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[Powered by Google Translate] [Wiki 2, 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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Wote haki. Hii ni CS50, na hii ni mwisho wa wiki 2.

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Kama wewe wanatarajia kuwa na njaa kote wakati huu kesho,

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tunajua kwamba sisi ni kwenda kuitisha kama kesho kikundi kidogo, Alhamisi, 13:15.

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Kuna URL hii hapa kama wewe Ningependa RSVP.

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Nafasi ni mdogo, hivyo tafadhali kusamehe ikiwa fomu ya kujaa kwa muda kujaza hii nje.

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Mwingine URL, ingawa, ambayo inaweza kuwa ya riba ni hii.

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Katika tu kuhusu muda wa mwezi mmoja, bila shaka ni kwenda kuwa inapatikana

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wote kwa mapana zaidi kupitia edX, via ambayo folks kwenye mtandao itakuwa na uwezo wa kufuata pamoja,

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kushiriki katika kozi kabisa kikamilifu, kwa kweli.

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Wao utakuwa kutumia Appliance CS50 na CS50 Jadili

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na zaidi ya zana mbalimbali programu kwamba sisi tayari wamekuwa wakitumia huu muhula.

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Na moja ya mipango tunatarajia kuchukua kama majaribio mwaka huu

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ni kuona tu kiasi gani maudhui tunaweza kutafsiri

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katika lugha nyingine zinazozungumzwa na kuandikwa.

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Hivyo kama unaweza kuwa na maslahi katika kushiriki katika mradi huu

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ambapo sisi kutoa nakala ya Kiingereza na subtitles kwa mihadhara kozi ya

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na kaptula na semina na sehemu na kama,

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kama wewe kusema fluently au kuandika fluently baadhi lugha nyingine,

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tunataka upendo kushiriki kwa mradi huu ambapo wewe kuchukua moja au zaidi ya video,

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kutafsiri yao katika lugha ya wewe kujua vizuri kabisa.

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>> Ili kukupa hisia ya interface, kuna hii ya mtandao msingi user interface

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kwamba tutaweza kutumia ambayo kujenga kimsingi UI kama hii.

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Hii ilikuwa yangu kufundisha baadhi Halloween iliyopita,

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na upande wa kulia kuna katika nyeusi karibu na mihuri wakati hizi,

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utaona mambo mbalimbali waliotoka kinywa yangu kwamba siku,

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na kisha chini yake wewe utakuwa na uwezo wa kutafsiri katika lugha nyingine

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hasa nini ramani ni kati ya, katika kesi hii, Kiingereza na, kusema, Kihispania.

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Hivyo ni kweli sana user-kirafiki chombo.

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Unaweza Rewind na kufunga-mbele sana kwa urahisi na keyboard shortcuts.

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Hivyo kama ungependa kushiriki katika jaribio hili na kuwa na maneno yako kuonekana na kusoma

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na maelfu uwezekano wa folks huko nje, tafadhali jisikie huru kushiriki.

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Neno moja kuhusu kitten kutoka Jumatatu.

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Isije tumetuma ujumbe overly inatisha, kufanya kutambua kwamba, kama ofisi masaa zinaonyesha

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na kama sehemu kupendekeza, kubuni bila shaka ni mengi sana

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kuwa wanafunzi kushirikiana na kuzungumza na kazi kupitia seti tatizo

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na matatizo kwa pamoja, na kwa kweli mstari tu inakuja chini,

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tena, kazi wewe hatimaye kuwasilisha lazima yako mwenyewe.

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Na hivyo kabisa kwa uaminifu, katika masaa ya ofisi ni kabisa ya kawaida,

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ni kabisa kutarajiwa hata, kuwa kuzungumza na baadhi ya rafiki karibu na wewe.

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>> Kama yeye au yeye ni ikikabiliwa na mada baadhi na wewe ni kama,

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"Oh, vizuri, nikupe glimpse ya baadhi mstari wa kanuni kwamba mimi aliandika," hiyo ni nzuri,

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kinachotokea, na kwamba ni mazuri sana, nadhani, na mchakato wa kujifunza.

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Ambapo line anapata walivuka ni wakati kichwa ni aina ya tilted zaidi ya hapa kwa sekunde nyingi mno

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au dakika kwa kuwa kweli kuwa tu imekuwa nafasi kumfungulia kwa rafiki yako,

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na kwa hakika wakati mambo kupata kubadilishana kupitia barua pepe na Dropbox na kama,

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kuna pia ni mstari.

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Hivyo kwa njia zote kujisikia vizuri na kujisikia moyo wa kuzungumza na marafiki

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na wanafunzi kuhusu psets na zaidi na tu kutambua kwamba yale hatimaye kuwasilisha

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lazima kweli kuwa bidhaa ya uumbaji wako na si mtu mwingine.

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Na hivyo moja ya matatizo ya uwanja maalum kwa pset2,

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ambayo atakuja nje marehemu kesho usiku, ni kupiga mbizi katika ulimwengu wa cryptography,

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ambayo ni sanaa ya encrypting au scrambling habari,

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na hii inahusiana na hatimaye dunia ya usalama.

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Sasa, usalama kwa ajili ya wengi wetu huja katika namna ya taratibu uungwana mundane.

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Sisi sote tuna usernames na password,

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na sisi wote kuwa na majina ya watumiaji mbaya sana na nywila, uwezekano mkubwa.

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>> Kama nywila yako ni sawa kwenye tovuti nyingi, kwamba pengine si wazo bora,

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kama tutaweza kujadili kuelekea mwisho wa muhula.

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Kama nywila yako imeandikwa katika kumbuka nata - hakuna utani - juu ya kufuatilia yenu,

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kwamba pia ni si lazima kubuni bora kabisa lakini hali ya kawaida.

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Na kama wewe si kutumia cryptography encrypt nywila yako,

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wao ni hasa katika mazingira magumu.

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Hivyo kama unafikiri wewe kuwa super wajanja kwa kuwa na siri Neno hati

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mahali fulani kwenye gari yako ngumu ambayo ina yote ya nywila yako

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lakini ni katika folder kwamba hakuna mtu kwenda kuangalia katika, kwamba pia ni si utaratibu salama sana.

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Na hivyo kile pset2 itaanzisha ni sanaa hii ya cryptography

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na scrambling habari ili mambo kama nywila wote ni salama zaidi.

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muktadha hapa ni kwamba pamoja na data zenye shida

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inakuja fursa encrypt yake na kwa kinyang'anyiro yake.

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Na hivyo hii, kwa mfano, ni mfano wa ujumbe ambao umefungiwa.

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Hii kwa kweli anasema kitu katika Kiingereza, lakini ni wazi kabisa kabisa ni dhahiri.

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Na tutaweza kuja duara kamili leo tease mbali nini ujumbe huu ni siri hapa.

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Lakini katika ulimwengu halisi ya kompyuta, mambo si hata kuangalia kama wanaweza kuwa Kiingereza misemo.

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Kwa mfano, hii ni nini unaweza kupata kwenye Linux kiwango au Mac au UNIX kompyuta

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katika faili kwamba mara kwa mara juu ya muda kuitwa faili password.

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>> Siku hizi imekuwa ni wakiongozwa na maeneo mengine.

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Lakini kama wewe kuangalia katika mahali sahihi juu ya mfumo, utaona si tu jina lako

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au ile ya watu wengine juu ya mfumo, lakini utaona version encrypted ya password yao.

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Hakika, kuna neno crypt unaonyesha kwamba mambo yafuatayo ni encrypted,

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na mfululizo huu wa barua inaonekana random na wahusika na idadi na kadhalika

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inaweza decrypted tu kwa ujumla kujua baadhi ya siri -

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neno siri, idadi siri -

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na hivyo kweli kweli, sanaa ya cryptography majipu hatimaye chini kwa uaminifu wa aina fulani

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na kujua kitu ambacho mtu mwingine hana.

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Hivyo tutaweza kuchunguza hili kwa undani zaidi kidogo leo na katika pset kuja.

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Na sasa neno juu ya kupita haitaisha /.

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Hasa kama baadhi yenu dived katika pset1, Appliance,

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na dunia mpya sana kwa ajili yako mwenyewe, kutambua kwamba frustrations na machafuko

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na tu matatizo ya kiufundi ni kabisa kutarajiwa,

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hasa kwa pset kwanza, ambapo kuna kiasi tu mpya,

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kupata tu ukoo na ls na cd na amri hizi zote arcane

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na mazingira mapya, na kwamba ni tofauti na nyenzo halisi na programu yenyewe.

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Hivyo kutambua pia kwamba kuna shaka ni masaa ya ofisi ambazo zipo kama muundo msaada.

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>> Sehemu hii kuanza Jumapili ijayo.

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Lakini muhimu zaidi, kama wewe ni hisia tu kuwa hii si dunia kwa ajili yenu,

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kutambua kwamba ni kweli haina kuchukua muda tu.

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Na lau kuwa si kwa ajili ya nafasi hii miaka iliyopita kwa ajili yangu ya kuchukua pasi darasa / kushindwa,

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uaminifu, mimi kamwe ingekuwa hata kuweka mguu katika darasa.

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Na unaweza kubadilisha hili hadi, kusema, Jumatatu ya tano ya shaka,

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hivyo kama wewe ni makali ya sasa, kutambua kwamba badala ya kichwa katika baadhi ya maji nyingine kabisa,

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je, hakika kufikiria tu kubadilisha kupita / kushindwa.

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Tena, kuna si kweli utamaduni huu hapa katika Harvard ya kuchukua mambo kupita / kushindwa

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tangu kila mtu kweli anataka kufikia au overachieve,

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lakini kusema ukweli, hii ni njia ya ajabu ya kujaribu kitu nje

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kwamba wanaweza kuwa familiar na wewe, na kuishia kufanya, katika hali nyingi, kabisa faini,

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labda sana kwa mshangao wako.

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Na katika suala thabiti zaidi, nini nadhani kupita / kushindwa ujumla gani,

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hasa kama unaweza kuwa na uzoefu na pset0,

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kama wewe kuweka katika masaa 10, masaa 15, masaa 25 katika baadhi pset

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na wewe tu banging kichwa yako dhidi ya ukuta na ni kupata super marehemu wakati wa usiku

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lakini umechukua pset 90% ya njia na wewe tu hawezi kufikiri jambo moja,

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kupita / kushindwa kweli inachukua makali mbali ya darasa kama hii,

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ambapo unaweza aina ya furaha kusema, "Sawa, Najua ni si kamili,

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lakini mimi kazi punda wangu mbali juu ya hili, nina pretty furaha na ambapo ni kuishia, "

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na kwamba watakutana na matarajio kwa kupita / kushindwa.

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Hivyo kufanya kuendelea kuwa katika akili. Wote haki.

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>> Hivyo wale ambao Jihadi kwa kutumia Chuo Kikuu cha Harvard Wi-Fi,

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kujua kwamba kuna SSID CS50, uhusiano Wi-Fi, yaliyo karibu

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kwamba unaweza kuwa bora zaidi kwa bahati.

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Ni kejeli kidogo kwamba nywila kwa ajili ya hii, kama ungependa kujaribu kuunganisha na hii

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kwa kasi bora - na hebu kujua kama ni hakuna bora - ni 12,345, njia yote hadi 8

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kwa sababu 8 ni salama zaidi kuliko 5.

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Hivyo kama unahitaji password Wi-Fi, kuungana na CS50 wirelessly hapa, 12345678,

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na baada ya juu CS50 Jadili kama bado una masuala kuunganishwa vipindi

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na tutaweza basi mamlaka zilizopo kujua kwa nafasi hii. Wote haki.

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Hivyo teaser haraka, hasa kwa wale ambao ni shabiki wavulana na wasichana au ya yote Apple mambo.

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Nini mimi kuchimbwa kutoka miaka michache nyuma ilikuwa faili hii hapa, iUnlock.c,

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tu kwa aina ya kufanya zaidi ya saruji na ngumu zaidi

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baadhi ya mipango ya msingi zaidi C sisi tumekuwa kuandika.

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Basi, mimi kufunguliwa faili hii, iUnlock.c. Ni inapatikana kwenye ukurasa Mihadhara kwa leo.

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Kwa upande wa mkono wa kushoto, unaweza kuona orodha ndefu ya kazi.

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Hivyo wenzao ambao aliandika hii aliandika juu sana ya utendaji, zaidi kuliko tu kuu.

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Alitumia rundo zima la maktaba hapa, na kama tunaanza scrolling kupitia,

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nini hii kwa kweli ni ni ya kwanza kabisa, naamini, ufa kwa iPhone ya awali.

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>> Wakati alitaka jailbreak iPhone ya awali, ambayo ina maana untether ni kutoka AT & T

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na kweli kufunga programu maalum juu yake na kufanya mambo ambayo Apple hakutaka watu kufanya,

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mtu alichukua muda wa kufikiri hasa jinsi gani wanaweza kutumia madhaifu programu,

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makosa, mende, katika programu ya Apple, na hivyo alizaliwa iUnlock.c--

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kwamba kama wewe ni compiled kwenye kompyuta yako na imewekwa kwenye iPhone

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kwamba alikuwa kushikamana na kompyuta yako kupitia, kusema, USB cable,

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hii ingekuwa kukupa marupurupu ya utawala au mizizi ya iPhone yako

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na basi wewe kufanya pretty much chochote unataka.

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Na hivyo kuna kuwa hii paka kuvutia na mchezo wa panya

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kati ya Apple na wengine wa dunia hasa kama wao, kama makampuni mengi,

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kujaribu lock mambo yao chini hivyo kwamba unaweza tu kufanya na ni nini wanataka.

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Lakini, shukrani kwa watu kama hii na ufahamu wa maelezo ya ngazi ya chini -

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na katika kesi hii C programu - na mengi ya constructs familiar

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kwamba tumekuwa walianza kucheza na, wewe ni uwezo wa kweli kujiinua vifaa

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katika namna unaweza kuona inafaa na si lazima baadhi chombo ushirika.

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Hivyo kwa mfano, mimi sielewi nini yote haya ni kufanya,

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lakini GetVersion sauti pretty moja kwa moja,

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na inaonekana kama hii ni kazi ambayo mtu huyu aliandika.

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Inachukua baadhi ya aina ya integer kama hoja, haina kurudi kitu chochote,

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lakini inaonekana kitanzi na kwa kitanzi hapa na kama hali, kama mapumziko hali,

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na kwa namna fulani inahusiana na idadi version kama sisi kitabu chini,

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ingawa mengi ya maneno haya ni kwenda kuwa mpya.

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Na kuna mengi yote ya utendaji katika hapa sisi sijawahi kuona na wanaweza milele kuona

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juu ya kozi ya muhula.

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>> Wakati wa mwisho wa siku, ni sawa ifuatavyo sheria na mantiki kwamba sisi tumekuwa kucheza kwa hivi sasa.

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Hivyo hii ni mbali mzee sana ufa yako 3s iPhone au 4s au hivi karibuni 5s siku hizi,

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lakini najua kwamba yote hayo sana inayotokana na dunia hii ambayo tumekuwa dived katika.

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Hebu tuangalie mfano kidogo zaidi rahisi:

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moja hii, ili tu kupata moto juu na baadhi ya kisintaksia na pia baadhi ya wengine data aina

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kwamba tumekuwa kuongelea lakini si kweli kuonekana katika C.

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Hii ni faili inayoitwa positive1.c, na kwa maoni juu,

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hii tu madai kwamba mtumiaji kutoa idadi chanya.

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Hivyo ni mfano wa kitanzi do-wakati, ambayo ni nzuri kwa ajili ya mipango ya mtumiaji maingiliano

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ambapo unahitaji kuwaambia user kufanya kitu fulani,

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na kama hawana kushirikiana wewe yell saa yao au kukataa mchango wao.

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Uchunguzi katika kumweka: Mimi nitaenda kufanya mistari 19 kupitia 24

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hivyo muda mrefu kama user kwamba hakunipa idadi chanya.

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Hii undani hapa kwenye mstari 18, kwa nini mimi kutangaza n juu looping hii nzima kujenga

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kinyume na haki ya karibu na mstari 22 ambapo mimi kwa kweli huduma ya kupata n? Yeah.

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[Mwanafunzi] Scope. >> Yeah, hivyo suala hili la wigo.

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Na katika suala layman, nini wigo rejea?

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Yeah. >> [Inaudible mwanafunzi majibu] >> Je, unaweza kusema kidogo nguvu zaidi?

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[Mwanafunzi] wapi unaweza kupata kwamba kutofautiana. >> Perfect.

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Ambapo unaweza kupata variable fulani.

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Na kwa ujumla, utawala wa thumb hivi sasa imekuwa kwamba wigo wa baadhi variable

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hufafanuliwa kwa braces hivi karibuni curly kwamba ve kuonekana.

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>> Na hivyo katika kesi hii, kama mimi alifanya makosa ya kutangaza n kwenye mstari 22, mstari kwamba ingekuwa kazi.

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Ningependa kupata int, na napenda kuiweka katika n kwamba kutofautiana katika mstari 22,

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lakini ambayo mstari wa kanuni ingekuwa sasa sielewi nini mimi kuzungumza kuhusu? >> [Mwanafunzi] 25.

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[Malan] 25, na zinageuka 24 kama vizuri kwa sababu katika kesi hii ni falls nje ya braces curly.

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Hivyo tu kidogo ya kero lakini kwa urahisi sana kutatuliwa kwa kifupi kutangaza variable

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nje ya kazi yenyewe.

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Tutaweza kuona baadaye leo unaweza kwenda hatua moja zaidi

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na unaweza hata kupata kidogo wavivu.

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Na hii si kwa kuwa ilipendekeza kwa ujumla, lakini unaweza hata kupata wavivu

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na kuweka variable kimataifa, ili kuzungumza, si ndani ya kazi, si ndani ya kitanzi,

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lakini katika faili yenyewe, nje ya yote ya kazi ve imeandikwa, kama mimi hapa kwenye mstari 15.

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Hii ni kwa ujumla kipaji juu, lakini kutambua hili ni suluhisho wakati mwingine matatizo mengine,

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kama tutaweza hatimaye kuona.

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Hivyo kwa sasa tutaweza kuondoka ni kama hii, lakini hebu tuone kama tunaweza rewrite hii

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tu ya kuanza kuonyesha wenyewe tofauti kidogo.

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Mpango huu, tu kuwa wazi, ni positive1.

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Hebu kwenda mbele hapa na katika terminal dirisha yangu kufanya positive1, Ingiza.

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Inaandaa sawa. Mimi nina kwenda kukimbia positive1, hit Enter.

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Mimi kudai kwamba wewe nipe sifuri. Nitasema -1. Kwamba hawakuwa na kazi.

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0, 99. Hiyo inaonekana kazi.

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Labda si mtihani ukali zaidi, lakini angalau ni nzuri sanity hundi

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kuwa tuko katika njia sahihi.

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>> Hivyo sasa napenda kwenda mbele na kufungua toleo 2 ya hili,

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na nini ni tofauti tayari?

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Ni kutekeleza jambo hilo, lakini kile kuruka nje kama wakati wazi tofauti hii?

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Hii bool katika kijani. Ni ni yalionyesha katika kijani, hii Keyword inayojulikana kama bool, ambayo ni aina data.

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Haina kuja kujengwa katika yote ya matoleo ya C.

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Unahitaji ni pamoja na maktaba maalum.

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Katika kesi yetu, mimi ni pamoja maktaba CS50 ili sisi kupata bool.

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Lakini katika mstari 18, sisi tunaonekana kuwa na thamani Boolean hapa aitwaye kushukuru.

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Ningeweza kuitwa hii kitu chochote, lakini mimi kuitwa ni kushukuru

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tu aina ya kufikisha baadhi maana semantic.

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Hivyo awali kwenye mstari 18, mimi nina inaonekana si kushukuru

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kwa sababu thamani Boolean kushukuru ni initialized na uongo katika mstari 18.

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Na basi inaonekana kile nimepata kufanyika hapa katika mistari 21 kupitia 23

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Nimekuwa ni aina tu ya rewritten mantiki yangu.

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Hivyo hakuna functionally tofauti, lakini katika mstari 22 sasa mimi kuangalia kama int mtumiaji imetoa

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ni mkubwa kuliko 0, basi mimi kubadili tu thamani ya kushukuru kwa kweli.

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Na kwa nini mimi kufanya hivyo? Kwa sababu katika mstari 25, inaonekana mimi nina kwenda kuangalia hali.

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Je, hii kitanzi wakati kushukuru ni uongo.

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Basi, mimi mapendekezo hii kama njia mbadala ya toleo 1

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sababu ni angalau kidogo Intuitive zaidi labda, ni zaidi kidogo msingi katika Kiingereza.

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Hivyo kufanya yafuatayo wakati wewe si kushukuru, au wakati kushukuru ni uongo.

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Na wakati huu pia mimi inaonekana hawajali kukumbuka kile mtumiaji typed katika

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kwa sababu hakuna taarifa n variable, hivyo kweli, nyeupe kidogo uongo huko.

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>> Functionally, mpango huo ni tofauti kidogo mara moja sisi kupata chini yake

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kwa sababu mimi si kukumbuka kile n ni.

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Lakini nilitaka kuonyesha hapa pia kwamba hata kama tumeona GetInt

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na GetString kuwa kutumika upande wa kulia wa alama ya usawa hivi sasa

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ili sisi kukumbuka thamani, kitaalam, kwamba si madhubuti muhimu.

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Kama kwa sababu yoyote wewe tu hawajali kuokoa thamani,

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wewe tu unataka kuangalia thamani, taarifa kwamba tunaweza tu kuandika hii kama GetInt,

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wazi Paren, karibu Paren.

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Kwamba kazi ni kwenda na kurudi thamani, kama tumekuwa akisema.

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Ni kwenda kukupa nyuma int.

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Na hivyo kama wewe kiakili kufikiri ya kinachotokea hii,

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wakati ninapoandika katika 99, GetInt anarudi idadi 99,

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na hivyo conceptually, ni kama ingawa code yangu walikuwa kweli hii.

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Hivyo kama kweli ni 99 zaidi kuliko 0, basi inakuwa kweli kushukuru,

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kisha mstari 25 anatambua ooh, sisi ni kosa kwa sababu mimi nina kushukuru sasa,

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na katika mstari 26, sisi tu kusema, "Asante kwa integer chanya!"

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chochote kilichotokea kuwa.

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Sasa hebu kufanya kidogo kisintaksia sukari hapa, hivyo kusema.

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Hebu tuone kama tunaweza kusafisha line hii ya 25 na lahaja hii tatu na ya mwisho katika positive3.

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>> Taarifa tofauti tu sasa ni nini mstari wa kanuni? >> [Mwanafunzi] 25. >> [Malan] Yeah, 25.

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Na tumekuwa si kweli kuonekana hila hii bado tu, lakini hatukuwa kuona uhakika Moderators Jumatatu,

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ambayo inaashiria nini? >> [Mwanafunzi] Si. Si >> au kukanusha.

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Hivyo kuchukua thamani Boolean na flip thamani yake.

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Kweli inakuwa uongo, uongo inakuwa kweli.

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Hivyo hii, napenda kupendekeza, ni hata kidogo Intuitive zaidi njia ya kuandika code

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kwa sababu mimi bado initialize kushukuru kwa uongo, mimi bado kufanya yafuatayo,

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Mimi kuweka kushukuru kwa kweli wakati unakuja,

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lakini sasa kweli unaweza tu kutafsiri kanuni hii kwa maneno kushoto na kulia,

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wakati (kushukuru!); kwa sababu bang au Moderators kumweka inaashiria dhana ya si,

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hivyo wakati si kushukuru.

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Hivyo tena, hatuna ilianzisha dhana yoyote mpya per se.

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Kuongelea Booleans nyuma wakati sisi alicheza na Scratch,

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lakini kutambua sasa tunaweza kuanza tu kuandika code yetu katika njia nyingi tofauti.

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Hivyo hasa katika pset1 kama wewe ni aina ya wanajitahidi kufikiri njia ya kuandika baadhi ya mpango,

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tabia mbaya ni wewe ni katika bahati kwa sababu kuna kuwa na idadi yoyote ya ufumbuzi

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kwamba unaweza kutokea juu.

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Kwa mfano, hii ni 3 tu maana hata rahisi ya mipango. Wote haki.

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Na sasa wanakumbuka juu ya Jumatatu sisi kushoto juu ya kumbuka hii na maadili kurudi.

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Hivyo kwa mara ya kwanza sisi aliandika mpango kwamba si tu kuwa na kuu;

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pia ina desturi yake mwenyewe kazi kwamba mimi aliandika hapa.

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Hivyo katika mstari 31 kupitia 34 Nimekuwa kutekelezwa kazi mchemraba.

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Ni si ngumu. Ni tu * a * a katika kesi hii.

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Lakini jambo muhimu juu yake ni kwamba mimi nina kuchukua pembejeo katika fomu ya

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na mimi nina kurudi pato katika fomu ya * a * a.

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Hivyo sasa nina uwezo, kiasi kama mimi kutumika kwa prinf peke yake,

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kuwaita kazi hii kwa wito kazi mchemraba.

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>> Na kazi mchemraba inachukua baadhi ya pembejeo, na kazi ya mchemraba anarudi baadhi pato.

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Kwa kulinganisha, printf tu alifanya kitu.

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Ni hakurudi chochote kwamba sisi kumjali kuhusu, ingawa kama kando haina kurudi thamani;

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wewe kwa ujumla tu kupuuza.

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Printf tu alifanya kitu. Ni alikuwa na athari upande wa uchapishaji kwa screen.

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Kwa kulinganisha hapa, tuna kazi mchemraba, ambayo kwa kweli anarudi kitu.

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Hivyo kwa wale jamaa na hii, ni wazo haki moja kwa moja.

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Lakini kwa wale chini ya ukoo na hili wazo la kupita katika pembejeo na kupata nyuma matokeo,

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hebu jaribu tu kitu super rahisi.

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Kuna mtu yeyote starehe kuja juu ya hatua kwa ufupi?

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Wewe kuwa starehe na kamera juu yenu pia. Yeah? Sawa.

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Nini jina lako? >> [Mwanafunzi] Ken. >> Ken. Wote haki. Ken, kuja juu juu.

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Ken ni kwenda kuwa kazi ya aina hapa.

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Hebu kwenda mbele na kufanya hili. Hebu kupata dhana kidogo.

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Nice kukutana na wewe. Karibu hatua katikati. Wote haki.

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Hebu hit button hii hapa. Wote haki.

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Hivyo hapa una ubao wa kisasa,

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na kile Mimi ni kazi kuu, kwa mfano,

293
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na mimi si kuwa na iPad katika mkono wangu.

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>> Mimi si kweli kumbuka jinsi - Naam, mimi siwezi kusema kwamba.

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Mimi si kweli kuwa mwandiko mzuri,

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na hivyo mimi nataka wewe magazeti kitu kwenye screen kwa ajili yangu.

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Mimi kuwa mpango kuu, na mimi naenda kuwa wewe kusema hili

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kwa kuandika katika kuku scratch yangu na kisha kupita wewe pembejeo.

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Hivyo silly ingawa zoezi hili ni, dhana ya kazi na wito kazi

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na kurudi kazi kweli majipu chini hii.

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Mimi ni kuu, mimi tu imeandikwa printf, quote-unquote kitu kwenye screen,

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Mimi mbio mpango huu, na kwa haraka kama printf anapata walioitwa,

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inachukua moja au hoja moja parameter wakati mwingine kati ya quotes mbili.

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Hapa ni hoja kuwa. Mimi nina kupita kwa Ken.

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Yeye ni sanduku jeusi imeandikwa baadhi idadi ya miaka iliyopita

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kwamba inaonekana tu anajua jinsi ya magazeti mambo kwenye screen.

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Hivyo nitafanya.

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Hiyo si mbaya. Nzuri sana.

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Hivyo sasa Ken inafanywa utekelezaji. Je, yeye haja ya kumsaliti mimi kitu nyuma?

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Si kwamba tumekuwa kuonekana hivi sasa.

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Tena, printf haina kweli kurudi idadi, lakini tunakwenda kupuuza kwamba kwa sasa

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kwa sababu tumekuwa kamwe kutumika. Basi hiyo ni kwa ajili ya Ken.

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Na hivyo sasa kuu inachukua zaidi ya udhibiti wa mpango tena

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kwa sababu ya kuwa mstari wa kanuni, printf, ni kosa utekelezaji.

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Na sisi kwenda juu ya njia zetu, utekelezaji chochote mistari nyingine ni pale.

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Hivyo sasa hebu jaribu mfano tofauti kidogo.

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Wakati huu hapa hebu kwanza wazi screen, na wakati huu tutaweza kufanya kazi cubing,

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lakini wakati huu, mimi kutarajia thamani ya pato.

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>> Basi hebu kwenda mbele na kufanya hili.

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Sasa nina mstari wa kanuni kwamba anasema x anapata mchemraba wa x.

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mstari wa kanuni, wanakumbuka, inaonekana kama hii: x = mchemraba (x);

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Hivyo ni jinsi gani hii kwenda kufanya kazi? Hebu kwenda mbele na kukupa screen nyeupe tena.

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Mimi naenda kuandika sasa thamani ya x,

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ambayo katika wakati huu katika muda hutokea kwa kuwa, hebu sema, 2 kwa kuitunza rahisi.

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Nimeandika kwenye kipande cha karatasi thamani ya 2, ambayo ni thamani yangu x.

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Mimi mkono kwa Ken. >> Na mimi tu kuandika jibu? >> Yeah, hebu tu kuandika jibu.

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Sawa. Na sasa yeye ana kurudi mimi kitu. Perfect. Nice segue.

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Hivyo sasa hukabidhi mimi nyuma thamani ya 8 katika kesi hii, na nini mimi kufanya na hayo?

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Kweli - hebu angalia, kupata haki hii. Je, Mimi naenda kufanya na hayo?

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Sasa mimi naenda kuchukua thamani hii na kwa kweli kuhifadhi katika bits wale sawa katika kumbukumbu.

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Lakini taarifa mimi nina aina ya wanajitahidi hapa.

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Mimi nina kuchanganyikiwa kidogo kwa sababu ambapo mimi kweli kuandika thamani ya x,

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sababu kile nimekuwa tu kufanyika ni kimwili mkono Ken kipande cha karatasi ya kuwa alikuwa thamani 2,

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ambayo ilikuwa x, na kwa kweli, hilo ni just nini kilichotokea.

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Hivyo ni zinageuka kuwa wakati wewe piga kazi na wewe kupita katika hoja

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kama hello, dunia au kupita katika hoja kama 2,

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00:20:53,290 --> 00:20:57,110
ujumla, wewe ni kupita katika nakala ya hoja hiyo.

338
00:20:57,110 --> 00:21:00,730
Na hivyo tu kama mimi aliandika chini ya idadi 2 hapa na kukabidhiwa kwa Ken,

339
00:21:00,730 --> 00:21:04,720
kwamba lazima maana kwamba mimi bado kuwa na nakala ya thamani 2 mahali fulani

340
00:21:04,720 --> 00:21:08,890
kwa sababu kwa kweli, sasa kwamba nimepata wamezipata nyuma thamani 8, mimi haja ya kwenda nyuma katika RAM

341
00:21:08,890 --> 00:21:12,130
na kweli kuandika 8 ambapo mimi mara moja alikuwa na idadi 2.

342
00:21:12,130 --> 00:21:16,950
Hivyo kuibua, kumbuka wazo hili la kupita katika, literally, nakala ya thamani.

343
00:21:16,950 --> 00:21:20,780
>> Ken haina kitu wake, hukabidhi mimi nyuma kitu - katika kesi hii thamani kama 8 -

344
00:21:20,780 --> 00:21:24,980
na kisha mimi kufanya kitu na thamani ya kwamba kama nataka kuweka ni kuzunguka.

345
00:21:24,980 --> 00:21:29,650
Basi wote wa hii kuja nyuma kwa kuwa wote pia familiar kabla ya muda mrefu.

346
00:21:29,650 --> 00:21:34,920
Asante sana kwa demo hii hapa, Ken. [Applause]

347
00:21:34,920 --> 00:21:36,920
Vizuri sana kufanyika.

348
00:21:36,920 --> 00:21:42,690
Hebu angalia jinsi ya kuwa hatimaye inahusiana na baadhi ya kazi wito kwamba sisi tumekuwa kufanya hapa.

349
00:21:42,690 --> 00:21:47,910
Hebu kwenda mbele na kutuleta kwa mfano cubing hapa.

350
00:21:47,910 --> 00:21:53,300
Ona kwamba kama tunataka kweli kuanza kuchukua hii zaidi,

351
00:21:53,300 --> 00:21:57,570
sisi itawabidi kukumbuka ukweli kwamba x idadi hiyo ni kuwa alipita katika hapa

352
00:21:57,570 --> 00:22:01,530
ni tofauti na yale ya kweli kuwa alipita katika kufanya kazi.

353
00:22:01,530 --> 00:22:05,880
Hivyo tena, hii wapitao nakala inaenda kuwa kabisa germane katika muda tu.

354
00:22:05,880 --> 00:22:09,580
Hebu tuangalie kitu ambacho haina kabisa kazi ya haki bado.

355
00:22:09,580 --> 00:22:13,250
Mimi nina kwenda mbele na kufungua tatu Buggy mfano, ambayo ni kiujanja kwa asili,

356
00:22:13,250 --> 00:22:18,550
na ni kuitwa buggy3 na ni kutekeleza kazi swapping.

357
00:22:18,550 --> 00:22:25,110
Hapa tuna kazi kuu ambayo ina x na y kiholela initialized kwa 1 na 2, kwa mtiririko huo.

358
00:22:25,110 --> 00:22:27,700
Tunaweza kutumia GetInt, lakini sisi tu haja ya zoezi rahisi,

359
00:22:27,700 --> 00:22:30,170
hivyo ni vigumu-coded kama 1 na 2.

360
00:22:30,170 --> 00:22:35,340
Katika mistari ya 21 na 22, sisi inaonekana magazeti nje x na y, 1 kwa kila mstari.

361
00:22:35,340 --> 00:22:39,720
Kisha kwenye mstari 23, mimi kudai Mimi swapping maadili haya, dot, dot, dot.

362
00:22:39,720 --> 00:22:44,170
Mimi inaonekana piga kazi katika mstari 24 walioitwa byta kwamba inachukua hoja 2.

363
00:22:44,170 --> 00:22:48,300
Ni kabisa legit kwa ajili ya kazi ya kuchukua hoja 2. Tumeona printf kufanya hivyo tayari.

364
00:22:48,300 --> 00:22:51,830
>> Hivyo byta inaonekana inachukua x na y, na kama jina lake anapendekeza,

365
00:22:51,830 --> 00:22:54,670
Napenda matumaini kwamba ni kwenda wabadilishane maadili haya 2.

366
00:22:54,670 --> 00:23:00,090
Hivyo basi mimi kudai kwenye mstari 25 "swapped!" na mimi kikachapishwa x na y

367
00:23:00,090 --> 00:23:03,070
chini ya dhana kwamba wameweza kweli imekuwa swapped.

368
00:23:03,070 --> 00:23:06,080
Lakini kama mimi kwa kweli kuendesha programu hii - basi mimi kufungua dirisha terminal,

369
00:23:06,080 --> 00:23:09,860
basi mimi kufanya buggy3 - kama jina linavyosema, hii si kwenda mwisho vizuri

370
00:23:09,860 --> 00:23:15,770
sababu wakati mimi hit Enter, taarifa kwamba ni x 1, y ni 2,

371
00:23:15,770 --> 00:23:19,420
na bado mwisho wa mpango, bado, kwa kweli, sawa.

372
00:23:19,420 --> 00:23:22,960
Hivyo kwa kuzingatia maandamano tu sasa na Ken, nini hasa kinachoendelea?

373
00:23:22,960 --> 00:23:28,710
Hebu tuzame ndani ya kazi hii byta. Ni super mfupi. Ni tu mistari michache ya maadili ya muda mrefu.

374
00:23:28,710 --> 00:23:34,520
Lakini nini tatizo la msingi kuzingatia hadithi rahisi aliiambia hapa juu na Ken?

375
00:23:34,520 --> 00:23:36,670
Kwa nini byta kuvunjwa?

376
00:23:36,670 --> 00:23:39,660
[Mwanafunzi] Wewe hifadhi kwa nakala, hazibadiliki.

377
00:23:39,660 --> 00:23:43,980
Hasa. Sisi ni hifadhi kwa nakala, hazibadiliki yenyewe.

378
00:23:43,980 --> 00:23:47,170
Kwa maneno mengine, byta inaonekana inachukua hoja 2, int,

379
00:23:47,170 --> 00:23:49,370
na ni kiholela kuitwa b na,

380
00:23:49,370 --> 00:23:54,420
na hapa nimepata kupita katika x na y, ambayo ni mtiririko 1 na 2,

381
00:23:54,420 --> 00:23:58,770
lakini nina si halisi kupita katika x, mimi si halisi kupita katika y,

382
00:23:58,770 --> 00:24:01,450
Mimi nina kupita nakala ya x na nakala ya y.

383
00:24:01,450 --> 00:24:04,510
Ni karibu kama wewe ingawa kunakiliwa na pasted katika byta

384
00:24:04,510 --> 00:24:07,810
maadili ambayo unataka kwa kweli kuendesha.

385
00:24:07,810 --> 00:24:14,480
Hivyo kama hiyo kesi, wakati mimi kuanza mpango wa utekelezaji mstari 35 kisha 36,

386
00:24:14,480 --> 00:24:18,650
wakati mimi kupata mstari 37, katika hatua hii ya hadithi, ni nini thamani ya?

387
00:24:21,040 --> 00:24:25,050
Katika hatua hii ya hadithi, line 37, ni nini thamani ya wakati huu? >> [Mwanafunzi] 1.

388
00:24:25,050 --> 00:24:29,280
[Malan] Ni lazima tu kuwa 1, haki, kwa sababu x ilipitishwa katika kama hoja ya kwanza,

389
00:24:29,280 --> 00:24:33,080
na kazi hii tu kiholela ni wito hoja yake ya kwanza.

390
00:24:33,080 --> 00:24:38,200
Vile vile ni y hoja ya pili, na ni tu kiholela wito pili hoja b.

391
00:24:38,200 --> 00:24:40,990
>> Dichotomy Hii ni kweli kwa haki tu alielezea. Fikiria kuhusu hilo.

392
00:24:40,990 --> 00:24:43,320
Hakuna kati yetu na alikutana mtu ambaye aliandika printf,

393
00:24:43,320 --> 00:24:50,770
hivyo hakika, yeye au yeye hana wazo nini vigezo wetu miaka 30 baadaye wanaenda kuitwa.

394
00:24:50,770 --> 00:24:56,650
Hivyo inabidi kuwe na tofauti kati ya nini wito vigezo katika kazi wewe kuandika

395
00:24:56,650 --> 00:25:02,080
na nini wito vigezo katika kazi wewe ni wito au kutumia.

396
00:25:02,080 --> 00:25:05,340
Hivyo kwa maneno mengine, nimeandika vigezo wangu kama x na y,

397
00:25:05,340 --> 00:25:08,890
lakini kama mtu mwingine ameandika kazi byta, yeye au yeye bila shaka hawezi kujua

398
00:25:08,890 --> 00:25:10,690
nini vigezo yangu ni kwenda kuitwa,

399
00:25:10,690 --> 00:25:13,830
hivyo kutambua kwamba hii ni kwa nini una hii pande mbili za majina.

400
00:25:13,830 --> 00:25:16,750
Kitaalam, mimi naweza kufanya hivyo kwa bahati mbaya,

401
00:25:16,750 --> 00:25:20,080
lakini bado wataendelea kuwa kupita katika kama nakala.

402
00:25:20,080 --> 00:25:23,650
Itakuwa bahati mbaya tu kuwa safi aesthetically ikiwa mtu huyo ambaye aliandika byta

403
00:25:23,650 --> 00:25:26,150
walitumia majina sawa.

404
00:25:26,150 --> 00:25:32,370
Hivyo katika hatua hii ya hadithi, line 37, ni 1, b ni 2, na sasa mimi kuendelea wabadilishane yao.

405
00:25:32,370 --> 00:25:34,900
Awali ya yote, napenda kwa kweli kufanya hili zaidi tu.

406
00:25:34,900 --> 00:25:36,690
Sijui nini wale mistari 3 ya maadili walikuwa wakifanya.

407
00:25:36,690 --> 00:25:41,210
Hebu tu kufanya hivyo: b = a; a = b; kufanyika.

408
00:25:41,210 --> 00:25:44,690
Kwa nini hii ni kuvunjwa, mantiki?

409
00:25:46,490 --> 00:25:48,900
Ni aina ya kitu Intuitive, haki?

410
00:25:48,900 --> 00:25:52,560
Hivyo b inakuwa na b inakuwa,

411
00:25:52,560 --> 00:25:57,730
lakini tatizo ni kwamba haraka kama mstari 37 executes, nini thamani ya b na?

412
00:25:57,730 --> 00:26:03,410
huo, 1, kwa sababu wewe clobbered, hivyo kusema, ve iliyopita b sawa.

413
00:26:03,410 --> 00:26:08,890
Hivyo mara mstari 37 ina kunyongwa, kwamba ni kubwa, sasa una 2 nakala ya namba 1

414
00:26:08,890 --> 00:26:13,350
ndani ya kazi hii, hivyo basi wakati wewe kusema katika mstari 38 a = b,

415
00:26:13,350 --> 00:26:17,640
wewe ni aina ya Star sababu wewe tu assigning 1-1.

416
00:26:17,640 --> 00:26:20,580
Umefanikiwa aina ya kupoteza thamani wewe kumjali kuhusu.

417
00:26:20,580 --> 00:26:23,220
Hivyo katika toleo asili ya hili, taarifa nilivyopatenda.

418
00:26:23,220 --> 00:26:26,850
Mimi badala yake alikuwa mstari wa tatu wa kificho kwamba inaonekana kama hii.

419
00:26:26,850 --> 00:26:28,580
Mimi kutangaza variable muda.

420
00:26:28,580 --> 00:26:32,170
>> TMP ni jina la kawaida kabisa kwa variable muda, na ni int

421
00:26:32,170 --> 00:26:34,580
kwa sababu ina mechi nini nataka kufanya nakala ya.

422
00:26:34,580 --> 00:26:39,770
Mimi kuhifadhi nakala ya ndani ya TMP, hivyo mara moja line 37 ina kunyongwa,

423
00:26:39,770 --> 00:26:45,860
thamani ya ni - haraka sanity hundi - 1, thamani ya b ni 2,

424
00:26:45,860 --> 00:26:48,970
na thamani ya TMP pia ni 1.

425
00:26:48,970 --> 00:26:52,060
Hivyo sasa mimi nitafanya line 38.

426
00:26:52,060 --> 00:27:00,540
Mara mstari 38 executes, inachukua juu ya thamani ya b. Na b ilikuwa 2, hivyo ni sasa 2.

427
00:27:00,540 --> 00:27:05,210
Hivyo katika hatua hii ya hadithi, ni 2, b ni 2, na TMP ni 1,

428
00:27:05,210 --> 00:27:11,060
hivyo sasa kimantiki, tunaweza thamani tu plop TMP wa ndani ya b na sisi ni kosa.

429
00:27:11,060 --> 00:27:12,800
Hivyo tumekuwa kutatuliwa kuwa tatizo.

430
00:27:12,800 --> 00:27:17,720
Bahati mbaya, wakati mimi kukimbia programu hii katika fomu hii, haina kweli wabadilishane maadili yoyote.

431
00:27:17,720 --> 00:27:20,100
Lakini kwa kuwa wazi, kwa nini?

432
00:27:23,660 --> 00:27:26,450
Mimi fasta tatizo mantiki kutoka muda tu iliyopita,

433
00:27:26,450 --> 00:27:31,020
lakini tena, kama mimi kukimbia katika mpango huu, x na y haitabadilishwa

434
00:27:31,020 --> 00:27:33,310
na mwisho wa utekelezaji wa programu hiyo.

435
00:27:33,310 --> 00:27:37,220
[Inaudible mwanafunzi maoni] >> Sisi si kurudi kitu chochote, hivyo hiyo ni kweli.

436
00:27:37,220 --> 00:27:39,670
Lakini zinageuka kuna kidogo ya tatizo hapa kwa sababu hivi sasa,

437
00:27:39,670 --> 00:27:44,170
Kitu tu tumekuwa na uwezo wa kurudi ni jambo moja, na hii ni kizuizi cha C.

438
00:27:44,170 --> 00:27:49,070
Unaweza tu kurudi kwa kweli moja ya thamani, katika kesi ambayo mimi nina aina ya kukwama hapa

439
00:27:49,070 --> 00:27:53,310
kwa sababu mimi naweza kurudi thamani mpya ya x au mimi naweza kurudi thamani mpya ya y,

440
00:27:53,310 --> 00:27:55,190
lakini nataka wote nyuma.

441
00:27:55,190 --> 00:27:58,650
Hivyo kurudi si ufumbuzi rahisi hapa.

442
00:27:58,650 --> 00:28:01,710
Lakini tatizo la msingi ni kwa nini? Nini sisi kweli swapped?

443
00:28:01,710 --> 00:28:04,190
[Mwanafunzi] a na b. >> A na b.

444
00:28:04,190 --> 00:28:08,230
Lakini na b ni nakala za x na y, ambayo ina maana sisi tu alifanya yote wa kazi hii,

445
00:28:08,230 --> 00:28:11,650
sisi tu alitumia dakika 3 kuzungumza juu ya kazi byta na wote 3 ya vigezo hivi,

446
00:28:11,650 --> 00:28:15,420
na kwamba ni kubwa, kikamilifu sahihi katika upweke,

447
00:28:15,420 --> 00:28:20,740
lakini na upeo b tu ni katika mistari haya hapa.

448
00:28:20,740 --> 00:28:24,790
>> Hivyo tu kama kwa kitanzi, kama wewe kutangaza integer i ndani kwa kitanzi,

449
00:28:24,790 --> 00:28:28,760
vile vile, kama wewe ni kutangaza na b ndani ya kazi ambayo umefanya imeandikwa,

450
00:28:28,760 --> 00:28:33,320
wao uko halali tu ndani ya kazi kwamba, ambayo ina maana kama haraka kama byta inafanywa utekelezaji

451
00:28:33,320 --> 00:28:38,470
na sisi kwenda kutoka mstari 24 kwa mstari 25, x na y haijabadilishwa wakati wote.

452
00:28:38,470 --> 00:28:42,790
Wewe tu kupita mengi yote ya wakati swapping nakala ya variables.

453
00:28:42,790 --> 00:28:47,010
Hivyo ni zinageuka kuwa ufumbuzi wa hili ni kweli zisizo dhahiri.

454
00:28:47,010 --> 00:28:50,670
Ni kabisa kutosha kurudi maadili kwa sababu tunaweza tu kurudi 1 thamani,

455
00:28:50,670 --> 00:28:53,470
na kwa kweli mimi nataka wabadilishane wote x na y wakati huo huo,

456
00:28:53,470 --> 00:28:55,210
hivyo sisi ni kwenda na kurudi huu.

457
00:28:55,210 --> 00:29:01,020
Lakini kwa sasa, kutambua kwamba suala kimsingi umetokana na ukweli kwamba ni nakala na b

458
00:29:01,020 --> 00:29:03,630
na wao ni katika upeo wao wenyewe.

459
00:29:03,630 --> 00:29:05,050
Hebu jaribu kutatua hili katika baadhi ya njia.

460
00:29:05,050 --> 00:29:11,250
Hebu kweli kitabu nyuma hapa na kufungua, hebu sema, lahaja ya nne ya hili, buggy4.

461
00:29:11,250 --> 00:29:13,370
Nini kuhusu hili?

462
00:29:13,370 --> 00:29:17,810
Hili ni tatizo sawa lakini rahisi kuangalia kabla ya sisi kuchukua kumchoma katika kulitatua.

463
00:29:17,810 --> 00:29:24,190
Mpango huu huitwa increment, na inaonekana initializes integer x kwa 1 katika mstari 18.

464
00:29:24,190 --> 00:29:28,150
Mimi kisha kudai x ni 1, mimi kisha kudai "Incrementing ..."

465
00:29:28,150 --> 00:29:33,730
Mimi kisha piga increment, lakini basi katika mistari 22 na 23, mimi kudai ni kuwa incremented,

466
00:29:33,730 --> 00:29:40,220
Mimi kudai x ni sasa chochote ni - 2, labda - lakini mpango huu ni Buggy.

467
00:29:40,220 --> 00:29:42,610
Nini tatizo?

468
00:29:43,440 --> 00:29:50,160
Yeah. >> [Inaudible mwanafunzi majibu] >> Hasa.

469
00:29:50,160 --> 00:29:52,490
Hivyo x ametangazwa, ni wazi, kwenye mstari 18.

470
00:29:52,490 --> 00:29:54,700
Hiyo ni ndani ya braces kuu ya curly.

471
00:29:54,700 --> 00:29:58,440
Hivyo jibu rahisi hapa ni kwamba wakati x lipo hapa,

472
00:29:58,440 --> 00:30:03,930
haipo katika mstari 32, hivyo mpango huu kwa kweli si hata kukusanya.

473
00:30:03,930 --> 00:30:07,940
compiler wakati mimi kujaribu kuandaa kanuni hii ni kwenda yell saa yangu

474
00:30:07,940 --> 00:30:14,100
kuhusu baadhi kitambulisho Undeclared au kitu na athari hiyo. Kwa kweli, hebu jaribu.

475
00:30:14,100 --> 00:30:18,470
Hii ni kufanya buggy4. Kuna ni.

476
00:30:18,470 --> 00:30:22,110
Matumizi ya 'x' Undeclared kitambulisho katika mstari 32.

477
00:30:22,110 --> 00:30:25,580
Na kweli, hebu kuwa wazi zaidi hapa leo ili kwamba hii ni muhimu

478
00:30:25,580 --> 00:30:27,580
katika masaa ya ofisi na nyumbani.

479
00:30:27,580 --> 00:30:29,300
>> Ona kwamba ni kidogo isiyoeleweka kirahisi imeandikwa.

480
00:30:29,300 --> 00:30:37,270
Lakini ukweli kwamba Clang ina yelled saa yetu, akisema buggy4.c: 32:5, ni kweli muhimu.

481
00:30:37,270 --> 00:30:42,050
Ina maana kwamba kosa ni juu ya mstari 32 katika tabia nafasi 5.

482
00:30:42,050 --> 00:30:46,700
Hivyo 1, 2, 3, 4, 5. Hiyo, kwa kweli, ambapo tatizo ni.

483
00:30:46,700 --> 00:30:49,790
Na pia, pia, kumbuka katika masaa ya ofisi na nyumbani, mimi nina bahati hapa.

484
00:30:49,790 --> 00:30:52,990
Nina moja kosa. Ni kwenda kuwa rahisi kurekebisha.

485
00:30:52,990 --> 00:30:55,990
Lakini kama wewe kupata screen nzima kamili ya ujumbe balaa kosa,

486
00:30:55,990 --> 00:31:00,330
tena kutambua kwamba moja bottommost ili tu kuwa dalili ya moja topmost.

487
00:31:00,330 --> 00:31:03,450
Hivyo baada ya daima chini mende wako kutoka juu kwenda chini

488
00:31:03,450 --> 00:31:05,820
kwa sababu kuna inaweza tu kuwa mnyororo daisy athari

489
00:31:05,820 --> 00:31:09,240
kwamba ni kupendekeza una matatizo njia zaidi ya wewe kweli kufanya.

490
00:31:09,240 --> 00:31:15,150
Hivyo ni jinsi gani tunaweza kurekebisha hii ikiwa lengo langu ni increment x? >> [Mwanafunzi] Matokeo x kimataifa.

491
00:31:15,150 --> 00:31:17,060
Sawa, hivyo tunaweza kufanya x kimataifa.

492
00:31:17,060 --> 00:31:20,480
Hebu kuchukua njia ya mkato kwamba mimi alionya kuhusu mapema, lakini heck, sisi tu haja ya kurekebisha haraka,

493
00:31:20,480 --> 00:31:25,730
hivyo hebu sema tu x int hapa juu. Kwamba inafanya x kimataifa.

494
00:31:25,730 --> 00:31:31,800
Hivyo sasa kuu ina huduma hiyo na increment ina upatikanaji wake,

495
00:31:31,800 --> 00:31:34,110
na hivyo basi mimi kwenda mbele na kukusanya hii sasa.

496
00:31:34,110 --> 00:31:37,630
Matokeo buggy4, Ingiza. Inaonekana kukusanya sasa.

497
00:31:37,630 --> 00:31:41,230
Hebu kukimbia buggy4. Na inaonekana kwa kweli kazi.

498
00:31:41,230 --> 00:31:45,150
Hii ni moja ya mambo haya hiyo ni kufanya kama mimi kusema, si kama mimi,

499
00:31:45,150 --> 00:31:47,010
kama nimekuwa tu kufanyika hapa, kwa sababu kwa ujumla,

500
00:31:47,010 --> 00:31:50,440
mipango yetu ni kwenda kupata zaidi ya kuvutia na muda mrefu zaidi kuliko huu,

501
00:31:50,440 --> 00:31:56,390
na kama ufumbuzi yako ya matatizo ya maisha ni tu kuweka vigezo vyote katika juu ya faili yako,

502
00:31:56,390 --> 00:31:59,690
haraka sana kufanya mipango kupata horrifically vigumu kusimamia.

503
00:31:59,690 --> 00:32:02,190
Ni anapata vigumu kufikiria juu majina mapya variable,

504
00:32:02,190 --> 00:32:05,240
anapata vigumu kuelewa nini variable ni kufanya nini,

505
00:32:05,240 --> 00:32:08,460
na hivyo katika ujumla, hii si ufumbuzi mzuri.

506
00:32:08,460 --> 00:32:10,030
Basi hebu kufanya hili vizuri.

507
00:32:10,030 --> 00:32:12,160
Hatutaki kutumia variable kimataifa hapa.

508
00:32:12,160 --> 00:32:16,240
>> Mimi nataka increment x, hivyo mimi nilikuwa wazi -

509
00:32:16,240 --> 00:32:18,670
mwisho wa siku, hii ni aina ya hadithi silly sababu sisi tu kufanya hivyo -

510
00:32:18,670 --> 00:32:24,450
lakini kama sikujua kuhusu operator kwamba au mimi sikuruhusiwa mabadiliko hayo katika kuu yenyewe,

511
00:32:24,450 --> 00:32:30,730
jinsi mwingine inaweza mimi kutekeleza Ken juu hapa wakati huu si kwa mchemraba lakini kwa nyongeza ya?

512
00:32:31,380 --> 00:32:33,190
Ninawezaje kubadilisha jambo hili hapa? Yeah.

513
00:32:33,190 --> 00:32:38,480
[Mwanafunzi] Pass katika x na kisha kurudi [inaudible] >> Okay, nzuri.

514
00:32:38,480 --> 00:32:41,900
Sasa kwa nini basi si mimi kupita katika x na kisha badala ya kurudi,

515
00:32:41,900 --> 00:32:44,870
nini si mimi tu wala kurudi x + 1.

516
00:32:44,870 --> 00:32:47,710
wanandoa zaidi mambo kuwa na mabadiliko ya hapa. Mimi nina juu ya kufuatilia haki.

517
00:32:47,710 --> 00:32:49,770
Ni kitu gani zaidi nahitaji tweak? Mtu mwingine. Yeah.

518
00:32:49,770 --> 00:32:51,740
[Inaudible mwanafunzi majibu]

519
00:32:51,740 --> 00:32:54,730
Mimi haja ya kubadili aina ya kurudi increment sababu ni si tupu.

520
00:32:54,730 --> 00:32:57,780
Tupu chochote njia ni kuwa walirudi, lakini ni wazi sasa ni,

521
00:32:57,780 --> 00:32:59,830
hivyo hii mahitaji na mabadiliko ya - >> [mwanafunzi] int.

522
00:32:59,830 --> 00:33:02,740
int kuwa thabiti na chochote mimi nina kweli kurudi.

523
00:33:02,740 --> 00:33:05,180
Sasa kitu kingine ni bado Buggy hapa. Yeah.

524
00:33:05,180 --> 00:33:08,400
[Inaudible mwanafunzi majibu] >> [Malan] Basi nahitaji increment x?

525
00:33:08,400 --> 00:33:12,080
[Inaudible mwanafunzi majibu] >> [Malan] Ah, hivyo mimi haja ya kupita x.

526
00:33:12,080 --> 00:33:16,660
Kwa hiyo mimi haja ya kufanya hivyo hapa. >> [Inaudible mwanafunzi maoni]

527
00:33:16,660 --> 00:33:20,050
[Malan] Basi mfano, mimi kuwa na mabadiliko ya hii hapa.

528
00:33:20,050 --> 00:33:22,930
Hivyo hii ina kuwa int, hii ina kuwa -

529
00:33:22,930 --> 00:33:25,620
hmm, mimi kwa kweli kuwa na mdudu chini hapa. Hebu kurekebisha hii moja kwanza.

530
00:33:25,620 --> 00:33:29,590
Nini hii kweli kuwa? Ni got kuwa ni kitu int.

531
00:33:29,590 --> 00:33:32,700
Ni inaweza kuwa x, lakini kusema ukweli, kama wewe kuanza wito yote ya x yako vigezo,

532
00:33:32,700 --> 00:33:35,390
ni kwenda kupata chini na chini ya wazi ambayo ni ambayo.

533
00:33:35,390 --> 00:33:39,560
>> Basi hebu tu kiholela kuchagua tofauti kumtaja mkataba kwa ajili ya kazi yangu msaidizi,

534
00:33:39,560 --> 00:33:41,940
kazi mimi nina maandishi. Tutaweza simu yake, au tunaweza kuiita -

535
00:33:41,940 --> 00:33:45,010
Hebu kuiita idadi kuwa hata zaidi ya wazi.

536
00:33:45,010 --> 00:33:47,560
Hivyo basi nina kurudi chochote idadi ni pamoja na 1,

537
00:33:47,560 --> 00:33:50,740
na sasa mimi kuwa na mabadiliko mengine 1 kitu hapa juu na nyingine moja kitu hapa.

538
00:33:50,740 --> 00:33:54,350
Nifanye kuwa na mabadiliko kwenye mstari 21 ya kwanza? >> [Inaudible mwanafunzi majibu]

539
00:33:54,350 --> 00:33:57,610
[Malan] nina hawawajui kwa x. Siwezi kuwaita tu increment (x).

540
00:33:57,610 --> 00:34:01,960
Mimi haja ya kukumbuka jibu kwa kubadilisha thamani ya x upande wa mkono wa kushoto.

541
00:34:01,960 --> 00:34:04,680
Na hata kama x ni sasa juu ya kushoto na kulia, hiyo ni kabisa faini

542
00:34:04,680 --> 00:34:08,860
kwa sababu upande wa kulia anapata kwanza kunyongwa kisha anapata plopped katika jambo mkono wa kushoto -

543
00:34:08,860 --> 00:34:10,600
x katika kesi hii.

544
00:34:10,600 --> 00:34:12,159
Na kisha mwisho, hii ni fix rahisi sasa.

545
00:34:12,159 --> 00:34:17,230
Hii lazima tu mechi nini chini chini, idadi int.

546
00:34:17,230 --> 00:34:20,570
Hivyo rundo zima la mabadiliko kwa ajili ya kazi kweli wajinga

547
00:34:20,570 --> 00:34:24,420
lakini mwakilishi wa mambo kwamba tutaweza inazidi wanataka kufanya.

548
00:34:24,420 --> 00:34:27,090
Hivyo kufanya buggy4. Nimekuwa Star up mahali fulani.

549
00:34:27,090 --> 00:34:30,139
Oh, Mungu wangu. Tano makosa katika mpango 6-line.

550
00:34:30,139 --> 00:34:35,690
Basi nini vibaya juu ya mstari 18, tabia ya 5?

551
00:34:35,690 --> 00:34:39,610
Hivyo nina kutangaza hii int.

552
00:34:39,610 --> 00:34:41,920
Hebu angalia. Kuna rundo zima la makosa mengine.

553
00:34:41,920 --> 00:34:47,010
Oh, Mungu wangu - 19, 18, 21 - lakini tena, hebu tu wazi screen, Udhibiti L hapa,

554
00:34:47,010 --> 00:34:49,380
na rerun Clang.

555
00:34:49,380 --> 00:34:51,340
Hivyo 5 matatizo ni kweli tu kwamba 1.

556
00:34:51,340 --> 00:34:57,520
Hivyo sasa hebu kukimbia buggy4, Ingiza. Whew, x imekuwa incremented usahihi.

557
00:34:57,520 --> 00:35:02,720
Wote haki. Maswali yoyote juu ya jinsi ya increment namba? Yeah.

558
00:35:02,720 --> 00:35:09,870
[Inaudible mwanafunzi swali] >> Bora swali.

559
00:35:09,870 --> 00:35:14,220
Jinsi ni kwamba naweza kubadili tu x kwa idadi na mpango kujua mara moja?

560
00:35:14,220 --> 00:35:16,200
>> Tena, unafikiri kama abstraction hii.

561
00:35:16,200 --> 00:35:21,600
Hivyo kama mimi ni kuu na Ken ni increment, kusema ukweli, mimi sijali nini Ken wito iPad wake.

562
00:35:21,600 --> 00:35:26,570
Mimi sijali kile anachokiita chochote kwamba ina nini na utekelezaji wake wa utendaji huu.

563
00:35:26,570 --> 00:35:33,340
Hii ni undani utekelezaji kuwa mimi, kuu, hawana huduma ya juu.

564
00:35:33,340 --> 00:35:38,250
Na hivyo tu kubadilisha mara kwa mara ndani ya kazi - idadi hapa na idadi hapa -

565
00:35:38,250 --> 00:35:40,960
ni yote inachukua muda mrefu kama mimi recompile.

566
00:35:40,960 --> 00:35:44,180
Ni aina ya kama kama unafikiri juu ya wengi wetu, wale wa wewe na leseni ya dereva

567
00:35:44,180 --> 00:35:46,770
ambao inaendeshwa au kama wameweza hata inaendeshwa katika gari,

568
00:35:46,770 --> 00:35:50,950
wengi wetu hawana wazo jinsi ya gari inafanya kazi chini ya Hood.

569
00:35:50,950 --> 00:35:54,970
Na literally, kama wewe kufungua Hood, wengi wetu - mimi mwenyewe pamoja -

570
00:35:54,970 --> 00:35:56,940
hawataenda kweli kujua nini sisi tunataka,

571
00:35:56,940 --> 00:35:59,220
aina ya kama unaweza kuhisi pamoja na mambo kama haki hii sasa.

572
00:35:59,220 --> 00:36:01,480
Lakini sisi si kweli kuwa na huduma jinsi gari inafanya kazi,

573
00:36:01,480 --> 00:36:05,970
hatuwezi kuwa na huduma zote za kile viboko na pistons na nyaya ndani ya gari

574
00:36:05,970 --> 00:36:08,160
ni kweli kufanya.

575
00:36:08,160 --> 00:36:12,770
Hivyo kitu kama nini wito piston Haijalishi hapa katika kesi hii. Same wazo.

576
00:36:12,770 --> 00:36:25,300
Yeah. >> [Inaudible mwanafunzi swali]

577
00:36:25,300 --> 00:36:29,180
Kama kuna matumizi zaidi ya dakika variable XA iliyopita,

578
00:36:29,180 --> 00:36:32,150
wewe, programu, unachoweza kubadilisha kila mahali.

579
00:36:32,150 --> 00:36:36,600
Au unaweza literally kufanya Picha, Menyu, na kisha Find, Replace - kitu kama hicho -

580
00:36:36,600 --> 00:36:39,170
lakini wewe ni kwenda na kufanya wale mabadiliko mwenyewe.

581
00:36:39,170 --> 00:36:47,450
Wewe kuwa thabiti. >> [Mwanafunzi] Kama kuna vigezo mbalimbali [inaudible]

582
00:36:47,450 --> 00:36:53,100
utaratibu maalum kama hapa, kama hii ilikuwa int mwingine namba? >> [Mwanafunzi] Sahihi.

583
00:36:53,100 --> 00:36:56,590
[Malan] Yeah. Ili mambo wakati wewe ni wito kazi.

584
00:36:56,590 --> 00:37:00,050
>> Hivyo kama mimi walikuwa wito increment hapa na kitu kitu comma,

585
00:37:00,050 --> 00:37:01,680
kuna ramani ya moja kwa moja.

586
00:37:01,680 --> 00:37:05,690
variable kwanza, chochote ni kuitwa, ni kufanywa nakala ya hoja ya kwanza zaidi ya hapa.

587
00:37:05,690 --> 00:37:07,760
Sorry. Hii haipaswi kuwa mabano.

588
00:37:07,760 --> 00:37:11,490
pili hoja yanaendana na la pili. Hivyo ili, ndiyo, mambo. Wote haki.

589
00:37:11,490 --> 00:37:17,020
Sorry. Nilitumia muda mrefu njia ya kufika huko. Maswali mengine? Wote haki.

590
00:37:17,020 --> 00:37:20,610
Basi hebu angalia kama hatuwezi kuchora picha ya nini kweli kinachoendelea hapa

591
00:37:20,610 --> 00:37:23,090
chini ya Hood, hivyo kusema.

592
00:37:23,090 --> 00:37:26,640
Hii ni mstatili kwamba wanaweza kuwakilisha kumbukumbu ya kompyuta yako.

593
00:37:26,640 --> 00:37:30,970
Hata kama una wazo jinsi kumbukumbu kazi au jinsi RAM matendo,

594
00:37:30,970 --> 00:37:33,940
angalau kudhani kwamba una mashada ya hiyo siku hizi.

595
00:37:33,940 --> 00:37:36,280
Nimepata megabaiti yake, nimepata gigabytes yake,

596
00:37:36,280 --> 00:37:40,870
na tunajua kutoka wiki 0 Byte kwamba ni kile tu? >> [Mwanafunzi] 8 bits.

597
00:37:40,870 --> 00:37:42,950
8 bits, haki? Hivyo 8 zeroes na 1.

598
00:37:42,950 --> 00:37:45,880
Hivyo kama kompyuta yako ina GIG ya RAM, 2 gigs ya RAM siku hizi,

599
00:37:45,880 --> 00:37:55,030
una bilioni au bilioni 2 ka ya kumbukumbu au bits takribani bilioni 8 au 16 bilioni

600
00:37:55,030 --> 00:37:56,890
ndani ya kompyuta yako.

601
00:37:56,890 --> 00:38:00,590
Tofauti na mfano kidogo sufu Willy, siyo magnetic chembe kawaida tena.

602
00:38:00,590 --> 00:38:04,450
Kuongezeka - katika Laptops angalau - ni hali mango anatoa, SSDs,

603
00:38:04,450 --> 00:38:08,580
kwamba tu kuwa na sehemu hakuna kusonga mbele. Ni wote elektroniki. Ni wote umeme-msingi.

604
00:38:08,580 --> 00:38:14,060
Hivyo kufikiri ya Mstatili hii kama tu anayewakilisha gigabytes 1 au 2 ya kumbukumbu kwamba wewe.

605
00:38:14,060 --> 00:38:16,020
>> Hivyo ni chunk ya kumbukumbu.

606
00:38:16,020 --> 00:38:19,830
ulimwengu wa sayansi ya kompyuta ina aina ya partitioned mbali

607
00:38:19,830 --> 00:38:22,950
bonge la kumbukumbu ya kufanya mambo tofauti.

608
00:38:22,950 --> 00:38:27,190
Kwa mfano, kama hii ni RAM kompyuta yako, kama ilivyopendekezwa na Mstatili huko,

609
00:38:27,190 --> 00:38:31,130
zinageuka kuwa na mkataba, juu ya RAM yako, ili kuzungumza,

610
00:38:31,130 --> 00:38:33,660
ujumla ni nini wito sehemu asilia.

611
00:38:33,660 --> 00:38:36,740
Wale ni sekunde 0 na 1s kwa kuwa compiled.

612
00:38:36,740 --> 00:38:39,020
Hivyo wakati tumekuwa inaonekana chini ya kofia katika kile a.out ni,

613
00:38:39,020 --> 00:38:41,980
yote haya sekunde 0 na 1s, wakati kukimbia mpango,

614
00:38:41,980 --> 00:38:46,290
sekunde 0 wale na 1s ni kubeba kutoka gari yako ngumu katika kitu kinachoitwa RAM,

615
00:38:46,290 --> 00:38:49,320
na katika RAM wao ni kuweka saa ya juu.

616
00:38:49,320 --> 00:38:52,770
Wakati huo huo, una mambo mengine: initialize data, uninitialize data.

617
00:38:52,770 --> 00:38:57,510
Wale 2 swaths ya kumbukumbu rejea vigezo kimataifa, ambayo huna mara nyingi matumizi ya

618
00:38:57,510 --> 00:39:00,760
lakini wakati mwingine kama wewe, wao kuishia huko pia.

619
00:39:00,760 --> 00:39:04,260
Kisha kuna baadhi ya mambo mengine: mazingira vigezo, ambayo sisi si kutumia muda mwingi juu ya,

620
00:39:04,260 --> 00:39:06,860
lakini kisha 2 mambo muhimu kwamba atakuja tena katika muhula,

621
00:39:06,860 --> 00:39:08,550
stack na lundo.

622
00:39:08,550 --> 00:39:12,210
Kwa hiyo wengi kumbukumbu ya kompyuta yako ni akiba wakati wa mbio mpango

623
00:39:12,210 --> 00:39:15,370
kwa kitu kinachoitwa stack na kitu kinachoitwa lundo.

624
00:39:15,370 --> 00:39:18,840
Sisi siyo kwenda kuzungumza kuhusu lundo leo, lakini tutaongea kuhusu stack.

625
00:39:18,840 --> 00:39:24,600
stack ni maana ya conjure up Visual ya dining trays mlo ukumbi katika Mather House

626
00:39:24,600 --> 00:39:28,110
au popote kutokea kwa kuwa ambapo ukumbi dining wafanyakazi safi yao ya kila siku,

627
00:39:28,110 --> 00:39:30,180
wao stack yao juu kutoka ghorofa ya juu juu,

628
00:39:30,180 --> 00:39:34,550
na vile vile, katika kumbukumbu, kuna hili wazo la kuweka kitu juu ya stack,

629
00:39:34,550 --> 00:39:36,860
kuweka kitu juu ya stack, kuweka kitu juu ya stack.

630
00:39:36,860 --> 00:39:38,240
Na nini sisi maana kwa mfano huu?

631
00:39:38,240 --> 00:39:41,860
>> Hebu zoom katika juu ya nusu tu ya chini ya picha hii, RAM kompyuta yako,

632
00:39:41,860 --> 00:39:44,330
kupendekeza yafuatayo.

633
00:39:44,330 --> 00:39:48,170
Ni zinageuka kuwa wakati kukimbia mpango kama a.out au hujambo -

634
00:39:48,170 --> 00:39:50,100
chochote mpango ni kwamba ve yameandikwa -

635
00:39:50,100 --> 00:39:54,020
tena, wale sekunde 0 na 1s ni kubeba kutoka gari yako ngumu, ambayo ni ya muda mrefu ya uhifadhi,

636
00:39:54,020 --> 00:39:57,230
anakaa huko hata wakati wewe vuta kuziba, kubeba katika RAM.

637
00:39:57,230 --> 00:40:00,610
RAM ni kasi kuliko anatoa ngumu - ni ndogo kuliko anatoa ngumu -

638
00:40:00,610 --> 00:40:03,300
lakini ni mipango ya kuishi ambapo wakati wewe mbio yao.

639
00:40:03,300 --> 00:40:08,230
Hivyo bonyeza mara mbili juu ya mpango Mac au PC, ni kubeba kutoka ndani ya gari ngumu RAM.

640
00:40:08,230 --> 00:40:11,520
Haraka kama ni kubeba katika RAM, go sekunde 0 na 1s kwa juu ya njia,

641
00:40:11,520 --> 00:40:16,610
kinachojulikana Nakala sehemu, lakini basi haraka kama mpango wako kweli kuanza kukimbia,

642
00:40:16,610 --> 00:40:21,360
Kazi kuu inaitwa, na kuu, kama tumeona, mara nyingi ina vigezo mitaa,

643
00:40:21,360 --> 00:40:24,870
na ina ints masharti na na chars na kama.

644
00:40:24,870 --> 00:40:29,180
Hivyo kama mpango wako kwamba umeandika au mpango kwamba una mbili clicked

645
00:40:29,180 --> 00:40:32,970
kutumika baadhi ya vigezo ndani ya kuu,

646
00:40:32,970 --> 00:40:37,240
wao kuishia chini ya stack yako ya kumbukumbu, hivyo kusema.

647
00:40:37,240 --> 00:40:39,410
Zaidi concretely, nini hii kwa kweli ina maana gani?

648
00:40:39,410 --> 00:40:48,450
Hii ina maana kwamba kama sisi walikuwa wanakwenda idadi bytes ya RAM katika kompyuta yako,

649
00:40:48,450 --> 00:40:55,750
taarifa kwamba hii inaweza kuwa Byte idadi 0, hii inaweza kuwa Byte namba 1, 2, 3, 4, 5, 6,

650
00:40:55,750 --> 00:41:01,480
njia yote hadi bilioni 2 itakuwa njia yote hadi pale saa ya juu.

651
00:41:01,480 --> 00:41:05,880
Hivyo kwa maneno mengine, wakati sisi majadiliano kuhusu RAM au kumbukumbu katika suala la ka,

652
00:41:05,880 --> 00:41:11,500
ni njia tu kwamba mtu imeamua nini kuzihesabu kila chunks wale wa kumbukumbu.

653
00:41:11,500 --> 00:41:16,650
Hivyo wakati unahitaji 32 bits kwa int au unahitaji 8 bits kwa Char,

654
00:41:16,650 --> 00:41:18,840
wapi wanaishia katika kumbukumbu?

655
00:41:18,840 --> 00:41:22,350
>> Conceptually, wao tu kuishia chini ya jambo hili aitwaye stack.

656
00:41:22,350 --> 00:41:25,870
Lakini nini kuvutia sasa ni wakati kuu wito kazi -

657
00:41:25,870 --> 00:41:28,750
kudhani kazi kuitwa foo, tu jina holela -

658
00:41:28,750 --> 00:41:32,330
kile kinachotokea ni kuu ni chini ya hii stack ya kumbukumbu;

659
00:41:32,330 --> 00:41:35,680
foo sasa ni kuweka juu ya kuu katika kumbukumbu.

660
00:41:35,680 --> 00:41:40,990
Hivyo yoyote vigezo vya ndani kuwa foo ina kuishia aina ya conceptually juu ya wale katika kuu.

661
00:41:40,990 --> 00:41:47,070
Kama foo wito kazi nyingine iitwayo bar, wale vigezo kuishia hapa.

662
00:41:47,070 --> 00:41:50,120
Kama bar wito kitu kingine, hapa, hapa, hapa.

663
00:41:50,120 --> 00:41:53,830
Basi nini kuvutia kuhusu mbio mpango ni kwamba kama wewe piga kazi

664
00:41:53,830 --> 00:41:57,750
na kama wale utendaji kazi na kuwaita kama wale majukumu piga kazi,

665
00:41:57,750 --> 00:42:01,470
wewe kujenga hii stack ya utendaji katika kumbukumbu.

666
00:42:01,470 --> 00:42:06,890
Na mara moja tu anarudi kazi gani unaweza kuanza kupata kwamba kumbukumbu nyuma.

667
00:42:06,890 --> 00:42:10,860
Hivyo moja ya njia rahisi ya kukimbia nje ya kumbukumbu katika programu ya kompyuta

668
00:42:10,860 --> 00:42:14,360
ni kuandika kazi ambayo kamwe kurudi.

669
00:42:14,360 --> 00:42:18,900
Hivyo kwa mfano, hebu kuonyesha kama kiasi na mpango kukusudia Buggy.

670
00:42:18,900 --> 00:42:22,230
Hebu kwenda mbele na kufanya # pamoja <stdio.h>,

671
00:42:22,230 --> 00:42:25,000
int kuu (utupu),

672
00:42:25,000 --> 00:42:32,940
na mimi naenda kufanya wakati (2> 1), ambayo pengine haitabadilika juu yetu,

673
00:42:32,940 --> 00:42:37,560
na napenda kwenda mbele sasa na kufanya printf.

674
00:42:37,560 --> 00:42:40,700
Kwa kweli, kwamba kinaendelea kuwa chini ya kuibua kuvutia. Hebu kufanya hili.

675
00:42:40,700 --> 00:42:50,240
Kwa int i = 0; i> 0 - wacha kufanya kosa hili - i + +.

676
00:42:50,240 --> 00:42:52,720
Na hebu printf hapa. Hebu mazoezi nini nilikuwa akihubiri.

677
00:42:52,720 --> 00:43:00,190
Hebu kuwa na mbinu hapa, utupu chorus, na tutaweza kusema int i,

678
00:43:00,190 --> 00:43:06,830
na kisha mimi nina kwenda kusema printf - hapana, wacha kufanya hii ya kuvutia zaidi.

679
00:43:06,830 --> 00:43:15,790
Hebu kweli si magazeti chochote wakati wote. Hebu tu kufanya hivyo: chorus (i).

680
00:43:15,790 --> 00:43:20,390
Wote haki. Hivyo hii ni kwa sababu Buggy kwa nini?

681
00:43:20,390 --> 00:43:23,380
Mimi nina kufanya hili kama mimi kwenda kwa sababu haina mpango kwa kweli kufanya kitu chochote cha riba.

682
00:43:23,380 --> 00:43:25,320
>> Lakini hilo sio lengo.

683
00:43:25,320 --> 00:43:29,630
Lengo ni kuandika mpango ambao kuu kazi anafanya nini, inaonekana?

684
00:43:30,720 --> 00:43:32,860
Wito yenyewe. Na kweli, hatuna haja ya kitanzi.

685
00:43:32,860 --> 00:43:37,200
Hebu hata kurahisisha hii tu ili kama si kupoteza mbele ya mdudu kweli ya msingi.

686
00:43:37,200 --> 00:43:39,640
Wito Kuu chorus kuimba baadhi chorus,

687
00:43:39,640 --> 00:43:41,440
basi mimi alifanya kitu kijinga na mimi alikuwa na chorus wito chorus

688
00:43:41,440 --> 00:43:43,760
kwa sababu mimi kudhani mtu mwingine alikuwa anaenda kutekeleza hilo labda,

689
00:43:43,760 --> 00:43:47,210
na sasa hii si kwenda kukusanya bado. Mimi haja ya kufanya nini?

690
00:43:47,210 --> 00:43:49,970
Nahitaji mfano, kumbuka.

691
00:43:49,970 --> 00:43:56,110
Kwa hiyo mimi haja ya kuwa juu hapa utupu chorus (int i);

692
00:43:56,110 --> 00:43:59,210
Hivyo sasa kama mimi kwenda chini hapa - kwa kweli, hebu kutumia dirisha kubwa.

693
00:43:59,210 --> 00:44:01,980
Hebu kwenda mbele na kufanya chorus.

694
00:44:01,980 --> 00:44:06,490
Hebu kwenda mbele na kufanya chorus.

695
00:44:06,490 --> 00:44:08,370
Matumizi ya kitambulisho Undeclared i.

696
00:44:08,370 --> 00:44:12,500
Oh, kwamba ilikuwa ya kijinga. Hatuna haja ya hoja. Hebu tu kufanya hili.

697
00:44:12,500 --> 00:44:16,370
Natamani tungeanza njia hii. Ingekuwa mpango rahisi sana kuandika.

698
00:44:16,370 --> 00:44:25,590
Kuna. Sasa hebu kwenda juu kwa terminal dirisha yangu, rerun Clang, na hapa sisi kwenda.

699
00:44:25,590 --> 00:44:28,460
Hiyo ilikuwa kweli kasi.

700
00:44:28,460 --> 00:44:31,150
Ni nini hasa ilitokea tu, ingawa?

701
00:44:31,150 --> 00:44:33,730
Naam, sasa mimi itabidi kuongeza line magazeti ili tuweze kuona.

702
00:44:33,730 --> 00:44:43,490
Ngoja niseme printf ("mimi niko katika hapa") - hakuna vigezo. Tutaweza kuondoka ni kama hiyo.

703
00:44:43,490 --> 00:44:47,480
Hebu rerun kufanya. Hebu rerun chorus.

704
00:44:47,480 --> 00:44:57,380
Na ... kuja juu. Kuendelea.

705
00:44:57,380 --> 00:44:59,930
Kama kando, kwa nini kuwa si kugonga bado?

706
00:44:59,930 --> 00:45:02,080
kosa segmentation kilichotokea super kufunga kabla.

707
00:45:02,080 --> 00:45:06,570
[Inaudible mwanafunzi majibu] >> Hasa. Hivyo inachukua muda na magazeti, haki?

708
00:45:06,570 --> 00:45:08,610
Ni tu inachukua zaidi ya kazi juu ya sehemu ya kompyuta.

709
00:45:08,610 --> 00:45:10,620
Na huko ni: Mkato kosa.

710
00:45:10,620 --> 00:45:12,340
>> Hivyo taarifa tu jinsi mipango haraka kukimbia.

711
00:45:12,340 --> 00:45:14,130
Kama wewe si kuchapa chochote, super haraka.

712
00:45:14,130 --> 00:45:18,770
Lakini sisi bado got hii kosa segmentation kwa sababu kile kinachotokea?

713
00:45:18,770 --> 00:45:21,210
Kama unafikiri kuhusu jinsi ya kumbukumbu ya kompyuta yako ni kuweka nje,

714
00:45:21,210 --> 00:45:28,740
hii hutokea kwa kuwa kuu, lakini hapa hebu piga tu hii chorus, na hebu piga hii chorus.

715
00:45:28,740 --> 00:45:34,550
Na sasa kama mimi kufanya aesthetics wangu wa kulia, hii ni kwenda tu kusema chorus, chorus, chorus,

716
00:45:34,550 --> 00:45:40,550
chorus, chorus, chorus, chorus, ad nauseum, na hatimaye, nini kitatokea?

717
00:45:40,550 --> 00:45:45,630
Kama picha kubwa, literally, ni hili, ni nini hutokea tu conceptually?

718
00:45:46,520 --> 00:45:48,630
kuongezeka stack lundo.

719
00:45:48,630 --> 00:45:51,940
Au, mbaya, wewe tu overrun kila kitu, ikiwa ni pamoja na sehemu ya maandishi,

720
00:45:51,940 --> 00:45:54,590
ambayo ni sekunde 0 na 1s kwamba kuwakilisha programu yako.

721
00:45:54,590 --> 00:45:57,080
Kwa kifupi, hii ni super, super mbaya.

722
00:45:57,080 --> 00:45:58,830
Mpango wako kuzidi kuwa mbaya nje ya kudhibiti.

723
00:45:58,830 --> 00:46:01,220
Unatumia zaidi njia kumbukumbu kuliko wewe lengo

724
00:46:01,220 --> 00:46:03,960
wote kwa sababu ya makosa ya kijinga katika kesi hii,

725
00:46:03,960 --> 00:46:08,040
au katika kesi hii kazi sana kwa makusudi kufanyika linalojiita.

726
00:46:08,040 --> 00:46:09,500
Sasa, hii si wote mbaya.

727
00:46:09,500 --> 00:46:13,800
Kazi wito wenyewe kweli ina nguvu kubwa wakati matumizi kwa usahihi.

728
00:46:13,800 --> 00:46:15,800
Mimi si kutumika kwa usahihi hapa.

729
00:46:15,800 --> 00:46:19,780
Hivyo hii si wote mbaya, lakini ukweli kwamba mimi kweli kamwe kuacha wito mwenyewe

730
00:46:19,780 --> 00:46:23,520
ni udhaifu msingi hapa ya mpango huu.

731
00:46:23,520 --> 00:46:26,400
Hivyo ambapo ni sisi kwenda kwa yote haya? Nini kinatokea kweli?

732
00:46:26,400 --> 00:46:30,340
Wakati mimi piga kazi increment kama sisi walikuwa wakifanya katika mifano hizo,

733
00:46:30,340 --> 00:46:33,420
Nina thamani kama 1 kwamba mimi kupita in

734
00:46:33,420 --> 00:46:37,570
Mimi kupita katika nakala ya namba 1, hivyo zifuatazo kinachotokea.

735
00:46:37,570 --> 00:46:44,240
Hebu kwenda katika mfano increment, hii guy haki zaidi ya hapa.

736
00:46:44,240 --> 00:46:46,870
Hapa ni nini ni kweli yanatokea.

737
00:46:46,870 --> 00:46:53,400
Wakati mimi kuwaita increment na mimi kupita katika x, pictorially, nini kinaendelea hapa ni hii.

738
00:46:53,400 --> 00:46:59,520
>> Kama mimi na thamani ya 1 kuhifadhiwa hapa na mimi kwa kweli kuwaita increment,

739
00:46:59,520 --> 00:47:04,330
ambayo sasa inaitwa chorus - iPad ni kutupa mimi mbali hapa.

740
00:47:04,330 --> 00:47:09,760
Hebu piga hii increment, na sisi hawajui nini kazi hii ya pili ni kwenda kuwa.

741
00:47:09,760 --> 00:47:14,840
Basi nini hasa kinachotokea ni hapa mahali fulani katika kuu nina chunk ya kumbukumbu

742
00:47:14,840 --> 00:47:17,000
kwamba ni hifadhi ya namba 1.

743
00:47:17,000 --> 00:47:19,380
Wakati mimi kuwaita increment, mimi nina kutumia mwingine chunk ya kumbukumbu,

744
00:47:19,380 --> 00:47:21,230
lakini sasa nina nakala ya 1.

745
00:47:21,230 --> 00:47:26,660
Wakati mimi increment kwamba thamani, hii inakuwa 2,

746
00:47:26,660 --> 00:47:30,560
lakini basi kile kinachotokea kwa haraka kama anarudi increment?

747
00:47:30,560 --> 00:47:33,630
Kumbukumbu hii tu anapata mitupu nyuma mfumo wa uendeshaji,

748
00:47:33,630 --> 00:47:37,450
ambayo ina maana wote umefanya kosa ni kitu muhimu.

749
00:47:37,450 --> 00:47:43,120
1 kuwa awali ilikuwa zilizomo katika kuu ni kweli bado kuna.

750
00:47:43,120 --> 00:47:44,890
Hivyo ambapo ni sisi kwenda na hili?

751
00:47:44,890 --> 00:47:49,770
Ni zinageuka kuwa katika kumbukumbu una mlolongo huu nyuma kwa nyuma ya ka

752
00:47:49,770 --> 00:47:53,050
kuwa unaweza kuweka mambo katika, na ni zinageuka kuwa tumekuwa tayari kuona kitu

753
00:47:53,050 --> 00:47:55,390
ambayo inahusisha kuweka mambo nyuma kwa nyuma kwa nyuma kwa nyuma.

754
00:47:55,390 --> 00:47:59,860
Je, ni kamba msingi wiki 1 na sasa wiki 2?

755
00:48:00,020 --> 00:48:01,980
Ni tu mkusanyiko wa wahusika.

756
00:48:01,980 --> 00:48:04,310
Hivyo zinageuka tu kama unaweza kuweka namba katika kumbukumbu,

757
00:48:04,310 --> 00:48:06,990
vile vile unaweza kuweka wahusika katika kumbukumbu.

758
00:48:06,990 --> 00:48:10,530
Na mara moja tunaanza wahusika kuweka katika kumbukumbu nyuma kwa nyuma kwa nyuma kwa nyuma,

759
00:48:10,530 --> 00:48:13,620
zinageuka kuwa kutumia rahisi ya mambo kama kwa kitanzi au kitanzi wakati,

760
00:48:13,620 --> 00:48:17,170
tunaweza iterate kutoka kushoto kwenda kulia juu ya wahusika katika string

761
00:48:17,170 --> 00:48:20,600
na kuanza massaging yao ndani ya wahusika tofauti kabisa -

762
00:48:20,600 --> 00:48:23,370
inaweza kuwa b, b inaweza kuwa c -

763
00:48:23,370 --> 00:48:27,780
ili hatimaye, tunaweza kuchukua sentensi Kiingereza kwamba kweli hufanya akili

764
00:48:27,780 --> 00:48:30,310
na kubadilisha kila barua hizo moja kwa wakati mmoja

765
00:48:30,310 --> 00:48:34,400
kutembea kupitia kumbukumbu ya kompyuta wetu wa kushoto na haki ya kweli encrypt.

766
00:48:34,400 --> 00:48:35,810
Basi hebu kuchukua yetu dakika tano mapumziko hapa,

767
00:48:35,810 --> 00:48:40,730
na wakati sisi kuja nyuma, tutaweza kuanza mchakato huu wa scrambling habari.

768
00:48:42,020 --> 00:48:43,520
>> Wote haki.

769
00:48:43,520 --> 00:48:48,070
Kabla ya sisi kupiga mbizi katika baadhi crypto na mambo haya kuitwa arrays,

770
00:48:48,070 --> 00:48:51,470
basi mimi pause kwa maswali yoyote kwa sababu mimi najisikia kama kweli aina ya msonge

771
00:48:51,470 --> 00:48:54,080
baadhi ya mada hizo. Basi hebu kurekebisha sasa kama tunaweza.

772
00:48:54,080 --> 00:48:58,700
Sisi tu kuongelea maadili kurudi, sisi aliyesema kuhusu hoja,

773
00:48:58,700 --> 00:49:03,250
na kuongelea wazo hili, ambayo tutaweza kurudi katika wiki ijayo,

774
00:49:03,250 --> 00:49:08,720
ya kuangalia kumbukumbu kama rundo zima la trays haya sifa, ili kuzungumza,

775
00:49:08,720 --> 00:49:12,660
kutoka chini juu juu, vile kwamba kila tray kwamba anapata kuweka kwenye stack

776
00:49:12,660 --> 00:49:16,530
inawakilisha kazi hiyo kwa sasa kuitwa.

777
00:49:17,900 --> 00:49:20,260
Maswali yoyote?

778
00:49:20,260 --> 00:49:22,640
Napenda kuuliza swali hapa.

779
00:49:22,640 --> 00:49:27,890
Hebu kurahisisha hii nyuma ilikuwa ni nini kabla ya baadhi ya Q & A. yetu mapema

780
00:49:27,890 --> 00:49:35,570
ukweli kwamba increment ina mabano wazi, int idadi, imefungwa mabano -

781
00:49:35,570 --> 00:49:39,110
nini idadi int kuwakilisha?

782
00:49:39,110 --> 00:49:42,790
[Mwanafunzi] hoja. >> Hoja. Sawa. Lakini nini hoja?

783
00:49:42,790 --> 00:49:46,370
[Inaudible mwanafunzi majibu] >> gani hiyo? >> [Mwanafunzi] Kitu ambacho wewe kupita in

784
00:49:46,370 --> 00:49:49,940
Okay, kwa hivyo kitu ambacho wewe kupita in Na zaidi kwa ujumla, ni tu pembejeo.

785
00:49:49,940 --> 00:49:52,450
Kama ungekuwa kuandika kazi na madhumuni kwamba kazi katika maisha

786
00:49:52,450 --> 00:49:55,770
ni kufanya kitu tofauti kidogo kila wakati matumizi yake,

787
00:49:55,770 --> 00:50:00,110
basi njia pekee kwa kuwa kutokea kwa kweli inaweza kuonekana kuwa kutoa ni pamoja na pembejeo

788
00:50:00,110 --> 00:50:03,510
hivyo kwamba wanaweza kufanya kitu tofauti na pembejeo kwamba kila wakati.

789
00:50:03,510 --> 00:50:06,650
>> Hivyo haja ya kutaja mambo mawili wakati kazi inachukua pembejeo.

790
00:50:06,650 --> 00:50:09,590
Unahitaji kubainisha jina kwamba unataka kutoa mchango kwamba

791
00:50:09,590 --> 00:50:12,700
rena kwa urahisi wako mwenyewe ili uweze rejea ni

792
00:50:12,700 --> 00:50:16,540
katika kazi na kwamba wewe binafsi ni kuandika, kama mimi hapa katika mstari 32.

793
00:50:16,540 --> 00:50:20,800
Lakini pia unahitaji kwa kutaja aina yake kwa sababu C ni lugha ya programu

794
00:50:20,800 --> 00:50:25,940
kwamba tu inahitaji kwamba kama unataka variable, mniambie kompyuta nini data aina hiyo ni,

795
00:50:25,940 --> 00:50:30,200
katika sehemu kubwa hivyo kwamba anajua jinsi wengi bits kutenga kwa variable kwamba

796
00:50:30,200 --> 00:50:33,020
kwa sababu inaweza kuwa 6 - sorry, itakuwa si 6.

797
00:50:33,020 --> 00:50:37,080
Inaweza kuwa 16, inaweza kuwa 8, inaweza kuwa 32, hata 64,

798
00:50:37,080 --> 00:50:39,130
lakini kompyuta mahitaji ya kujua.

799
00:50:39,130 --> 00:50:43,180
Sasa, int upande wa mkono wa kushoto inawakilisha nini, kwa kulinganisha?

800
00:50:46,350 --> 00:50:48,850
[Inaudible mwanafunzi majibu] >> gani hiyo? >> [Mwanafunzi] Aina ya kazi.

801
00:50:48,850 --> 00:50:53,610
aina ya kazi na, zaidi hasa, aina ya matokeo yake. Haki.

802
00:50:53,610 --> 00:50:57,380
Hivyo wakati kitu katika mabano inawakilisha mchango wake, kama wapo,

803
00:50:57,380 --> 00:50:59,660
kitu kwa upande wa kushoto inawakilisha matokeo yake.

804
00:50:59,660 --> 00:51:03,530
Na katika kesi hii, inaonekana increment anarudi int,

805
00:51:03,530 --> 00:51:07,690
na hivyo int ni aina ya kurudi kwa kazi hii.

806
00:51:07,690 --> 00:51:09,340
Nini maana ya kurudi?

807
00:51:09,340 --> 00:51:15,090
Literally, wewe kutumia kurudi Keyword na kisha kama nini wewe ni kurudi

808
00:51:15,090 --> 00:51:18,600
na haki ya Keyword ni integer,

809
00:51:18,600 --> 00:51:21,660
basi hakika hivyo ni sambamba na kile sisi ahadi.

810
00:51:21,660 --> 00:51:26,410
Unaweza si kufanya kitu kama hii - hello, ulimwengu - kwa sababu ni kamba.

811
00:51:26,410 --> 00:51:28,860
>> Ni dhahiri kuwa, si integer.

812
00:51:28,860 --> 00:51:33,140
Hivyo katika muda mfupi, ni mzigo kweli juu yetu, programu, kwa kuwa maalum

813
00:51:33,140 --> 00:51:37,770
kama kwa nini tuko kurudi na kisha kweli kwenda kuhusu kurudi yake.

814
00:51:37,770 --> 00:51:43,440
muktadha hapa sasa ni kwamba kumbukumbu ya kompyuta yako ni gigabyte, gigabytes 2 -

815
00:51:43,440 --> 00:51:45,920
chochote - labda ni zaidi, labda ni kidogo,

816
00:51:45,920 --> 00:51:49,050
lakini kompyuta maoni yake kama kuwa na sehemu mbalimbali.

817
00:51:49,050 --> 00:51:51,200
Kitu huenda chini pale, kitu kingine huenda juu huko,

818
00:51:51,200 --> 00:51:54,290
mambo mbalimbali huenda katika katikati, na leo sisi tu kuanza kusimulia hadithi,

819
00:51:54,290 --> 00:51:56,340
lakini tutaweza kuja nyuma wakati huu zaidi.

820
00:51:56,340 --> 00:51:59,980
Kwa sasa, kipande tu ya kumbukumbu sisi kweli huduma kuhusu ni sehemu asilia

821
00:51:59,980 --> 00:52:03,360
kwa sababu tu kwamba inawakilisha sekunde 0 na 1s kwamba Clang ina outputted.

822
00:52:03,360 --> 00:52:06,050
Hivyo wakati wewe kukimbia amri katika keyboard kama a.out

823
00:52:06,050 --> 00:52:09,110
au wewe bonyeza mara mbili icon kwenye Mac OS au Windows,

824
00:52:09,110 --> 00:52:11,880
programu yako ni kubeba kutoka gari yako ngumu katika RAM

825
00:52:11,880 --> 00:52:16,330
na ni plopped wakati juu ya RAM ya kompyuta yako, hivyo kusema.

826
00:52:16,330 --> 00:52:20,450
Wakati huo huo, kama mpango wako na kuanza mbio kuu anapata kuitwa

827
00:52:20,450 --> 00:52:23,640
katika mpango aliandika au Microsoft mpango au Apple aliandika,

828
00:52:23,640 --> 00:52:27,860
yoyote ya vigezo yake mitaa kuishia chini huko chini ya kumbukumbu ya kompyuta yako.

829
00:52:27,860 --> 00:52:33,230
Lakini kama kazi wito kuu mwingine kwamba yenyewe ina vigezo au hoja, wanaishia hapo juu.

830
00:52:33,230 --> 00:52:36,680
Na kama kazi kwamba wito kitu, wanaishia hapo juu, juu ya hayo, juu yake.

831
00:52:36,680 --> 00:52:41,460
>> Na mara moja tu kazi inafanywa utekelezaji haina stack ya sania, ili kuzungumza,

832
00:52:41,460 --> 00:52:43,240
kuanza kupata chini na chini.

833
00:52:43,240 --> 00:52:48,250
Na hii ni nini basi, kwa kifupi, anaelezea kwa nini wakati wewe piga mchemraba

834
00:52:48,250 --> 00:52:51,550
au wewe piga increment, wewe ni kupita katika nakala ya thamani.

835
00:52:51,550 --> 00:52:55,520
Na nini maana ya pictorially ni kwamba wewe ni literally kuandika namba 1

836
00:52:55,520 --> 00:53:00,460
katika sehemu nyingine ya kumbukumbu, kubadilisha kwamba 1-2 katika kesi ya increment

837
00:53:00,460 --> 00:53:04,820
au 8 katika kesi ya mchemraba na kisha kutupa kwamba kumbukumbu mbali

838
00:53:04,820 --> 00:53:09,140
haraka kama increment au anarudi mchemraba kazi. Swali.

839
00:53:09,140 --> 00:53:12,900
[Mwanafunzi] wapi vigezo kimataifa kuhifadhiwa?

840
00:53:12,900 --> 00:53:18,100
Vigezo Global ni kuhifadhiwa katika nini sasa inaitwa data initialized au data uninitialized,

841
00:53:18,100 --> 00:53:21,920
tofauti kuwa kama una variable kimataifa na wewe hawawajui ni mara moja thamani

842
00:53:21,920 --> 00:53:24,640
na alama ya usawa, inaishia kwa juu pale,

843
00:53:24,640 --> 00:53:29,200
na kama wewe tu kusema x int; na thamani hakuna, ni mwisho juu chini kidogo katika RAM

844
00:53:29,200 --> 00:53:31,710
tu kwa mkataba.

845
00:53:31,710 --> 00:53:34,940
Maswali mengine? Wote haki.

846
00:53:34,940 --> 00:53:37,340
Hivyo picha hii kuja nyuma kama sisi kupata nguvu zaidi

847
00:53:37,340 --> 00:53:39,170
kwa nini tunaweza kufanya kwa kompyuta,

848
00:53:39,170 --> 00:53:42,720
lakini kwa sasa, hebu kuwa intro mafupi kwa cryptography,

849
00:53:42,720 --> 00:53:46,080
aina maalum ya cryptography kwamba haina kutatua matatizo yote ya dunia

850
00:53:46,080 --> 00:53:47,720
lakini haina kutatua baadhi yao.

851
00:53:47,720 --> 00:53:51,700
Katika kesi hii hapa, tuna kitu kinachoitwa siri-ufunguo cryptography.

852
00:53:51,700 --> 00:53:56,410
Siri-key cryptography, kama jina linavyosema, hupata usalama wake kutoka siri.

853
00:53:56,410 --> 00:54:00,690
>> Kwa mfano, kama wewe walikuwa nyuma katika shule ya daraja na wewe walikuwa kupita kidogo siri upendo barua

854
00:54:00,690 --> 00:54:04,850
kwa mvulana au msichana wewe walikuwa kusagwa juu, kama alitaka kupita kwamba kumbuka kupitia watazamaji,

855
00:54:04,850 --> 00:54:08,380
wewe pengine bila kuandika kumbuka vile katika Kiingereza au lugha yoyote yako ya asili ni.

856
00:54:08,380 --> 00:54:13,340
Badala yake, unaweza encrypt au unaweza tu kutuma ujumbe wa maandishi yao siku hizi.

857
00:54:13,340 --> 00:54:15,460
Lakini wewe ili kweli kupita yao note katika darasa.

858
00:54:15,460 --> 00:54:18,700
Na kwa kufanya hivyo salama katika namna kwamba rafiki yako na mwalimu

859
00:54:18,700 --> 00:54:22,650
sijui nini wewe kuandika, unaweza kuja na algorithm haki rahisi,

860
00:54:22,650 --> 00:54:25,920
vijana ingawa unaweza kuwa, ili tu kinyang'anyiro maneno.

861
00:54:25,920 --> 00:54:28,130
Hivyo badala ya kuandika unaweza kuandika b,

862
00:54:28,130 --> 00:54:30,220
badala ya b unaweza kuandika c,

863
00:54:30,220 --> 00:54:32,140
badala ya c unaweza kuandika d, na kadhalika.

864
00:54:32,140 --> 00:54:34,360
Au unaweza kuja na tafsiri ya kisasa zaidi

865
00:54:34,360 --> 00:54:36,720
wa barua ya barua tofauti.

866
00:54:36,720 --> 00:54:39,740
Lakini catch ni mvulana au msichana ambaye wewe ni kutuma kumbuka hii

867
00:54:39,740 --> 00:54:45,020
mahitaji kujua kitu, ambayo ni nini, ni wazi? >> [Mwanafunzi] Nini wewe kutuma.

868
00:54:45,020 --> 00:54:49,720
Nini siri yako, kama kile ni kwamba kati ya ramani na b na c na d's.

869
00:54:49,720 --> 00:54:54,650
Je, ni kuongeza tu 1 kwa kila moja ya barua kwenda kwa kutoka b, b c?

870
00:54:54,650 --> 00:54:56,670
Je, ni ngumu zaidi kuliko hiyo?

871
00:54:56,670 --> 00:55:01,540
>> Hivyo wewe na kuponda yako haja ya kuwa na habari hii siri,

872
00:55:01,540 --> 00:55:03,190
lakini kuna aina ya samaki wanaovuliwa-22 hapa.

873
00:55:03,190 --> 00:55:06,830
Kama hii ni mara ya kwanza wewe ni kutuma barua hii upendo kwa njia ya darasa,

874
00:55:06,830 --> 00:55:10,720
jinsi ni kwamba kijana au msichana kwenda kujua nini siri hata ni?

875
00:55:10,720 --> 00:55:13,930
Hivyo siri-ufunguo crypto haina kutatua matatizo yote ya dunia,

876
00:55:13,930 --> 00:55:16,320
na kuna uhusiano kweli hapa kwamba tutaweza kurudi kuelekea mwisho wa muhula.

877
00:55:16,320 --> 00:55:25,110
Vile vile kufanya wengi wetu si kujua kwamba mtu anafanya kazi, kwa mfano, saa Amazon.com,

878
00:55:25,110 --> 00:55:28,190
na bado wengi wetu pengine kununuliwa stuff saa Amazon.com,

879
00:55:28,190 --> 00:55:31,990
na tumekuwa kufundishwa kwa kudhani kwamba haya mashirikiano ya e-commerce ni salama.

880
00:55:31,990 --> 00:55:36,470
URL pengine anasema https, kuna labda kidogo silly kufuli icon mahali fulani,

881
00:55:36,470 --> 00:55:39,930
kuna baadhi ya aina ya cryptography kupata kadi yako ya habari

882
00:55:39,930 --> 00:55:42,160
kati ya wewe na Amazon.com.

883
00:55:42,160 --> 00:55:45,430
Na bado kama cryptography inahusisha kujua baadhi ya siri

884
00:55:45,430 --> 00:55:48,620
na bado sijui mtu yeyote katika Amazon na nimekuwa hakika si mpangilio wa aina yoyote ya siri

885
00:55:48,620 --> 00:55:52,710
na mtu katika Amazon, jinsi ni kompyuta yangu au browser yangu kufanya hili?

886
00:55:52,710 --> 00:55:55,720
Ni zinageuka kuna aina nyingine ya cryptography kabisa kwamba kutatua tatizo.

887
00:55:55,720 --> 00:55:57,670
Lakini kwa leo, tutaweza kuzingatia moja rahisi

888
00:55:57,670 --> 00:56:00,290
ambapo unaweza kupanga mapema ili kujua baadhi ya siri

889
00:56:00,290 --> 00:56:03,760
kama 1 au baadhi ya ramani kati na b ya.

890
00:56:03,760 --> 00:56:05,840
Na mchakato wa cryptography ujumla unahusisha hii.

891
00:56:05,840 --> 00:56:08,620
Una baadhi Nakala wazi, taswira ya hapa kushoto,

892
00:56:08,620 --> 00:56:12,930
wewe kukimbia kupitia baadhi ya aina ya algorithm au utaratibu kwa ajili ya encrypting ni -

893
00:56:12,930 --> 00:56:15,100
labda kwamba tu inakuwa b, b inakuwa c -

894
00:56:15,100 --> 00:56:17,490
na kisha wewe kuishia na nakala ya siri.

895
00:56:17,490 --> 00:56:20,380
Wakati huo huo, mara kuponda yako inapata kumbuka hii siri,

896
00:56:20,380 --> 00:56:24,200
yeye au yeye ana kisha kuisimbua kwa ujumla kupunguza kwamba algorithm

897
00:56:24,200 --> 00:56:27,190
ili kupata nyuma Nakala wazi.

898
00:56:27,190 --> 00:56:28,960
Kuna incarnations ya kimwili ya hili.

899
00:56:28,960 --> 00:56:31,680
>> Kwa mfano, hii ni kidogo siri avkodare pete,

900
00:56:31,680 --> 00:56:35,110
na hii ni pete katika maana ya kwamba kuna wawili dials hapa.

901
00:56:35,110 --> 00:56:38,490
On pembezoni nje ya jambo hili, kuna barua kupitia Z,

902
00:56:38,490 --> 00:56:40,340
ingawa wao ni ili random,

903
00:56:40,340 --> 00:56:42,880
na juu ya ndani, kuna baadhi ya kweli idadi

904
00:56:42,880 --> 00:56:46,620
vile kwamba pamoja na pete hii unaweza aina ya kugeuka nje lakini si ndani ya

905
00:56:46,620 --> 00:56:49,140
ili yaendane idadi na barua.

906
00:56:49,140 --> 00:56:53,020
Kutoka movie inayoitwa Story Krismasi, utaona kwamba Ralphie kidogo

907
00:56:53,020 --> 00:56:58,000
alikuwa na shauku kubwa kufikiri nini Little Yatima Annie ujumbe wa siri ilikuwa kwake

908
00:56:58,000 --> 00:57:02,570
ambayo yamekuwa aliwasiliana, nadhani, katika mfumo wa ujumbe numeric juu ya sanduku nafaka

909
00:57:02,570 --> 00:57:07,220
na wewe alikuwa na kujilimbikiza kadi zote kidogo kwamba alikuja katika sanduku ya nafaka,

910
00:57:07,220 --> 00:57:09,770
alikuwa na barua yao katika, alikuwa na kupata nyuma siri avkodare pete

911
00:57:09,770 --> 00:57:13,910
hivyo kwamba unaweza hatimaye kufikiri nini ramani ni kati ya herufi na namba

912
00:57:13,910 --> 00:57:15,550
au barua na barua.

913
00:57:15,550 --> 00:57:19,520
Jinsi katika kompyuta tunaweza kwenda kuhusu kutekeleza au anayewakilisha mambo kama haya?

914
00:57:19,520 --> 00:57:22,560
Tunahitaji njia ya kuonyesha wenyewe zaidi kidogo smidigt

915
00:57:22,560 --> 00:57:25,080
kuliko vigezo yetu hivi sasa na kuruhusiwa.

916
00:57:25,080 --> 00:57:29,000
Tulikuwa ints, tumekuwa alikuwa chars, tumekuwa alikuwa ikifungwa DOUBLES na na wengine wachache,

917
00:57:29,000 --> 00:57:34,200
lakini wale ni vipande binafsi ya kumbukumbu kwamba si kweli kuruhusu sisi kueleza mambo

918
00:57:34,200 --> 00:57:36,440
kama maneno na sentensi na misemo.

919
00:57:36,440 --> 00:57:38,630
Hakika, tumekuwa aitwaye mambo kama hayo masharti,

920
00:57:38,630 --> 00:57:42,660
lakini sisi ahadi kwamba hii ni kweli tu kurahisisha katika maktaba CS50

921
00:57:42,660 --> 00:57:45,540
kwamba sisi ni wanaotaka peel nyuma.

922
00:57:45,540 --> 00:57:47,500
Na hivyo hebu kuanza kufanya hivyo hapa.

923
00:57:47,500 --> 00:57:49,840
Hebu kwenda mbele na kufungua faili -

924
00:57:49,840 --> 00:57:54,100
wote wa files hizi zinapatikana, kama kawaida, online - inayoitwa array.c

925
00:57:54,100 --> 00:57:58,960
kutatua tatizo lisilohusiana na masharti lakini kwamba inajenga picha hapa

926
00:57:58,960 --> 00:58:01,520
wa jinsi sisi inaweza kutumia kitu kinachoitwa safu.

927
00:58:01,520 --> 00:58:04,050
>> safu ni aina data.

928
00:58:04,050 --> 00:58:10,730
Ni aina ya kutofautiana wa aina yake kuwa ina aina nyingi data ndogo ndani yake

929
00:58:10,730 --> 00:58:12,680
nyuma kwa nyuma kwa nyuma kwa nyuma.

930
00:58:12,680 --> 00:58:16,980
Hivyo kwa mfano, kama sisi alitaka kuandika mpango kidogo kwamba anatoa Jaribio yako wastani

931
00:58:16,980 --> 00:58:19,780
kwa ajili ya kozi kama 50 ambayo ina 2 Quizzes,

932
00:58:19,780 --> 00:58:23,450
unaweza kwa urahisi sana kuandika mpango huu msingi hata kwenye baadhi ya nyenzo ya wiki iliyopita

933
00:58:23,450 --> 00:58:28,830
kwa kutumia GetInt na wanandoa wa vigezo: int quiz1, int quiz2.

934
00:58:28,830 --> 00:58:30,550
Na ni pretty moja kwa moja.

935
00:58:30,550 --> 00:58:33,500
Ni labda 10, 20 mstari wa kanuni max ya kutekeleza mpango wa

936
00:58:33,500 --> 00:58:38,940
kwamba anauliza mtumiaji kwa alama Jaribio 2 na kisha computes wastani yao

937
00:58:38,940 --> 00:58:42,020
na kuongeza yao pamoja, kugawa na 2, na kisha kuchapisha matokeo.

938
00:58:42,020 --> 00:58:46,400
Sisi inaweza pengine kufanya hivyo pretty urahisi sasa baada ya baadhi ya idadi ya dakika.

939
00:58:46,400 --> 00:58:49,450
Lakini tatizo ni kwamba tuseme kwamba alikuwa na 50 3 Quizzes au 4.

940
00:58:49,450 --> 00:58:52,830
Tuseme kwamba ulitaka kutumia mpango huo kwa ajili ya darasa kwamba alikuwa na kila wiki Quizzes.

941
00:58:52,830 --> 00:58:55,100
Fikiria juu ya darasa kwamba ina kila wiki Quizzes.

942
00:58:55,100 --> 00:58:58,840
Kama kuna 16 au hivyo wiki katika muhula, sasa una vigezo 16:

943
00:58:58,840 --> 00:59:03,030
int quiz1, int quiz2, int quiz3, int quiz4.

944
00:59:03,030 --> 00:59:06,870
Haraka kama wewe kuanza kuona hii redundancy, hii kuiga na pasting ya kificho,

945
00:59:06,870 --> 00:59:09,810
ni lazima kuanza kufanya unataka kulikuwa njia bora zaidi.

946
00:59:09,810 --> 00:59:13,610
Na nashiriki, kwa sababu ya arrays kuna. Basi hebu kufanya hili.

947
00:59:13,610 --> 00:59:16,700
Kwanza, napenda kuanzisha kitu rahisi sana kwamba tumekuwa si kutumika hivi sasa,

948
00:59:16,700 --> 00:59:18,820
lakini utaona ni mara kwa mara katika code.

949
00:59:18,820 --> 00:59:21,270
>> Hii ni nini ujumla huitwa mara kwa mara.

950
00:59:21,270 --> 00:59:24,410
Hivyo ni mara kwa mara katika maana ya kwamba thamani hii kamwe mabadiliko.

951
00:59:24,410 --> 00:59:26,450
mkataba wa binadamu wakati wa kujenga mara kwa mara

952
00:59:26,450 --> 00:59:30,420
ni kutumia barua zote mtaji ili tu kwamba ni kweli anasimama nje katika code yako,

953
00:59:30,420 --> 00:59:34,270
na Keyword maalum kwamba matumizi katika C ni # define.

954
00:59:34,270 --> 00:59:39,970
Hivyo tunasema # define, basi nafasi, basi neno kwamba unataka kutumia kwa ajili ya jina mara kwa mara ya

955
00:59:39,970 --> 00:59:41,730
na kisha thamani ya mara kwa mara.

956
00:59:41,730 --> 00:59:44,710
Taarifa hii ni tofauti na assigning kitu kutofautiana.

957
00:59:44,710 --> 00:59:46,430
Hakuna sawa saini, kuna semicolon hakuna.

958
00:59:46,430 --> 00:59:49,140
Hii ni nini ujumla inayojulikana kama agizo preprocessor,

959
00:59:49,140 --> 00:59:50,840
lakini zaidi juu ya kwamba wakati mwingine.

960
00:59:50,840 --> 00:59:56,350
Kwa sasa, hii inajenga thamani isiyobadilika kuitwa Quizzes

961
00:59:56,350 --> 00:59:58,290
ambaye halisi thamani numeric ni 2.

962
00:59:58,290 --> 01:00:02,180
Hivyo unaweza kuona mahali popote Quizzes, Quizzes, Quizzes katika faili hili,

963
01:00:02,180 --> 01:00:04,230
kwamba tu idadi 2.

964
01:00:04,230 --> 01:00:06,550
Kama mimi kuangalia kuu sasa, hebu angalia jinsi hii matendo.

965
01:00:06,550 --> 01:00:09,770
Kwanza inaonekana kidogo cryptic, lakini ni mambo yote kutoka wiki 1.

966
01:00:09,770 --> 01:00:12,210
Uliza mtumiaji kwa ajili ya darasa. Tutafanyaje hili?

967
01:00:12,210 --> 01:00:17,350
Katika mstari 22 - hii ni kweli sehemu Juicy - mimi kutangaza kuelea

968
01:00:17,350 --> 01:00:23,240
lakini si tu kuelea moja. Mimi kutangaza, badala yake, safu ya maadili yaliyo-uhakika.

969
01:00:23,240 --> 01:00:27,700
Hiyo variable ni kwenda kuitwa darasa, kama alisema hapa,

970
01:00:27,700 --> 01:00:31,420
lakini kipande tu ya syntax mpya basi ni haya mabano mraba.

971
01:00:31,420 --> 01:00:37,280
ukweli kwamba nilivyosema darasa kuelea na kisha bracket wazi na kisha idadi -

972
01:00:37,280 --> 01:00:40,980
taarifa kama hii ni mara kwa mara hii tu kama sisi gani huu -

973
01:00:40,980 --> 01:00:46,840
hii ina maana, "Hey kompyuta, nipe ikifungwa 2 na hebu pamoja kuwaita darasa."

974
01:00:46,840 --> 01:00:51,780
>> Hii ni tofauti na mchakato mengi zaidi tedious kama hii: kuelea grade1;

975
01:00:51,780 --> 01:00:54,580
kuelea grade2; na kadhalika.

976
01:00:54,580 --> 01:00:58,310
Hivyo safu inaruhusu sisi kutekeleza wazo hili lakini kiasi kidogo messily,

977
01:00:58,310 --> 01:01:04,560
katika namna ambayo tunaweza kuandika 1 mstari wa kanuni badala ya, kusema, 16 kwa muhula 16-wiki.

978
01:01:04,560 --> 01:01:09,060
Mimi sitaki ngumu-code 2 kwa sababu kama wewe kufikiri juu ya hili sasa mantiki,

979
01:01:09,060 --> 01:01:12,560
tuseme mwaka ujao CS50 mabadiliko ya 3 Quizzes badala

980
01:01:12,560 --> 01:01:15,010
na mimi alikuwa na idadi 2 hapa, mimi alikuwa na idadi 2 hapa,

981
01:01:15,010 --> 01:01:17,210
Mimi nilikuwa na idadi 2 hapa, idadi 2 hapa.

982
01:01:17,210 --> 01:01:19,890
Inakuwa tedious sana na rahisi sana screw up

983
01:01:19,890 --> 01:01:26,550
na kwa ajali kubadilisha 1 thamani kwa 3 na miss baadhi thamani nyingine ya 2.

984
01:01:26,550 --> 01:01:30,660
Hivyo nina kwenda kwa badala abstract hii mbali na kutumia hii mara kwa mara kwamba,

985
01:01:30,660 --> 01:01:32,520
kama jina lake anapendekeza, kamwe mabadiliko.

986
01:01:32,520 --> 01:01:35,870
Na sasa bila kujali kama tuna tofauti Quizzes mwaka huu au ujao,

987
01:01:35,870 --> 01:01:39,380
Mimi tu mabadiliko hayo katika sehemu moja hadi hapa juu.

988
01:01:39,380 --> 01:01:41,230
Basi hiyo ni ya mara kwa mara zote ni.

989
01:01:41,230 --> 01:01:47,100
Wakati huo huo, kipengele mpya conceptual ni ile ya safu.

990
01:01:47,100 --> 01:01:55,030
Hivyo mabano mraba nipe ikifungwa hii wengi na lets mimi pamoja kuwaita darasa hapa.

991
01:01:55,030 --> 01:01:56,720
Hivyo sasa hebu angalia nini mimi kwenda kufanya.

992
01:01:56,720 --> 01:01:59,220
Hapa katika mstari 24 ni mwanzo wa kwa kitanzi.

993
01:01:59,220 --> 01:02:03,380
>> Hii ni kitu kweli dhana. Ni tu kwa kutumia Quizzes badala ya idadi ngumu-coded.

994
01:02:03,380 --> 01:02:06,740
Lakini kuna kitu kielimu tofauti huko kutoka wiki iliyopita.

995
01:02:06,740 --> 01:02:11,650
Hii ni printf, hivyo printf ("Quiz #% d ya% d:")

996
01:02:11,650 --> 01:02:16,670
kwa sababu mimi nataka tu magazeti nje nipe Quiz namba 1 ya 2 na kisha 2 ya 2.

997
01:02:16,670 --> 01:02:18,480
Hivyo hii ni kitu rena estetiska.

998
01:02:18,480 --> 01:02:21,000
Lakini sehemu ya kuvutia sasa ni katika mstari wa 27.

999
01:02:21,000 --> 01:02:27,840
Ili kujaza katika moja ya placeholders mbili na thamani yaliyo-uhakika,

1000
01:02:27,840 --> 01:02:29,640
wewe tena kutumia mabano mraba.

1001
01:02:29,640 --> 01:02:35,170
Katika kesi hiyo, mimi nina kutumia i kwa sababu hii kwa kitanzi imeanza na i sawa na thamani gani, inaonekana?

1002
01:02:35,170 --> 01:02:36,670
[Mwanafunzi] 0. >> [Malan] 0.

1003
01:02:36,670 --> 01:02:40,990
Kadhalika iteration kwanza ya kitanzi hii, ni kama ingawa niliandika hii katika kanuni,

1004
01:02:40,990 --> 01:02:46,310
lakini juu ya iteration pili ya kitanzi hii, ni kama ingawa niliandika hii katika code yangu.

1005
01:02:46,310 --> 01:02:49,970
Lakini ukweli kwamba mimi nina kutumia kutofautiana ni kamili kwa sababu, kama jina linavyosema,

1006
01:02:49,970 --> 01:02:52,600
ni tofauti na thamani yake juu ya kila iteration,

1007
01:02:52,600 --> 01:02:55,900
hivyo mimi nina kujaza hii safu moja doa kwa wakati.

1008
01:02:55,900 --> 01:02:57,380
Je safu hii kuangalia kama?

1009
01:02:57,380 --> 01:03:01,570
sababu nilitoa super rahisi Mstatili juu ya screen hapa kabla ilikuwa kwa sababu hiyo.

1010
01:03:01,570 --> 01:03:05,590
safu ni tu chunk ya kumbukumbu na kufuatiwa na mwingine chunk ya kumbukumbu

1011
01:03:05,590 --> 01:03:08,570
kufuatiwa na mwingine chunk ya kumbukumbu na kadhalika.

1012
01:03:08,570 --> 01:03:13,120
Hivyo kama safu yangu ni ya kawaida 2 katika kesi hii hapa, wote mimi itakuwa kufanya

1013
01:03:13,120 --> 01:03:20,200
na kuandika katika alama yangu Jaribio kama hapa - I got 100 juu ya hili na kisha mimi got 99 juu ya hili -

1014
01:03:20,200 --> 01:03:24,970
kisha kumbukumbu hii inaweza hata kutumika kwa sababu nimekuwa tu aliuliza kompyuta

1015
01:03:24,970 --> 01:03:26,840
kwa safu ya ukubwa 2.

1016
01:03:26,840 --> 01:03:28,600
Wale mraba bado kuna, haki?

1017
01:03:28,600 --> 01:03:32,670
Bado una 2 gigabytes ya RAM hata kama wewe ni tu kuuliza kwa ikifungwa 2.

1018
01:03:32,670 --> 01:03:36,840
Hivyo wazo nyuma ya arrays ni kwamba kompyuta tu huchukua chunk ya kumbukumbu

1019
01:03:36,840 --> 01:03:41,340
na kisha apportions vipande vidogo nyuma kwa nyuma kwa nyuma kwa nyuma.

1020
01:03:41,340 --> 01:03:43,310
Na hivyo ndiyo safu yote ni.

1021
01:03:43,310 --> 01:03:47,350
>> Ni chunk contiguous ya ndani ya kumbukumbu ya ambayo unaweza kuweka mambo.

1022
01:03:47,350 --> 01:03:50,700
Hii hufanyika kisha kufanya baadhi tu arithmetic boring.

1023
01:03:50,700 --> 01:03:54,640
Kama mimi kitabu chini hapa, hii ni pale ambapo mimi basi iterate juu ya safu.

1024
01:03:54,640 --> 01:03:58,020
Mimi kuja na summation ya yote ya maadili katika safu,

1025
01:03:58,020 --> 01:04:02,470
na kisha mimi kutumia kazi pande zote hapa kwa kweli kufanya Jumla kugawanywa na Quizzes.

1026
01:04:02,470 --> 01:04:06,320
Lakini ngoja kupitisha mkono wangu kwamba kama aina ya hesabu za kutosha kwa sasa.

1027
01:04:06,320 --> 01:04:08,370
Lakini yote anafanya kwa ajili yangu hatimaye ni kompyuta wastani.

1028
01:04:08,370 --> 01:04:13,580
Hivyo kwanza Jaribio plus Jaribio pili kugawanywa na 2 na kisha kuchapisha nje kama int.

1029
01:04:13,580 --> 01:04:17,280
Lakini hebu sasa ya mpito kwa mfano tofauti inayoitwa string1,

1030
01:04:17,280 --> 01:04:20,700
ambayo inajenga picha sawa lakini masharti ya kutumia.

1031
01:04:20,700 --> 01:04:23,940
Hebu kwenda mbele na kurahisisha hii kwa muda tu.

1032
01:04:23,940 --> 01:04:27,090
Tughufirie indentation kwa sasa.

1033
01:04:27,090 --> 01:04:30,870
Tangazo katika mstari 19 ya mfano huu, mimi kupata kamba kutoka kwa mtumiaji.

1034
01:04:30,870 --> 01:04:34,640
Lakini taarifa nini mimi ijayo kufanya katika mistari 22 na kuendelea.

1035
01:04:34,640 --> 01:04:41,250
Mimi kwa kweli iterating kutoka i hadi - na hii ni hila mpya - strlen, kamba urefu.

1036
01:04:41,250 --> 01:04:44,880
Hii ni kazi ambayo inakuja na C kwamba kama wewe kupita kamba,

1037
01:04:44,880 --> 01:04:47,730
ni anaelezea jinsi wengi wahusika ni katika kamba hiyo. Hayo ni yote.

1038
01:04:47,730 --> 01:04:51,550
Na ukweli kwamba ni strlen badala ya urefu wa kamba ni kwa sababu tu ni zaidi succinct.

1039
01:04:51,550 --> 01:04:55,100
Miaka thelathini iliyopita, watu walipenda kuandika mambo kama succinctly kama inawezekana,

1040
01:04:55,100 --> 01:04:57,630
hivyo tumekuwa agizo hilo mkataba hapa.

1041
01:04:57,630 --> 01:05:00,660
i + + tu ina maana increment i katika kila iteration.

1042
01:05:00,660 --> 01:05:02,990
Na sasa taarifa hii, ambayo ni kweli kuvutia.

1043
01:05:02,990 --> 01:05:09,180
Katika mstari 24, nasema, "Kompyuta, nipe tabia, bits 8, na simu yake c."

1044
01:05:09,180 --> 01:05:12,630
Lakini ni nini hii upande wa kulia akisema?

1045
01:05:13,490 --> 01:05:16,530
Kwa Kiingereza, ni nini kwamba kuwakilisha?

1046
01:05:16,530 --> 01:05:18,730
[Mwanafunzi] tabia ya kwanza katika safu.

1047
01:05:18,730 --> 01:05:20,790
Hasa. Nipe tabia ya kwanza katika safu.

1048
01:05:20,790 --> 01:05:24,090
Au, kwa ujumla zaidi, nipe tabia idh katika safu.

1049
01:05:24,090 --> 01:05:26,100
Na kutambua ni muhimu sasa kwamba kama kompyuta wanasayansi,

1050
01:05:26,100 --> 01:05:27,890
sisi ni kweli kuhesabu toka 0.

1051
01:05:27,890 --> 01:05:29,720
>> Huna busara sasa kuanza kufanya hili.

1052
01:05:29,720 --> 01:05:34,160
Sasa una kuishi kwa mujibu wa matarajio ya kompyuta na kuhesabu kutoka 0

1053
01:05:34,160 --> 01:05:38,180
kwa sababu [0] ni kwenda kuwa tabia ya kwanza katika kamba,

1054
01:05:38,180 --> 01:05:42,150
[1] ni kwenda kuwa ya pili, [2] ni kwenda kuwa ya tatu, na kadhalika.

1055
01:05:42,150 --> 01:05:49,720
Hivyo mpango huu, ikiwa mimi kukusanya kuwa, hii ni tena string1, hivyo kufanya string1,

1056
01:05:49,720 --> 01:05:54,670
na sasa nimekuwa kukimbia string1 katika terminal dirisha yangu.

1057
01:05:54,670 --> 01:05:58,330
Ni kusubiri kwa ajili ya pembejeo, hivyo mimi nina kwenda aina katika Daudi, Ingieni,

1058
01:05:58,330 --> 01:06:02,540
na sasa Prints Daudi wote juu ya mistari tofauti kwa sababu taarifa nini mimi kufanya.

1059
01:06:02,540 --> 01:06:05,820
Mimi nina uchapishaji moja tabia kwa wakati.

1060
01:06:05,820 --> 01:06:10,100
Sisi si kuingia kwa undani juu ya leo hii, lakini mimi ilifutwa wakati iliyopita hundi hii hapa.

1061
01:06:10,100 --> 01:06:15,480
Ni zinageuka kuwa kama mtumiaji ni misbehaving, adversarial, au kuchanganyikiwa tu,

1062
01:06:15,480 --> 01:06:20,210
unaweza kweli kushindwa kutoa kamba ya urefu fulani.

1063
01:06:20,210 --> 01:06:22,860
Kama hit muhimu vibaya kwenye keyboard, unaweza kutoa hakuna kamba wakati wote,

1064
01:06:22,860 --> 01:06:26,950
au kama wewe ni malicious, unaweza kujaribu kuweka katika thamani ya gigabyte ya insha

1065
01:06:26,950 --> 01:06:29,290
kujaza hii kamba, na kama kompyuta anaendesha nje ya kumbukumbu,

1066
01:06:29,290 --> 01:06:32,710
zinageuka kuwa sisi ni kwenda kupata nyuma thamani hii maalum iitwayo null.

1067
01:06:32,710 --> 01:06:35,580
Hivyo kwa sasa, tu kujua kwamba kuna thamani hii maalum iitwayo null

1068
01:06:35,580 --> 01:06:39,580
ambayo itaruhusu sisi kuangalia wakati tuko nje ya kumbukumbu, miongoni mwa mambo mengine.

1069
01:06:39,580 --> 01:06:45,630
Lakini kama mimi kufungua sasa string2, taarifa moja tofauti hapa.

1070
01:06:45,630 --> 01:06:48,210
Notice moja tofauti hapa na string2.

1071
01:06:48,210 --> 01:06:51,340
Kwa string2, hii kwa kitanzi ni tofauti kidogo.

1072
01:06:51,340 --> 01:06:55,010
>> Hebu kufuta NULLs ili tuweze kuzungumza kuhusu wale wakati mwingine.

1073
01:06:55,010 --> 01:06:57,800
Nini tofauti kuhusu kwa kitanzi wakati huu?

1074
01:06:59,620 --> 01:07:01,670
Siwezi kurudi mfano uliopita.

1075
01:07:01,670 --> 01:07:08,580
Basi hiyo ni toleo 2, hili ni toleo 1. 1, 2.

1076
01:07:08,580 --> 01:07:11,980
1, 2.

1077
01:07:13,520 --> 01:07:16,660
wito strlen ni wapi?

1078
01:07:16,660 --> 01:07:18,860
Ni katika sehemu ya kwanza ya kwa kitanzi.

1079
01:07:18,860 --> 01:07:21,830
Mawazo yoyote kama kwa nini mimi kufanya hili? Yeah.

1080
01:07:21,830 --> 01:07:24,560
[Mwanafunzi] Hivyo huna piga kazi kila wakati.

1081
01:07:24,560 --> 01:07:26,440
[Malan] Basi sisi wala kuwaita kazi kila wakati. Hasa.

1082
01:07:26,440 --> 01:07:28,300
Kumbuka kutoka kwa matanzi kwamba wao ni super rahisi

1083
01:07:28,300 --> 01:07:31,770
mara moja aina ya kuelewa kwamba hii ni initialization, hali, na update.

1084
01:07:31,770 --> 01:07:34,750
Tatizo ni kwamba hali hufanyika kwenye kila iteration ya kitanzi.

1085
01:07:34,750 --> 01:07:40,010
Na hivyo katika mfano huu hapa, ni nini mbaya kuhusu ukweli kwamba huu ni hali yangu?

1086
01:07:40,010 --> 01:07:41,830
[Mwanafunzi] Wewe wito strlen.

1087
01:07:41,830 --> 01:07:44,340
[Malan] Wewe wito strlen tena na tena na tena.

1088
01:07:44,340 --> 01:07:47,410
Lakini mara nimekuwa typed katika Daudi, urefu wa kamba kwamba ni 5,

1089
01:07:47,410 --> 01:07:49,650
na si kwenda na mabadiliko juu ya kila iteration ya kitanzi

1090
01:07:49,650 --> 01:07:51,670
kwa sababu kamba bado ni D-a-v-i-d.

1091
01:07:51,670 --> 01:07:55,320
Hivyo hii ni ladha katika nini kinaendelea kuwa wazo la muhimu

1092
01:07:55,320 --> 01:08:00,410
inayojulikana kama uamuzi kubuni ambapo si tu kufanya kompyuta kufanya kazi ya lazima.

1093
01:08:00,410 --> 01:08:03,920
>> Tu kama sneak preview ya pset2, pset2 katika toleo la kawaida

1094
01:08:03,920 --> 01:08:07,030
ni kwenda changamoto kweli kutekeleza baadhi ya idadi ya ciphers,

1095
01:08:07,030 --> 01:08:10,410
baadhi ya idadi ya algorithms kuficha, ili unaweza wote encrypt

1096
01:08:10,410 --> 01:08:13,840
na ujumbe siri decrypt kiasi kama Ralphie moja huko Decoded.

1097
01:08:13,840 --> 01:08:16,810
Katika toleo la hacker ya pset2, tunakwenda kwenda kidogo zaidi.

1098
01:08:16,810 --> 01:08:19,649
Sisi ni kwenda mkono wewe faili kutoka mfumo halisi wa kompyuta

1099
01:08:19,649 --> 01:08:23,479
kwamba ina rundo zima la usernames na halisi nywila encrypted,

1100
01:08:23,479 --> 01:08:26,939
na changamoto kwa ajili ya toleo hacker ni kwenda kuwa kwa kuvunja nywila wale

1101
01:08:26,939 --> 01:08:33,200
na kufikiri nini cryptography au nini siri ilitumika kweli kuzalisha nywila hizo.

1102
01:08:33,200 --> 01:08:36,109
Na sisi ni kwenda kufanya hivyo kwa kutumia kipengele mpya hapa ya C

1103
01:08:36,109 --> 01:08:40,630
kwamba mimi nitakupa tu demo ya inajulikana kama hoja amri-line.

1104
01:08:40,630 --> 01:08:44,229
Ni zinageuka, kama baadhi ya unaweza tumeona katika sehemu au katika vitabu,

1105
01:08:44,229 --> 01:08:48,260
kuu haina daima kuwa utupu katika mabano.

1106
01:08:48,260 --> 01:08:52,430
Ni zinageuka kuwa kuu pia inaweza kuandikwa kama hii, kwa hoja mbili,

1107
01:08:52,430 --> 01:08:56,870
argc na argv, ambapo argc ni idadi ya maneno

1108
01:08:56,870 --> 01:09:00,020
kwamba unapoandika jina baada ya mpango juu ya mstari amri yako

1109
01:09:00,020 --> 01:09:03,420
na argv ni maneno halisi.

1110
01:09:03,420 --> 01:09:07,540
Na kama mabano mraba kuna kupendekeza, argv ni inaonekana safu.

1111
01:09:07,540 --> 01:09:12,210
Ni kwenda kuwa string baada ya kamba baada ya kamba katika kumbukumbu.

1112
01:09:12,210 --> 01:09:16,010
>> Basi nini tunakwenda kuwa na uwezo wa kufanya kwa kuanzia na pset 2 ni kitu kama hiki.

1113
01:09:16,010 --> 01:09:21,350
Kama mimi kufanya argv1, ambayo ni mfano tutaweza kurudi Jumatatu, na kukimbia,

1114
01:09:21,350 --> 01:09:23,370
taarifa kwamba haionekani kufanya chochote bado.

1115
01:09:23,370 --> 01:09:25,490
Ni tu Prints nje ya jina lake mwenyewe.

1116
01:09:25,490 --> 01:09:31,479
Lakini kama mimi kusema kwaheri darasa, taarifa kwamba mpango huu inaonekana iterates

1117
01:09:31,479 --> 01:09:35,479
juu ya kila moja ya maneno kwamba walikuwa typed katika haraka.

1118
01:09:35,479 --> 01:09:41,630
Na njia ambayo sisi kupata maneno ya kwamba mtumiaji typed katika kuchochea

1119
01:09:41,630 --> 01:09:49,160
ni kwa kubadilisha kuu kuanzia mwishoni mwa wiki hii kutoka int kuu (utupu) kwa int kuu (argc, argv)

1120
01:09:49,160 --> 01:09:52,050
na hivyo kuzaliwa hoja amri-line.

1121
01:09:52,050 --> 01:09:57,100
Na mara moja kupata kweli kisasa katika hili, wewe utakuwa na uwezo wa kuandika mipango kweli trippy

1122
01:09:57,100 --> 01:09:59,610
kama hii moja hapa, ambayo inakwenda juu na zaidi ya

1123
01:09:59,610 --> 01:10:03,940
baadhi ya utendaji tumefanya hivi sasa lakini yote kabisa nguvu.

1124
01:10:03,940 --> 01:10:08,950
>> Hivyo tutaweza kuondoka na hii kwenye screen, na sisi kuona juu ya Jumatatu.

1125
01:10:17,570 --> 01:10:20,000
>> [CS50.TV]