupata majengo hayo mawili?

494
00:21:09,470 --> 00:21:15,170
Hivyo kama hatimaye, baada ya hayo mimi wakati
kwenda katika chanzo code ya leo na kukusanya

495
00:21:15,170 --> 00:21:22,110
Swap na kukimbia ./swap, hatimaye, kwa
mara ya kwanza sisi kweli kuona kwamba

496
00:21:22,110 --> 00:21:25,330
maadili yangu na kwa kweli
wamekuwa swapped kwa mafanikio.

497
00:21:25,330 --> 00:21:30,860
Na sasa, tunaweza hata kuchukua
kumbuka ya hii katika, kusema, GDB.

498
00:21:30,860 --> 00:21:32,740
>> Hivyo basi mimi kwenda katika faili moja.

499
00:21:32,740 --> 00:21:35,010
Hebu kwenda mbele na kukimbia GDB ya ./swap.

500
00:21:35,010 --> 00:21:36,590

501
00:21:36,590 --> 00:21:40,547
Na sasa, katika Swap, mimi nina kwenda
mbele na kuweka hatua ya mapumziko katika Kuu.

502
00:21:40,547 --> 00:21:42,630
Na sasa mimi nina kwenda
mbele na kuendesha programu.

503
00:21:42,630 --> 00:21:45,810
Na sasa tunaona code yangu
paused katika mstari huo.

504
00:21:45,810 --> 00:21:48,330
>> Kama mimi kwenda mbele na magazeti
x, nini anatakiwa kuona hapa?

505
00:21:48,330 --> 00:21:49,314

506
00:21:49,314 --> 00:21:49,980
Ni swali.

507
00:21:49,980 --> 00:21:51,030

508
00:21:51,030 --> 00:21:51,530
Sema tena?

509
00:21:51,530 --> 00:21:52,295
>> Watazamaji: [inaudible].

510
00:21:52,295 --> 00:21:53,910
>> DAVID J. Malan: Hivyo
namba random, labda.

511
00:21:53,910 --> 00:21:56,010
Labda mimi kupata bahati, na ni
nzuri na rahisi, kama 0.

512
00:21:56,010 --> 00:21:57,230
Lakini labda ni baadhi ya idadi random.

513
00:21:57,230 --> 00:21:58,090
Katika kesi hiyo, mimi got bahati.

514
00:21:58,090 --> 00:21:59,030
Ni hutokea tu kuwa 0.

515
00:21:59,030 --> 00:22:00,780
Lakini ni kweli bahati,
kwa sababu si mpaka mimi

516
00:22:00,780 --> 00:22:06,280
aina ya pili na kisha magazeti x ina kuwa
mstari wa kanuni, line 19, ameuawa.

517
00:22:06,280 --> 00:22:10,942
>> Wakati huo huo, kama mimi aina ya pili yake, na
sasa magazeti nje y, mimi nina kwenda kuona 2.

518
00:22:10,942 --> 00:22:13,900
Sasa, kama mimi aina ya pili, ni kwenda kwa
kupata utata kidogo, kwa sababu sasa,

519
00:22:13,900 --> 00:22:17,250
printf ni kwenda kuonekana kwenye
screen, kama ilivyokuwa. x ni 1.

520
00:22:17,250 --> 00:22:18,606
>> Hebu kufanya hii tena.

521
00:22:18,606 --> 00:22:20,480
Na sasa, hapa ambapo
mambo kupata kuvutia.

522
00:22:20,480 --> 00:22:21,580

523
00:22:21,580 --> 00:22:26,580
Kabla ya mimi wito Swap au hata hatua
ndani yake, hebu kuchukua peek kidogo.

524
00:22:26,580 --> 00:22:28,980
x ni, tena, 1.

525
00:22:28,980 --> 00:22:33,240
Y ni, bila shaka, haraka sanity
kuangalia, 2, hivyo si ngumu huko.

526
00:22:33,240 --> 00:22:35,740
Lakini Ampersand x ni nini?

527
00:22:35,740 --> 00:22:36,760

528
00:22:36,760 --> 00:22:39,350
Jibu, ni aina ya funky kuangalia.

529
00:22:39,350 --> 00:22:43,500
Lakini nyota int katika mabano ni tu
njia Pato la Taifa ya kusema hii ni mahali.

530
00:22:43,500 --> 00:22:48,290
Ni si int, ni pointer kwa
int, au vinginevyo inajulikana kama mahali.

531
00:22:48,290 --> 00:22:49,742
>> Jambo hili mambo ni nini?

532
00:22:49,742 --> 00:22:51,825
Sisi sijawahi kuona kitu
kabisa kama kwamba kabla.

533
00:22:51,825 --> 00:22:53,650

534
00:22:53,650 --> 00:22:58,120
Hivyo hii ni mahali katika kompyuta yangu ya
kumbukumbu ya ambapo x hutokea kuishi.

535
00:22:58,120 --> 00:22:59,040
Ni Ox-kitu.

536
00:22:59,040 --> 00:23:01,290
Na hii ni, kusema ukweli, kwa nini
Nimekuwa kuanza kuchora mishale,

537
00:23:01,290 --> 00:23:03,340
badala ya namba,
kwa sababu ambao kwa kweli wasiwasi

538
00:23:03,340 --> 00:23:06,890
kwamba int yako ni saa fulani
anwani hiyo ni kwamba kubwa.

539
00:23:06,890 --> 00:23:12,160
Lakini bffff0c4, haya yote ni
kweli hexadecimal tarakimu,

540
00:23:12,160 --> 00:23:13,720
ambayo ni 0 kupitia f.

541
00:23:13,720 --> 00:23:16,590
>> Hivyo sisi ni si kwenda kukaa pia
muda mrefu juu ya nini mambo hayo ni.

542
00:23:16,590 --> 00:23:19,400
Lakini kama mimi magazeti nje y,
bila shaka, naona 2.

543
00:23:19,400 --> 00:23:22,440
Lakini Ampersand y, naona anwani hii.

544
00:23:22,440 --> 00:23:26,527
Na taarifa, kwa curious,
jinsi mbali mbali ni x na y?

545
00:23:26,527 --> 00:23:27,985
Unaweza kupuuza zaidi ya mahali.

546
00:23:27,985 --> 00:23:29,330

547
00:23:29,330 --> 00:23:29,920
Tarakimu ka.

548
00:23:29,920 --> 00:23:33,510
Na kwamba ni sambamba na yetu
mapema kudai kwamba jinsi kubwa ni int?

549
00:23:33,510 --> 00:23:34,130
Tarakimu ka.

550
00:23:34,130 --> 00:23:37,420
Hivyo inaonekana kama kila kitu ni bitana up
nicely, kama unaweza matumaini, katika kumbukumbu.

551
00:23:37,420 --> 00:23:40,010
>> Hivyo sasa, hebu haraka tu mbele
hadi mwisho wa hadithi hii.

552
00:23:40,010 --> 00:23:43,290
Hebu kwenda mbele na aina hatua,
kupiga mbizi katika Swap kazi.

553
00:23:43,290 --> 00:23:46,880
Sasa angalia, kama mimi aina, ni
kufanana na anwani ya x.

554
00:23:46,880 --> 00:23:52,130
Kama mimi aina b, ni kufanana
kwa anwani ya y.

555
00:23:52,130 --> 00:23:57,020
Hivyo kile lazima mimi kuona kama mimi
kusema, kwenda mahali?

556
00:23:57,020 --> 00:23:58,120
Hivyo magazeti nyota.

557
00:23:58,120 --> 00:24:00,130
Hivyo nyota ina maana kwenda huko, katika muktadha huu.

558
00:24:00,130 --> 00:24:02,730
Ampersand ina maana nini pepe ya.

559
00:24:02,730 --> 00:24:05,000
Hivyo nyota njia 1.

560
00:24:05,000 --> 00:24:09,590
Na magazeti nyota b inatoa me 2.

561
00:24:09,590 --> 00:24:15,750
>> Na napenda kudhani, kwa wakati huu,
kwamba angalau kificho kwamba

562
00:24:15,750 --> 00:24:18,950
kuendelea kutekeleza sasa unaweza kuwa
kujadiliana kupitia katika njia hiyo.

563
00:24:18,950 --> 00:24:21,150
Lakini tutaweza kupitia upya wazo hili kabla ya muda mrefu.

564
00:24:21,150 --> 00:24:23,850
Hivyo toleo hili la Swap
ni sasa sahihi na inaruhusu

565
00:24:23,850 --> 00:24:26,650
sisi wabadilishane data ya aina fulani.

566
00:24:26,650 --> 00:24:29,120
>> Kwa hiyo, maswali yoyote basi juu ya Swap?

567
00:24:29,120 --> 00:24:29,890
On nyota?

568
00:24:29,890 --> 00:24:30,690
On pepe ya?

569
00:24:30,690 --> 00:24:33,270
Na utaona, na
tatizo kuweka 4, aina ya,

570
00:24:33,270 --> 00:24:37,310
lakini tatizo kuweka 5, dhahiri, ni jinsi gani hizi
mambo ni muhimu na kupata mengi zaidi

571
00:24:37,310 --> 00:24:39,584
vizuri pamoja nao, kama matokeo.

572
00:24:39,584 --> 00:24:40,430
Chochote wakati wote?

573
00:24:40,430 --> 00:24:40,930
Wote haki.

574
00:24:40,930 --> 00:24:44,350
Hivyo malloc ni, tena, kazi hii
kwamba tu kutenga kumbukumbu, kumbukumbu

575
00:24:44,350 --> 00:24:45,330
mgao.

576
00:24:45,330 --> 00:24:47,024
Na kwa nini hii ni muhimu?

577
00:24:47,024 --> 00:24:48,940
Naam, muda wote huu,
tumekuwa kutumia malloc.

578
00:24:48,940 --> 00:24:52,230
Kama wewe kufikiria sasa jinsi
GetString kazi, labda, ni

579
00:24:52,230 --> 00:24:56,140
wamekuwa kuuliza mtu kwa chunk ya
kumbukumbu, wakati wowote aina ya mtumiaji kamba

580
00:24:56,140 --> 00:24:59,040
katika, kwa sababu sisi hakika
hakujua, kama CS50 wafanyakazi,

581
00:24:59,040 --> 00:25:02,710
jinsi kubwa masharti wale ambao binadamu
ni kwenda aina inaweza kuwa.

582
00:25:02,710 --> 00:25:07,910
>> Basi hebu, kwa mara ya kwanza, kuanza kwa
peel nyuma jinsi matendo CS50 maktaba,

583
00:25:07,910 --> 00:25:10,990
kwa njia ya mifano michache
ambayo itasababisha yetu huko.

584
00:25:10,990 --> 00:25:15,300
Hivyo kama mimi kufungua gedit
na kufungua scanf 0,

585
00:25:15,300 --> 00:25:17,055
tunakwenda kuona kanuni zifuatazo.

586
00:25:17,055 --> 00:25:18,720

587
00:25:18,720 --> 00:25:23,530
Scanf 0, inapatikana kwenye tovuti kwa ajili ya
leo, ina mistari wachache wa kanuni

588
00:25:23,530 --> 00:25:25,351
hapa, 14 mpaka 20.

589
00:25:25,351 --> 00:25:26,600
Na hebu angalia nini ni kufanya.

590
00:25:26,600 --> 00:25:28,920
Ni anatangaza int, iitwayo x.

591
00:25:28,920 --> 00:25:30,850
Ni anasema kitu kama, idadi tafadhali.

592
00:25:30,850 --> 00:25:33,940
Na sasa inasema, scanf% i, & x.

593
00:25:33,940 --> 00:25:35,620
Hivyo kuna rundo la mambo mpya huko.

594
00:25:35,620 --> 00:25:38,420
>> Lakini scanf, unaweza aina ya kufikiri
ya kama kinyume cha printf.

595
00:25:38,420 --> 00:25:40,090
printf, bila shaka, prints kwa screen.

596
00:25:40,090 --> 00:25:44,410
scanf aina ya scans kutoka mtumiaji
keyboard kitu yeye au yeye ana typed.

597
00:25:44,410 --> 00:25:46,550
>> % I ni tu kama printf.

598
00:25:46,550 --> 00:25:49,410
Hii ina maana kutarajia
user aina int.

599
00:25:49,410 --> 00:25:52,820
Na sasa, kwa nini unafikiri mimi
inaweza kuwa kupita scanf & x?

600
00:25:52,820 --> 00:25:54,030

601
00:25:54,030 --> 00:25:57,770
Kama kusudi katika maisha ya scanf
ni kupata kitu kutoka kwa mtumiaji,

602
00:25:57,770 --> 00:26:02,480
nini maana ya
kupita, & x, sasa?

603
00:26:02,480 --> 00:26:02,980
Yeah?

604
00:26:02,980 --> 00:26:03,896
>> Watazamaji: [inaudible].

605
00:26:03,896 --> 00:26:05,540

606
00:26:05,540 --> 00:26:06,540
DAVID J. Malan: Hasa.

607
00:26:06,540 --> 00:26:12,900
Chochote mimi, binadamu, aina katika, pembejeo yangu
ni kwenda kuokolewa katika eneo hilo.

608
00:26:12,900 --> 00:26:17,660
Ni si ya kutosha, kukumbuka, tu
kupita katika x, kwa sababu tumeona tayari,

609
00:26:17,660 --> 00:26:21,630
wakati wowote, unaweza kupita tu variable mbichi,
kama int, kwa baadhi ya kazi nyingine,

610
00:26:21,630 --> 00:26:25,640
uhakika, inaweza kubadilika kwamba
variable, lakini si moja kwa moja.

611
00:26:25,640 --> 00:26:27,360
Ni hawezi kuwa na athari juu ya Kuu.

612
00:26:27,360 --> 00:26:29,420
Ni inaweza tu mabadiliko nakala yake mwenyewe ndani.

613
00:26:29,420 --> 00:26:32,560
Lakini kama, badala yake, huna
nipe int halisi,

614
00:26:32,560 --> 00:26:36,640
lakini nipe maelekezo kwa
kwamba int, mimi sasa, kuwa scanf,

615
00:26:36,640 --> 00:26:41,050
Hakika, siwezi kufuata kwamba
kushughulikia na kuweka idadi huko

616
00:26:41,050 --> 00:26:43,280
hivyo kuwa na huduma hiyo kama vizuri.

617
00:26:43,280 --> 00:26:45,120
>> Hivyo wakati mimi kukimbia mpango huu, hebu angalia.

618
00:26:45,120 --> 00:26:49,660
Kufanya scanf 0 dot slash, scanf 0.

619
00:26:49,660 --> 00:26:54,030
Na kama mimi sasa aina ya simu
kama 50, shukrani kwa ajili ya 50.

620
00:26:54,030 --> 00:26:58,150
Kama mimi sasa aina ya simu kama
hasi 1, kwa hasi 1.

621
00:26:58,150 --> 00:27:04,200
Mimi sasa aina ya simu kama 1.5, hm.

622
00:27:04,200 --> 00:27:06,030
Kwa nini mpango wangu kupuuza mimi?

623
00:27:06,030 --> 00:27:07,300

624
00:27:07,300 --> 00:27:09,880
Naam, kwa sababu tu, mimi aliiambia
ni kwa kutarajia int tu.

625
00:27:09,880 --> 00:27:10,380
Wote haki.

626
00:27:10,380 --> 00:27:11,630
Hivyo hiyo ni toleo moja ya hili.

627
00:27:11,630 --> 00:27:16,600
Hebu kuchukua mambo up notch na
kupendekeza kwamba hii si nzuri.

628
00:27:16,600 --> 00:27:20,530
Na humu uongo mfano rahisi sana
jinsi gani tunaweza kuanza kuandika code

629
00:27:20,530 --> 00:27:24,450
kwamba watu wengine wanaweza kutumia au
maelewano kwa kufanya mambo mabaya.

630
00:27:24,450 --> 00:27:28,336
Hivyo mstari 16, hivyo sawa
katika roho kwa mbele,

631
00:27:28,336 --> 00:27:29,960
lakini mimi si kutangaza ni int wakati huu.

632
00:27:29,960 --> 00:27:32,970
Mimi nina kutangaza ni char nyota, aka kamba.

633
00:27:32,970 --> 00:27:35,190
>> Lakini ni nini kwamba kweli maana yake nini?

634
00:27:35,190 --> 00:27:38,790
Hivyo kama mimi si bayana address-- na
Mimi nina wito ni kiholela, buffer,

635
00:27:38,790 --> 00:27:43,370
lakini mimi naweza kuiita s, kuwa simple--
na kisha mimi kufanya hivyo, kueleza kwangu,

636
00:27:43,370 --> 00:27:48,630
kama unaweza, kwa kuzingatia uliopita
mantiki, ni nini scanf kufanya katika line 18,

637
00:27:48,630 --> 00:27:55,000
kama kupita% s na buffer,
ambayo ni anwani?

638
00:27:55,000 --> 00:27:58,210
Scanf ni kitu gani, kama wewe kuomba
halisi mantiki hiyo kama toleo 0,

639
00:27:58,210 --> 00:28:00,640
kwenda kujaribu kufanya hapa, wakati
aina ya mtumiaji kitu katika?

640
00:28:00,640 --> 00:28:02,630

641
00:28:02,630 --> 00:28:03,409
Yeah?

642
00:28:03,409 --> 00:28:04,407
>> Watazamaji: [inaudible].

643
00:28:04,407 --> 00:28:07,401

644
00:28:07,401 --> 00:28:08,890
>> DAVID J. Malan: Hasa.

645
00:28:08,890 --> 00:28:11,577
Scanf, kwa mantiki ya awali,
ni kwenda kuchukua kamba

646
00:28:11,577 --> 00:28:13,410
kwamba typed binadamu
in-- ni sasa kamba,

647
00:28:13,410 --> 00:28:15,790
si ya simu, labda,
kama yeye au yeye cooperates--

648
00:28:15,790 --> 00:28:19,310
na ni kwenda kujaribu kuweka kwamba
kamba katika kumbukumbu katika chochote anwani

649
00:28:19,310 --> 00:28:20,340
buffer bayana.

650
00:28:20,340 --> 00:28:23,870
Na hii ni kubwa, kwa sababu buffer
ni kweli maana ya kuwa ya mahali.

651
00:28:23,870 --> 00:28:30,470
>> Lakini mimi kudai mpango huu ni Buggy katika
njia kubwa sana, kwa sababu kile thamani ya kitu

652
00:28:30,470 --> 00:28:31,330
buffer na default?

653
00:28:31,330 --> 00:28:33,380

654
00:28:33,380 --> 00:28:34,790
Nini mimi initialized katika?

655
00:28:34,790 --> 00:28:35,770
Nini chunk ya kumbukumbu?

656
00:28:35,770 --> 00:28:37,480

657
00:28:37,480 --> 00:28:38,620
Mimi sina, haki?

658
00:28:38,620 --> 00:28:42,265
>> Hivyo ingawa nimekuwa zilizotengwa
nyota Char hiyo tena kuitwa s,

659
00:28:42,265 --> 00:28:48,030
ni badala kuitwa, buffer-- hivyo
hebu kuteka jina variable ya

660
00:28:48,030 --> 00:28:53,380
sasa kama buffer-- kama nina si
kuitwa GetString au malloc hapa,

661
00:28:53,380 --> 00:28:56,030
kwamba ufanisi ina maana kwamba
buffer ni baadhi tu ya thamani ya takataka.

662
00:28:56,030 --> 00:28:57,030
>> Sasa nini maana gani?

663
00:28:57,030 --> 00:29:00,220
Ina maana kwamba mimi aliiambia scanf
kutarajia kamba kutoka kwa mtumiaji.

664
00:29:00,220 --> 00:29:01,300
Na unajua nini?

665
00:29:01,300 --> 00:29:03,883
Kitu chochote hii ni akizungumzia
to-- na mimi kuteka alama swali,

666
00:29:03,883 --> 00:29:07,060
lakini katika hali halisi, ni kwenda kuwa
kitu kama OX1, 2, 3, haki?

667
00:29:07,060 --> 00:29:10,730
Ni baadhi ya thamani bogus kwamba tu
hutokea kwa kuwa kuna kutoka kabla.

668
00:29:10,730 --> 00:29:13,440
Hivyo kuweka njia nyingine, ni
kana kwamba buffer ni tu

669
00:29:13,440 --> 00:29:16,180
akizungumzia kitu katika kumbukumbu.

670
00:29:16,180 --> 00:29:17,610
Mimi sijui nini.

671
00:29:17,610 --> 00:29:24,130
>> Hivyo kama mimi aina katika Gabe sasa, ni kwenda
kujaribu kuweka g-b-e / 0 huko.

672
00:29:24,130 --> 00:29:25,530
Lakini ambaye anajua nini kwamba ni?

673
00:29:25,530 --> 00:29:27,480
Na katika siku za nyuma, yoyote
wakati tumekuwa alijaribu kugusa

674
00:29:27,480 --> 00:29:29,770
kumbukumbu kwamba hana mali
kwetu, nini kilichotokea?

675
00:29:29,770 --> 00:29:31,020

676
00:29:31,020 --> 00:29:32,870
Au karibu kila wakati.

677
00:29:32,870 --> 00:29:34,310
Mkato wa soko kosa, haki?

678
00:29:34,310 --> 00:29:37,829
>> Arrow hii, mimi hawana wazo ambapo ni
akizungumzia. ni baadhi tu thamani random.

679
00:29:37,829 --> 00:29:40,370
Na bila shaka, kama wewe kutafsiri
thamani random kama ya mitaani,

680
00:29:40,370 --> 00:29:42,610
wewe ni kwenda kwa
baadhi random marudio.

681
00:29:42,610 --> 00:29:46,810
Hivyo Gabe nguvu kweli ajali
mpango wangu katika kesi hii hapa.

682
00:29:46,810 --> 00:29:50,600
>> Hivyo tunaweza kufanya nini hiyo ni karibu kama mbaya?

683
00:29:50,600 --> 00:29:52,660
Fikiria hili tatu na
Mfano wa mwisho scanf.

684
00:29:52,660 --> 00:29:53,890

685
00:29:53,890 --> 00:29:56,870
Toleo hili ni bora katika maana gani?

686
00:29:56,870 --> 00:29:57,990

687
00:29:57,990 --> 00:30:01,400
Kama wewe ni starehe na
tatizo uliopita, hii ni bora.

688
00:30:01,400 --> 00:30:02,250
Kwa nini?

689
00:30:02,250 --> 00:30:03,250
>> Watazamaji: [inaudible].

690
00:30:03,250 --> 00:30:06,235

691
00:30:06,235 --> 00:30:07,110
DAVID J. Malan: Good.

692
00:30:07,110 --> 00:30:09,970
Hivyo kesi hii ya mstari 16
ni bora zaidi, kwa maana ya

693
00:30:09,970 --> 00:30:12,030
kwamba sisi ni wazi
kugawa baadhi ya kumbukumbu.

694
00:30:12,030 --> 00:30:14,190
Sisi siyo kutumia malloc,
sisi ni kutumia wiki 2

695
00:30:14,190 --> 00:30:16,060
mfumo wa tu kutangaza safu.

696
00:30:16,060 --> 00:30:18,130
Na tumekuwa alisema kuwa kabla ya kamba
ni tu safu ya wahusika,

697
00:30:18,130 --> 00:30:19,690
hivyo hii ni kinyume kabisa halali.

698
00:30:19,690 --> 00:30:22,910
Lakini ni, bila shaka, kama
wewe kumbuka, fasta ukubwa, 16.

699
00:30:22,910 --> 00:30:25,440
>> Hivyo mpango huu ni
salama kabisa, kama mimi aina

700
00:30:25,440 --> 00:30:29,760
katika masharti tabia ya moja, mbili tabia ya
masharti, 15 masharti tabia.

701
00:30:29,760 --> 00:30:34,970
Lakini kwa haraka kama mimi kuanza kuandika 16,
17, 18, 1000 tabia ya masharti,

702
00:30:34,970 --> 00:30:37,390
ambapo ni string kwamba kwenda kuishia?

703
00:30:37,390 --> 00:30:39,570
Ni kwenda kuishia sehemu hapa.

704
00:30:39,570 --> 00:30:42,820
Lakini basi ambaye anajua kile kingine
ni nje ya mipaka

705
00:30:42,820 --> 00:30:44,270
ya safu hii hasa?

706
00:30:44,270 --> 00:30:48,015
>> Ni kana kwamba nimekuwa
alitangaza 16 masanduku hapa.

707
00:30:48,015 --> 00:30:49,300

708
00:30:49,300 --> 00:30:52,690
Hivyo badala ya kuteka zote 16, tutaweza
tu kujifanya kuwa nimekuwa inayotolewa 16.

709
00:30:52,690 --> 00:30:56,540
Lakini kama mimi kisha kujaribu kusoma kamba
hiyo ni kwa muda mrefu, kama wahusika 50,

710
00:30:56,540 --> 00:31:01,270
Mimi nina kwenda kuanza kuweka
a, b, c, d, x, y, z.

711
00:31:01,270 --> 00:31:04,916
Na hii ni labda
baadhi ya wengine kumbukumbu sehemu

712
00:31:04,916 --> 00:31:06,790
tena kuwa, inaweza kusababisha
mpango wangu kwa ajali,

713
00:31:06,790 --> 00:31:10,600
kwa sababu nimekuwa si aliuliza kwa
chochote zaidi ya ka 16 tu.

714
00:31:10,600 --> 00:31:12,260
>> Hivyo ni nani anayejali?

715
00:31:12,260 --> 00:31:13,880
Naam, hapa maktaba CS50.

716
00:31:13,880 --> 00:31:17,220
Na zaidi ya hii ni tu
kama maelekezo juu juu.

717
00:31:17,220 --> 00:31:21,670
Maktaba CS50, muda wote huu,
imekuwa na mstari huu katika line 52.

718
00:31:21,670 --> 00:31:23,680
Tumeona typedef, au
utaona typedef

719
00:31:23,680 --> 00:31:27,930
katika pset 4, ambayo inajenga tu
kisawe ambapo char nyota inaweza kuwa zaidi

720
00:31:27,930 --> 00:31:29,290
tu inajulikana kama kamba.

721
00:31:29,290 --> 00:31:31,540
Hivyo hii ni moja ya
magurudumu mafunzo chache

722
00:31:31,540 --> 00:31:34,120
tumekuwa kutumika kwa siri chini ya kofia.

723
00:31:34,120 --> 00:31:36,490
>> Wakati huo huo, hapa ni kazi, getchar.

724
00:31:36,490 --> 00:31:38,190
Sasa inaonekana, hakuna mwili yake.

725
00:31:38,190 --> 00:31:40,273
Na kwa kweli, kama mimi kuweka
scrolling, mimi si kweli

726
00:31:40,273 --> 00:31:42,080
kuona utekelezaji yoyote
ya kazi hizi.

727
00:31:42,080 --> 00:31:43,140

728
00:31:43,140 --> 00:31:45,516
Kama sanity hundi, kwa nini ni kwamba?

729
00:31:45,516 --> 00:31:46,795
>> Watazamaji: [inaudible].

730
00:31:46,795 --> 00:31:47,670
DAVID J. Malan: Yeah.

731
00:31:47,670 --> 00:31:48,950
Hivyo hii ni header file.

732
00:31:48,950 --> 00:31:52,520
Na header files vyenye prototypes,
pamoja na baadhi ya mambo mengine, inaonekana,

733
00:31:52,520 --> 00:31:53,780
kama typedefs.

734
00:31:53,780 --> 00:31:56,910
Lakini katika CS50.c, ambayo tumekuwa
kamwe kupewa wewe moja kwa moja,

735
00:31:56,910 --> 00:32:02,100
lakini imekuwa katika CS50 appliance wote
wakati huu, ndani ya folders yake,

736
00:32:02,100 --> 00:32:04,990
taarifa kwamba kuna zima
rundo la kazi katika hapa.

737
00:32:04,990 --> 00:32:06,720
>> Kwa kweli, hebu kitabu chini.

738
00:32:06,720 --> 00:32:08,810
Hebu kupuuza wengi wao, kwa sasa.

739
00:32:08,810 --> 00:32:12,670
Lakini kitabu chini ya GetInt
na kuona jinsi GetInt kazi.

740
00:32:12,670 --> 00:32:13,890
Hivyo hapa ni GetInt.

741
00:32:13,890 --> 00:32:17,727
Na kama wewe milele kweli kumjali jinsi kupata
int kazi, hapa ni kuweka kumbukumbu yake.

742
00:32:17,727 --> 00:32:19,560
Na miongoni mwa mambo
anasema ni anakwambia

743
00:32:19,560 --> 00:32:21,340
nini ni kati ya maadili inaweza kurudi.

744
00:32:21,340 --> 00:32:24,400
Ni kimsingi hasi bilioni 2
chanya bilioni 2, kutoa au kuchukua.

745
00:32:24,400 --> 00:32:26,420
>> Na zinageuka, yote hii
wakati, ingawa tumekuwa kamwe

746
00:32:26,420 --> 00:32:28,570
alikuwa na wewe kuangalia kwa ajili yake,
kama kitu fulani kitaenda vibaya,

747
00:32:28,570 --> 00:32:30,680
zinageuka kuwa wote
wakati huu, GetInt ina

748
00:32:30,680 --> 00:32:33,600
anarudi maalum
mara kwa mara, si null,

749
00:32:33,600 --> 00:32:36,760
lakini badala int_max, ambayo ni
tu programu ya mkataba.

750
00:32:36,760 --> 00:32:38,846
Ina maana hapa ni thamani maalum.

751
00:32:38,846 --> 00:32:41,470
Kuhakikisha na kuangalia kwa hii, tu
katika kesi kitu kitaenda vibaya.

752
00:32:41,470 --> 00:32:43,261
Lakini tumekuwa kamwe bothered
na kwamba hadi sasa,

753
00:32:43,261 --> 00:32:45,200
kwa sababu tena, hii
ni maana ya kurahisisha.

754
00:32:45,200 --> 00:32:46,950
>> Lakini jinsi gani GetInt kupata kutekelezwa?

755
00:32:46,950 --> 00:32:48,450
Naam, moja, inachukua hakuna hoja.

756
00:32:48,450 --> 00:32:49,390
Tunajua kwamba.

757
00:32:49,390 --> 00:32:50,820
Ni anarudi int.

758
00:32:50,820 --> 00:32:51,950
Tunajua kwamba.

759
00:32:51,950 --> 00:32:54,460
Hivyo ni jinsi gani kazi chini ya Hood?

760
00:32:54,460 --> 00:32:58,290
>> Hivyo kuna inaonekana usio
kitanzi, angalau muonekano wa moja.

761
00:32:58,290 --> 00:33:00,290
Taarifa kwamba sisi ni kutumia GetString.

762
00:33:00,290 --> 00:33:04,000
Hivyo kwamba ni ya kuvutia. GetInt
wito kazi yetu wenyewe, GetString.

763
00:33:04,000 --> 00:33:05,645
Na sasa kwa nini huenda hii kuwa kesi?

764
00:33:05,645 --> 00:33:07,400

765
00:33:07,400 --> 00:33:09,842
Kwa nini mimi kuwa kujihami
hapa katika line 165?

766
00:33:09,842 --> 00:33:11,390

767
00:33:11,390 --> 00:33:15,639
Nini inaweza kutokea katika line
164, tu kuwa wazi?

768
00:33:15,639 --> 00:33:16,930
Ni jibu sawa mbele.

769
00:33:16,930 --> 00:33:18,660

770
00:33:18,660 --> 00:33:20,089
Ili tu kuwa nje ya kumbukumbu.

771
00:33:20,089 --> 00:33:23,130
Kitu fulani kitaenda vibaya na GetString,
sisi nimepata kuwa na uwezo wa kushughulikia hiyo.

772
00:33:23,130 --> 00:33:27,070
Na sababu mimi si kurudi null ni
kwamba, kitaalam, null ni pointer.

773
00:33:27,070 --> 00:33:29,120
GetInt ina kurudi int.

774
00:33:29,120 --> 00:33:31,060
Hivyo nimekuwa kiholela
aliamua, kimsingi,

775
00:33:31,060 --> 00:33:34,600
kwamba bilioni 2, kutoa au kuchukua, ni kwenda
kuwa thamani maalum kwamba naweza kamwe

776
00:33:34,600 --> 00:33:35,970
kweli kupata kutoka kwa mtumiaji.

777
00:33:35,970 --> 00:33:39,930
Ni tu thamani moja mimi nina kwenda
kupoteza kuwakilisha kosa code.

778
00:33:39,930 --> 00:33:41,540
>> Hivyo sasa, mambo kupata dhana kidogo.

779
00:33:41,540 --> 00:33:44,670
Na si kabisa kazi moja
kama kabla, lakini ni sawa sana.

780
00:33:44,670 --> 00:33:50,120
Hivyo taarifa, mimi kutangaza hapa, katika line
172, wote int n na char c.

781
00:33:50,120 --> 00:33:53,600
Na kisha mimi kutumia mstari huu funky,
sscanf, ambayo ni zamu nje

782
00:33:53,600 --> 00:33:55,990
haina Scan kamba kutoka keyboard.

783
00:33:55,990 --> 00:33:59,226
Ni anasimama kamba zilizopo ambazo
user tayari typed katika.

784
00:33:59,226 --> 00:34:02,100
Kwa hiyo mimi tayari kuitwa GetString, ambayo
ina maana nina kamba katika kumbukumbu.

785
00:34:02,100 --> 00:34:05,020
sscanf ni nini wewe d
wito parsing kazi.

786
00:34:05,020 --> 00:34:07,760
Inaonekana katika kamba nimekuwa
typed katika, tabia ya na tabia,

787
00:34:07,760 --> 00:34:09,250
na anafanya kitu muhimu.

788
00:34:09,250 --> 00:34:10,969
Kamba kwamba ni kuhifadhiwa katika mstari.

789
00:34:10,969 --> 00:34:13,560
Nami najua kuwa tu kwa kwenda
nyuma hadi hapa na kusema, oh, OK,

790
00:34:13,560 --> 00:34:15,143
Mimi kuitwa ni si s wakati huu, lakini line.

791
00:34:15,143 --> 00:34:15,989

792
00:34:15,989 --> 00:34:18,080
>> Na sasa hii ni tofauti kidogo.

793
00:34:18,080 --> 00:34:22,480
Lakini hii ina maana ufanisi, kwa sababu
tutaweza kiasi fulani wimbi mikono yetu katika leo,

794
00:34:22,480 --> 00:34:26,070
kwamba sisi ni kuangalia kwa
kuona kama user typed katika

795
00:34:26,070 --> 00:34:29,909
na int na labda tabia nyingine.

796
00:34:29,909 --> 00:34:33,610
Kama mtumiaji typed katika int, ni
kwenda kuhifadhiwa katika n, kwa sababu mimi nina

797
00:34:33,610 --> 00:34:36,739
kupita hili kwa mitaani,
hila mpya tumeona leo.

798
00:34:36,739 --> 00:34:41,570
Kama mtumiaji typed pia
katika kama 123x, kwamba x

799
00:34:41,570 --> 00:34:45,060
ni kwenda kuishia
barua katika tabia ya c.

800
00:34:45,060 --> 00:34:48,739
>> Sasa ni zamu nje kwamba sscanf
wataniambia, akili,

801
00:34:48,739 --> 00:34:54,750
jinsi vigezo vingi mara sscanf
mafanikio na uwezo wa kujaza.

802
00:34:54,750 --> 00:34:58,770
Hivyo kwa mantiki hii, kama kazi
Mimi nina kutekeleza ni GetInt,

803
00:34:58,770 --> 00:35:00,900
lakini mimi nina kuangalia,
uwezekano, kwa mtumiaji

804
00:35:00,900 --> 00:35:04,190
kwa kuwa typed katika int
ikifuatiwa na kitu kingine,

805
00:35:04,190 --> 00:35:08,580
nini nataka sscanf ya
thamani ya kurudi kweli kuwa?

806
00:35:08,580 --> 00:35:10,950
Kama lengo ni kupata
tu int kutoka kwa mtumiaji?

807
00:35:10,950 --> 00:35:13,980

808
00:35:13,980 --> 00:35:19,300
>> Hivyo kama anarudi sscanf
2, hiyo ina maana gani?

809
00:35:19,300 --> 00:35:21,660
user typed katika
kitu kama, literally,

810
00:35:21,660 --> 00:35:24,770
123x, ambayo ni nonsense tu.

811
00:35:24,770 --> 00:35:27,490
Ni hali makosa, na
Nataka kuangalia kwa ajili hiyo.

812
00:35:27,490 --> 00:35:32,960
>> Hivyo kama aina ya mtumiaji hii katika, na
mantiki hii, nini sscanf kurudi,

813
00:35:32,960 --> 00:35:33,740
unaweza kusema?

814
00:35:33,740 --> 00:35:35,070

815
00:35:35,070 --> 00:35:39,130
Hivyo ni kwenda na kurudi 2, kwa sababu
123 ni kwenda katika hapa,

816
00:35:39,130 --> 00:35:41,580
na x ni kwenda kuishia katika hapa.

817
00:35:41,580 --> 00:35:43,970
Lakini sitaki x kupata kujazwa.

818
00:35:43,970 --> 00:35:48,580
Nataka sscanf kwa tu kufanikiwa katika
kujaza kwanza ya vigezo wake.

819
00:35:48,580 --> 00:35:52,490
Na hivyo ndiyo sababu mimi
wanataka sscanf kurudi 1.

820
00:35:52,490 --> 00:35:55,750
>> Na kama hii ni kidogo juu ya kichwa
kwa wakati huu, hiyo ni kabisa faini.

821
00:35:55,750 --> 00:36:00,030
Kutambua kuwa, moja ya
maadili ya GetInt na GetString

822
00:36:00,030 --> 00:36:03,630
ni kwamba sisi ni kufanya heck ya
mengi ya makosa ya kuangalia kama hii ili

823
00:36:03,630 --> 00:36:07,130
kwamba, hadi sasa, unaweza pretty much
aina kitu chochote katika keyboard yako,

824
00:36:07,130 --> 00:36:08,490
na sisi kukamata yake.

825
00:36:08,490 --> 00:36:10,592
Na sisi hakika,
wafanyakazi, utakuwa dhahiri si

826
00:36:10,592 --> 00:36:13,300
kuwa chanzo cha mdudu katika yako
mpango, kwa sababu sisi ni kujitetea

827
00:36:13,300 --> 00:36:16,270
kuangalia kwa wote wa kijinga
mambo ambayo mtumiaji anaweza kufanya,

828
00:36:16,270 --> 00:36:18,900
kama kuandika kamba, wakati
kweli alitaka int.

829
00:36:18,900 --> 00:36:21,350
Hivyo kwa now-- tutaweza kuja
nyuma ya hii kabla ya long--

830
00:36:21,350 --> 00:36:23,710
lakini muda wote huu,
GetString na GetInt na

831
00:36:23,710 --> 00:36:29,950
imekuwa chini ya Hood kutumia hii
wazo msingi ya anwani ya kumbukumbu.

832
00:36:29,950 --> 00:36:32,580
>> Hivyo sasa, hebu kufanya mambo a
user-kirafiki kidogo zaidi.

833
00:36:32,580 --> 00:36:38,740
Kama unaweza kukumbuka, kutoka Binky mwisho
time-- kama panya yangu cooperate-- hivyo

834
00:36:38,740 --> 00:36:42,560
tulikuwa na kanuni hii, ambayo
kusema ukweli, ni haki nonsensical.

835
00:36:42,560 --> 00:36:45,330
Kanuni hii kinafikia chochote
muhimu, lakini ilikuwa ni mfano

836
00:36:45,330 --> 00:36:48,330
kwamba profesa Parlante
kutumika ili kuwakilisha

837
00:36:48,330 --> 00:36:51,840
nini kinachoendelea katika
mpango kuwashirikisha kumbukumbu.

838
00:36:51,840 --> 00:36:54,850
>> Basi hebu retell hii
hadithi super kwa ufupi.

839
00:36:54,850 --> 00:36:58,720
Hizi kwanza mistari miwili, katika
Kiingereza, kufanya nini, unaweza kusema?

840
00:36:58,720 --> 00:37:01,230

841
00:37:01,230 --> 00:37:05,430
Tu katika sababu za binadamu, lakini
kidogo suala kiufundi, kuchukua kumchoma.

842
00:37:05,430 --> 00:37:06,346
Watazamaji: [inaudible].

843
00:37:06,346 --> 00:37:07,705

844
00:37:07,705 --> 00:37:11,080
>> DAVID J. Malan: Sawa, wewe ni kuanzisha
anwani kwa x yako na y vigezo.

845
00:37:11,080 --> 00:37:15,520
Si kabisa, kwa sababu x na y ni si
vigezo katika maana ya asili.

846
00:37:15,520 --> 00:37:18,054
x na y ni anwani
au kuhifadhi mahali.

847
00:37:18,054 --> 00:37:19,220
Basi hebu jaribu hii mara moja zaidi.

848
00:37:19,220 --> 00:37:21,010
Si mwanzo mbaya, ingawa.

849
00:37:21,010 --> 00:37:21,510
Yeah?

850
00:37:21,510 --> 00:37:22,426
>> Watazamaji: [inaudible].

851
00:37:22,426 --> 00:37:23,966

852
00:37:23,966 --> 00:37:24,840
DAVID J. Malan: Good.

853
00:37:24,840 --> 00:37:26,173
Nadhani hiyo ni safi kidogo.

854
00:37:26,173 --> 00:37:28,630
Kutangaza kuyatumia mbili, integers mbili.

855
00:37:28,630 --> 00:37:30,150
Na sisi ni kuwaita x na y.

856
00:37:30,150 --> 00:37:32,790
Au kama tulikuwa na kuteka
hii kama picha, tena,

857
00:37:32,790 --> 00:37:36,410
kukumbuka kwa urahisi kabisa kwamba wote
sisi ni kufanya na kwamba mstari wa kwanza

858
00:37:36,410 --> 00:37:39,690
ni kuchora sanduku kama hii,
pamoja na baadhi ya thamani ya takataka ndani yake,

859
00:37:39,690 --> 00:37:41,920
na kuiita X, na kisha
sanduku mwingine kama huu,

860
00:37:41,920 --> 00:37:43,880
pamoja na baadhi ya thamani ya takataka
ndani yake, na kuiita y.

861
00:37:43,880 --> 00:37:45,810
Tumekuwa alitangaza mbili
kuyatumia kwamba hatimaye

862
00:37:45,810 --> 00:37:47,860
mapenzi kuhifadhi pepe ya int.

863
00:37:47,860 --> 00:37:49,170
Hivyo kwamba ni yote kuna.

864
00:37:49,170 --> 00:37:53,290
>> Hivyo wakati Binky alifanya hivyo,
udongo tu inaonekana kama hii.

865
00:37:53,290 --> 00:37:55,350
Na Nick aina tu ya
ilimalizika mishale,

866
00:37:55,350 --> 00:37:57,590
kana kwamba wao siyo akizungumzia popote
hasa, kwa sababu wao ni tu

867
00:37:57,590 --> 00:37:58,250
takataka maadili.

868
00:37:58,250 --> 00:38:01,670
Wao ni si wazi initialized
mahali popote hasa.

869
00:38:01,670 --> 00:38:03,980
>> Sasa line ya pili ya
code, kukumbuka, ilikuwa hii.

870
00:38:03,980 --> 00:38:07,510
Hivyo katika sababu user-kirafiki,
lakini kwa kiasi fulani ya kiufundi Kiingereza,

871
00:38:07,510 --> 00:38:09,790
ni mstari wa code kufanya nini?

872
00:38:09,790 --> 00:38:10,391
Yeah?

873
00:38:10,391 --> 00:38:11,333
>> Watazamaji: [inaudible].

874
00:38:11,333 --> 00:38:12,746

875
00:38:12,746 --> 00:38:13,950
>> DAVID J. Malan: Perfect.

876
00:38:13,950 --> 00:38:17,016
Ni kugawa chunk ya
kumbukumbu hiyo ni ya ukubwa wa int.

877
00:38:17,016 --> 00:38:18,140
Na kwamba ni jibu nusu.

878
00:38:18,140 --> 00:38:20,056
You akajibu haki
nusu wa kujieleza.

879
00:38:20,056 --> 00:38:22,473
Nini kinatokea kwenye
mkono wa kushoto upande wa ishara sawa?

880
00:38:22,473 --> 00:38:22,972
Yeah?

881
00:38:22,972 --> 00:38:24,814
Watazamaji: Na chukueni
ni kwa x variable?

882
00:38:24,814 --> 00:38:27,690
>> DAVID J. Malan: Na chukueni
ni kwa x kutofautiana.

883
00:38:27,690 --> 00:38:31,650
Hivyo kwa kurejea, mkono wa kulia upande kutenga
kumbukumbu ya kutosha kuhifadhi int.

884
00:38:31,650 --> 00:38:34,150
Lakini malloc hasa
anarudi anwani

885
00:38:34,150 --> 00:38:37,270
ya kwamba chunk ya kumbukumbu, ambayo wewe wameweza
tu mapendekezo anapata kuhifadhiwa katika x.

886
00:38:37,270 --> 00:38:42,560
>> Basi nini Nick alifanya mara ya mwisho kwa Binky ni
yeye dragged kwamba pointer nje, udongo,

887
00:38:42,560 --> 00:38:46,820
kwa uhakika sasa katika chunk ya kumbukumbu nyeupe
ambayo ni sawa na ukubwa wa int.

888
00:38:46,820 --> 00:38:49,360
Na hakika, hiyo ni maana
kuwakilisha ka nne.

889
00:38:49,360 --> 00:38:55,310
>> Sasa, line ya pili ya code
alifanya hivyo, nyota x anapata 42.

890
00:38:55,310 --> 00:38:58,530
Hivyo 42 ni moja kwa moja juu ya
mkono wa kulia upande, maana ya maisha.

891
00:38:58,530 --> 00:39:00,500
Upande mkono wa kushoto, nyota x nini maana ya?

892
00:39:00,500 --> 00:39:01,600

893
00:39:01,600 --> 00:39:03,280
Hiyo pia wanaweza kuwa na gone-- kwamba ni sawa.

894
00:39:03,280 --> 00:39:04,220
OK.

895
00:39:04,220 --> 00:39:06,875
>> Watazamaji: Kimsingi,
kwenda [inaudible]

896
00:39:06,875 --> 00:39:07,750
DAVID J. Malan: Good.

897
00:39:07,750 --> 00:39:08,760
Watazamaji: [inaudible].

898
00:39:08,760 --> 00:39:09,760
DAVID J. Malan: Hasa.

899
00:39:09,760 --> 00:39:11,979
Upande wa mkono wa kushoto ina maana kwenda x.

900
00:39:11,979 --> 00:39:12,520
x ni mahali.

901
00:39:12,520 --> 00:39:15,520
Ni kama 33 Oxford Street, au OX1.

902
00:39:15,520 --> 00:39:18,690
Na nyota x maana kwenda kuwa
kushughulikia na kuweka kile huko?

903
00:39:18,690 --> 00:39:19,520
42.

904
00:39:19,520 --> 00:39:21,290
>> Hivyo kweli, kwamba ni nini hasa Nick alivyofanya.

905
00:39:21,290 --> 00:39:23,740
Alianza na na,
kimsingi, kiakili

906
00:39:23,740 --> 00:39:26,270
kunyooshea kidole
x, kufuatia arrow

907
00:39:26,270 --> 00:39:30,670
kwa sanduku nyeupe juu ya mkono wa kulia
upande, na kuweka namba 42 hapo.

908
00:39:30,670 --> 00:39:34,120
Lakini basi mambo got
kidogo hatari, sawa?

909
00:39:34,120 --> 00:39:35,860
Binky ya juu ya kupoteza kichwa chake.

910
00:39:35,860 --> 00:39:39,465
>> Star y sawa na 13, bahati mbaya, maana yake nini?

911
00:39:39,465 --> 00:39:43,620
Hivyo nyota y njia kwenda mahali katika y.

912
00:39:43,620 --> 00:39:45,630
Lakini ni mahali katika y nini?

913
00:39:45,630 --> 00:39:47,899

914
00:39:47,899 --> 00:39:49,440
Zote haki, ni thamani ya takataka, haki?

915
00:39:49,440 --> 00:39:50,800
Mimi akauchomoa kama alama ya swali.

916
00:39:50,800 --> 00:39:54,850
Nick akauchomoa kama curled up mshale.

917
00:39:54,850 --> 00:39:59,600
Na kama hivi karibuni kama wewe kujaribu
kufanya nyota y, akisema kwenda huko,

918
00:39:59,600 --> 00:40:03,872
lakini kuna si halali
anwani, ni baadhi anuani ya bogus,

919
00:40:03,872 --> 00:40:05,080
mpango kinaendelea kwa ajali.

920
00:40:05,080 --> 00:40:08,580
Na kichwa Binky ni kwenda
kuruka mbali hapa, kama ilivyokuwa.

921
00:40:08,580 --> 00:40:12,130
>> Hivyo katika mwisho, mpango huu
mara tu gorofa ya nje flaw.

922
00:40:12,130 --> 00:40:13,540
Ilikuwa ni mpango buggy.

923
00:40:13,540 --> 00:40:14,760
Na zinahitajika kuwa fasta.

924
00:40:14,760 --> 00:40:18,260
Na njia pekee, kwa kweli, kurekebisha
itakuwa, kwa mfano, mstari huu,

925
00:40:18,260 --> 00:40:21,010
ambayo sisi hawakuwa hata kupata, kwa sababu
mpango wa kugonga mapema mno.

926
00:40:21,010 --> 00:40:26,170
Lakini kama sisi walikuwa na kurekebisha hili, nini
athari gani kufanya y x sawa na?

927
00:40:26,170 --> 00:40:30,010
Naam, ni kimsingi anasema y katika
chochote thamani x ni akizungumzia katika.

928
00:40:30,010 --> 00:40:32,430
>> Hivyo katika hadithi Nick ya,
au hadithi Binky ya, wote

929
00:40:32,430 --> 00:40:34,640
x na y walikuwa akionyesha
chunk nyeupe ya kumbukumbu,

930
00:40:34,640 --> 00:40:38,300
hivyo kwamba, hatimaye, wakati wewe
je nyota y sawa na 13 tena,

931
00:40:38,300 --> 00:40:43,080
wewe kuishia kuweka 13 katika
eneo sahihi.

932
00:40:43,080 --> 00:40:47,640
Basi wote wa mistari haya ni kikamilifu
halali, ila kwa ajili ya hii moja,

933
00:40:47,640 --> 00:40:51,730
wakati kilichotokea kabla ya
kweli kwa ajili y baadhi ya thamani.

934
00:40:51,730 --> 00:40:54,290
>> Sasa nashiriki, huna
lazima nizungumze kwa njia zote

935
00:40:54,290 --> 00:40:56,560
wa aina hii ya masuala juu yako mwenyewe.

936
00:40:56,560 --> 00:40:59,310
Hebu kwenda mbele na kufungua
up window terminal hapa

937
00:40:59,310 --> 00:41:03,050
na kufungua, kwa muda tu,
mpango super short kwamba

938
00:41:03,050 --> 00:41:04,360
pia ni aina ya pointless.

939
00:41:04,360 --> 00:41:05,152
Ni mbaya.

940
00:41:05,152 --> 00:41:06,610
Ni haina kufikia kitu chochote muhimu.

941
00:41:06,610 --> 00:41:10,180
Lakini haina kuonyesha masuala
ya kumbukumbu, hivyo hebu kuchukua kuangalia.

942
00:41:10,180 --> 00:41:11,830
>> Kuu, super rahisi.

943
00:41:11,830 --> 00:41:14,830
Ni inaonekana wito kazi,
f, na kisha anarudi 0.

944
00:41:14,830 --> 00:41:16,310
Ni aina ya ngumu kwa fujo hii up.

945
00:41:16,310 --> 00:41:18,540
Hivyo Kuu ni nzuri, hivyo mbali.

946
00:41:18,540 --> 00:41:20,100
>> Hivyo f ni tatizo.

947
00:41:20,100 --> 00:41:22,120
Na tu hakuwa na kuweka kiasi
juhudi katika kumtaja ni

948
00:41:22,120 --> 00:41:23,990
hapa, kuweka umakini juu ya kanuni.

949
00:41:23,990 --> 00:41:25,740
f ina mistari miwili.

950
00:41:25,740 --> 00:41:27,610
Na hebu angalia nini sasa kinachoendelea.

951
00:41:27,610 --> 00:41:29,840
Hivyo kwa upande mmoja
here-- na napenda kufanya

952
00:41:29,840 --> 00:41:32,680
hii inaendana na uliopita
example-- kwa upande mmoja,

953
00:41:32,680 --> 00:41:35,830
upande wa mkono wa kushoto ni
kufanya nini, kwa Kiingereza?

954
00:41:35,830 --> 00:41:36,493
Ni is--

955
00:41:36,493 --> 00:41:37,701
Watazamaji: Kujenga pointer.

956
00:41:37,701 --> 00:41:40,830
DAVID J. Malan: Kujenga pointer
kwa int na kuiita x.

957
00:41:40,830 --> 00:41:43,789
Hivyo ni kujenga moja ya masanduku wale
Mimi kuendelea kuchora juu ya screen ya kugusa.

958
00:41:43,789 --> 00:41:45,913
Na sasa, juu ya mkono wa kulia
upande, malloc, bila shaka,

959
00:41:45,913 --> 00:41:47,420
ni kugawa chunk ya kumbukumbu.

960
00:41:47,420 --> 00:41:49,989
Na tu kuwa wazi, jinsi
kumbukumbu kiasi gani ni inaonekana

961
00:41:49,989 --> 00:41:52,030
kugawa, kama wewe tu
aina ya kufanya hesabu hapa?

962
00:41:52,030 --> 00:41:53,200

963
00:41:53,200 --> 00:41:54,040
>> Hivyo ni 40 ka.

964
00:41:54,040 --> 00:41:57,400
Nami najua kuwa tu kwa sababu mimi najua
int, juu ya CS50 appliance, angalau,

965
00:41:57,400 --> 00:41:58,060
ni ka nne.

966
00:41:58,060 --> 00:41:59,610
Hivyo mara 10 4 ni 40.

967
00:41:59,610 --> 00:42:04,924
Hivyo hii ni hifadhi ya x, anwani
ya nje ya kwanza ya 40 ints kwamba

968
00:42:04,924 --> 00:42:07,340
zimetengwa nafasi nyuma,
kwa nyuma, kwa nyuma, kwa nyuma.

969
00:42:07,340 --> 00:42:08,470
>> Na kwamba ni nini muhimu kuhusu malloc.

970
00:42:08,470 --> 00:42:11,261
Haina kuchukua kumbukumbu kidogo
hapa, kidogo hapa, kidogo hapa.

971
00:42:11,261 --> 00:42:14,220
Ni anakupa chunk moja ya kumbukumbu,
contiguously, kutoka uendeshaji

972
00:42:14,220 --> 00:42:15,240
mfumo.

973
00:42:15,240 --> 00:42:18,500
>> Sasa nini kuhusu hili,
x bracket 10 sawa na 0?

974
00:42:18,500 --> 00:42:19,470
Holela mstari wa kanuni.

975
00:42:19,470 --> 00:42:21,100
Ni haina kufikia kitu chochote muhimu.

976
00:42:21,100 --> 00:42:26,128
Lakini ni ya kuvutia,
kwa sababu x bracket 10--?

977
00:42:26,128 --> 00:42:26,628
Yeah?

978
00:42:26,628 --> 00:42:27,912
>> Watazamaji: [inaudible]?

979
00:42:27,912 --> 00:42:30,500
>> DAVID J. Malan: x bracket
10 haina kuwa null.

980
00:42:30,500 --> 00:42:35,070
null undani tu anakuja katika kucheza
na masharti, mwishoni mwa kamba.

981
00:42:35,070 --> 00:42:36,700
Lakini wazo nzuri.

982
00:42:36,700 --> 00:42:39,615
>> Jinsi kubwa ni safu hii, hata
ingawa nimekuwa zilizotengwa 40 ka?

983
00:42:39,615 --> 00:42:42,560

984
00:42:42,560 --> 00:42:43,690
Ni kwa njia ya tisa 0, haki?

985
00:42:43,690 --> 00:42:45,120
Ni 10 ints, jumla.

986
00:42:45,120 --> 00:42:48,790
40 ka, lakini 10 ints,
indexed 0 kupitia 0.

987
00:42:48,790 --> 00:42:50,930
>> Hivyo ni kwamba x bracket 10 nini?

988
00:42:50,930 --> 00:42:53,090
Ni kweli baadhi
jamii haijulikani thamani ya takataka.

989
00:42:53,090 --> 00:42:54,780
Ni kumbukumbu hiyo haina mali yangu.

990
00:42:54,780 --> 00:42:59,650
Mimi haipaswi kugusa kwamba
Byte idadi 41, 42, 43, 44.

991
00:42:59,650 --> 00:43:01,420
Mimi nina kwenda kidogo mbali sana.

992
00:43:01,420 --> 00:43:04,490
>> Na hakika, kama mimi kukimbia hii
mpango, ili vizuri sana ajali.

993
00:43:04,490 --> 00:43:05,790
Lakini wakati mwingine, tutaweza kupata bahati.

994
00:43:05,790 --> 00:43:07,706
Na hivyo tu kuonyesha
Haya na kusema ukweli,

995
00:43:07,706 --> 00:43:11,000
huwezi kujua kabla ya
je it-- hebu kukimbia hii.

996
00:43:11,000 --> 00:43:12,480
Haikuwa kweli ajali.

997
00:43:12,480 --> 00:43:15,032
>> Lakini kama mimi kubadili hali hii, kwa
mfano, kuwa kama 1,000,

998
00:43:15,032 --> 00:43:16,740
kufanya kweli hii
makusudi, hebu angalia

999
00:43:16,740 --> 00:43:18,710
kama tunaweza kupata ajali wakati huu.

1000
00:43:18,710 --> 00:43:20,070
OK, haikuwa ajali.

1001
00:43:20,070 --> 00:43:22,600
Vipi kuhusu 100,000?

1002
00:43:22,600 --> 00:43:25,000
Hebu remake yake, na sasa rerun yake.

1003
00:43:25,000 --> 00:43:25,500
OK.

1004
00:43:25,500 --> 00:43:25,960
Phew.

1005
00:43:25,960 --> 00:43:26,460
Wote haki.

1006
00:43:26,460 --> 00:43:29,090
Hivyo inaonekana, tena, hizi
makundi ya kumbukumbu, hivyo kusema,

1007
00:43:29,090 --> 00:43:32,660
ni sababu kubwa, hivyo tunaweza
kupata bahati tena na tena.

1008
00:43:32,660 --> 00:43:36,510
Lakini hatimaye, mara moja kupata ridiculous
na kwa kweli kwenda mbali nje ya screen,

1009
00:43:36,510 --> 00:43:39,120
wewe kugusa kumbukumbu kwamba kwa kweli,
kweli haina ni yako.

1010
00:43:39,120 --> 00:43:40,870
>> Lakini kusema ukweli, hizi
aina ya mende ni kwenda

1011
00:43:40,870 --> 00:43:43,020
kuwa vigumu na vigumu
kufikiri juu yako mwenyewe.

1012
00:43:43,020 --> 00:43:47,880
Lakini nashiriki, kama programmers, tuna
zana kwamba kuruhusu sisi kufanya hili kwa ajili yetu.

1013
00:43:47,880 --> 00:43:50,140
Hivyo hii ni, pengine, moja
wa mipango ya ugliest,

1014
00:43:50,140 --> 00:43:52,060
hata uglier ya pato GDB ya.

1015
00:43:52,060 --> 00:43:55,670
Lakini daima ina line au
mbili ambazo ni super muhimu.

1016
00:43:55,670 --> 00:44:00,310
>> Valgrind ni programu ambayo husaidia
wewe si Debug mpango, per se,

1017
00:44:00,310 --> 00:44:03,500
lakini kupata kumbukumbu-kuhusiana
matatizo, hasa.

1018
00:44:03,500 --> 00:44:07,590
Itakuwa moja kwa moja kukimbia code yako kwa
wewe na kuangalia kwa mambo mawili.

1019
00:44:07,590 --> 00:44:10,680
Moja, je, kufanya kitu
ajali kama kugusa kumbukumbu

1020
00:44:10,680 --> 00:44:11,980
kwamba hakuwa na mali yenu?

1021
00:44:11,980 --> 00:44:13,590
Ni itakusaidia kupata kesi hizo.

1022
00:44:13,590 --> 00:44:15,710
>> Na mbili, itasaidia
kupata kitu kinachoitwa

1023
00:44:15,710 --> 00:44:19,270
uvujaji kumbukumbu, ambayo tuna
kupuuzwa kabisa, naively,

1024
00:44:19,270 --> 00:44:21,380
kwa baadhi ya wakati na blissfully.

1025
00:44:21,380 --> 00:44:23,140
Lakini zinageuka, kila
wakati huu, wakati wowote

1026
00:44:23,140 --> 00:44:26,620
umetumia GetString katika
hivyo, wengi wa mipango yetu,

1027
00:44:26,620 --> 00:44:28,930
wewe ni kuuliza uendeshaji
mfumo kwa kumbukumbu,

1028
00:44:28,930 --> 00:44:32,070
lakini una kumbukumbu yoyote
ya milele kutoa ni

1029
00:44:32,070 --> 00:44:36,169
nyuma, kufanya unalloc, au
bure, kama ni kuitwa.

1030
00:44:36,169 --> 00:44:37,960
Hapana, kwa sababu tumekuwa kamwe
aliuliza wewe kufanya hivyo.

1031
00:44:37,960 --> 00:44:41,250
>> Lakini muda wote huu, mipango
tumekuwa kuandika katika C

1032
00:44:41,250 --> 00:44:43,800
wamekuwa kinachovuja kumbukumbu,
kuuliza uendeshaji

1033
00:44:43,800 --> 00:44:46,190
mfumo kwa zaidi na zaidi
kumbukumbu kwa masharti na whatnot,

1034
00:44:46,190 --> 00:44:47,870
lakini kamwe kuikabidhi nyuma.

1035
00:44:47,870 --> 00:44:50,080
Na sasa hii ni kidogo
ya kurahisisha,

1036
00:44:50,080 --> 00:44:53,550
lakini kama wameweza milele kukimbia Mac yako au
PC yako kwa muda kabisa, ufunguzi

1037
00:44:53,550 --> 00:44:55,790
kura ya mipango,
labda kufunga programu,

1038
00:44:55,790 --> 00:44:57,795
na hata kama wako
kompyuta hana kugonga,

1039
00:44:57,795 --> 00:45:01,690
ni kupata hivyo polepole sana,
kana kwamba ni kweli

1040
00:45:01,690 --> 00:45:04,290
kutumia mengi ya kumbukumbu au
rasilimali, ingawa,

1041
00:45:04,290 --> 00:45:06,070
kama wewe si hata
kugusa keyboard,

1042
00:45:06,070 --> 00:45:10,430
ambayo inaweza be-- lakini si always-- inaweza
kuwa mipango wewe ni mbio

1043
00:45:10,430 --> 00:45:11,920
kuwa wao wenyewe na uvujaji kumbukumbu.

1044
00:45:11,920 --> 00:45:15,645
Na wao kuendelea kuuliza OS kwa zaidi na
zaidi ya kumbukumbu, lakini kusahau kuhusu hilo,

1045
00:45:15,645 --> 00:45:18,470
si kweli kutumia, lakini
kwa hiyo kuchukua kumbukumbu mbali

1046
00:45:18,470 --> 00:45:20,500
na programu nyingine ambao wanaweza kutaka yake.

1047
00:45:20,500 --> 00:45:23,940
Hivyo hiyo ni maelezo ya kawaida.

1048
00:45:23,940 --> 00:45:25,940
Sasa hapa ni ambapo Valgrind ya
pato ni kabisa

1049
00:45:25,940 --> 00:45:29,290
mauaji kwa wale chini
na vizuri zaidi sawa.

1050
00:45:29,290 --> 00:45:32,690
Lakini ya kuvutia
mambo ni haki hapa.

1051
00:45:32,690 --> 00:45:37,060
Ni ananiambia kuandika batili ya
ukubwa nne kinachotokea katika mpango huu,

1052
00:45:37,060 --> 00:45:40,640
hasa, katika mstari wa 21 ya memory.c.

1053
00:45:40,640 --> 00:45:45,450
>> Kama mimi kwenda kwa mstari 21, hm, kuna kweli
ni kuandika batili ya ukubwa nne.

1054
00:45:45,450 --> 00:45:46,250
Kwa nini ukubwa nne?

1055
00:45:46,250 --> 00:45:49,500
Naam, hii number-- na
inaweza kuwa anything-- ni int.

1056
00:45:49,500 --> 00:45:50,450
Hivyo ni ka nne.

1057
00:45:50,450 --> 00:45:52,550
Hivyo mimi nina kuweka ka nne
ambapo wao si.

1058
00:45:52,550 --> 00:45:55,080
Hiyo ni nini Valgrind
ni kweli kuniambia.

1059
00:45:55,080 --> 00:45:57,600
Aidha, itakuwa pia
kuniambia, kama tutaweza kuona,

1060
00:45:57,600 --> 00:46:01,490
kama wewe kukimbia hii katika pset siku zijazo, kama na
wakati ve kuvuja kumbukumbu, ambayo kwa hakika

1061
00:46:01,490 --> 00:46:05,300
Mimi, kwa sababu nimekuwa inayoitwa
malloc, lakini nina si kweli

1062
00:46:05,300 --> 00:46:08,010
kuitwa, katika kesi hii, huru,
ambayo tutaweza hatimaye kuona

1063
00:46:08,010 --> 00:46:09,830
ni kinyume cha malloc.

1064
00:46:09,830 --> 00:46:10,860

1065
00:46:10,860 --> 00:46:12,930
>> Hivyo sasa, nadhani, Mfano wa mwisho.

1066
00:46:12,930 --> 00:46:14,050

1067
00:46:14,050 --> 00:46:16,690
Hivyo hii moja kidogo zaidi
arcane, lakini ni labda

1068
00:46:16,690 --> 00:46:19,180
sababu kubwa kwa
kuwa makini na kumbukumbu,

1069
00:46:19,180 --> 00:46:24,490
na mipango ya sababu kwamba wengi
na / au servrar mtandao, hata siku hii ya leo,

1070
00:46:24,490 --> 00:46:28,200
ni yamechukuliwa na wabaya mahali fulani
kwenye mtandao ambao ni kwa namna fulani

1071
00:46:28,200 --> 00:46:33,390
kutuma packets bogus kwa server yako
kujaribu maelewano akaunti yako,

1072
00:46:33,390 --> 00:46:36,420
au kuchukua data yako, au tu
kwa ujumla kuchukua juu ya mashine.

1073
00:46:36,420 --> 00:46:38,910
Buffer kufurika, kama
jina la kupendekeza, njia

1074
00:46:38,910 --> 00:46:40,740
wingi si int, lakini buffer.

1075
00:46:40,740 --> 00:46:43,490
Na buffer ni njia tu dhana
ya kusema ni rundo la kumbukumbu.

1076
00:46:43,490 --> 00:46:46,710
>> Na hakika, mimi kuitwa kamba
kabla ya buffer, badala ya s.

1077
00:46:46,710 --> 00:46:49,234
Kwa sababu kama ni buffer,
kama katika akili YouTube,

1078
00:46:49,234 --> 00:46:52,400
au wakati wowote wewe ni kuangalia video,
unaweza kuwa na kuonekana neno buffering,

1079
00:46:52,400 --> 00:46:53,040
dot, dot, dot.

1080
00:46:53,040 --> 00:46:54,240
Ni incredibly annoying.

1081
00:46:54,240 --> 00:46:55,990
Na kwamba tu ina maana
kuwa mchezaji video yako

1082
00:46:55,990 --> 00:46:58,710
ni kujaribu kushusha kura
ya ka, kura ya ka

1083
00:46:58,710 --> 00:47:00,170
kutoka video kutoka katika mtandao.

1084
00:47:00,170 --> 00:47:02,920
Lakini ni polepole, hivyo ni kujaribu
download rundo la yao

1085
00:47:02,920 --> 00:47:06,430
kujaza buffer, chombo, ili
una ka kutosha kwamba unaweza kisha

1086
00:47:06,430 --> 00:47:09,174
kuonyesha video,
bila pausing mara kwa mara.

1087
00:47:09,174 --> 00:47:11,340
Lakini zinageuka, unaweza
na buffer kwa hii kubwa.

1088
00:47:11,340 --> 00:47:15,710
Lakini kujaribu kuweka hii data sana katika
yake, na sana mambo mabaya yanaweza kutokea.

1089
00:47:15,710 --> 00:47:22,780
Hivyo kwa mfano, hebu tuangalie
teaser hii ya mwisho ya mfano.

1090
00:47:22,780 --> 00:47:24,720
Hii ni mpango mwingine
kwamba, katika mtazamo wa kwanza,

1091
00:47:24,720 --> 00:47:26,540
haina kufanya kitu chochote super muhimu.

1092
00:47:26,540 --> 00:47:29,590
Ni got Kuu ya kazi
kwamba wito kazi hiyo, f.

1093
00:47:29,590 --> 00:47:36,640
Na kazi hiyo, f, hapa juu, ina
char safu, iitwayo c, ukubwa 12.

1094
00:47:36,640 --> 00:47:39,340
Na kisha ni kwa kutumia hii
kazi mpya iitwayo strncpy.

1095
00:47:39,340 --> 00:47:40,430

1096
00:47:40,430 --> 00:47:45,190
>> Ni zinageuka kuwa, pamoja na hii rahisi,
rahisi mstari wa kanuni, mistari miwili tu,

1097
00:47:45,190 --> 00:47:49,130
tumefanya mpango wangu nzima,
na kwa hiyo, kompyuta yangu yote,

1098
00:47:49,130 --> 00:47:54,000
na user akaunti yangu, na ngumu wangu
gari uwezekano wa mazingira magumu kwa mtu yeyote

1099
00:47:54,000 --> 00:47:58,170
ambaye anajua na ni nzuri ya kutosha ya kuendesha
mpango huu na baadhi ya mstari amri

1100
00:47:58,170 --> 00:47:58,900
hoja.

1101
00:47:58,900 --> 00:48:03,400
Kwa maneno mengine, kama hii guy mbaya
unaweka ndani ya argvargv [1] na kuandika

1102
00:48:03,400 --> 00:48:08,750
katika keyboard hasa crafted sana
kamba, si abc, 123, lakini kimsingi,

1103
00:48:08,750 --> 00:48:15,180
alama binary kwamba kuwakilisha executable
code, mpango kwamba yeye au yeye aliandika,

1104
00:48:15,180 --> 00:48:19,190
na mpango huu rahisi, ambayo ni
mwakilishi wa maelfu ya programu

1105
00:48:19,190 --> 00:48:23,610
kwamba ni vile vile katika mazingira magumu, daresay,
yeye au yeye inaweza hatimaye kufuta yote

1106
00:48:23,610 --> 00:48:26,680
files kwenye gari yangu ngumu, kupata
blinking haraka hivyo kwamba yeye au yeye anaweza

1107
00:48:26,680 --> 00:48:30,170
aina amri juu yao wenyewe,
email files kila mmoja kwangu.

1108
00:48:30,170 --> 00:48:34,660
Kitu chochote ambacho siwezi kufanya, yeye
au anaweza kufanya na kanuni hii.

1109
00:48:34,660 --> 00:48:36,575
>> Sisi si kabisa kutatua hii bado.

1110
00:48:36,575 --> 00:48:38,700
Na kwa kweli, ni kwenda kwa
kuhusisha picha kidogo

1111
00:48:38,700 --> 00:48:41,470
kama hii, ambayo tutaweza karibuni kuja
kuelewa wote bora.

1112
00:48:41,470 --> 00:48:44,480
Lakini kwa leo, hebu mwisho juu ya
nini, hopefully, kidogo zaidi

1113
00:48:44,480 --> 00:48:48,360
kueleweka XKCD utani,
mpaka sisi kuendelea mara ya pili.

1114
00:48:48,360 --> 00:48:51,100

1115
00:48:51,100 --> 00:48:51,600
Wote haki.

1116
00:48:51,600 --> 00:48:53,446
Angalia wewe juu ya Jumatano.

1117
00:48:53,446 --> 00:48:54,754
>> [MUSIC KUCHEZA]

1118
00:48:54,754 --> 00:48:57,790
>> SPIKA: Na sasa, kina
mawazo, na Daven Farnham.

1119
00:48:57,790 --> 00:49:00,890

1120
00:49:00,890 --> 00:49:04,770
Kumbukumbu ni kama kuruka ndani ya rundo la
majani ya dhahabu juu ya Jumapili alasiri.

1121
00:49:04,770 --> 00:49:09,000
Upepo unavuma, tossing yako
hair-- oh, I miss siku when--

1122
00:49:09,000 --> 00:49:11,100

1123
00:49:11,100 --> 00:49:12,650
>> [Kicheko]

1124
00:49:12,650 --> 00:49:13,750