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[Powered by Google Translate] [Wiki 4, Inaendelea]

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[David J. Malan - Chuo Kikuu cha Harvard]

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[Hii ni CS50. - CS50.TV]

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>> Hii ni CS50, na hii ni mwisho wa wiki 4.

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Hivyo baadhi ya habari njema na baadhi ya habari mbaya.

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Hakuna hotuba ya Jumatatu, hakuna tatizo kuweka wiki ijayo. [Wanafunzi cheering]

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Wewe si kwenda kama ambapo hii ni kwenda.

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Lakini hatuwezi kuwa na hii badala Jumatano ijayo,

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na pia kuna kila hotuba mtaala 1 Ijumaa ijayo Ijumaa ili tuweze kukaa njiani.

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Lakini kila kitu itakuwa zingine kama kawaida, hivyo usiwe na wasiwasi.

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>> Na kuhusiana na Quiz 0 nini tutaweza kufanya kuelekea mwisho wa wiki

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ni baada ya juu cs50.net homepage kozi ya maelezo

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ya aina gani ya matarajio unapaswa kuwa linapokuja quiz ya kwanza.

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Kwa ujumla, itakuwa nyingi uchaguzi, kweli-uongo, short jibu, short matatizo coding.

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Wewe hutaenda kutarajiwa kutekeleza sawa

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ya tatizo kwamba ungependa kuona kwenye pset, ambayo una kompyuta

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na debugger na kama, lakini kutakuwa na ndogo coding matatizo.

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>> Na hakika, kiongozi bora ya kupata hisia ya kile CS50 Quizzes ni kama

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ni kwenda cs50.net, kwenda kiungo Quizzes,

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na unaweza kuona nyuma ya miaka kadhaa yenye thamani ya Quizzes.

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Tu kutambua kwamba mitaala imekuwa daima imekuwa si sawa zaidi ya miaka.

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Wakati mwingine sisi kuongeza, wakati mwingine Ondoa,

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hivyo kama unaweza kuona baadhi ya mada juu ya moja ya wale kale Quizzes

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kwamba hawana wazo nini ni kuzungumza juu, ni aidha kwamba hatukuwa kuifunika

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au kwamba hatukuwa kuifunika.

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Lakini kwa namna ya kitaalam, hii Jumapili, Jumatatu, Jumanne na

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kama vile kozi nzima mapitio kikao siku ya Jumapili usiku -

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muda na mahali kwa kuwa alitangaza juu ya homepage ya shaka -

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wewe wote kuwa na fursa ya kupitia upya na wenzake kozi ya mafundisho

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vifaa kwa ajili ya mwaka huu, katika sehemu na kama darasa kamili,

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na wale itakuwa zingine kama kawaida vilevile.

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>> Wote haki. Hivyo bila wasiwasi zaidi, moja ya maoni juu ya kupita / kushindwa na kuongeza / tone.

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Unaweza tumeona maelezo yangu jana usiku, na hii ni kweli baadhi tu ya ziada reassurance

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kwamba kama wewe ni miongoni mwa wale hasa chini ya starehe au mahali fulani katika kati ya

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na wewe ni hisia tu kidogo katika juu ya kichwa yako,

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kutambua kwamba ni kweli kabisa ya kawaida, na kuna kutosha msaada muundo katika mahali,

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moja ambayo masaa ya ofisi walikuwa dhamira ya kuboresha zaidi wote kwa usiku barua pepe yangu ya mwisho,

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na kutambua pia kwamba chaguo kama kupita / kushindwa kwa darasa kama hili

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kweli ni maana kama utaratibu wa kuchukua makali mbali bila shaka kama hii,

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ili tena kama wewe ni matumizi ya wale 10, 15, masaa 20

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tu kujaribu kupata baadhi pset kufanya kazi na wewe kujua wewe ni 90-95% ya njia pale

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lakini huwezi kupata baadhi mdudu damn, katika kupita / kushindwa mfano kwamba ni aina ya sawa.

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>> Wazo ni kwamba, kwa utaratibu kwamba unaweza kisha kwenda kuzingatia psets yako mengine

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au kulala au chochote ni kwamba unataka kuzingatia.

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Hivyo kutambua kwamba una mpaka Jumanne hii kuja - kitaalam Jumatatu 5,

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lakini ni likizo, hivyo hii Jumanne ijayo - kubadili kutoka kupita / kushindwa kinyume graded au kinyume chake.

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Na kama wewe ni kweli juu ya poromoko na ni mawazo ya kuacha kabisa,

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tafadhali catch me baada ya hotuba au kuacha mimi kumbuka.

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Tunatarajia upendo na mazungumzo angalau kabla nikawaage.

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Wote haki. Hivyo sisi kuanza kuchukua magurudumu mafunzo mbali wakati wa mwisho.

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Hasa, sisi ililenga katika kamba.

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Kamba ni kitu ambacho alisema katika maktaba CS50,

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hasa katika kuwa faili inayoitwa cs50.h ambayo tutaweza kuanza kuangalia wiki hii na ijayo.

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Lakini string ni kweli tu kurahisisha kitu

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hiyo kidogo zaidi arcanely kama ilivyoelezwa * Char.

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Char tuko familiar with. Ni tu tabia moja.

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Lakini * kama ya Jumatatu ulionyehsa nini? >> [Mwanafunzi] pointer.

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pointer. Na nini pointer? >> [Mwanafunzi] anuani.

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>> Ni kama anuani, mahali katika kumbukumbu.

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Nini anwani au mahali au kumbukumbu?

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Tena, sisi sote tuna Laptops na GIG au gigabytes 2 ya RAM zaidi uwezekano siku hizi,

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na hiyo ina maana una ka bilioni au bilioni 2 thamani ya kumbukumbu.

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Na ni kweli haina jambo gani kimwili inaonekana kama,

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lakini kuchukua imani kwamba unaweza kuzihesabu yote ya ka mtu kuwa mbali yako mwenyewe ana -

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hii ni Byte 0, hii ni Byte 1, hii ni Byte bilioni 2 -

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na kwamba ni nini hasa kompyuta gani.

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Wakati wewe kutenga nafasi kwa ajili ya tabia moja, kwa mfano,

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ni wazi ana kuishi mahali fulani katika kumbukumbu ya kompyuta yako,

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na labda ni katika idadi Byte 12,345,

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na kwamba ni mahali fulani hapa juu katika kumbukumbu ya kompyuta yako.

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Na anuani ya basi ya tabia ya kuwa ni 12,345.

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>> Sasa, katika wiki 0 kupitia sasa hivi sasa, sisi si kweli kumjali

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ambapo katika mambo kumbukumbu ni kuhifadhiwa kwa sababu sisi kawaida kutumia ishara,

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vigezo, na arrays kwa kweli kupata katika takwimu zetu.

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Lakini kama ya Jumatatu na zaidi wote leo, wewe sasa kwenda na

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uwezo wote zaidi expressive na mipango kuandika

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kwa kweli kuendesha kumbukumbu ya kompyuta hata hivyo unaweza kuona inafaa,

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kwa wote madhumuni mazuri na mabaya,

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Bugs kuwa matokeo ya kawaida sana katika hatua hii ya kujifunza mambo haya.

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Lakini ni nini kweli maana ya kuwa * Char?

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Hebu kwenda mbele nyuma - na tutaweza kurudi Binky kama alivyoahidi leo.

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Hebu kwenda mfano rahisi hapa.

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Hebu kuokoa faili hii kama compare.c, na napenda tu kupata baadhi ya kanuni template hapa

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hivyo ni pamoja na stdio.h, napenda pia kutoa mwenyewe ni pamoja cs50.h. Mimi itabidi zoom katika huko.

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Napenda kuanza kuandika int kuu, kuu (utupu), na sasa nataka kufanya kitu kama hii:

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printf ("Nipe string:") na kisha nitatumia string s anapata GetString

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kupata kamba kutoka kwa mtumiaji, basi mimi naenda kuuliza mtumiaji kwa ajili ya mtu mwingine.

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("Nipe mwingine string:") na mimi nina kwenda kuuliza yao kupitia GetString kupata hiyo.

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Mimi nitakuita ni t sababu t inakuja baada ya s na s ni jina nzuri kwa kamba kama ni pretty generic.

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Hivyo GetString, na sasa mimi nataka tu kufanya kuangalia sanity na mimi nina kwenda kusema

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kama (s == t) basi Mimi tu kwenda kuwaambia mtumiaji printf ("Wewe typed kitu kimoja \ n!");

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mwingine nitakacho magazeti nje kitu kama ("Wewe typed kitu tofauti \! n")

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au chochote hukumu itakuwa. Hivyo kitu kama hicho.

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Kisha kama kawaida, mimi itabidi kurudi 0 ambayo tu akabashiri kwamba hakuna kitu kibaya kilichotokea,

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na mimi nina kwenda mbele na kukusanya na kukimbia mpango huu.

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>> Lakini Jumatatu sisi mbio katika mpango huu,

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na kweli waliambiwa kwamba HELLO si HELLO na kwaheri si kwaheri.

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tabia tuliona ilikuwa ni kidogo zaidi kama hii.

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Hebu kwenda katika chanzo saraka yangu, zoom katika hapa, na hebu kufanya kufanya kulinganisha.

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Imekusanywa sawa. Hebu kukimbia kulinganisha. Nipe string: HELLO.

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Nipe mwingine string: HELLO.

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Uliyoandika kitu tofauti!

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Vizuri, basi mimi kujaribu kitu rahisi kama 50, 50. Uliyoandika kitu tofauti!

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hi, hi. Hivyo ni wazi, kuna kitu kinachoendelea hapa.

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Lakini kile ambacho kilikuwa maelezo kwa nini?

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Inavyoonekana, mstari 12 ni kabisa dysfunctional.

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Nini tatizo la msingi hapa? Yeah. >> [Mwanafunzi] Ni kulinganisha anwani.

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Yeah, kwa uhakika. Ni kweli kulinganisha anwani

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ambayo HELLO na HELLO ni kuhifadhiwa.

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Siyo kulinganisha barua HELLO tena na tena,

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kwa sababu ni nini hasa kilichotokea, wakati huu wote tumekuwa kutumia GetString -

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Ubao huu ni tena kumbukumbu ya kompyuta yetu,

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na hebu sema mimi wito GetString baada ya kutangaza s kutofautiana.

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Nini kumbukumbu yangu kuangalia kama?

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Hebu kiholela kusema kwamba s inaonekana kama hii. Ni mraba.

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Na pretty much yoyote wakati nimekuwa inayotolewa kipande cha kumbukumbu kwenye screen

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kama ni 32 bits Nimekuwa kuchora mraba kama hii kwa sababu kwa kweli katika appliance,

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pointer, anuani, ni 32 bits. Ni sawa kama int.

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Hiyo inaweza kutofautiana kulingana na mfumo wa kompyuta.

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Wale ambao ni vaguely familiar na ukweli kwamba Mac au PC yako ni 64 bits,

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kwamba kweli inaashiria kuwa kompyuta yako kwa kutumia kuyatumia 64-bit,

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64-bit anwani, na kati ya upsides ya kwamba ni kompyuta yako

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unaweza kuwa na mengi zaidi kuliko RAM yesteryear.

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Long hadithi fupi, nyuma katika siku wakati kompyuta tu kutumika bits 32

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kuwakilisha anwani, namba kubwa ya ka unaweza kuwakilisha

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katika kesi hiyo ilikuwa nini kama una bits 32?

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Hivyo bilioni 4, haki, kwa sababu 2-32 ni bilioni 4.

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Idadi hii imekuwa mara kwa mara katika shaka.

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>> Hivyo kama wewe tu bits 32, idadi kubwa zaidi unaweza kuhesabu kwa ni takribani bilioni 4.

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Lakini hiyo ilikuwa kiwango cha juu ya msingi ya kompyuta hadi miaka michache iliyopita

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kwa sababu kama unaweza tu kuhesabu kama juu kama bilioni 4,

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haijalishi kama wewe kununua 8 gigabytes ya RAM au hata gigabytes 5 ya RAM;

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huwezi kuhesabu kwamba juu, hivyo ilikuwa ya maana.

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Unaweza tu kupata kwanza gigabytes 3 au 4 ya kumbukumbu ya kompyuta yako.

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Hiyo ni chini ya suala sasa, na unaweza kununua pros MacBook na Dells

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na 8 gigabytes ya RAM au hata zaidi siku hizi.

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Lakini kama mimi kutenga urahisi kabisa katika mpango huu pointer, pointer kuitwa s,

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inaweza kuangalia kama hii kwenye screen kwa sababu kwa kweli tunahitaji peel nyuma safu hii.

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Naendelea kusema kamba, lakini kama ya Jumatatu, kamba ni kweli Char *,

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anuani ya tabia fulani.

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Basi hebu kuchukua gurudumu mafunzo mbali hata kama tutaweza kuendelea kutumia GetString kwa sasa.

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Hivyo nimekuwa alitangaza, na hii ni chunk ya kumbukumbu, bits 32.

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Nini katika hapa katika kumbukumbu na default? >> [Inaudible mwanafunzi majibu]

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Nini hiyo? >> [Mwanafunzi] Takataka. >> Takataka. Hasa.

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Kama programu wala kuweka thamani katika variable, ambaye anajua ni nini?

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Wakati mwingine unaweza kupata bahati na ni 0, ambayo ni aina ya thamani nzuri, safi default,

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lakini kama tuliona Jumatatu, wakati mwingine ni kamili nonsense,

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baadhi kubwa kweli kweli chanya au hasi idadi kwamba alikuja kutoka wapi?

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Yeah. >> [Mwanafunzi] kazi kabla. >> Yeah.

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>> Mara nyingi kazi kwamba got kuitwa mbele kwa sababu kumbuka,

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kama wewe piga kazi katika kumbukumbu, wao kuchukua zaidi na nafasi zaidi kutoka chini kwenda juu,

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na haraka kama anarudi kazi, kumbukumbu kwamba anapata reused

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kwa guy ijayo kwamba anapata kuitwa, ambaye ni kutumia kipande yako hiyo ya kumbukumbu.

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Na kama wewe wameweza takataka kushoto huko, uliopita maadili,

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sisi ili makosa s kama baada ya baadhi ya thamani wakati kwa kweli sisi si kuweka chochote huko.

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Hivyo RAM wetu katika hatua hii inaonekana kama hii.

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Sasa upande wa kulia wa mstari 7 tuko wito GetString,

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ambayo tumekuwa kufanya sasa kwa wiki, lakini kile GetString kweli kufanya?

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GetString zilizoandikwa na wafanyakazi CS50 ni kidogo akili

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kwa kuwa haraka kama mtumiaji kuanza kuandika funguo na hits Ingiza,

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GetString takwimu nje jinsi wengi keystrokes alifanya hit user,

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ngapi wahusika nahitaji kutenga RAM kwa.

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Na pale ambapo RAM kwamba anakuja kutoka, ambaye anajua?

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Ni mahali fulani katika gigabytes kompyuta yako 2 au whatnot wa kumbukumbu.

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Lakini hebu tuseme kwamba kompyuta kupatikana nafasi kwa neno HELLO haki hapa.

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neno mimi typed ilikuwa H-E-L-L-O.

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Na kama sisi kuteka hii kama mlolongo wa wahusika, tupate kuteka ni kama hii.

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Lakini mimi haja ya kufanya kitu 1 ziada. Kile ambacho ni mali ya mwisho wa kamba yoyote katika C?

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tabia null, ambayo sisi kuandika kama \ 0.

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Ni kitaalam 0 idadi, lakini backslash hufanya wazi wote

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kwamba hii ni halisi idadi 0, 0 integer;

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siyo, kwa mfano 0, quote-unquote kwamba unaweza aina katika keyboard.

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Hivyo hii ni HELLO.

174
00:10:33,940 --> 00:10:36,350
>> Na nini sisi kusema juu ya Jumatatu kwamba kazi kama GetString

175
00:10:36,350 --> 00:10:39,580
ni kweli kurudi wiki haya yote?

176
00:10:39,580 --> 00:10:43,960
Ni si kurudi string per se sababu kwamba kweli haina maana kuwa

177
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kwa sababu masharti hazipo. Wao ni aina ya upotoshaji katika maktaba CS50.

178
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Je, ni kweli kamba, zaidi kitaalam? >> [Mwanafunzi] Ni tabia ya kwanza.

179
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Hasa. Ni rahisi kabisa anuani ya tabia ya kwanza kwamba mtumiaji typed in

180
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Hivyo kama neno langu HELLO mwisho ni juu katika 123 Byte idadi na kisha saa idadi Byte 124,

181
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125, 126, na kadhalika, kama mimi tu idadi bytes yangu kutoka 0 juu juu,

182
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kile kwa kweli ni GetString kurudi ni literally 123 idadi.

183
00:11:12,650 --> 00:11:19,270
Basi nini anapata kuweka katika s ni 123 idadi, si H barua, si neno HELLO,

184
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kabisa tu anuani ya saa ambayo naweza kupata barua ya kwanza ya HELLO.

185
00:11:23,130 --> 00:11:26,500
Lakini hiyo haina kuonekana kama kutosha. Nilimuuliza wewe kwa kamba, si tabia.

186
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Hivyo ni jinsi gani sisi au kompyuta kujua kwamba ELLO aina ya kuja pamoja na H?

187
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Nini aina ya mkataba tuna? Yeah.

188
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[Mwanafunzi] Inalifanya kuwaambia yenyewe kupata wahusika baadhi zaidi. >> Hasa.

189
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>> Kuna hii mkataba binadamu-kompyuta ambapo wakati wewe ni kushughulika na masharti,

190
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inayojulikana sasa kama nyota Char, wewe tu kuwa na takwimu kutoka

191
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ambapo mwisho wa kila uzi katika maisha ni kwa kweli tu iterating juu yake na kwa kitanzi,

192
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kitanzi wakati, na kwa chochote, hivyo kwamba wakati wewe kupata mwisho wa kamba

193
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sasa unaweza infer kutoka kwamba, oh, neno zima lilikuwa HELLO.

194
00:12:02,160 --> 00:12:04,820
Wale wa wewe na uzoefu kabla ya programu wapate kujua katika Java

195
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unaweza kuwaita tu urefu. na katika lugha nyingine unaweza kupiga urefu au sawa.

196
00:12:09,880 --> 00:12:14,060
Hiyo ni kwa sababu katika mengi ya lugha, hasa mambo kuitwa kitu-oriented lugha,

197
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urefu wa kitu ni aina ya ndani ya zimegawanywa ya kipande cha data yenyewe,

198
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kiasi kama sisi Vitambulisho zimegawanywa na majina na nyumba ndani ya mwanafunzi Jumatatu.

199
00:12:24,000 --> 00:12:28,700
Lakini C ni ya chini sana ngazi. Hakuna vitu au madarasa, kama wewe Nimesikia sheria hizo kabla.

200
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Wote una kweli ni kumbukumbu anwani.

201
00:12:31,490 --> 00:12:35,540
Hivyo hii ni aina ya njia ya zamani-fashioned ya anayewakilisha data kuvutia miundo.

202
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Una thamani ya kuanza kama anuani ya tabia ya kwanza

203
00:12:38,760 --> 00:12:42,340
na kisha baadhi tu mkataba holela kwamba kila mtu anakubaliana na kufuata.

204
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Hivyo ni jinsi gani string urefu kutekelezwa, gani sisi kupendekeza?

205
00:12:46,420 --> 00:12:51,360
Strlen, strlen, ambayo baadhi yenu sasa kutumika mara chache. Ni pretty rahisi, sawa?

206
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Ni kama mistari 2 ya maadili.

207
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Ni pretty much kitanzi kwa wa aina fulani, labda kwa variable ya ziada ya mitaa.

208
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Lakini strlen tu ana kuchukua pointer na kisha kuanza kuangalia kwa \ 0.

209
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>> Na haraka kama huikuta, inaweza kurudi idadi ya jumla ya hatua ya kuwa ni kuchukuliwa katika kamba hiyo.

210
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Hivyo tunaweza infer kutoka hii yale yanayoendelea ijayo.

211
00:13:07,150 --> 00:13:11,850
Tuseme basi mimi kutangaza t kama nimepata kufanyika katika mstari wa 10.

212
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Hii ni baadhi ya thamani ya takataka. Nani anajua kwa mara ya kwanza?

213
00:13:14,280 --> 00:13:18,490
Lakini upande wa kulia wa mstari wa 10 mimi nina wito GetString tena.

214
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Nani anajua ambapo hii inaishia?

215
00:13:20,050 --> 00:13:23,830
Hebu kiholela kusema kwamba mfumo wa uendeshaji kupatikana chumba kwa njia zaidi ya hapa.

216
00:13:23,830 --> 00:13:28,610
Mimi kutokea kwa bahati aina ya H-E-L-L-O tena,

217
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na hivyo tunaweza kuchora moja aina ya picha.

218
00:13:31,260 --> 00:13:34,290
Lakini ukweli kwamba nimekuwa redrawn picha hii ni makusudi

219
00:13:34,290 --> 00:13:37,720
sababu ni tofauti HELLO kuliko huu.

220
00:13:37,720 --> 00:13:43,920
Hivyo hapa kuwa hii inaweza kuwa mahali 456, hii ni 457, na kadhalika.

221
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Basi nini anapata kuweka ambapo alama swali moja mara?

222
00:13:47,170 --> 00:13:50,190
Katika kesi hii 456.

223
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Sisi ni kuokota namba hizi kiholela kwa sababu kwa kweli baada ya leo

224
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tuko hataenda kujali sana kuhusu nini anwani ya kitu chochote ni.

225
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Wote sisi huduma ya juu ni kwamba tunaweza kufikiri anuani ya baadhi kipande cha data kama HELLO.

226
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>> Hivyo kweli nini watu wengi katika sayansi ya kompyuta wakati wakizungumza kuhusu anwani kumbukumbu

227
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na kuzungumza juu ya kuyatumia hasa,

228
00:14:10,210 --> 00:14:14,220
badala ya bother kuhesabia 123 - anayejali ambapo mambo haya kwa kweli ni,

229
00:14:14,220 --> 00:14:17,440
sisi tu kujua kwamba ni katika anuani baadhi namba -

230
00:14:17,440 --> 00:14:22,180
sisi kurahisisha dunia na kusema tu kwamba s ni akizungumzia tabia ya kuwa

231
00:14:22,180 --> 00:14:25,080
na t akizungumzia tabia hiyo.

232
00:14:25,080 --> 00:14:27,430
Na ukweli kwamba ni mshale ni kabisa kukusudia

233
00:14:27,430 --> 00:14:31,610
sababu halisi sasa s ananyoosha katika H na t akionyesha H nyingine

234
00:14:31,610 --> 00:14:34,720
kwa sababu mwisho wa siku, haijalishi nini anwani ni,

235
00:14:34,720 --> 00:14:40,240
lakini haina suala kwamba tuna uwezo wa kueleza kwamba anuani na baadhi ya kipande cha code.

236
00:14:40,240 --> 00:14:42,730
Sisi si kweli manipulated anwani hizi bado tu

237
00:14:42,730 --> 00:14:47,770
hivyo tutaweza kuona ambapo tunaweza interject na aina ya kufanya mambo kwa kuyatumia,

238
00:14:47,770 --> 00:14:52,030
lakini kwa sasa katika mstari 12 literally nini maadili ni sisi kulinganisha

239
00:14:52,030 --> 00:14:55,500
kulingana na hadithi hii katika mstari wa 12?

240
00:14:56,570 --> 00:15:01,290
Sisi ni kusema ni 123 sawa sawa na 456? Na kwamba ni dhahiri si kesi.

241
00:15:01,290 --> 00:15:05,320
Na hata conceptually, pointer hii ni dhahiri si sawa kama hii

242
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kwa sababu wewe kuitwa GetString mara mbili, na GetString haina kujaribu kuwa super wajanja,

243
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haina kujaribu kutambua, oh, uliyoandika HELLO dakika 5 iliyopita;

244
00:15:12,470 --> 00:15:15,090
nikupe pointer sawa niliokupa kabla,

245
00:15:15,090 --> 00:15:18,450
tu kutenga fungu jipya la kumbukumbu kila wakati simu yake.

246
00:15:18,450 --> 00:15:20,350
>> Hivyo ni jinsi gani sisi kurekebisha tatizo hili?

247
00:15:20,350 --> 00:15:24,270
Kama ngazi nataka kulinganisha masharti HELLO na HELLO -

248
00:15:24,270 --> 00:15:28,680
Mimi sijali kuhusu kuyatumia - jinsi gani mimi kwenda kuhusu kujibu swali,

249
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hakuwa mtumiaji aina kitu kimoja? Nini lazima hapa? Yeah.

250
00:15:31,980 --> 00:15:35,200
[Mwanafunzi] Matumizi ya kazi. >> Naweza kutumia kazi nje ya boksi.

251
00:15:35,200 --> 00:15:38,170
Naweza kutumia kazi kuitwa strcmp, s-t-r-c-m-p,

252
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tu toleo abbreviated ya kusema string kulinganisha.

253
00:15:41,190 --> 00:15:45,070
Na kama sisi kwenda katika, kwa mfano, kulinganisha 2, ambayo ni kati ya takrima ya leo,

254
00:15:45,070 --> 00:15:46,690
Mimi kufanya hasa kwamba.

255
00:15:46,690 --> 00:15:51,750
Mimi naendelea kila kitu kingine huo kutoka mstari 1 juu ya chini 26 au hivyo,

256
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na sasa taarifa sehemu hii imebadilika kidogo tu.

257
00:15:54,360 --> 00:15:57,690
Hebu kupuuza mstari 28 kwa wakati na kuzingatia tu juu ya hili.

258
00:15:57,690 --> 00:16:00,410
Nini sisi kusema kwamba Jumatatu kulinganisha str gani?

259
00:16:00,410 --> 00:16:05,200
Hushughulikia mchakato wa kuchukua kuyatumia 2, s na t katika kesi hii,

260
00:16:05,200 --> 00:16:08,480
aina ya karibu kuweka kidole chake juu ya barua hizo 2,

261
00:16:08,480 --> 00:16:11,530
na nini ni lazima kufanya ni kitu kama kitanzi wakati au kwa kitanzi,

262
00:16:11,530 --> 00:16:16,050
na anasema ni hizo hizo? Kama ni hivyo, ni hatua ya vidole au kuyatumia mbele.

263
00:16:16,050 --> 00:16:17,970
Je, haya sawa, hawa, hizi, sawa

264
00:16:17,970 --> 00:16:22,710
hizi, hawa? Na ooh, mimi nina katika mwisho wa kamba saa mbili s na t.

265
00:16:22,710 --> 00:16:26,780
Sijayaona utata wowote. Ndiyo, haya masharti ni sawa.

266
00:16:26,780 --> 00:16:31,940
Na nini str kulinganisha kurudi ikiwa 2 masharti ni sawa, inaonekana? Zero.

267
00:16:31,940 --> 00:16:35,900
Hivyo 0 ni nzuri katika kesi hii kwa sababu kama hiyo anarudi -1 au 1,

268
00:16:35,900 --> 00:16:40,560
hiyo ina maana kwamba tu kinachotokea kuja kabla ya t alphabetically au baada ya t.

269
00:16:40,560 --> 00:16:43,760
Na ni kwa nini kwamba kuwa na manufaa kwa kuwa na kazi anayewaambia ambayo string huja kabla ya

270
00:16:43,760 --> 00:16:46,720
au baada ya katika kamusi?

271
00:16:46,720 --> 00:16:48,740
[Mwanafunzi] Searching. >> Searching na kuchagua.

272
00:16:48,740 --> 00:16:51,730
>> Hivyo unaweza kufanya mambo kama tafuta binary au aina Bubble au kuunganisha aina

273
00:16:51,730 --> 00:16:53,230
ambapo una kulinganisha vitu.

274
00:16:53,230 --> 00:16:56,420
Hivi sasa tumekuwa aina ya kukata pembe na baadhi tu aliyesema kuhusu uchambuaji

275
00:16:56,420 --> 00:16:59,430
katika mazingira ya idadi kwa sababu ni nzuri na rahisi kwa majadiliano juu,

276
00:16:59,430 --> 00:17:02,430
lakini unaweza shaka kulinganisha masharti, apple na ndizi,

277
00:17:02,430 --> 00:17:05,349
kwa sababu kama apple inajulikana kuja kabla ya ndizi, vile vile,

278
00:17:05,349 --> 00:17:09,319
unaweza hoja masharti kuzunguka katika kumbukumbu tu kama alivyofanya kwa Rob aina kuunganisha katika video

279
00:17:09,319 --> 00:17:15,880
na sisi tulikuwa hapa juu ya hatua kwa uteuzi aina, aina insertion, na aina Bubble.

280
00:17:15,880 --> 00:17:18,710
Hivyo ambapo mwingine tunaweza kuchukua hii? Hebu jaribu hii.

281
00:17:18,710 --> 00:17:23,980
Aina Hebu ya kusahau kwamba somo kwa wakati na kujaribu sasa na nakala 1.c kufanya yafuatayo.

282
00:17:23,980 --> 00:17:26,800
Katika mstari 21 mimi kusema magazeti kitu,

283
00:17:26,800 --> 00:17:28,520
basi nina kupata kamba kutoka kwa mtumiaji,

284
00:17:28,520 --> 00:17:30,690
basi mimi nina kuangalia hii.

285
00:17:30,690 --> 00:17:33,620
Sisi si kweli wamezipata katika tabia hii bado, lakini hebu sasa kufanya hili.

286
00:17:33,620 --> 00:17:40,990
Hebu kweli peel nyuma safu hii. Hii ni kweli Char *. Guy huu ni kweli Char *.

287
00:17:40,990 --> 00:17:45,690
Hivyo ni nini maana ya kuwa kuangalia kama s == null?

288
00:17:45,690 --> 00:17:48,380
Ni zinageuka kuwa wakati wewe piga kazi kama GetString

289
00:17:48,380 --> 00:17:51,540
au zaidi kwa ujumla tu kuuliza kompyuta kutoa baadhi ya kumbukumbu,

290
00:17:51,540 --> 00:17:53,030
kitu inaweza kwenda vibaya.

291
00:17:53,030 --> 00:17:56,630
Unaweza kuwa mambo na kuuliza kompyuta kwa terabyte ya kumbukumbu

292
00:17:56,630 --> 00:18:01,780
kwa kuuliza kwa matrilioni ya ka ya kumbukumbu ya kwamba tu hazipo katika kompyuta,

293
00:18:01,780 --> 00:18:05,130
lakini GetString na kazi nyingine haja ya baadhi ya njia ya kunguruma katika wewe

294
00:18:05,130 --> 00:18:06,820
kama wameweza aliuliza kwa sana.

295
00:18:06,820 --> 00:18:10,450
Na njia GetString gani hii ni kama una aliuliza kwa zaidi ya kumbukumbu

296
00:18:10,450 --> 00:18:14,250
kuliko inapatikana katika kompyuta, hata kama kwamba ni super, super Asili uwezekano

297
00:18:14,250 --> 00:18:17,730
kwa sababu hakuna hata mmoja wetu ni kwenda andika herufi trilioni na kisha hit Enter,

298
00:18:17,730 --> 00:18:21,980
lakini chini uwezekano ingawa inaweza kuwa, mimi bado wanataka kuangalia kwa ajili yake tu katika kesi,

299
00:18:21,980 --> 00:18:26,120
na thamani maalum kwamba GetString, jibu, na kazi nyingine anarudi

300
00:18:26,120 --> 00:18:30,630
kama kitu amekwenda vibaya ni null katika kofia wote.

301
00:18:30,630 --> 00:18:36,520
>> Na ni nini null? Null tu hivyo hutokea kuwakilisha pointer. Ni kumbukumbu ya anuani 0.

302
00:18:36,520 --> 00:18:40,800
dunia aliamua kwamba kiholela, kama hii ni kumbukumbu ya kompyuta yangu - unajua nini? -

303
00:18:40,800 --> 00:18:46,260
tunakwenda kuiba tu 1 Byte ya kumbukumbu kila kompyuta, na hii ni mahali 0.

304
00:18:46,260 --> 00:18:49,560
Sisi ni kwenda kuwapa jina la utani la null, na tunakwenda ahadi

305
00:18:49,560 --> 00:18:52,660
kuwa sisi kamwe kweli kuweka data halisi kuna

306
00:18:52,660 --> 00:18:56,770
kwa sababu sisi tu kiholela haja thamani maalum, 0, aka null,

307
00:18:56,770 --> 00:19:00,230
ili tuweze yell katika watumiaji kama kitu fulani kitaenda vibaya.

308
00:19:00,230 --> 00:19:03,590
Vinginevyo unaweza kujua haina maana 0 kuweka kitu hapa

309
00:19:03,590 --> 00:19:05,490
au haina maana kitu potoka?

310
00:19:05,490 --> 00:19:09,190
Tuna kwa wote wanakubaliana kwamba null chochote njia zilizorudishwa,

311
00:19:09,190 --> 00:19:11,700
anuani hakuna halisi zilizorudishwa.

312
00:19:11,700 --> 00:19:15,210
Sasa, hapa mimi tu kupitisha mkataba wangu binadamu ya mimi kurudi kutoka 1 kuu

313
00:19:15,210 --> 00:19:17,040
kama kitu fulani kitaenda vibaya.

314
00:19:17,040 --> 00:19:20,650
Hiyo ni kwa sababu kurudi kuu ya mkataba ni kurudi 0 ikiwa nzuri,

315
00:19:20,650 --> 00:19:22,990
1 au baadhi thamani mengine ikiwa mbaya.

316
00:19:22,990 --> 00:19:28,200
Lakini GetString na kazi yoyote ambayo inahusika katika anarudi kumbukumbu null kama kitu fulani kitaenda vibaya.

317
00:19:28,200 --> 00:19:33,480
>> Sawa. Hivyo kwa bahati mbaya, line 27, super rahisi ingawa ni, kabisa inashindwa nakala kamba.

318
00:19:33,480 --> 00:19:35,740
Kwa nini? Tunaweza kuona hii kama ifuatavyo.

319
00:19:35,740 --> 00:19:40,120
Mimi nina wakidai katika mstari 27 kuwa maamuzi nakala ya s na kuiita t.

320
00:19:40,120 --> 00:19:45,790
Hivyo Mimi si kuuliza mtumiaji kwa masharti 2 wakati huu; Mimi tu kusema thamani katika s

321
00:19:45,790 --> 00:19:47,870
atafukuzwa katika t pia.

322
00:19:47,870 --> 00:19:52,890
Hivyo sasa tu kuonyesha jinsi hii ni kuvunjika, katika mstari 29 kuendelea je, Mimi kufanya?

323
00:19:52,890 --> 00:19:56,980
Kwanza mimi nina kuangalia kama urefu wa t, ni mkubwa kuliko 0.

324
00:19:56,980 --> 00:19:59,330
Kuna baadhi ya kamba huko. user typed kitu in

325
00:19:59,330 --> 00:20:03,410
Nini ni mstari 32 kufanya, inaonekana?

326
00:20:03,410 --> 00:20:08,910
[Inaudible mwanafunzi majibu] >> Haki. Unaweza aina ya infer kutoka kile alisema ni kufanya.

327
00:20:08,910 --> 00:20:13,200
Lakini kitaalam, ni nini hii kufanya? t [0] inawakilisha nini?

328
00:20:13,200 --> 00:20:15,140
[Mwanafunzi] tabia 0. >> [Malan] tabia 0.

329
00:20:15,140 --> 00:20:19,620
Au, zaidi ya binadamu-kama, tabia ya kwanza katika t, chochote kile, H labda katika kesi hii.

330
00:20:19,620 --> 00:20:24,990
Na toupper anafanya nini anasema. Ni capitalizes tabia 0 wa t na ni mabadiliko hayo.

331
00:20:24,990 --> 00:20:28,430
Hivyo hii ina maana kuchukua tabia ya t 0, kufanya hivyo uppercase,

332
00:20:28,430 --> 00:20:30,320
na kuiweka nyuma katika eneo hilo hilo.

333
00:20:30,320 --> 00:20:35,540
Hivyo kama ninapoandika hujambo katika lowercase, hii inapaswa kubadilika h lowercase kwa H. mtaji

334
00:20:35,540 --> 00:20:41,400
Lakini tatizo ni kwamba katika mistari 35 na 36 mimi nina nini kuhusu kufanya ni kuchapa nje kwa ajili yetu s na t.

335
00:20:41,400 --> 00:20:43,120
Na nini hunch yako?

336
00:20:43,120 --> 00:20:47,250
Hivi mimi kweli kwenda kuona kama mimi typed katika hujambo katika lowercase wote?

337
00:20:47,250 --> 00:20:52,280
Nini kinaendelea kupata kuchapishwa? >> [Inaudible mwanafunzi majibu] >> gani hiyo?

338
00:20:52,280 --> 00:20:58,360
[Mwanafunzi] Big H na wengine wadogo. >> H kubwa na ndogo kwa ajili ya mapumziko ambayo, s au t?

339
00:20:58,360 --> 00:21:03,170
[Mwanafunzi] Wote. >> Wote. Hasa. Basi hebu angalia nini kinaendelea hapa.

340
00:21:03,170 --> 00:21:08,380
>> Hebu kwenda mbele na kukusanya hii. Hii ni copy1, hivyo kufanya copy1. Wote haki.

341
00:21:08,380 --> 00:21:14,840
Zoom in Hebu kwenda mbele na kukimbia copy1, Ingieni, Sema kitu: hello katika lowercase.

342
00:21:14,840 --> 00:21:19,570
Ni mtaji nakala, lakini inaonekana kama mtaji awali vizuri,

343
00:21:19,570 --> 00:21:22,070
sababu kile kinachotokea sasa katika hadithi hii?

344
00:21:22,070 --> 00:21:27,030
Katika mstari 27 mimi si kweli wanaonekana kuwa kuiga kamba,

345
00:21:27,030 --> 00:21:30,450
lakini hata ingawa unaweza kuwa na matumaini kwamba intuitively kuwa kesi,

346
00:21:30,450 --> 00:21:33,680
kama unafikiri kuhusu picha hii, kweli yale nimefanya?

347
00:21:33,680 --> 00:21:35,410
Nusu ya picha ni sawa.

348
00:21:35,410 --> 00:21:39,390
Basi hebu nirudishe katika muda ili t bado haina zipo katika hadithi.

349
00:21:39,390 --> 00:21:43,160
S unaweza kuwepo katika hadithi, lakini hebu Herufi za chini hujambo wakati huu.

350
00:21:43,160 --> 00:21:46,710
Hivyo basi mimi kurekebisha kile Mimi kweli typed in

351
00:21:46,710 --> 00:21:51,280
Katika kesi hii hapa tuna h-e-l-l-o.

352
00:21:51,280 --> 00:21:58,050
Tutaweza kuteka ni kama mlolongo wa wahusika, kuweka separator mistari yangu hapa na yangu \ 0.

353
00:21:58,050 --> 00:22:05,980
Hivyo hii ni mahali ambapo sisi ni haraka kama mstari 1 24 kupitia-ish, kutoa au kuchukua, haijanyonga.

354
00:22:05,980 --> 00:22:07,800
Hii ni picha ya kumbukumbu yangu.

355
00:22:07,800 --> 00:22:10,800
Wakati mimi kupata mstari 27, nini kitatokea?

356
00:22:10,800 --> 00:22:14,730
Tu kama kabla, mimi kupata pointer, ambayo mimi itabidi kuteka kama mraba huu.

357
00:22:14,730 --> 00:22:19,740
Ni wito t. Na nini thamani yake na default? Nani anajua? Baadhi ya thamani ya takataka.

358
00:22:19,740 --> 00:22:22,060
>> Hivyo mimi itabidi abstract kwamba mbali kama alama swali.

359
00:22:22,060 --> 00:22:27,670
Na haraka kama upande wa kulia ya mstari 27 executes, je, Mimi kuweka ndani ya t?

360
00:22:27,670 --> 00:22:30,770
kitu kimoja kwamba katika s.

361
00:22:30,770 --> 00:22:34,120
Hivyo kama sisi kwa muda kuondoa hii abstraction ya mshale na sisi kusema,

362
00:22:34,120 --> 00:22:40,330
oh, hii ni kumbukumbu ya mzigo anuani 123, wakati wewe kusema t anapata s, semicolon,

363
00:22:40,330 --> 00:22:42,700
wewe ni literally kuweka 123 hapa.

364
00:22:42,700 --> 00:22:45,200
Sasa kama sisi aina ya kurahisisha dunia yetu tena na picha,

365
00:22:45,200 --> 00:22:48,750
nini umefanya kweli kufanyika ni tu aliongeza mwingine mshale dunia yako

366
00:22:48,750 --> 00:22:52,910
hiyo akizungumzia kutoka t kwa kamba huo halisi.

367
00:22:52,910 --> 00:22:59,730
Hivyo wakati katika mstari 31 na 32 mimi kweli kwenda juu ya kubadilisha t [0],

368
00:22:59,730 --> 00:23:05,580
kile ni t [0] inaonekana sawa na sasa? s [0]

369
00:23:05,580 --> 00:23:07,030
Basi hiyo ni yote yale yanayotokea.

370
00:23:07,030 --> 00:23:09,900
Na hata kama aina hii ya anahisi kidogo kiwango cha chini na arcane

371
00:23:09,900 --> 00:23:12,760
na aina hii ya anahisi kama labda intuitively hii lazima tu kazi -

372
00:23:12,760 --> 00:23:15,410
Nimekuwa alifanya nakala za mambo kabla na ni haki kazi -

373
00:23:15,410 --> 00:23:18,590
kama kweli kufikiri kuhusu nini string kweli ni, ni * Char.

374
00:23:18,590 --> 00:23:21,700
Naam, hiyo ni nini? Ni anuani ya tabia fulani.

375
00:23:21,700 --> 00:23:24,930
Kisha labda inakuwa na mantiki zaidi kwamba wakati wewe kujaribu kufanya kitu

376
00:23:24,930 --> 00:23:29,220
super inaonekana rahisi kama hii, yote wewe kufanya ni kuiga anuani kumbukumbu.

377
00:23:29,220 --> 00:23:32,530
Wewe si kweli kufanya kitu chochote kwa kamba yenyewe.

378
00:23:32,530 --> 00:23:37,500
Hivyo hata kama huna wazo jinsi gani kutatua tatizo hili katika kanuni,

379
00:23:37,500 --> 00:23:45,080
ngazi ya juu, conceptually, nini tunahitaji kufanya ili kufanya ta kweli nakala ya s, inaonekana?

380
00:23:46,670 --> 00:23:48,820
Yeah. >> [Mwanafunzi] Kuwapa eneo jipya? >> Hasa.

381
00:23:48,820 --> 00:23:50,800
>> Sisi haja ya kutoa t bidhaa mpya mahali.

382
00:23:50,800 --> 00:23:55,230
Tunahitaji namna fulani kujenga dunia ambayo sisi kupata chunk mpya ya kumbukumbu,

383
00:23:55,230 --> 00:24:00,090
ambayo kwa ajili tu ya ufafanuzi mimi itabidi kuteka haki chini ya hii moja, lakini haina haja ya kuwa huko.

384
00:24:00,090 --> 00:24:04,880
Lakini inahitaji kuwa muziki huo, hivyo mimi itabidi kuteka mistari haya wima katika sehemu moja.

385
00:24:04,880 --> 00:24:09,720
Ni faini kama hii yote ni takataka awali. Nani anajua huko?

386
00:24:09,720 --> 00:24:13,850
Lakini hatua ya 1 ni kwenda kuwa nipe kama kumbukumbu kiasi kama nahitaji

387
00:24:13,850 --> 00:24:18,630
walionao nakala ya hello, kisha kufikiri jinsi ya nakala h hapa, e hapa,

388
00:24:18,630 --> 00:24:20,390
l hapa na kadhalika.

389
00:24:20,390 --> 00:24:24,880
Lakini hii tayari anatakiwa kujisikia kidogo dhahiri hata kama baadhi ya maelezo ni bado kufikirika.

390
00:24:24,880 --> 00:24:28,690
Kwa nakala hii kamba katika hili, ni tu kwa kitanzi au kitanzi wakati

391
00:24:28,690 --> 00:24:31,580
au kitu fulani na ambayo umefanya kuwa wote zaidi ya ukoo.

392
00:24:31,580 --> 00:24:35,970
Basi hebu jaribu hii. Hebu kwenda katika copy2.c.

393
00:24:35,970 --> 00:24:43,270
Katika copy2.c tuna karibu mpango huo ila kwa mstari 27.

394
00:24:43,270 --> 00:24:47,260
Inaonekana tata kidogo, lakini kama sisi kuvunja chini kipande kwa kipande,

395
00:24:47,260 --> 00:24:48,950
upande wa mkono wa kushoto ni sawa.

396
00:24:48,950 --> 00:24:52,790
Char * t inajenga jambo hili katika kumbukumbu, angalau kwa swali alama

397
00:24:52,790 --> 00:24:54,680
kwa sababu sisi hatuna wazo nini huko na default.

398
00:24:54,680 --> 00:24:57,920
Upande wa kulia tuko sasa kuanzisha mpya kazi, malloc,

399
00:24:57,920 --> 00:25:00,640
kwa kumbukumbu kutenga, nipe kumbukumbu,

400
00:25:00,640 --> 00:25:06,900
na inaonekana inachukua jinsi hoja nyingi, mambo mangapi ndani ya mabano?

401
00:25:09,660 --> 00:25:12,130
Nikasikia manung'uniko ya 1 na 2, lakini ni 1 tu.

402
00:25:12,130 --> 00:25:15,320
Hakuna comma, ambayo ina maana kuna kitu tu 1 ndani ya mabano.

403
00:25:15,320 --> 00:25:17,720
Hata ingawa kuna mabano nyingine, napenda kuonyesha

404
00:25:17,720 --> 00:25:21,460
nini ndani ya mabano yttersta, na ni hii kujieleza:

405
00:25:21,460 --> 00:25:25,880
(Strlen (s) + 1) * sizeof (Char).

406
00:25:25,880 --> 00:25:29,190
Hivyo kama sisi kweli nadhani hii kupitia, hii ni kusema nipe urefu wa s.

407
00:25:29,190 --> 00:25:34,440
Kwa nini mimi, ingawa, akiongeza 1 kwenye urefu? >> [Inaudible mwanafunzi majibu]

408
00:25:34,440 --> 00:25:40,200
Hasa. Tunahitaji nafasi kwa guy hii ifikapo mkia, tabia ya sita kwamba haina maana Kiingereza

409
00:25:40,200 --> 00:25:42,250
lakini haina una maalum kimpango maana.

410
00:25:42,250 --> 00:25:46,800
>> Hivyo tunahitaji + 1 kwa kuwa kwa sababu strlen anarudi matumaini ya binadamu ya urefu,

411
00:25:46,800 --> 00:25:50,890
hujambo au 5, haina kukupa ziada null tabia.

412
00:25:50,890 --> 00:25:52,980
Hivyo mimi manually kuongeza hii kwa + 1.

413
00:25:52,980 --> 00:25:56,060
Na kisha hii, ukubwa wa * (Char), hatujaona hii kabla.

414
00:25:56,060 --> 00:25:57,480
Hii si kitaalam kazi.

415
00:25:57,480 --> 00:26:04,150
Ni Keyword maalum kwamba tu anakwambia kile kawaida ni ya baadhi ya aina data kwenye komputa

416
00:26:04,150 --> 00:26:06,980
kwa sababu katika hali halisi, baadhi ya sisi kuwa na kompyuta 32-bit.

417
00:26:06,980 --> 00:26:10,900
Mimi kuwa na kompyuta pretty umri wa nyumbani, na anatumia tu bits 32 kuwakilisha kuyatumia.

418
00:26:10,900 --> 00:26:13,900
Na hivyo kama mimi ukubwa wa aina data, inaweza kuwa 32 bits.

419
00:26:13,900 --> 00:26:18,300
Lakini kama mimi nina kutumia dhana yangu mpya ya kompyuta, mimi ili kupata nyuma thamani ya bits 64

420
00:26:18,300 --> 00:26:20,510
kwa kitu kama anwani.

421
00:26:20,510 --> 00:26:25,400
Hivyo katika kesi hii, tu kuwa super salama, sisi siyo kwenda kitu ngumu code kama -

422
00:26:25,400 --> 00:26:28,740
vizuri, ni nini na ukubwa wa Char kulingana na kile ambacho tumekuwa alisema hadi sasa?

423
00:26:28,740 --> 00:26:34,450
Tumekuwa pretty much alisema maneno kwamba ni 1 Byte, na kwamba ni kiasi pretty kweli katika bodi.

424
00:26:34,450 --> 00:26:37,000
Lakini tena, mawazo huwa na kuwa mbaya.

425
00:26:37,000 --> 00:26:40,850
Wao kusababisha programu Buggy ikiwa watu kutumia programu yako katika njia wewe hakuwa na nia.

426
00:26:40,850 --> 00:26:44,750
Hivyo hebu abstract hii mbali na tu zaidi generically kusema

427
00:26:44,750 --> 00:26:46,830
Nahitaji chunks hayo, wengi wa kumbukumbu

428
00:26:46,830 --> 00:26:50,210
na kila chunk ya kumbukumbu inapaswa kuwa sawa na ukubwa wa tabia,

429
00:26:50,210 --> 00:26:54,870
ambao kwa kweli ni sawa na 1 katika kesi hii, lakini ni njia zaidi generic ya kuandika hivyo.

430
00:26:54,870 --> 00:27:00,460
Hivyo kama neno ni hello, jinsi wengi ka haina malloc inaonekana kutenga kwa hujambo?

431
00:27:00,460 --> 00:27:04,980
[Mwanafunzi] Sita. >> Sita. Hasa kama wengi kama tuna swali alama juu ya screen.

432
00:27:04,980 --> 00:27:07,800
Na kisha kuchukua nadhani sasa kwa kuzingatia uelewa wako wa GetString

433
00:27:07,800 --> 00:27:12,790
nini malloc pengine kurudi? >> [Mwanafunzi] anuani.

434
00:27:12,790 --> 00:27:17,020
anuani ya nini? Ya chunk ya kwanza ya kumbukumbu.

435
00:27:17,020 --> 00:27:20,670
>> Sisi hatuna wazo nini huko kwa sababu baadhi ya kazi nyingine

436
00:27:20,670 --> 00:27:23,010
wangeweza kutumia kumbukumbu hii hapo awali.

437
00:27:23,010 --> 00:27:28,380
Lakini malloc, kama GetString, anarudi anuani ya Byte kwanza ya kumbukumbu

438
00:27:28,380 --> 00:27:30,540
kwamba imetenga kwa ajili yenu.

439
00:27:30,540 --> 00:27:38,380
Hata hivyo, nini haina kufanya ni kujaza tupu hii na tabia null backslash

440
00:27:38,380 --> 00:27:43,030
kwa sababu ni zamu nje unaweza kutumia malloc kutenga chochote: ints, masharti, arrays,

441
00:27:43,030 --> 00:27:45,700
ikifungwa, mwanafunzi miundo.

442
00:27:45,700 --> 00:27:47,750
Unaweza kutumia malloc kabisa generically.

443
00:27:47,750 --> 00:27:51,470
Ni hajali au kujua nini wewe kugawa kumbukumbu kwa.

444
00:27:51,470 --> 00:27:55,810
Hivyo itakuwa presumptuous kwa malloc kuweka 0 \

445
00:27:55,810 --> 00:27:58,340
mwisho wa kila chunk ya kumbukumbu ni kutoa

446
00:27:58,340 --> 00:28:02,620
kwa sababu hii \ 0 kitu ni mkataba kwa masharti.

447
00:28:02,620 --> 00:28:06,310
Ni si kutumika kwa ajili ya ints, siyo kutumika kwa ajili ya ikifungwa, siyo kutumika kwa ajili ya wanafunzi.

448
00:28:06,310 --> 00:28:11,730
Na hivyo gotcha na malloc ni kwamba mzigo ni wewe kabisa juu ya programu

449
00:28:11,730 --> 00:28:16,790
kukumbuka jinsi wengi ka wewe zilizotengwa na si kwa milele kutumia kwa kitanzi

450
00:28:16,790 --> 00:28:21,570
au kitanzi wakati na kwenda nyuma ya mpaka wa chunk ya kumbukumbu tumekuwa aliyopewa.

451
00:28:21,570 --> 00:28:23,540
Weka kwa njia nyingine, haraka kama wewe kutenga kumbukumbu,

452
00:28:23,540 --> 00:28:28,510
huwezi kuuliza mfumo wa uendeshaji, oh, kwa njia, jinsi kubwa ya chunk ya kumbukumbu ilikuwa hii?

453
00:28:28,510 --> 00:28:32,080
Ni kabisa hadi wewe kukumbuka kama unahitaji kuwa thamani.

454
00:28:32,080 --> 00:28:34,330
>> Basi hebu angalia jinsi mimi kuendelea kutumia kumbukumbu.

455
00:28:34,330 --> 00:28:38,430
Katika mstari 28 na 29 kwa nini mimi kufanya hili?

456
00:28:39,850 --> 00:28:42,260
Tu jumla sanity hundi.

457
00:28:42,260 --> 00:28:45,110
Tu katika kesi kitu potoka, naomba kwa kiasi fulani mambo ya kumbukumbu

458
00:28:45,110 --> 00:28:48,690
au mimi mambo mengi mbio juu ya kompyuta kwamba kuna tu siyo kumbukumbu ya kutosha,

459
00:28:48,690 --> 00:28:51,780
kitu kama hicho, mimi angalau wanataka kuangalia kwa null.

460
00:28:51,780 --> 00:28:55,260
Katika hali halisi, wengi kompyuta nitakupa udanganyifu kwamba kila mpango

461
00:28:55,260 --> 00:28:57,080
Unaweza kutumia ukamilifu wa RAM yako,

462
00:28:57,080 --> 00:29:00,740
lakini hata hivyo, kama mtumiaji aina katika string baadhi crazy muda mrefu labda kwa sababu ni mtu mbaya

463
00:29:00,740 --> 00:29:03,440
na wao ni kweli kujaribu ajali programu yako au hack ndani yake,

464
00:29:03,440 --> 00:29:07,300
unataka angalau kuangalia thamani ya kurudi kwa malloc na kama ni sawa null.

465
00:29:07,300 --> 00:29:11,630
Na ikiwa hivyo, hebu tu kuacha haki sasa kwa sababu mimi sijui nini cha kufanya katika kesi hiyo.

466
00:29:11,630 --> 00:29:13,950
Ninawezaje nakala kamba? Kuna njia kadhaa za kufanya hivyo.

467
00:29:13,950 --> 00:29:18,850
Kuna str nakala kazi katika C, lakini ni super rahisi kwa sisi kufanya hii ya zamani-fashioned njia.

468
00:29:18,850 --> 00:29:23,110
>> Kwanza napenda kufikiri nini urefu wa s ni.

469
00:29:23,110 --> 00:29:26,930
Ningeweza kuweka hii katika kitanzi lakini badala yake mimi tu kuweka nje hapa kwa ufafanuzi.

470
00:29:26,930 --> 00:29:30,610
Hivyo n sasa maduka ya urefu wa kamba ya awali, ambayo ni inaonekana 5.

471
00:29:30,610 --> 00:29:35,290
Kisha katika kitanzi yangu kwa mimi nina iterating kutoka juu ya 0 hadi n,

472
00:29:35,290 --> 00:29:40,940
na juu ya kila iteration mimi nina kuweka s [i] ndani ya t [i].

473
00:29:40,940 --> 00:29:45,060
Hivyo kwamba ni nini mimi alisema kwa vidole vyangu 2 akionyesha masharti kabla.

474
00:29:45,060 --> 00:29:49,260
Kama hii kwa kitanzi iterates kama hii, mimi nina kwenda kuwa kuiga h ndani ya hapa,

475
00:29:49,260 --> 00:29:52,890
e katika hapa, l ndani ya hapa kwa sababu hii ni s, hii ni t.

476
00:29:52,890 --> 00:29:58,770
Na kisha mwishowe, katika mstari 35 kwa nini mimi kufanya hili?

477
00:29:58,770 --> 00:30:03,770
Mimi haja ya kuhakikisha kwamba mimi nina kumaliza t kamba.

478
00:30:03,770 --> 00:30:06,170
Na mimi ni njia hii kuwa super wazi.

479
00:30:06,170 --> 00:30:09,510
Lakini kupendekeza, mtu, kama unaweza, njia mbalimbali za kufanya hivi.

480
00:30:09,510 --> 00:30:13,930
Mimi si kweli wanahitaji line 35. Kuna njia nyingine ya kufanya hili.

481
00:30:13,930 --> 00:30:18,880
Yeah. >> [Inaudible mwanafunzi majibu] >> Sema nguvu zaidi.

482
00:30:18,880 --> 00:30:20,960
[Mwanafunzi] Chini ya au sawa na. >> Hasa.

483
00:30:20,960 --> 00:30:24,450
Tunaweza tu kusema chini ya au sawa na n, ambayo kwa ujumla imekuwa mbaya

484
00:30:24,450 --> 00:30:28,190
kwa sababu karibu kila mara wakati sisi kwenda sawa na kitu sisi ni kuhesabu

485
00:30:28,190 --> 00:30:30,000
sisi kwenda 1 hatua mbali mno.

486
00:30:30,000 --> 00:30:32,170
Lakini kumbuka, jinsi ka wengi hawakuwa sisi kutenga?

487
00:30:32,170 --> 00:30:37,210
Sisi zilizotengwa strlen ya s, hivyo 5 + 1 kwa jumla ya 6.

488
00:30:37,210 --> 00:30:39,980
Hivyo katika kesi hii tunaweza kufanya kitu kama hiki

489
00:30:39,980 --> 00:30:46,450
hivyo kwamba sisi ni kuiga si tu hujambo lakini pia 0 \ mwishoni sana.

490
00:30:46,450 --> 00:30:49,860
Vinginevyo, tunaweza kutumia kazi kuitwa str nakala, strcpy,

491
00:30:49,860 --> 00:30:51,700
lakini kwamba itakuwa si kuwa karibu kama furaha sana.

492
00:30:51,700 --> 00:30:54,000
Lakini hiyo yote ni gani chini ya Hood.

493
00:30:54,000 --> 00:30:56,050
Kisha mwisho, sisi kufanya kitu kimoja kama kabla.

494
00:30:56,050 --> 00:31:01,620
Mimi capitalize t na kisha mimi kudai kwamba awali inaonekana kama hii na nakala inaonekana kama kwamba.

495
00:31:01,620 --> 00:31:08,570
Basi hebu jaribu hii sasa. Hebu kwenda katika hapa. Matokeo copy2. Tutaweza kukuza ndani na kukimbia copy2.

496
00:31:08,570 --> 00:31:13,840
Mimi naenda aina katika hujambo katika lowercase, na kwa kweli mimi kupata Herufi za chini hujambo kama awali

497
00:31:13,840 --> 00:31:16,930
lakini mtaji Wapendwa kwa nakala.

498
00:31:16,930 --> 00:31:20,300
Lakini mimi nina kufanyika bado tu. Mimi haja ya kufanya mwisho 1 kitu hapa.

499
00:31:20,300 --> 00:31:28,000
46 na 47 ni wazi kumkomboa kumbukumbu, lakini ni nini maana ya kwamba kweli?

500
00:31:28,000 --> 00:31:33,250
Hivi mimi nafanya nini, unafikiri, kwa wito line 46 na mstari 47?

501
00:31:33,250 --> 00:31:38,900
Nini athari gani kwamba kuwa? Yeah.

502
00:31:38,900 --> 00:31:43,140
[Inaudible mwanafunzi majibu] >> Hasa.

503
00:31:43,140 --> 00:31:46,380
>> Wewe ni tu kuwaambia mfumo wa uendeshaji, hey, shukrani kwa ajili ya kumbukumbu hii.

504
00:31:46,380 --> 00:31:48,320
Unaweza sasa matumizi yake kwa mtu mwingine.

505
00:31:48,320 --> 00:31:50,790
Na hapa ni mfano kamili wa maadili ya takataka.

506
00:31:50,790 --> 00:31:55,430
Mimi tu kutumika kumbukumbu hii kwa kuandika neno hujambo katika maeneo 2,

507
00:31:55,430 --> 00:31:57,490
hapa, hapa, hapa, na hapa.

508
00:31:57,490 --> 00:32:00,910
Hivyo hii ni h-e-l-l-o-\ 0.

509
00:32:00,910 --> 00:32:06,960
Lakini basi mimi piga mstari 46 na mstari 47, na wewe kujua nini kinatokea pale katika suala la picha?

510
00:32:06,960 --> 00:32:10,010
Kweli, ngoja, picha hii ni moja ya zamani.

511
00:32:10,010 --> 00:32:12,550
Mara sisi kufanya nakala, guy hii ni kweli akizungumzia hapa,

512
00:32:12,550 --> 00:32:16,110
hivyo hebu kuondoa idadi na tu abstract mbali kama mishale yetu tena.

513
00:32:16,110 --> 00:32:19,370
Nini kinatokea katika picha hii wakati mimi kuwaita bure?

514
00:32:19,370 --> 00:32:22,750
[Inaudible mwanafunzi majibu] >> Si hata.

515
00:32:22,750 --> 00:32:29,510
Kama mimi wito bure kwenye s na t - aina ya swali hila - picha hii haina mabadiliko wakati wote

516
00:32:29,510 --> 00:32:33,880
kwa sababu wito s na wito t tu anaelezea mfumo wa uendeshaji,

517
00:32:33,880 --> 00:32:39,010
hey, unaweza kutumia kumbukumbu hii tena, lakini haibadilishi hii null

518
00:32:39,010 --> 00:32:41,840
au baadhi ya tabia maalum, haina mabadiliko hayo,

519
00:32:41,840 --> 00:32:47,350
haibadilishi h au e au l au l au o katika aidha mahali pa kitu kingine chochote.

520
00:32:47,350 --> 00:32:51,610
Katika suala la picha, haraka kama wewe piga mabadiliko bure kitu,.

521
00:32:51,610 --> 00:32:56,570
Na humo uongo asili ya maadili ya takataka kwa sababu kama mimi kisha baadaye katika mpango huu

522
00:32:56,570 --> 00:33:01,010
kuuliza mfumo wa uendeshaji kwa ajili ya kumbukumbu zaidi na GetString au malloc au kitu kama hicho

523
00:33:01,010 --> 00:33:04,900
na mfumo wa uendeshaji anasema, hakika, nina ka 12 ya kumbukumbu tu zilizotolewa,

524
00:33:04,900 --> 00:33:08,080
matumizi haya, nini unakwenda kuwa mitupu?

525
00:33:08,080 --> 00:33:10,830
Mtakuja kuwa mitupu chunk ya kumbukumbu kwamba sisi ingekuwa kawaida kuteka

526
00:33:10,830 --> 00:33:13,700
na alama ya kuuliza, lakini nini ni alama swali hizo?

527
00:33:13,700 --> 00:33:17,000
Wao kutokea kwa kuwa h-e-l-l-o, h-e-l-l-o.

528
00:33:17,000 --> 00:33:20,940
Hizi ni takataka wetu mpya maadili haraka kama wewe bure juu ya kwamba kumbukumbu.

529
00:33:20,940 --> 00:33:22,750
>> Kuna ulimwengu halisi Kidokezo hapa pia.

530
00:33:22,750 --> 00:33:24,720
Hii hutokea kwa kufanya na RAM, lakini kompyuta yako

531
00:33:24,720 --> 00:33:26,720
kweli kufanya kitu kimoja na disk.

532
00:33:26,720 --> 00:33:30,620
Tutazungumzia hili hasa kwa kuweka baadaye tatizo kwamba inalenga katika forensics.

533
00:33:30,620 --> 00:33:36,170
Lakini nini hasa kinatokea kama una baadhi ya nyeti ya fedha faili kwenye desktop yako

534
00:33:36,170 --> 00:33:39,600
au baadhi JPEG sketchy na wewe Drag ni ndani ya takataka yako,

535
00:33:39,600 --> 00:33:44,390
kile kinachotokea wakati Drag ni ndani ya takataka au kusaga bin?

536
00:33:44,390 --> 00:33:47,240
Ulijua nini nilikuwa kuzungumza juu. [Kicheko]

537
00:33:47,240 --> 00:33:52,370
Nini kinatokea wakati umeweka dragged kuwa ushahidi katika bin yako kusaga au takataka unaweza?

538
00:33:52,370 --> 00:33:55,920
[Inaudible mwanafunzi majibu]

539
00:33:55,920 --> 00:33:58,000
Naam, hivyo makini. Nini kinatokea wakati wewe kufanya hivyo?

540
00:33:58,000 --> 00:34:01,030
jibu fupi ni kitu, sawa?

541
00:34:01,030 --> 00:34:04,790
Sketchy au nyeti faili bado wamekaa tu pale mahali fulani katika gari yako ngumu.

542
00:34:04,790 --> 00:34:07,940
Wengi wetu angalau wamejifunza njia ngumu kwamba unahitaji tupu takataka yako

543
00:34:07,940 --> 00:34:10,429
au yako kusaga bin kwa kweli kufuta files.

544
00:34:10,429 --> 00:34:13,440
Na kwa kweli, wakati wewe haki bonyeza au Udhibiti click juu ya takataka yako inaweza

545
00:34:13,440 --> 00:34:15,580
au kuchagua faili, Tupu Trash au chochote

546
00:34:15,580 --> 00:34:21,420
na kweli tupu takataka unaweza au kusaga bin, nini hasa kinachotokea basi kwa picha hii?

547
00:34:22,810 --> 00:34:25,969
Zaidi chochote. Hivyo kitu kweli kinachotokea kwenye disk.

548
00:34:25,969 --> 00:34:30,880
>> Na kama sisi tu muda digress na kuandika - I'll tu kutumia nyuma ya hii.

549
00:34:30,880 --> 00:34:34,639
Hivyo sasa ni kubadilisha hadithi kutoka RAM, ambayo ni programu ambapo zipo

550
00:34:34,639 --> 00:34:39,250
wakati wewe mbio yao, ili disk, ambayo ni ambapo wao ni kuhifadhiwa muda mrefu

551
00:34:39,250 --> 00:34:42,920
hata wakati nguvu huenda nje, kwa sasa - na tutaweza kurudi huu katika siku zijazo -

552
00:34:42,920 --> 00:34:46,380
hebu tu kujifanya kuwa hii inawakilisha bidii gari ndani ya kompyuta yako

553
00:34:46,380 --> 00:34:50,110
kwa sababu nyuma katika siku waliyo kuwa mviringo disks, kiasi kama disks floppy.

554
00:34:50,110 --> 00:34:55,130
Hivyo kama wewe kufanya kuwa na baadhi ya nyeti Excel faili, inaweza kuchukua hadi hii chunk ya kumbukumbu

555
00:34:55,130 --> 00:34:59,770
kwenye disk ya kompyuta yako, na Mimi tu kuchora huo holela 1s na sekunde 0.

556
00:34:59,770 --> 00:35:03,970
Wakati wewe Drag faili kama kwamba kwa takataka yako inaweza au kusaga bin,

557
00:35:03,970 --> 00:35:07,750
literally hakuna kinachotokea kwa sababu Apple na Microsoft kuwa tu aliamua

558
00:35:07,750 --> 00:35:10,450
takataka unaweza na kusaga bin ni kweli tu placeholder muda.

559
00:35:10,450 --> 00:35:14,710
Labda hatimaye OS itakuwa tupu ni kwa ajili yenu, lakini kwa kawaida, haina kufanya kitu chochote,

560
00:35:14,710 --> 00:35:17,090
angalau mpaka uko kweli chini juu ya nafasi.

561
00:35:17,090 --> 00:35:20,870
>> Hata hivyo, wakati wa kwenda takataka tupu au tupu ya kusaga bin,

562
00:35:20,870 --> 00:35:23,460
vile vile, hakuna kinachotokea kwa picha hii.

563
00:35:23,460 --> 00:35:28,590
Yote ambayo hufanyika ni mahali pengine kwenye kompyuta yako, kuna baadhi ya aina ya meza.

564
00:35:28,590 --> 00:35:35,400
Ni aina ya kama karatasi kidogo kudanganya kwamba anasema kwamba, hebu sema, resume.doc,

565
00:35:35,400 --> 00:35:40,920
hivyo resume yako katika faili Microsoft Word kutumika kuishi katika eneo 123 juu ya hard disk yako,

566
00:35:40,920 --> 00:35:43,710
si katika kumbukumbu na si katika RAM lakini juu ya hard disk yako,

567
00:35:43,710 --> 00:35:49,050
na JPEG yako sketchy maisha katika 456, na yako Excel faili anaishi 789 au popote.

568
00:35:49,050 --> 00:35:53,640
Wakati wewe kufuta kwa kweli kuondoa takataka au kusaga bin,

569
00:35:53,640 --> 00:35:59,530
picha hii haina mabadiliko. Sekunde 0 na 1s kwenye gari yako ngumu hawaendi popote.

570
00:35:59,530 --> 00:36:03,930
Lakini hii meza, hii database kidogo ya aina, anafanya mabadiliko.

571
00:36:03,930 --> 00:36:08,750
Wakati wewe kufuta resume yako, ni kana kwamba faili ni ilifutwa kwa maana ya baadhi,

572
00:36:08,750 --> 00:36:12,790
lakini kompyuta wote gani ni kusahau ambapo kitu kwamba anaishi kwenye gari yako ngumu.

573
00:36:12,790 --> 00:36:17,870
Sekunde 0 na 1s kwamba compose resume yako au yeyote wa files haya mengine ni bado intact.

574
00:36:17,870 --> 00:36:21,960
>> Hivyo kama wewe alifanya hii ajali, bado kuna uwezekano zisizo sifuri

575
00:36:21,960 --> 00:36:25,800
kwamba unaweza kupona data zako kwa kutumia Norton Utilities au baadhi programu ya kibiashara

576
00:36:25,800 --> 00:36:29,810
kusudi lake katika maisha ni kupata sekunde 0 na 1s ambayo aina ya wamekuwa yatima,

577
00:36:29,810 --> 00:36:33,300
wamesahau hapa lakini kushoto hapa, ili uweze kupata data yako ya nyuma.

578
00:36:33,300 --> 00:36:38,410
Au kuchunguza mauaji wapelelezi na polisi au FBI ingekuwa kweli kuchukua gari ngumu

579
00:36:38,410 --> 00:36:42,550
na kwa kweli kuangalia kwa mifumo ya sekunde 0 na 1s kwamba kuangalia kama JPEGs, kuangalia kama files Excel,

580
00:36:42,550 --> 00:36:46,400
na kuokoa wale njia hata kama kompyuta ina wamesahau yao huko.

581
00:36:46,400 --> 00:36:49,820
Hivyo njia pekee ya kweli kufuta data, kama tutaweza kujadili katika siku zijazo,

582
00:36:49,820 --> 00:36:54,190
ni kwa kusugua au kuifuta faili au disk ngumu na -

583
00:36:54,190 --> 00:36:56,540
Unaweza si kweli kujikwamua na sekunde 0 1s

584
00:36:56,540 --> 00:36:59,440
kwa sababu vinginevyo wewe d kuanza na gari gigabyte ngumu

585
00:36:59,440 --> 00:37:02,380
na wewe d kuishia na gari megabyte ngumu kama wewe daima walikuwa kufuta,

586
00:37:02,380 --> 00:37:04,380
literally, sekunde 0 na 1s.

587
00:37:04,380 --> 00:37:06,310
Basi nini ungefanya kama kweli alitaka cover tracks yako

588
00:37:06,310 --> 00:37:10,510
na tatizo la msingi ni kwamba bado kuna sekunde 0 na 1s kwenye disk?

589
00:37:10,510 --> 00:37:14,930
Naona mtu gesticulating kwamba ungependa kimwili kuvunja kifaa. Hiyo itakuwa kazi.

590
00:37:14,930 --> 00:37:19,600
[Kicheko] Lakini kama kwamba ni aina ya ufumbuzi ghali, nini itakuwa busara zaidi?

591
00:37:19,600 --> 00:37:23,270
Yeah. >> [Mwanafunzi] overwrite yao. >> Overwrite yao na nini? >> [Mwanafunzi] Nyingine data.

592
00:37:23,270 --> 00:37:29,070
Nyingine data. Unaweza tu overwrite disk yako kwa sekunde 0 au 1s au yote sekunde 0, wote 1s.

593
00:37:29,070 --> 00:37:31,230
>> Na kwamba ni kweli nini baadhi ya programu gani.

594
00:37:31,230 --> 00:37:33,570
Unaweza kununua software au hata kupata programu huru,

595
00:37:33,570 --> 00:37:36,610
na hata kujengwa katika Mac OS siku hizi, chini hivyo katika Windows,

596
00:37:36,610 --> 00:37:38,660
ni uwezo wa kufuta salama.

597
00:37:38,660 --> 00:37:41,960
Kweli, kama unataka nyumbani wote kukimbia leo kama una Mac na kufanya hili,

598
00:37:41,960 --> 00:37:45,740
kama nimepata baadhi ya mambo katika takataka yako inaweza, unaweza kufanya salama Tupu Trash,

599
00:37:45,740 --> 00:37:47,610
ambayo haina hasa ile.

600
00:37:47,610 --> 00:37:53,350
Badala tu ya kufuta files hapa, haina kufuta hapa na sekunde 0 1s,

601
00:37:53,350 --> 00:38:01,240
badala yake, ni tu kuvibadilisha wote, kwa mfano, kwa sekunde 0 na dot, dot, dot.

602
00:38:01,240 --> 00:38:05,330
Basi mmoja wa psets yako ya baadaye itakuwa kweli kuwa kwa makusudi kuokoa data -

603
00:38:05,330 --> 00:38:08,430
picha kwamba tumekuwa kuchukuliwa wa watu, mahali, na mambo ya chuo

604
00:38:08,430 --> 00:38:12,810
ambayo tutaweza kufanya sanamu ya kuchunguza mauaji ya kadi ya kumbukumbu kamera ya digital ya,

605
00:38:12,810 --> 00:38:17,120
ambayo ni exact wazo - na itabidi wapewe changamoto ya kweli kupata

606
00:38:17,120 --> 00:38:20,160
mwelekeo kwamba kuwakilisha JPEGs kwenye gari yako ngumu,

607
00:38:20,160 --> 00:38:23,610
kiasi kama mwanafunzi wa zamani ambaye kwamba mimi kusoma barua pepe wiki chache zilizopita alifanya

608
00:38:23,610 --> 00:38:25,860
kuokoa picha ya dada yake.

609
00:38:25,860 --> 00:38:30,300
Mbona sisi kuchukua mapumziko 5-dakika hapa, na tutaweza regroup na zaidi juu ya kumbukumbu.

610
00:38:33,030 --> 00:38:38,610
Hivyo hapa ni ambapo mambo kupata kidogo akili-bending, lakini hii ni hatua ya nguvu sana

611
00:38:38,610 --> 00:38:40,480
kuelekea kuelewa hii yote zaidi.

612
00:38:40,480 --> 00:38:42,900
Hapa ni mpango ujulikanao pointers.c.

613
00:38:42,900 --> 00:38:45,430
Ni kati ya sampuli code ya leo.

614
00:38:45,430 --> 00:38:51,280
Ona kwamba katika mistari michache ya kwanza, 19 kupitia 22, wote sisi ni kufanya ni kitu kama GetString

615
00:38:51,280 --> 00:38:54,460
na kurudi anuani, hifadhi hiyo katika s.

616
00:38:54,460 --> 00:38:58,380
Tangu sasa kwa pset hata 3 kama unataka lakini pset 4 na juu ya

617
00:38:58,380 --> 00:39:01,030
ambapo unaweza kuanza kuchukua magurudumu haya mafunzo mbali mwenyewe,

618
00:39:01,030 --> 00:39:04,030
hakuna sababu ya kujifanya kuwa masharti kuwepo tena.

619
00:39:04,030 --> 00:39:07,030
Ni hakika sawa na kuanza tu kusema * Char.

620
00:39:07,030 --> 00:39:12,610
>> Kama kando, katika marejeo online na katika vitabu unaweza kuona mara nyingi nyota baada ya kutofautiana.

621
00:39:12,610 --> 00:39:15,600
Unaweza hata kuona maeneo kuzunguka pande zote mbili ya hiyo.

622
00:39:15,600 --> 00:39:17,680
Wale wote ni functionally sahihi.

623
00:39:17,680 --> 00:39:21,180
Kwa sasa, ingawa, tutaweza standardize juu ya mbinu hii kufanya super wazi

624
00:39:21,180 --> 00:39:24,000
kwamba * Char ni kama kusema tabia pointer.

625
00:39:24,000 --> 00:39:25,680
Hiyo ni aina data.

626
00:39:25,680 --> 00:39:28,730
Na kisha jina la kutofautiana ni s katika kesi hii.

627
00:39:28,730 --> 00:39:31,180
Hivyo tumekuwa Gotten kamba na tumekuwa kuitwa ni s.

628
00:39:31,180 --> 00:39:35,180
Na kisha chini hapa taarifa kwamba mimi nina kufanya kweli kidogo ya udanganyifu.

629
00:39:35,180 --> 00:39:39,080
Hii inaitwa pointer arithmetic, ambayo ni aina ya rahisi super.

630
00:39:39,080 --> 00:39:41,790
Ni njia tu kuongeza na Ondoa idadi ya kuyatumia.

631
00:39:41,790 --> 00:39:43,660
Lakini hii kweli kazi.

632
00:39:43,660 --> 00:39:49,170
Mpango huu inaonekana Prints string s 1 tabia kwa kuwa mstari wa vile matokeo ya mwisho -

633
00:39:49,170 --> 00:39:54,920
Hivyo tu tunaweza nyara ambapo hii ni kwenda, kufanya kuyatumia, kukimbia kuyatumia, basi mimi zoom in

634
00:39:54,920 --> 00:39:58,940
Sasa basi mimi aina katika kitu kama HELLO na aina Ingiza

635
00:39:58,940 --> 00:40:01,080
na Prints 1 tabia kwa kila mstari.

636
00:40:01,080 --> 00:40:04,730
Hadi pili iliyopita, sisi ingekuwa amefanya hili na nukuu za mraba mabano.

637
00:40:04,730 --> 00:40:09,760
Tunatarajia kuwa kwa kitanzi na tunatarajia kufanya printf ya s [i] na tunatarajia kufanya hivyo tena na tena na tena

638
00:40:09,760 --> 00:40:11,950
na n backslash mwisho wa kila mstari.

639
00:40:11,950 --> 00:40:16,800
Lakini mpango huu ni tofauti. Mpango huu ni kutumia, literally, hesabu.

640
00:40:16,800 --> 00:40:18,860
Basi nini kinaendelea hapa?

641
00:40:18,860 --> 00:40:24,720
Awali ya yote, kabla ya kitanzi hii hata executes, nini, tu kuwa wazi, ni ya kweli?

642
00:40:24,720 --> 00:40:27,270
S ni? >> [Mwanafunzi] anuani. >> Anuani.

643
00:40:27,270 --> 00:40:32,980
>> Na ni anuani ya, katika kesi ya hello, tabia ya kwanza katika neno kwamba, ambayo ni h.

644
00:40:32,980 --> 00:40:37,370
Hivyo ni s, katika mfano huu, hasa anuani ya h.

645
00:40:37,370 --> 00:40:41,850
Hivyo ni nini maana ya kufanya s + i?

646
00:40:41,850 --> 00:40:46,280
Naam, i kuanza saa 0 katika hii kwa kitanzi. Tumefanya mara nyingi.

647
00:40:46,280 --> 00:40:49,760
Mimi ni kwenda hadi urefu wa kamba, inaonekana.

648
00:40:49,760 --> 00:40:53,950
Kadhalika iteration kwanza ya kitanzi hii, i ni wazi 0.

649
00:40:53,950 --> 00:41:01,740
Hivyo msemo huu ni kusema s + i - badala yake, s +0--hiyo ni wazi tu s.

650
00:41:01,740 --> 00:41:04,320
Hiyo ni nini * s hapa?

651
00:41:04,320 --> 00:41:08,530
Sasa sisi ni kutumia nyota katika njia tofauti kidogo.

652
00:41:08,530 --> 00:41:13,080
Hebu kwenda mbele na kujikwamua t kwa sababu sisi ni kosa kuzungumza juu ya t na nakala ya s.

653
00:41:13,080 --> 00:41:15,540
Sasa sisi tu nataka kuwaambia hadithi kuwashirikisha s.

654
00:41:15,540 --> 00:41:20,090
Na hivyo kwa wakati huu, baada ya kuwa na aina kamba, dunia yetu inaonekana kabisa kama ilivyokuwa kabla ya

655
00:41:20,090 --> 00:41:26,630
pamoja na haki ya hifadhi ya anuani ya h na kwa ujumla zaidi akionyesha string hello.

656
00:41:26,630 --> 00:41:33,170
Kama mimi sasa kufanya mstari kama * (s + i), hebu jaribu hii nje.

657
00:41:33,170 --> 00:41:40,140
Hivyo * (s + i). Hebu kurahisisha hii kwa sababu hii ni 0, hivyo hii ni * (s 0).

658
00:41:40,140 --> 00:41:43,790
Naam, kusubiri dakika. Kurahisisha zaidi. Hii ni * (s).

659
00:41:43,790 --> 00:41:47,020
Naam, sasa mabano ni aina ya kijinga, hivyo sasa hebu tu kufanya * s.

660
00:41:47,020 --> 00:41:50,540
Hivyo katika iteration ya kwanza ya hii kitanzi, kwamba line hiyo yalionyesha, 26,

661
00:41:50,540 --> 00:41:53,650
ni kiasi pretty sawa na uchapishaji huu.

662
00:41:53,650 --> 00:41:56,040
Je, ni aina ya data * s?

663
00:41:56,040 --> 00:42:00,770
Katika hali hii, kwa sababu nyota hutokea kwa kuwa karibu na s yenyewe,

664
00:42:00,770 --> 00:42:04,930
lakini zaidi hasa, kwa sababu sisi ni tena kutangaza s,

665
00:42:04,930 --> 00:42:09,730
sisi siyo kujenga variable tena, hakuna kutaja ya * Char katika mstari 26,

666
00:42:09,730 --> 00:42:14,280
hakuna kutaja ya kamba Keyword, sisi ni tu kwa kutumia variable kuitwa s,

667
00:42:14,280 --> 00:42:19,650
zinageuka sasa nyota ina tofauti kidogo na, admittedly, kuwachanganya maana.

668
00:42:19,650 --> 00:42:26,590
* S hapa ina maana ya kwenda anuani katika s na magazeti chochote ni pale.

669
00:42:26,590 --> 00:42:33,750
Hivyo s ni hapa, * s ni - aina ya kama Chutes na Ladders, kufuata mshale - hapa.

670
00:42:33,750 --> 00:42:35,850
Hivyo hii ni * s.

671
00:42:35,850 --> 00:42:39,060
>> Basi nini anapata kuchapishwa kwenye iteration ya kwanza ya kwamba kitanzi katika mstari 26?

672
00:42:39,060 --> 00:42:42,170
Mimi magazeti nje% c, ambayo ni placeholder kwa tabia,

673
00:42:42,170 --> 00:42:48,520
kisha \ n kwa mstari mpya. * (S + i) ambapo i ni 0 ni tu hii.

674
00:42:48,520 --> 00:42:53,670
Basi nini Char gani mimi kuweka katika kwa c%? H.

675
00:42:53,670 --> 00:42:56,900
Katika iteration ya pili ya kitanzi - pengine unaweza kuona ambapo hii ni kwenda -

676
00:42:56,900 --> 00:43:01,350
iteration ijayo i ni wazi 1, hivyo njia hii ya 1,

677
00:43:01,350 --> 00:43:05,580
na kisha sasa sijui haja mabano kwa sababu sasa nyota anahitaji kusema

678
00:43:05,580 --> 00:43:08,620
kwenda kumbukumbu anuani ya 1.

679
00:43:08,620 --> 00:43:14,170
Je, ni s? Hebu roll nyuma katika wakati na kusema arrow hii sasa si kweli kufanya sisi neema yoyote.

680
00:43:14,170 --> 00:43:18,450
Hebu zaidi hasa kusema kwamba hii ni hifadhi ya 123 idadi

681
00:43:18,450 --> 00:43:25,110
kwa sababu ya kuanza kwa kamba hii hello, hii ni anwani ya 123, hii ni 124, na kadhalika.

682
00:43:25,110 --> 00:43:30,550
Kadhalika iteration pili wakati mimi kusema s 1, hiyo ni kama kusema 123 1,

683
00:43:30,550 --> 00:43:35,340
inayojulikana kama 124, hivyo nini Char anapata kuchapishwa kwenye iteration pili?

684
00:43:35,340 --> 00:43:37,850
E katika kumbukumbu anuani 124.

685
00:43:37,850 --> 00:43:44,440
Ndipo + tena, 125, 126, 127, na kitanzi hii nashiriki ataacha kabla ya sisi kupata hapa

686
00:43:44,440 --> 00:43:49,040
kwa sababu mimi nina kutumia strlen kuhakikisha kwamba i haina hesabu kubwa mno.

687
00:43:49,040 --> 00:43:50,810
Hivyo kwamba pia ni yake.

688
00:43:50,810 --> 00:43:55,000
Tena, hii ni kama tu kwamba sisi tulikuwa kufanyika wiki iliyopita.

689
00:43:55,000 --> 00:43:59,200
Hebu kuandika kwenye mstari chini hata kama hatutaki kufanya wote.

690
00:43:59,200 --> 00:44:02,500
Hii ni sawa sasa kwa hii.

691
00:44:02,500 --> 00:44:08,310
>> Hivyo hata kama ni s kamba, kama tumekuwa na kuiita kwa wiki, s ni kweli * Char.

692
00:44:08,310 --> 00:44:13,270
Hivyo kama tunataka kuwa super anal, ni kweli sahihi kuandika tabia maalum

693
00:44:13,270 --> 00:44:17,490
katika eneo idh kutumia anwani hizi numeric na hii operator nyota,

694
00:44:17,490 --> 00:44:20,470
lakini kusema ukweli, hii ni kiasi tu safi. Hivyo hii si mbaya.

695
00:44:20,470 --> 00:44:26,720
Hakuna sababu ya kuacha kufanya mstari 27 hapa, lakini 26 ni functionally sawa,

696
00:44:26,720 --> 00:44:31,570
na ni functionally sawa kwa sababu hasa kwamba sisi tumekuwa kujadili hivi sasa.

697
00:44:31,570 --> 00:44:33,650
Na Mwisho, 29 ni nzuri tu ya mazoezi.

698
00:44:33,650 --> 00:44:38,420
Wito bure ya s ina maana kwamba sasa wewe ni kutoa nyuma kumbukumbu kwamba GetString akakupeni

699
00:44:38,420 --> 00:44:41,630
kwa sababu tena, kama nilivyoeleza Jumatatu, GetString kwa wiki

700
00:44:41,630 --> 00:44:44,180
imekuwa kuanzisha mdudu katika kanuni yako.

701
00:44:44,180 --> 00:44:46,490
Code yako kwa wiki imekuwa na uvujaji kumbukumbu

702
00:44:46,490 --> 00:44:49,970
ambapo tumekuwa kuuliza GetString kwa kumbukumbu lakini wewe sijawahi kutoa ni nyuma.

703
00:44:49,970 --> 00:44:53,410
Na kwamba alikuwa makusudi waliochaguliwa na sisi pedagogically

704
00:44:53,410 --> 00:44:55,880
sababu ni tu sana kufikiria kuhusu mapema.

705
00:44:55,880 --> 00:44:57,710
Lakini sasa tunahitaji zaidi ulinganifu.

706
00:44:57,710 --> 00:45:00,830
Ukiuliza kompyuta kwa ajili ya kumbukumbu, kama ilivyo kwa ajili GetString,

707
00:45:00,830 --> 00:45:02,820
kama ni kesi inaonekana kwa malloc,

708
00:45:02,820 --> 00:45:07,970
lazima sasa kwa pset kuendelea 4 pia bure yoyote kumbukumbu hizo.

709
00:45:07,970 --> 00:45:11,650
Taarifa hii ni tofauti na kusema n int.

710
00:45:11,650 --> 00:45:15,040
Huna haja ya bure hii kwa sababu wewe hakutuita GetString

711
00:45:15,040 --> 00:45:16,890
na wewe hakutuita malloc.

712
00:45:16,890 --> 00:45:20,610
>> Na hata kama wewe kuitwa GetInt kama tutaweza hatimaye kuona,

713
00:45:20,610 --> 00:45:25,520
GetInt haina kutenga kumbukumbu kwa sababu wewe unaweza kweli kupita karibu integers

714
00:45:25,520 --> 00:45:29,430
na ikifungwa na chars njia tu tumekuwa kufanya kwa wiki.

715
00:45:29,430 --> 00:45:33,960
Strings, ingawa, ni maalum kwa sababu kwa kweli wao ni concatenation ya chars nyingi.

716
00:45:33,960 --> 00:45:37,450
Hivyo wao ni tu tofauti na chars na ikifungwa na ints na kama.

717
00:45:37,450 --> 00:45:39,980
Lakini tutaweza kuja nyuma na kwamba kabla ya muda mrefu.

718
00:45:39,980 --> 00:45:44,920
Maswali yoyote juu ya hili kisha mwanzo ya kuyatumia? Yeah.

719
00:45:44,920 --> 00:45:49,690
[Inaudible mwanafunzi swali]

720
00:45:49,690 --> 00:45:51,440
Ah, vizuri sana swali.

721
00:45:51,440 --> 00:45:55,790
Moja ya mambo machache C kweli haina maana wewe, ambayo ni rahisi,

722
00:45:55,790 --> 00:46:00,110
je, ni takwimu nje kwa nini ya kawaida ni wa aina data

723
00:46:00,110 --> 00:46:03,060
na kisha gani kwamba aina ya kuzidisha kwa ajili yenu.

724
00:46:03,060 --> 00:46:06,610
Hii ni lisilo katika kesi ya chars kwa sababu karibu kila mara Char ni 1 Byte,

725
00:46:06,610 --> 00:46:08,150
hivyo hii kazi tu.

726
00:46:08,150 --> 00:46:11,220
Lakini kwa ajili ya majadiliano, kama wewe walikuwa kweli uchapishaji integers

727
00:46:11,220 --> 00:46:15,500
na wewe walikuwa wakijaribu magazeti nje baadhi ya thamani ya kwamba alikuwa akionyesha integer,

728
00:46:15,500 --> 00:46:20,720
wewe vile vile bila haja ya kufanya + 4 * i tu kwa sababu ni int 4 ka.

729
00:46:20,720 --> 00:46:25,780
Pointer arithmetic ina maana kuwa C na compiler kufanya math kwamba wote kwa ajili yenu.

730
00:46:25,780 --> 00:46:29,190
Wote una jali ni hesabu katika aina ya hisia za binadamu. Yeah.

731
00:46:29,190 --> 00:46:35,200
[Mwanafunzi] Kama wewe kutangaza string ndani kwa kitanzi, je, una huru baadaye?

732
00:46:35,200 --> 00:46:36,760
Nzuri swali.

733
00:46:36,760 --> 00:46:41,390
>> Kama alitangaza ndani ya kamba ya kwa kitanzi, unahitaji huru baadaye?

734
00:46:41,390 --> 00:46:47,520
Wewe tu haja ya kumbukumbu bure kwamba kutenga na GetString au na malloc.

735
00:46:47,520 --> 00:46:53,110
Hivyo kama wewe tu kusema kitu kama - basi mimi kuweka braces curly sasa ili code wote ni kuhusiana.

736
00:46:53,110 --> 00:46:58,580
Kama alifanya kitu, angalau buggily, kama hii, char * t = s,

737
00:46:58,580 --> 00:47:03,450
huna haja ya t bure kwa sababu t hawakuwa kuhusisha yoyote kutaja malloc au GetString.

738
00:47:03,450 --> 00:47:08,960
Kama kwa kulinganisha wewe alifanya hivyo, GetString, basi ndiyo, ungependa haja ya t bure.

739
00:47:08,960 --> 00:47:14,350
Na kwa kweli, nafasi yako ya pekee ya kufanya hivyo ni sasa ndani ya kitanzi hii, kwa suala hilo hilo la wigo

740
00:47:14,350 --> 00:47:16,060
kwamba tumekuwa kujadiliwa katika siku za nyuma.

741
00:47:16,060 --> 00:47:18,830
Vinginevyo wewe d kuwa kugawa kumbukumbu, kugawa kumbukumbu, kugawa kumbukumbu,

742
00:47:18,830 --> 00:47:21,230
na mwisho wa mpango kwa sababu wewe ni nje ya kitanzi kwamba,

743
00:47:21,230 --> 00:47:24,240
t haipo, lakini kamwe aliiambia mfumo wa uendeshaji

744
00:47:24,240 --> 00:47:26,750
kwamba hawakuwa na haja ya kuwa kumbukumbu tena.

745
00:47:26,750 --> 00:47:30,430
Na kabla ya muda mrefu, kwa pset 4 au 5 tutaweza kuvipa wewe na programu inayoitwa Valgrind,

746
00:47:30,430 --> 00:47:34,160
ambayo ni sawa katika roho kwa GDB katika kwamba ni got kiasi fulani ya interface arcane,

747
00:47:34,160 --> 00:47:35,750
lakini kusudi lake katika maisha ni kukusaidia.

748
00:47:35,750 --> 00:47:39,380
Na Valgrind ni mpango huo katika siku za baadaye kutafuta mipango yako

749
00:47:39,380 --> 00:47:42,550
kuangalia kwa uvujaji kumbukumbu, kama kutoka GetString au malloc,

750
00:47:42,550 --> 00:47:47,800
ambayo tutaweza kuanza kutumia zaidi ya yote kama sisi kuacha kutumia maktaba CS50 kama mengi.

751
00:47:47,800 --> 00:47:53,030
Sisi hatimaye sasa kuwa na aina ya msamiati na aina ya mtindo wa akili katika nadharia

752
00:47:53,030 --> 00:47:55,170
na katika kutatua mpango kuvunjwa.

753
00:47:55,170 --> 00:47:59,410
>> Hivyo katika mpango huu kuvunjwa, wabadilishane kazi ndani ya kubadilishana,

754
00:47:59,410 --> 00:48:05,280
lakini kamwe kweli kazi katika kuu kwa sababu kuu kupita katika x na y, wanakumbuka,

755
00:48:05,280 --> 00:48:07,260
na wale zimepitishwa na maadili, hivyo kusema.

756
00:48:07,260 --> 00:48:09,330
Nakala za wamepewa wabadilishane.

757
00:48:09,330 --> 00:48:12,520
Na mwisho wa kubadilishana, a na b alikuwa kweli imekuwa kubadilishana,

758
00:48:12,520 --> 00:48:16,120
lakini bila shaka x na y, kama sisi kujadiliwa siku ya Jumatatu, isingekuwa.

759
00:48:16,120 --> 00:48:19,940
Hivyo napendekeza katika kijani hapa kwamba hii ni kweli suluhisho hapa.

760
00:48:19,940 --> 00:48:22,640
Na kweli, basi mimi hoja nyota wangu tu kuwa thabiti

761
00:48:22,640 --> 00:48:24,440
hata ingawa, tena, functionally hii haijalishi.

762
00:48:24,440 --> 00:48:28,730
Katika wiki baadaye tutaweza kueleza lini na kwa nini ni gani jambo.

763
00:48:28,730 --> 00:48:30,600
Hivyo katika kijani sasa ni ufumbuzi.

764
00:48:30,600 --> 00:48:33,700
Kusema ukweli, inaonekana sana nzima messier kwa sababu mimi na wote wa nyota hizi.

765
00:48:33,700 --> 00:48:35,380
Hebu kumweka nje jambo moja.

766
00:48:35,380 --> 00:48:40,040
line ya juu hapa ambapo anasema int * a na b int *

767
00:48:40,040 --> 00:48:42,820
ni kimsingi kufanya kitu kimoja kama daima ina.

768
00:48:42,820 --> 00:48:47,070
Ni kutangaza hoja 2 au vigezo wabadilishane,

769
00:48:47,070 --> 00:48:49,940
ya kwanza ambayo ni pointer int walioitwa,

770
00:48:49,940 --> 00:48:53,100
pili ambayo ni ya pointer int kuitwa b.

771
00:48:53,100 --> 00:48:55,770
Kitu tu kwamba ni mpya katika hatua hii ni ukweli kwamba kuna nyota huko.

772
00:48:55,770 --> 00:48:59,340
>> Hiyo ina maana gani? si int, b si int.

773
00:48:59,340 --> 00:49:04,100
ni anuani ya int na b ni anuani ya int tofauti.

774
00:49:04,100 --> 00:49:06,980
Chini hapa, hii ni pale ambapo mimi kukubali C anapata utata.

775
00:49:06,980 --> 00:49:09,790
Sasa sisi ni kutumia nyota, lakini ina maana tofauti katika muktadha huu.

776
00:49:09,790 --> 00:49:13,150
Kwa sababu sisi siyo kutangaza kuyatumia kama sisi ni hapa juu,

777
00:49:13,150 --> 00:49:15,500
hapa sisi ni dereferencing mambo.

778
00:49:15,500 --> 00:49:21,520
Basi kitaalam, nyota katika muktadha huu wa mstari wa kwanza, wa pili, na wa tatu ndani ya kubadilishana

779
00:49:21,520 --> 00:49:24,560
ni operator dereference, ambayo ina maana tu kwenda huko.

780
00:49:24,560 --> 00:49:27,400
Hivyo tu kama kidole changu ikifuatiwa mshale h,

781
00:49:27,400 --> 00:49:31,100
* Njia kwenda kwa anwani hiyo na kupata mimi int kwamba pale.

782
00:49:31,100 --> 00:49:34,250
* B njia kwenda anuani na kupita kwangu kuna nini huko.

783
00:49:34,250 --> 00:49:40,730
Basi hebu redraw picha kutoka Jumatatu sasa kutumia stack ya muafaka,

784
00:49:40,730 --> 00:49:43,130
moja chini ambayo ni ya kwenda kuwa kuu,

785
00:49:43,130 --> 00:49:47,600
moja juu ya ambayo ni kwenda kuwa byta,

786
00:49:47,600 --> 00:49:50,880
hivyo kwamba dunia yetu inaonekana, kama Jumatatu, kama hii.

787
00:49:50,880 --> 00:49:53,620
Hapa ni chunk ya kumbukumbu kwamba kuu ni kwenda kutumia.

788
00:49:53,620 --> 00:49:56,520
>> Kumbuka kutoka Jumatatu kwamba mpango tu alikuwa vigezo 2,

789
00:49:56,520 --> 00:50:01,930
mtu mmoja aitwaye x na mtu mmoja aitwaye y, na mimi alikuwa na kuweka namba 1 na 2 hapo.

790
00:50:01,930 --> 00:50:06,580
Sasa wakati mimi kuwaita wabadilishane kama mimi alifanya juu ya Jumatatu,

791
00:50:06,580 --> 00:50:11,000
hapo awali wakati mimi kutumika version nyekundu ya mpango huu, ambayo inaonekana kama hii,

792
00:50:11,000 --> 00:50:17,470
I got vigezo 2, b na, na ni nini sisi kuandika hapa na hapa?

793
00:50:17,470 --> 00:50:21,160
Tu 1 na 2, literally nakala za x na y.

794
00:50:21,160 --> 00:50:23,070
Leo sisi mabadiliko hayo.

795
00:50:23,070 --> 00:50:28,510
Leo badala ya kupita katika ints na b tunakwenda kupita katika anwani 2.

796
00:50:28,510 --> 00:50:34,290
Wale anwani kutokea kwa uhakika na ints, lakini wale anwani si ints wenyewe.

797
00:50:34,290 --> 00:50:37,330
Wao ni anwani. Ni kama anwani ya posta badala yake.

798
00:50:37,330 --> 00:50:40,580
Hivyo sasa tunahitaji tu kutoa mwenyewe kidogo zaidi kwa undani juu ya screen.

799
00:50:40,580 --> 00:50:43,250
Hii ni kumbukumbu ya kompyuta yangu kama ni kuwa siku zote.

800
00:50:43,250 --> 00:50:45,120
Sasa tunahitaji baadhi holela hesabu ya mfuko huo.

801
00:50:45,120 --> 00:50:50,580
Basi hebu kusema tu, tu kwa bahati, kwamba hii ni kumbukumbu ya anuani 123, 124.

802
00:50:50,580 --> 00:50:55,660
Hebu tu kusema hii ni 125, hii ni 126, na kadhalika, lakini hiyo ni kabisa holela.

803
00:50:55,660 --> 00:50:58,590
Sisi tu haja ya baadhi ya mpango wa nambari katika kumbukumbu yangu.

804
00:50:58,590 --> 00:51:04,030
Hivyo sasa wakati mimi kwa kweli kupita katika x na y, Sitakuja kupita katika x na y;

805
00:51:04,030 --> 00:51:08,400
Mimi naenda kupita katika anwani ya posta, ili kuzungumza, ya x na y ya

806
00:51:08,400 --> 00:51:11,870
ili kile anapata kuhifadhiwa hapa na hapa ni si 1 na 2,

807
00:51:11,870 --> 00:51:16,030
lakini kama unaweza kuona Nakala yangu ndogo, nini anapata kupita hapa na hapa?

808
00:51:16,030 --> 00:51:23,340
[Inaudible mwanafunzi majibu] >> Hasa. 123 anapata kuweka hapa na 124 anapata kuweka hapa.

809
00:51:23,340 --> 00:51:28,910
>> Sasa, kwa sababu mimi kutumika nyota katika njia hii ya kwanza kabisa line up hapa kwa juu,

810
00:51:28,910 --> 00:51:34,340
mpango wangu tu anajua kwamba 123 na 124, ingawa wao ni wazi integers

811
00:51:34,340 --> 00:51:40,160
kwamba binadamu yeyote anaweza taarifa, wanapaswa kufasiriwa kama anwani, nambari anwani.

812
00:51:40,160 --> 00:51:43,250
Wao si katika na wenyewe ints, wao uko anwani,

813
00:51:43,250 --> 00:51:46,120
na kwamba kwa sababu mimi waziwazi kuweka nyota huko.

814
00:51:46,120 --> 00:51:51,360
Hivyo sasa katika line yangu ya kwanza, ya pili, na wa tatu wa code halisi kile kinachotokea hapa?

815
00:51:51,360 --> 00:51:53,380
Hebu kuteka wengine wa picha.

816
00:51:53,380 --> 00:51:56,980
TMP ni kama ilikuwa siku ya Jumatatu. Hakuna kitu maalum kuhusu TMP.

817
00:51:56,980 --> 00:52:03,060
Ni haki ya mitaa 32 bits variable, na ndani ya kwamba mimi inaonekana kuhifadhi thamani ya *.

818
00:52:03,060 --> 00:52:08,580
Sasa, kama mimi tu alisema TMP = a, gani mimi kuweka hapa? >> [Mwanafunzi] 123.

819
00:52:08,580 --> 00:52:10,370
123. Lakini si kwamba nini mimi kufanya.

820
00:52:10,370 --> 00:52:13,670
Mimi kusema TMP = * a. Star njia kwenda huko.

821
00:52:13,670 --> 00:52:19,370
Hivyo hapa ni, 123. Jinsi gani mimi kwenda huko? Kujifanya kama kuna mshale.

822
00:52:19,370 --> 00:52:24,460
Naam, kuna ni, 1. Basi nini anapata kuhifadhiwa katika TMP, inaonekana? 1 tu.

823
00:52:24,460 --> 00:52:29,620
Hivyo kwa maneno mengine, TMP ni * a, * njia kwenda kwa anwani hiyo kwa sasa ni katika,

824
00:52:29,620 --> 00:52:31,320
ambayo ni inaonekana 123.

825
00:52:31,320 --> 00:52:33,910
>> Okay, hapa sisi ni katika eneo 123, naona idadi 1,

826
00:52:33,910 --> 00:52:35,670
hivyo mimi nina kwenda kuweka namba 1 hapo.

827
00:52:35,670 --> 00:52:39,020
Sasa nini mimi katika mstari 2, * a = * b?

828
00:52:39,020 --> 00:52:44,570
Hii moja ni kidogo zaidi kushiriki kwa sababu sasa ni nini? Ni 123.

829
00:52:44,570 --> 00:52:50,220
Hivyo * ni wapi? Haki ambapo nilikuwa kabla. Hivyo kwenda huko. Sawa.

830
00:52:50,220 --> 00:52:53,420
Sasa, mwishowe, na kisha hatimaye huu utaanza kufanya akili, hopefully,

831
00:52:53,420 --> 00:53:00,280
* B ina maana nini katika b? 124. Kwa hiyo mimi haja ya kwenda huko, ambayo ni 2.

832
00:53:00,280 --> 00:53:03,430
Basi je, mimi kuweka wapi?

833
00:53:03,430 --> 00:53:10,100
2 huenda katika hapa kwa sababu * b huenda katika *. Hivyo mimi itabidi kufanya hivyo.

834
00:53:10,100 --> 00:53:13,120
Na unaweza tayari kuona, pengine, kwamba sisi ni hivyo karibu sana

835
00:53:13,120 --> 00:53:17,710
kutatua hayo ya kijinga, rahisi tatizo kikamilifu, kwa mara ya kwanza

836
00:53:17,710 --> 00:53:20,920
kwa sababu sasa bado tuna kumbukumbu ya kile x ilikuwa,

837
00:53:20,920 --> 00:53:23,230
tuna nakala 2, admittedly, ya y,

838
00:53:23,230 --> 00:53:25,850
lakini mstari 3 sasa anasema * b.

839
00:53:25,850 --> 00:53:31,080
Hivyo hapa ni b. * B njia kwenda huko. Hivyo ambapo ni mahali 124?

840
00:53:31,080 --> 00:53:35,560
Ni dhahiri hapa. Basi je, mimi kuweka hapa? Ni wazi, TMP.

841
00:53:35,560 --> 00:53:39,600
Hivyo sasa mimi kufanya hili. Hivyo nina 1 hapa na 2 hapa.

842
00:53:39,600 --> 00:53:43,560
Na sasa nini kuhusu haya yote, 123, 124, na 1?

843
00:53:43,560 --> 00:53:47,910
Haraka kama byta anarudi, kumbukumbu hii ni nzuri kama waliopotea

844
00:53:47,910 --> 00:53:51,070
kwa sababu haraka kama byta anarudi, mfumo wa uendeshaji

845
00:53:51,070 --> 00:53:54,190
ni huru kutumia kwamba kumbukumbu tena katika siku zijazo.

846
00:53:54,190 --> 00:53:58,870
Tu kuu ya kumbukumbu chini ya hii stack kinachojulikana vijiti kuzunguka.

847
00:53:58,870 --> 00:54:01,470
>> Na hivyo sisi hatimaye kuwa sasa version kazi.

848
00:54:01,470 --> 00:54:06,310
Hebu kwenda katika swap.c, na taarifa zifuatazo.

849
00:54:06,310 --> 00:54:11,280
Katika juu ya mpango nimekuwa iliyopita mfano wangu kuwa int * a na int * b.

850
00:54:11,280 --> 00:54:15,000
Hivyo kitu pekee mimi iliyopita na kwenda kutoka nyekundu, ambayo ilikuwa mbaya, kwa kijani, ambayo ni nzuri,

851
00:54:15,000 --> 00:54:17,350
ni mimi aliongeza nyota hizi leo.

852
00:54:17,350 --> 00:54:21,520
Lakini kisha chini hapa katika wabadilishane yenyewe nilikuwa na nakala, kuweka nini ilikuwa tu kwenye slide.

853
00:54:21,520 --> 00:54:24,140
Nina nyota hapa, nyota hapa - kwamba mechi mfano -

854
00:54:24,140 --> 00:54:27,930
na kisha mambo yote haya sasa kuwa na nyota isipokuwa kwa TMP

855
00:54:27,930 --> 00:54:30,680
kwa sababu matumizi ya variable muda, kuna kitu kipya huko.

856
00:54:30,680 --> 00:54:33,040
Mimi tu haja ya kuhifadhi muda kwa int.

857
00:54:33,040 --> 00:54:34,820
Hivyo hatuna haja nyota huko.

858
00:54:34,820 --> 00:54:39,310
Sisi tu haja ya nyota ili tuweze kuvuka mipaka ya aina hii ya holela

859
00:54:39,310 --> 00:54:42,900
kati ya hizi muafaka 2 katika kumbukumbu ya kompyuta yangu.

860
00:54:42,900 --> 00:54:45,630
Lakini jambo moja mwisho kubadilika, na unaweza kuwa glimpsed tayari.

861
00:54:45,630 --> 00:54:48,810
Gani nyingine mstari ni wazi tofauti na sasa? >> [Mwanafunzi] & x.

862
00:54:48,810 --> 00:54:53,270
>> Yeah, hivyo ni 25 mstari wa mwisho wa code mimi haja ya kubadili kwa hii kazi.

863
00:54:53,270 --> 00:54:58,360
wiki iliyopita na hata juu ya Jumatatu mstari 25 inaonekana kama hii, wabadilishane x na y,

864
00:54:58,360 --> 00:55:02,020
na hii mara tu kuvunjwa kwa sababu kama wewe kusema byta (x, y)

865
00:55:02,020 --> 00:55:05,660
wewe ni kutoa nakala za x na y wabadilishane, basi ni kufanya jambo yake,

866
00:55:05,660 --> 00:55:09,080
lakini wewe ni kweli kamwe kubadilisha x na y yenyewe.

867
00:55:09,080 --> 00:55:12,880
Hivyo hata kama wewe sijawahi kuona tabia hii kabla na ampersand katika kanuni,

868
00:55:12,880 --> 00:55:15,860
tu kuchukua nadhani. Je ampersand kufanya, inaonekana?

869
00:55:15,860 --> 00:55:17,890
[Mwanafunzi] Takes anuani. >> Takes anuani.

870
00:55:17,890 --> 00:55:21,160
Hivyo ni kusema ampersand nipe anuani ya x.

871
00:55:21,160 --> 00:55:25,590
Nani anajua ambapo ni? Hutokea kwa kuwa 123. Mimi sijali. Tu nipe anuani ya x.

872
00:55:25,590 --> 00:55:28,340
& Y maana nipe anuani ya y.

873
00:55:28,340 --> 00:55:34,450
Na katika hadithi ni kwamba hatua kikamilifu sambamba na picha tulianzisha wakati iliyopita.

874
00:55:34,450 --> 00:55:38,310
>> Hivyo mimi itabidi kukubali kuyatumia, hakika kwa mimi wakati mimi kwanza kuanza kujifunza hii,

875
00:55:38,310 --> 00:55:40,570
walikuwa dhahiri moja ya mambo ya gumu wrap akili yangu kote.

876
00:55:40,570 --> 00:55:43,760
Lakini kutambua, hasa kama sisi kuendelea kucheza na aina hii ya mambo,

877
00:55:43,760 --> 00:55:48,030
kama wewe kuvunja chini kwa aina hizi super rahisi ya kielimu uninteresting matatizo

878
00:55:48,030 --> 00:55:52,270
ya kusonga tu idadi kote, jibu mkanganyiko na kuyatumia

879
00:55:52,270 --> 00:55:56,590
kweli inaweza kuwa derived kutoka mechanics haya ya msingi sana.

880
00:55:56,590 --> 00:55:59,070
Hapa ni anuani. Kwenda huko na nyota.

881
00:55:59,070 --> 00:56:03,830
Au kinyume chake, hapa ampersand. Kufikiri nini anwani kweli ni.

882
00:56:03,830 --> 00:56:06,270
Wote haki.

883
00:56:06,270 --> 00:56:09,000
Hivyo ambapo ni aina ya kumbukumbu hii kuja kutoka?

884
00:56:09,000 --> 00:56:12,360
Tumepata picha hii michache ya nyakati, na mimi kuendelea kuahidi tutaweza kuja nyuma yake,

885
00:56:12,360 --> 00:56:14,920
lakini hapa ni uwakilishi wa kumbukumbu ya kompyuta yako

886
00:56:14,920 --> 00:56:17,420
hiyo kidogo zaidi kuliko labeled ubao wetu hapa ni.

887
00:56:17,420 --> 00:56:21,590
Nakala sehemu ya juu inawakilisha nini kwa heshima na mpango wako?

888
00:56:21,590 --> 00:56:26,090
[Inaudible mwanafunzi majibu] >> Samahani? Sema tena.

889
00:56:26,090 --> 00:56:28,660
[Mwanafunzi] mpango halisi. >> Mpango halisi.

890
00:56:28,660 --> 00:56:32,430
>> Hivyo Clang sekunde 0 na 1s kwa kuwa compiled baada ya kuandika code C na kisha kukimbia

891
00:56:32,430 --> 00:56:35,910
na kuzalisha ncha sekunde 0 na 1s up kupata tucked huko katika kumbukumbu

892
00:56:35,910 --> 00:56:38,570
sababu wakati wewe bonyeza mara mbili icon kwenye Mac au PC yako

893
00:56:38,570 --> 00:56:43,010
au kukimbia amri kama Mario katika haraka yako, sekunde 0 yako na 1s kutoka disk

894
00:56:43,010 --> 00:56:45,700
kupata kubeba katika kumbukumbu ili kompyuta inaweza kuendesha yao

895
00:56:45,700 --> 00:56:47,540
na kuitekeleza kwa haraka zaidi.

896
00:56:47,540 --> 00:56:50,880
Hivyo initialized data na data uninitialized, sisi si kuzungumza mengi juu ya hizo,

897
00:56:50,880 --> 00:56:52,420
lakini wale ni tu kimataifa vigezo.

898
00:56:52,420 --> 00:56:54,710
Initialized maana vigezo kimataifa uliyonipatia maadili;

899
00:56:54,710 --> 00:56:59,300
uninitialized maana vigezo kimataifa kwamba hawakuwa bado kutoa maadili kwa.

900
00:56:59,300 --> 00:57:01,900
Kisha kuna vigezo mazingira haya ambayo mimi itabidi kabisa kupitisha mkono wangu,

901
00:57:01,900 --> 00:57:04,860
lakini wao wapo na kuwa maduka mambo kama user jina lako

902
00:57:04,860 --> 00:57:08,090
na mengine ya aina ya maelezo ya chini ya kiwango.

903
00:57:08,090 --> 00:57:12,880
Lakini vipande juiciest ya layout kumbukumbu yako ni hiki kitu kinachoitwa stack na lundo.

904
00:57:12,880 --> 00:57:17,470
stack tena, kwa kuwa wazi, ni kumbukumbu kuwa alitumia kila kazi ni wito,

905
00:57:17,470 --> 00:57:19,710
wakati wowote kuna vigezo mitaa

906
00:57:19,710 --> 00:57:22,120
na wakati wowote kuna vigezo kuwa alipita kote.

907
00:57:22,120 --> 00:57:24,490
Yote ambayo hufanyika katika stack.

908
00:57:24,490 --> 00:57:29,570
lundo sisi si aliongea juu, lakini kuchukua nadhani ambaye anatumia lundo.

909
00:57:31,120 --> 00:57:32,690
Tu chunk tofauti ya kumbukumbu.

910
00:57:32,690 --> 00:57:36,620
Hufanyika kwa kuwa inayotolewa hapa kwa juu, lakini hiyo ni holela pictorial mkataba.

911
00:57:36,620 --> 00:57:41,670
Nani amefunguliwa kutumia kumbukumbu kutoka lundo kwa wiki?

912
00:57:41,670 --> 00:57:44,830
Ni kitaalam wewe lakini si moja kwa moja. >> [Mwanafunzi] GetString.

913
00:57:44,830 --> 00:57:47,950
GetString na malloc. Hivyo hapa ni tofauti ya kimsingi.

914
00:57:47,950 --> 00:57:51,300
>> Unajua kwa wiki chache zilizopita kwamba kama unahitaji kumbukumbu, tu kutangaza kutofautiana.

915
00:57:51,300 --> 00:57:54,560
Kama unahitaji kura ya kumbukumbu, kutangaza haki ndani ya safu ya kazi yako.

916
00:57:54,560 --> 00:57:59,620
Lakini tatizo tumekuwa naendelea yanayowakabili ni kama wewe kutangaza vigezo ndani ya nchi ndani ya utendaji,

917
00:57:59,620 --> 00:58:05,340
haraka kama anarudi kazi, nini kinatokea kwa kumbukumbu na vigezo wale?

918
00:58:05,340 --> 00:58:09,620
Tu aina ya ni tena kwako, sawa? Ni tu kutoweka aina ya conceptually.

919
00:58:09,620 --> 00:58:13,950
Ni bado kuna kimwili, ni wazi, lakini ni hakuna tena haki yako ya kutumia.

920
00:58:13,950 --> 00:58:17,160
Hii ni wazi tatizo kama unataka kuandika kazi katika maisha

921
00:58:17,160 --> 00:58:20,440
kwamba kweli kutenga kumbukumbu na si kutoa ni nyuma mara moja.

922
00:58:20,440 --> 00:58:24,180
Uchunguzi katika kumweka: kusudi GetString katika maisha ni kuwa hakuna wazo mapema

923
00:58:24,180 --> 00:58:26,390
jinsi kubwa ya kamba nitakacho andika katika keyboard,

924
00:58:26,390 --> 00:58:30,390
lakini ni got kuwa na uwezo wa kutenga kumbukumbu kushikilia Daudi au hujambo

925
00:58:30,390 --> 00:58:32,860
au insha nzima kwamba mtumiaji anaweza kuwa typed in

926
00:58:32,860 --> 00:58:35,280
Hivyo GetString imekuwa ikitumia malloc.

927
00:58:35,280 --> 00:58:38,910
Malloc hiyo lazima kutumia si stack;

928
00:58:38,910 --> 00:58:40,770
badala ni kutumia kitu kinachoitwa lundo.

929
00:58:40,770 --> 00:58:44,430
Kuna kitu tofauti kuhusu kumbukumbu. Ni si kwa kasi au polepole au kitu kama hicho.

930
00:58:44,430 --> 00:58:46,570
Ni tu kimwili katika eneo tofauti.

931
00:58:46,570 --> 00:58:50,120
>> Lakini utawala ni kwamba kumbukumbu hiyo zilizotengwa katika kifusi

932
00:58:50,120 --> 00:58:56,180
kamwe ataondolewa wewe mpaka kuwaita - kuchukua nadhani - bure.

933
00:58:56,180 --> 00:59:00,510
Kwa kulinganisha, kumbukumbu yoyote ya kuuliza kwa juu ya stack na tu kutangaza safu

934
00:59:00,510 --> 00:59:03,320
au kutangaza variable kama tumekuwa kufanya kwa wiki,

935
00:59:03,320 --> 00:59:05,640
kwamba kwa default inaishia kwenye stack.

936
00:59:05,640 --> 00:59:09,550
Na kwamba kazi kubwa 90% ya muda, lakini juu ya matukio hayo rarer

937
00:59:09,550 --> 00:59:12,470
ambapo unataka kutenga kumbukumbu na kushika ni kuzunguka,

938
00:59:12,470 --> 00:59:14,730
basi unahitaji kutumia kazi kama malloc.

939
00:59:14,730 --> 00:59:19,370
Au tuna kutumika kazi kama GetString, ambayo kwa upande anatumia malloc.

940
00:59:19,370 --> 00:59:23,300
Hebu angalia ambapo hii inaweza kuvunja chini na kisha kuchukua Peek saa Binky.

941
00:59:23,300 --> 00:59:25,820
Tutaweza kuja nyuma na kwamba katika siku zijazo.

942
00:59:25,820 --> 00:59:29,270
Hapa ni super rahisi mpango kwamba katika mistari ya kwanza 2 anafanya nini?

943
00:59:29,270 --> 00:59:33,460
Katika lugha ya Kiingereza, je, hizi kwanza mistari 2 ya maadili ya kufanya ndani ya kuu?

944
00:59:33,460 --> 00:59:35,600
[Inaudible mwanafunzi majibu]

945
00:59:35,600 --> 00:59:37,880
Makini. Haina nipe anuani ya x au y.

946
00:59:37,880 --> 00:59:41,840
[Mwanafunzi] Hutoa kuyatumia kwa ints. >> Good. Nipe kuyatumia 2 kwa integers.

947
00:59:41,840 --> 00:59:45,130
Kwa maneno mengine, nipe chunks 2 ya kumbukumbu kwamba mimi kuendelea kuchora leo,

948
00:59:45,130 --> 00:59:46,950
hata mimi erased sasa, kama miraba.

949
00:59:46,950 --> 00:59:50,000
Nipe chunks 2 ya kumbukumbu, mtu mmoja aitwaye x, mtu mmoja aitwaye y -

950
00:59:50,000 --> 00:59:54,320
kabla ya hapo nilikuwa akawaita s na t - na nini ni ya aina ya kwamba chunk ya kumbukumbu?

951
00:59:54,320 --> 00:59:57,160
Ni kwenda kuhifadhi anwani.

952
00:59:57,160 --> 00:59:59,110
Ni aina ya * int.

953
00:59:59,110 --> 01:00:01,630
>> Hivyo anuani ya int hatimaye kuishi katika x,

954
01:00:01,630 --> 01:00:03,860
anuani ya int hatimaye kuishi katika y,

955
01:00:03,860 --> 01:00:08,460
lakini awali nini ndani ya x na y? Nani anajua? Takataka maadili.

956
01:00:08,460 --> 01:00:10,180
Ina chochote cha kufanya na kuyatumia.

957
01:00:10,180 --> 01:00:12,720
Kama sisi si kuweka kitu pale, ambaye anajua nini ni kweli huko?

958
01:00:12,720 --> 01:00:18,950
Sasa, x. Nini kinatokea hapa? Hii ni legit sasa kwa sababu x ni pointer. Ni * int.

959
01:00:18,950 --> 01:00:21,870
Hivyo kwamba maana siwezi kuweka katika x anuani ya baadhi chunk ya kumbukumbu.

960
01:00:21,870 --> 01:00:25,120
Je malloc kurudi? Perfect, kuirudisha anwani,

961
01:00:25,120 --> 01:00:28,510
anuani ya Byte kwanza katika chunk nzima ya kumbukumbu.

962
01:00:28,510 --> 01:00:31,140
Jinsi ka wengi ni hii inaonekana kugawa, kwa mfano, katika appliance?

963
01:00:31,140 --> 01:00:33,510
Nini ukubwa wa int? 4.

964
01:00:33,510 --> 01:00:36,600
Kama unafikiri nyuma kwa wiki 1, siyo super muhimu daima kukumbuka kwamba,

965
01:00:36,600 --> 01:00:38,870
lakini katika kesi hii ni muhimu kujua, ka 4.

966
01:00:38,870 --> 01:00:41,770
Hivyo hii ni kugawa juu ya lundo ka 4

967
01:00:41,770 --> 01:00:46,110
na ni kurudi anuani ya kwanza kwangu kiholela.

968
01:00:46,110 --> 01:00:47,700
Sasa, ni nini x kufanya?

969
01:00:47,700 --> 01:00:52,200
* X = 42 ni kufanya nini?

970
01:00:52,200 --> 01:00:57,150
Kama katika hatua hii kwa hadithi tuna x, ambayo inaonekana kama hii na thamani ya baadhi ya takataka,

971
01:00:57,150 --> 01:01:04,120
hii ni sasa na thamani y baadhi ya takataka, sasa katika mstari 3 nimekuwa zilizotengwa ka 4.

972
01:01:04,120 --> 01:01:06,950
Hii picha kimsingi inaonekana kama hii.

973
01:01:06,950 --> 01:01:12,010
Au zaidi hasa, kama hii ni holela anuani 123, hii ni nini hadithi yetu sasa inaonekana kama.

974
01:01:12,010 --> 01:01:23,940
* X = 42 sasa maana yake nini? Hiyo ina maana kwenda 123 anuani na kuweka namba 42 hapo.

975
01:01:23,940 --> 01:01:26,220
Sihitaji kuteka mistari haya kwa sababu sisi siyo kufanya masharti.

976
01:01:26,220 --> 01:01:29,480
>> Mimi lazima tu yaliyoandikwa ni kama hii, na kwa ajili tu ya maandamano,

977
01:01:29,480 --> 01:01:33,240
42 kama aina int ya inachukua hadi mengi ya nafasi, ka 4.

978
01:01:33,240 --> 01:01:35,960
Basi hiyo ni nini kilichotokea huko, lakini kuna tatizo sasa.

979
01:01:35,960 --> 01:01:40,580
* Y = 13. Nini kitatokea hapa?

980
01:01:40,580 --> 01:01:46,470
Tatizo ni * y katika dunia yetu kilichorahisishwa tu ina maana kwenda anuani katika y.

981
01:01:46,470 --> 01:01:48,590
Nini katika y? Ni baadhi ya thamani ya takataka.

982
01:01:48,590 --> 01:01:53,150
Basi hebu kudhani kwamba thamani ya takataka ni 5551212, kitu mambo kama hayo.

983
01:01:53,150 --> 01:01:56,750
* Y njia kwenda kushughulikia 5,551,212.

984
01:01:56,750 --> 01:02:00,450
Hiyo kama zaidi hapa. Ni haipo, kwa mfano.

985
01:02:00,450 --> 01:02:05,310
Hivyo * y anapata njia 13 mimi nina kujaribu kuteka 13 hapa. Ni haipo.

986
01:02:05,310 --> 01:02:08,790
Nimekuwa ilizidi sehemu ya ubao. Nini mimi kupata?

987
01:02:08,790 --> 01:02:14,930
Hiyo cryptic ujumbe segmentation kosa kwa sababu mimi nina kujaribu kuweka katika kumbukumbu

988
01:02:14,930 --> 01:02:19,470
thamani kama 13 katika eneo ambalo haipo.

989
01:02:19,470 --> 01:02:23,900
wengine wa mpango ili kazi sawa, lakini hadi kwamba hatua hiyo haina.

990
01:02:23,900 --> 01:02:25,350
Basi hebu jaribu kuwaambia hadithi hii.

991
01:02:25,350 --> 01:02:27,830
Tutaweza kurudi mara moja kwamba tumekuwa aliyesema kuhusu hex.

992
01:02:27,830 --> 01:02:30,290
Turudi kwa hii na kuhitimisha na hii kitu inayoitwa Binky,

993
01:02:30,290 --> 01:02:33,710
ambayo wanakumbuka ni profesa Stanford kukaa nyumbani kucheza na claymation,

994
01:02:33,710 --> 01:02:36,380
kuwaambia hadithi ya mpango hasa kwamba huo.

995
01:02:36,380 --> 01:02:40,580
Ni tu kuhusu 3 dakika ya muda mrefu. Hapa tuna Binky.

996
01:02:40,580 --> 01:02:45,030
[Kiume msemaji kwenye video] Hey Binky, kuamka. Ni wakati kwa ajili ya kujifurahisha pointer.

997
01:02:45,030 --> 01:02:50,080
[Binky] Nini hiyo? Jifunze kuhusu kuyatumia? Oh, GOODY!

998
01:02:50,080 --> 01:02:53,700
[Msemaji kiume] Naam, kwa kuanza, mimi nadhani sisi ni kwenda haja ya kuyatumia wanandoa.

999
01:02:53,700 --> 01:02:57,890
>> [Binky] Sawa. Kanuni hii inatenga kuyatumia 2 ambayo inaweza kumweka kwa integers.

1000
01:02:57,890 --> 01:03:02,220
[Kiume msemaji] Sawa. Naam, naona kuyatumia 2, lakini hawaonekani kuwa akizungumzia chochote.

1001
01:03:02,220 --> 01:03:05,550
[Binky] Hiyo ni haki. Awali, kuyatumia hawana uhakika na kitu chochote.

1002
01:03:05,550 --> 01:03:09,270
mambo ya wao wanaongelea wanaitwa pointees, na kuweka yao juu ni hatua tofauti.

1003
01:03:09,270 --> 01:03:12,330
[Kiume msemaji] Oh, haki, haki. Mimi nilijua kwamba. pointees ni tofauti.

1004
01:03:12,330 --> 01:03:15,630
Eri, hivyo ni jinsi gani unaweza kutenga pointee?

1005
01:03:15,630 --> 01:03:21,510
[Binky] Sawa. Kanuni hii inatenga mpya integer pointee, na sehemu hii seti x kwa uhakika na hilo.

1006
01:03:21,510 --> 01:03:23,500
[Kiume msemaji] Hey, kwamba inaonekana zaidi.

1007
01:03:23,500 --> 01:03:26,030
Hivyo kufanya hivyo kufanya kitu. >> [Binky] Sawa.

1008
01:03:26,030 --> 01:03:30,300
Mimi itabidi dereference x pointer kuhifadhi namba 42 katika pointee wake.

1009
01:03:30,300 --> 01:03:34,410
Kwa hila hii mimi itabidi wand yangu ya uchawi wa dereferencing.

1010
01:03:34,410 --> 01:03:38,610
[Kiume msemaji] wand yako uchawi wa dereferencing? Hiyo ni kubwa.

1011
01:03:38,610 --> 01:03:44,230
[Binky] Hii ni nini code inaonekana kama. Mimi itabidi kuweka idadi na ... [Popping sound]

1012
01:03:44,230 --> 01:03:46,100
[Kiume msemaji] Hey kuangalia, kuna unaendelea.

1013
01:03:46,100 --> 01:03:50,990
Kufanya hivyo dereference juu ya x ifuatavyo arrow kupata pointee yake,

1014
01:03:50,990 --> 01:03:53,230
katika kesi hii ya kuhifadhi 42 katika huko.

1015
01:03:53,230 --> 01:03:57,630
Hey, jaribu kutumia na kuhifadhi idadi 13 kupitia pointer nyingine, y.

1016
01:03:57,630 --> 01:04:03,250
[Binky] Sawa. Mimi itabidi kwenda juu hapa y na kupata namba 13 ya kuanzisha

1017
01:04:03,250 --> 01:04:08,360
na kisha kuchukua wand ya dereferencing na tu ... [Buzzing sound] Ho!

1018
01:04:08,360 --> 01:04:10,980
[Kiume msemaji] Oh hey, kwamba hawakuwa na kazi.

1019
01:04:10,980 --> 01:04:14,870
>> Sema, Binky, sidhani dereferencing y ni wazo nzuri

1020
01:04:14,870 --> 01:04:17,880
kwa sababu ya kuanzisha pointee ni hatua tofauti

1021
01:04:17,880 --> 01:04:19,850
na sidhani sisi milele alifanya hivyo.

1022
01:04:19,850 --> 01:04:21,770
[Binky] Hmm, nzuri uhakika.

1023
01:04:21,770 --> 01:04:26,640
[Kiume msemaji] Yeah. Sisi zilizotengwa y pointer lakini sisi kamwe kuweka kwa uhakika na pointee.

1024
01:04:26,640 --> 01:04:28,780
[Binky] Hmm, sana wachunguaji.

1025
01:04:28,780 --> 01:04:30,690
[Kiume msemaji] Hey, wewe ni kuangalia nzuri huko, Binky.

1026
01:04:30,690 --> 01:04:34,160
Je, unaweza kurekebisha ili y pointi pointee sawa kama x? >> [Binky] Uhakika.

1027
01:04:34,160 --> 01:04:37,100
Mimi itabidi kutumia wand yangu ya uchawi wa zoezi pointer.

1028
01:04:37,100 --> 01:04:39,070
[Kiume msemaji] Ni kwamba kwenda kuwa tatizo kama kabla?

1029
01:04:39,070 --> 01:04:40,840
[Binky] Hapana, hii haina kugusa pointees.

1030
01:04:40,840 --> 01:04:44,780
Ni tu mabadiliko moja pointer kwa uhakika na kitu sawa kama mwingine. [Popping sound]

1031
01:04:44,780 --> 01:04:48,570
[Kiume msemaji] Oh, naona. Sasa y pointi kwenye sehemu moja kama x.

1032
01:04:48,570 --> 01:04:51,140
Hivyo kusubiri. Sasa y ni fasta. Ina pointee.

1033
01:04:51,140 --> 01:04:54,520
Hivyo unaweza kujaribu wand ya dereferencing tena kwa kutuma zaidi ya 13.

1034
01:04:54,520 --> 01:04:58,130
[Binky] Uh, okay. Hapa unaendelea. [Popping sound]

1035
01:04:58,130 --> 01:05:01,250
[Kiume msemaji] Hey, kuangalia kwamba. Sasa dereferencing kazi juu y.

1036
01:05:01,250 --> 01:05:05,200
Na kwa sababu kuyatumia wanashiriki kwamba moja pointee, nao wote wawili kuona 13.

1037
01:05:05,200 --> 01:05:06,910
[Binky] Yeah, kugawana. Chochote.

1038
01:05:06,910 --> 01:05:08,880
>> Hivyo ni sisi kwenda kubadili maeneo sasa?

1039
01:05:08,880 --> 01:05:11,420
[Kiume msemaji] Oh kuangalia, tuko nje ya muda. >> [Binky] Lakini -

1040
01:05:11,420 --> 01:05:13,880
[Msemaji kiume] Kumbuka tu sheria pointer 3.

1041
01:05:13,880 --> 01:05:18,630
Idadi 1, muundo wa msingi ni kwamba una pointer na inaelekeza juu ya pointee.

1042
01:05:18,630 --> 01:05:23,120
Lakini pointer na pointee ni tofauti, na makosa ya kawaida ni kuanzisha pointer

1043
01:05:23,120 --> 01:05:25,680
lakini kusahau kuwapa pointee.

1044
01:05:25,680 --> 01:05:29,580
Idadi 2, pointer dereferencing kuanza saa pointer na ifuatavyo mshale wake juu ya

1045
01:05:29,580 --> 01:05:31,060
kupata pointee wake.

1046
01:05:31,060 --> 01:05:34,340
Kama sisi wote kujua, hii kazi tu kama kuna pointee,

1047
01:05:34,340 --> 01:05:36,460
ambayo aina ya anapata nyuma kutawala namba 1.

1048
01:05:36,460 --> 01:05:39,870
Idadi 3, pointer zoezi inachukua moja pointer na hulibadilisha

1049
01:05:39,870 --> 01:05:42,390
kwa uhakika na pointee sawa kama pointer mwingine.

1050
01:05:42,390 --> 01:05:45,890
Hivyo baada ya zoezi, kuyatumia 2 nitawaelekezeni kwa pointee sawa.

1051
01:05:45,890 --> 01:05:47,800
Wakati mwingine kwamba wito kugawana.

1052
01:05:47,800 --> 01:05:50,910
>> Na kwamba ni yote kuna ni kweli. Bye bye-sasa.

1053
01:05:50,910 --> 01:05:55,840
Hii ni Binky. Hii ni CS50. Tutaweza kuona wewe wiki ijayo. [Applause]

1054
01:05:55,840 --> 01:05:59,000
>> [CS50.TV]