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>> [Music kucheza]

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>> DOUG LLOYD: kuyatumia, hapa sisi ni.

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Hii pengine ni kwenda
kuwa mada ngumu sana

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kwamba sisi majadiliano juu katika CS50.

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Na kama wameweza kusoma
chochote kuhusu kuyatumia

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kabla unaweza kuwa kidogo
vitisho kwenda katika video hii.

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Ni kweli kuyatumia
je kuruhusu uwezo

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kwa labda screw up
pretty vibaya wakati uko

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kufanya kazi na vigezo, na data,
na kusababisha mpango wako kwa ajali.

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Lakini wao ni kweli muhimu kweli kweli
na wao kuruhusu sisi njia kubwa kweli kweli

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kupita data nyuma na
kurudi kati kazi,

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kuwa tuko vinginevyo hawawezi kufanya.

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>> Na hivyo kile sisi kweli
wanataka kufanya hapa ni mafunzo

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wewe kuwa nzuri pointer nidhamu, ili
kwamba unaweza kutumia kuyatumia kwa ufanisi

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kufanya mipango yako kuwa bora zaidi.

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Kama nilivyosema kuyatumia kutupa mbalimbali
njia ya kupita data kati ya kazi.

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Sasa kama unakumbuka kutoka
video hapo awali, wakati

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sisi walikuwa wanazungumza juu
wigo kutofautiana, nilivyoeleza

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kuwa data zote kwamba sisi kupita kati ya
kazi katika C ni wanapita thamani.

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Na siwezi wametumia kwamba
mrefu, kile maana kuna

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ni kwamba sisi ni kupita nakala za data.

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Wakati sisi kupita kutofautiana kwa kazi,
sisi siyo kweli kupita kutofautiana

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kwa kazi, haki?

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Sisi ni kupita nakala ya
kwamba data kwa kazi.

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Kazi gani itakuwa nini
na ni mahesabu ya baadhi ya thamani,

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na labda sisi kutumia thamani kwamba
wakati anatoa nyuma.

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>> Kulikuwa na ubaguzi moja kwa
huu utawala wa akipita thamani,

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na tutaweza kurudi kwa nini kwamba
ni kidogo baadaye katika video hii.

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Kama sisi kutumia kuyatumia badala
ya kutumia vigezo,

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au badala ya kutumia vigezo
wenyewe au nakala ya vigezo,

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sasa tunaweza kupita vigezo kuzunguka
kati ya majukumu kwa njia mbalimbali.

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Hii ina maana kwamba kama sisi kufanya
mabadiliko katika kazi moja,

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mabadiliko ambayo kweli kuchukua
athari katika kazi mbalimbali.

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Tena, hii ni kitu ambacho
sisi hakuweza kufanya hapo awali,

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na kama wameweza milele walijaribu wabadilishane
thamani ya vigezo mbili katika kazi,

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umegundua tatizo hili
aina ya kitambaacho juu, sawa?

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>> Kama tunataka wabadilishane X na Y, na sisi
kupita yao kwa kazi kuitwa wabadilishane,

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ndani ya kazi wabadilishane
vigezo kufanya maadili kubadilishana.

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Moja inakuwa wawili, wawili inakuwa
moja, lakini sisi si kweli

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kubadili jambo lolote katika awali
kazi, katika mpigaji.

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Kwa sababu hatuwezi, tuko tu
kufanya kazi na nakala za kwao.

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Na kuyatumia ingawa, tunaweza
kweli kupita X na Y kwa kazi.

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Kazi ambayo anaweza kufanya
kitu pamoja nao.

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Na wale maadili vigezo
kweli anaweza kubadilika.

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Hivyo hiyo ni mabadiliko kabisa katika
uwezo wetu wa kufanya kazi na data.

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>> Kabla ya kupiga mbizi katika
kuyatumia, nadhani ni thamani

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kuchukua dakika chache
kwenda nyuma ya msingi hapa.

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Na kuwa na kuangalia jinsi
matendo kumbukumbu ya kompyuta

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kwa sababu masuala haya mawili ni kwenda
kwa kweli kuwa pretty yanayohusiana.

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Kama pengine kujua,
juu ya mfumo wa kompyuta yako

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una gari ngumu au
labda hali gari imara,

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aina fulani ya kuhifadhi faili eneo.

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Ni kawaida mahali fulani katika
kitongoji cha 250 gigabytes

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kwa labda michache ya terabytes sasa.

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Na ni wapi wote wa yako
mafaili hatimaye kuishi,

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hata wakati kompyuta yako ni kufunga
mbali, unaweza kugeuka kuwa nyuma

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na utapata mafaili yako ni pale
tena wakati reboot mfumo wako.

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Lakini anatoa disk, kama gari ngumu disk,
HDD, au hali gari imara, SSD,

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ni nafasi tu ya kuhifadhi.

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>> Hatuwezi kwa kweli kufanya kitu chochote na
takwimu ambazo ni katika disk,

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au katika hali gari imara.

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Ili kweli mabadiliko
data au hoja ni kuzunguka,

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tuna hoja hiyo kwa
RAM, random kupata kumbukumbu.

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Sasa RAM, una mengi
chini ya katika kompyuta yako.

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Unaweza kuwa na mahali fulani katika
kitongoji cha 512 megabytes

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kama una kompyuta wakubwa,
kwa labda mbili, nne, nane, 16,

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pengine hata kidogo
zaidi, gigabytes ya RAM.

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Hivyo hiyo ni ndogo sana, lakini hiyo ni
ambapo wote wa takwimu tete lipo.

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Hapo ndipo tunaweza kubadili mambo.

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Lakini wakati sisi kugeuka kompyuta yetu mbali,
yote ya data katika RAM ni kuharibiwa.

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>> Hivyo ndiyo sababu tunahitaji kuwa na hard disk
kwa eneo kudumu zaidi ya hayo,

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hivyo kwamba exists- ingekuwa
kuwa kweli mbaya kama kila wakati sisi

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akageuka kompyuta yetu mbali, kila
faili katika mfumo wetu alikuwa obliterated.

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Hivyo tunafanya kazi ndani ya RAM.

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Na kila wakati tunazungumzia
kumbukumbu, pretty much, katika CS50,

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tunazungumzia RAM, si ngumu disk.

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>> Hivyo wakati sisi hoja mambo katika kumbukumbu,
inachukua hadi kiasi fulani cha nafasi.

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Wote wa aina data kwamba
tumekuwa kufanya kazi na

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kuchukua mbalimbali
kiasi cha nafasi katika RAM.

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Hivyo kila wakati kuunda integer
kutofautiana, ka nne ya kumbukumbu

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ni kuweka kando katika RAM hivyo
wanaweza kufanya kazi na kwamba integer.

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Unaweza kutangaza integer,
mabadiliko hayo, hawawajui

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kwa thamani 10 incremented
kwa moja, kadhalika na kadhalika.

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Wote kwamba mahitaji ya kutokea katika
RAM, na kupata ka nne

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kufanya kazi na kwa kila
integer kwamba kujenga.

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>> Kila tabia wewe
kujenga anapata Byte moja.

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Hiyo tu ni kiasi gani nafasi ni
zinahitajika ili kuhifadhi tabia.

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Kila kuelea, halisi
idadi, anapata ka nne

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isipokuwa ni mara mbili
usahihi floating kumweka

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idadi, ambayo inaruhusu
kuwa sahihi zaidi au zaidi ya tarakimu

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baada ya uhakika decimal
bila ya kupoteza usahihi,

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ambayo kuchukua ka nane ya kumbukumbu.

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Muda mrefu anatamani, integers kweli kubwa,
pia kuchukua ka nane ya kumbukumbu.

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Jinsi ka ya kumbukumbu wengi
Je, masharti kuchukua?

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Naam hebu kuweka siri katika swali kwamba
kwa sasa, lakini tutaweza kuja nyuma yake.

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>> Hivyo nyuma wazo hili la kumbukumbu kama
safu kubwa ya seli Byte kati.

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Hiyo ni kweli wote ni, ni
tu safu kubwa ya seli,

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kama safu nyingine yoyote ambayo
wewe ni ukoo na uone,

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isipokuwa kila kipengele ni byte moja pana.

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Na kama safu,
kila kipengele ina mahali.

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Kila kipengele cha safu
ina ripoti, na sisi

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Unaweza kutumia kwamba ripoti ya kufanya kinachojulikana
random kupata juu ya safu.

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Hatuna kuanza saa
mwanzo wa safu,

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iterate kupitia kila
kipengele moja vyake,

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kupata nini sisi ni kuangalia kwa.

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Tunaweza kusema tu, nataka kupata
15 kipengele au kipengele 100.

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Na unaweza tu kupita katika idadi hiyo
na kupata thamani wewe ni kuangalia kwa.

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>> Vile vile kila eneo
katika kumbukumbu ina mahali.

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Hivyo kumbukumbu yako nguvu
kuangalia kitu kama hii.

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Hapa ni chunk ndogo sana ya
kumbukumbu, hii ni 20 ka ya kumbukumbu.

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Kwanza 20 ka kwa sababu yangu
anazungumzia huko chini

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ni 0, 1, 2, 3, na kadhalika
juu ya njia yote hadi 19.

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Na wakati mimi kutangaza vigezo na
wakati mimi kuanza kufanya kazi pamoja nao,

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mfumo ni kwenda kuweka
kando baadhi ya nafasi kwa ajili yangu

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katika kumbukumbu hii kazi
na vigezo yangu.

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Hivyo mimi anaweza kusema, char c sawa na mitaji
H. Na nini kitatokea?

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Vizuri mfumo ni kwenda
kuweka kando kwa ajili yangu moja Byte.

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Katika kesi hiyo waliamua Byte idadi
nne, Byte kwa anwani nne,

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na ni kwenda kuhifadhi
herufi kubwa H katika huko kwa ajili yangu.

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Kama mimi basi kusema int kasi
kikomo ni sawa na 65, ni

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kwenda kuweka kando nne
ka ya kumbukumbu kwa ajili yangu.

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Na itakuja kutibu wale
ka nne kama kitengo moja

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kwa sababu gani sisi ni kazi
na ni integer hapa.

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Na ni kwenda kuhifadhi 65 katika huko.

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>> Sasa tayari mimi nina aina ya
nawaambia kidogo ya uongo,

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haki, kwa sababu tunajua kwamba
kompyuta kazi katika mapacha.

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Hawaelewi
lazima kile mji mkuu H ni

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au kile 65 ni, wao tu
kuelewa binary, zeros na ndio.

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Na hivyo nini hasa
sisi ni hifadhi huko katika

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si barua H na idadi 65,
bali uwakilishi binary

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yake, ambayo kuangalia
kitu kidogo kama hii.

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Na hasa katika
mazingira ya integer kutofautiana,

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si kwenda tu mate ndani,
si kwenda kutibu kama moja ya nne

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Byte chunk lazima,
ni kweli kwenda

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kutibu kama nne moja chunks Byte,
ambayo inaweza kuangalia kitu kama hii.

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Na hata hii si
kabisa kweli ama,

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kwa sababu ya kitu kinachoitwa
endianness, ambayo sisi siyo

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kwenda kupata katika sasa, lakini
kama wewe ni curious kuhusu,

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00:07:26,965 --> 00:07:29,030
unaweza kusoma juu ya kidogo
na endianness kubwa.

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Lakini kwa ajili ya mjadala huu,
kwa ajili ya video hii,

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00:07:31,640 --> 00:07:34,860
hebu tu kudhani yaani, katika
kweli, jinsi idadi 65 ingekuwa

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kuwakilishwa katika
kumbukumbu juu ya kila mfumo,

143
00:07:36,970 --> 00:07:38,850
ingawa si kweli kabisa.

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00:07:38,850 --> 00:07:41,700
>> Lakini hebu kweli tu kupata
kuondoa wote binary kabisa,

145
00:07:41,700 --> 00:07:44,460
na tu kufikiri kuhusu kama H
na 65, ni rahisi sana

146
00:07:44,460 --> 00:07:47,900
kufikiri juu yake kama
kuwa kama binadamu.

147
00:07:47,900 --> 00:07:51,420
Haki wote, hivyo ni pia inaonekana labda
kidogo random kwamba I've- mfumo wangu

148
00:07:51,420 --> 00:07:55,130
hamkunipa ka 5, 6, 7,
na 8 kuhifadhi integer.

149
00:07:55,130 --> 00:07:58,580
Kuna sababu kwa kuwa, pia, ambayo
sisi si kupata ndani ya sasa hivi, lakini inatosha

150
00:07:58,580 --> 00:08:00,496
kusema kwamba kile
kompyuta ni kufanya hapa

151
00:08:00,496 --> 00:08:02,810
pengine ni hatua nzuri kwa upande wake.

152
00:08:02,810 --> 00:08:06,020
Kwa kunipa kumbukumbu hiyo ni
lazima nyuma kwa nyuma.

153
00:08:06,020 --> 00:08:10,490
Ingawa ni kwenda kufanya hivyo sasa
kama nataka kupata kamba mwingine,

154
00:08:10,490 --> 00:08:13,080
aitwaye jina, na mimi nataka
kuweka Lloyd huko.

155
00:08:13,080 --> 00:08:18,360
Mimi nina kwenda haja ya fit moja
tabia, kila barua ya kwamba

156
00:08:18,360 --> 00:08:21,330
kwenda zinahitaji moja
tabia, byte moja ya kumbukumbu.

157
00:08:21,330 --> 00:08:26,230
Hivyo kama mimi naweza kuweka Lloyd katika safu yangu
kama hii mimi nina nzuri ya kwenda, haki?

158
00:08:26,230 --> 00:08:28,870
Kinachokosekana?

159
00:08:28,870 --> 00:08:31,840
>> Kumbuka kwamba kila kamba tunafanya kazi
na katika C kumalizika kwa sifuri backslash,

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na hatuwezi saza kwamba hapa, aidha.

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00:08:33,339 --> 00:08:36,090
Tunahitaji kuweka kando Byte moja
ya kumbukumbu kushikilia kwamba hivyo sisi

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00:08:36,090 --> 00:08:39,130
kujua wakati kamba yetu ina kumalizika.

163
00:08:39,130 --> 00:08:41,049
Hivyo tena utaratibu huu
ya jinsi mambo

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00:08:41,049 --> 00:08:42,799
kuonekana katika kumbukumbu uwezo
kuwa ni kidogo random,

165
00:08:42,799 --> 00:08:44,870
lakini kwa kweli ni jinsi
mifumo ya wengi ni iliyoundwa.

166
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Kwa line yao juu juu ya mafungu
ya nne, kwa sababu tena

167
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kwamba hatuna haja ya
kupata katika hivi sasa.

168
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Lakini hii, hivyo inatosha kusema kwamba
baada ya mistari hii mitatu ya maadili,

169
00:08:53,060 --> 00:08:54,810
hii ni nini kumbukumbu ili kuangalia kama.

170
00:08:54,810 --> 00:08:58,930
Kama mimi haja maeneo ya kumbukumbu
4, 8, na 12 kushikilia data zangu,

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hii ni nini kumbukumbu yangu ili kuangalia kama.

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>> Na tu kuwa na hasa
pedantic hapa, wakati

173
00:09:04,062 --> 00:09:06,020
tunazungumzia kumbukumbu
anwani sisi kwa kawaida

174
00:09:06,020 --> 00:09:08,390
kufanya hivyo kwa kutumia notations hexadesimoli.

175
00:09:08,390 --> 00:09:12,030
Hivyo kwa nini sio sisi kubadili yote haya
kutoka kwa nukuu hexadecimal alisema

176
00:09:12,030 --> 00:09:15,010
sababu tu kwamba kwa ujumla
jinsi sisi rejea kumbukumbu.

177
00:09:15,010 --> 00:09:17,880
Hivyo badala ya kuwa 0 kupitia
19, tuna nini ni sifuri

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00:09:17,880 --> 00:09:20,340
x sifuri kupitia sifuri x1 tatu.

179
00:09:20,340 --> 00:09:23,790
Hayo ni ka 20 ya kumbukumbu kwamba sisi
kuwa au sisi ni kuangalia kwa mfano huu

180
00:09:23,790 --> 00:09:25,540
hapa hapa.

181
00:09:25,540 --> 00:09:29,310
>> Basi wote wa kwamba kuwa alisema, hebu
hatua mbali na kumbukumbu kwa ajili ya pili

182
00:09:29,310 --> 00:09:30,490
na nyuma kuyatumia.

183
00:09:30,490 --> 00:09:32,420
Hapa ni muhimu zaidi
Jambo kukumbuka

184
00:09:32,420 --> 00:09:34,070
kama sisi kuanza kufanya kazi na kuyatumia.

185
00:09:34,070 --> 00:09:36,314
Pointer kitu
zaidi ya mahali.

186
00:09:36,314 --> 00:09:38,230
Mimi itabidi kusema tena kwa sababu
ni kwamba muhimu,

187
00:09:38,230 --> 00:09:42,730
pointer kitu
zaidi ya mahali.

188
00:09:42,730 --> 00:09:47,760
Kuyatumia ni anwani za maeneo kwa
katika kumbukumbu ambapo vigezo kuishi.

189
00:09:47,760 --> 00:09:52,590
Akijua kwamba inakuwa hopefully
rahisi kidogo kidogo kufanya kazi pamoja nao.

190
00:09:52,590 --> 00:09:54,550
Kitu kingine mimi kama
kufanya ni kuwa na aina

191
00:09:54,550 --> 00:09:58,510
ya diagrams kuibua anayewakilisha nini
kinachotokea na mistari mbalimbali wa kanuni.

192
00:09:58,510 --> 00:10:00,660
Na tutaweza kufanya hivyo wanandoa
mara nyingi katika kuyatumia,

193
00:10:00,660 --> 00:10:03,354
na wakati sisi majadiliano juu ya nguvu
mgao kumbukumbu pia.

194
00:10:03,354 --> 00:10:06,020
Kwa sababu nadhani kwamba vielelezo hivi
inaweza kuwa hasa kusaidia.

195
00:10:06,020 --> 00:10:09,540
>> Hivyo kama mimi kusema kwa mfano, int k
katika kanuni yangu, kinachojitokeza?

196
00:10:09,540 --> 00:10:12,524
Vizuri nini kimsingi kinachotokea ni
Mimi nina kupata kumbukumbu zilizotengwa kwa ajili yangu,

197
00:10:12,524 --> 00:10:14,690
lakini sijui hata kama
kufikiri juu yake kama hicho, mimi

198
00:10:14,690 --> 00:10:16,300
kama kufikiri kuhusu hilo kama eneo la hatari.

199
00:10:16,300 --> 00:10:20,090
Nina sanduku na ni
rangi ya kijani kwa sababu mimi

200
00:10:20,090 --> 00:10:21,750
unaweza kuweka integers katika masanduku ya kijani.

201
00:10:21,750 --> 00:10:23,666
Kama ilivyokuwa tabia mimi
inaweza kuwa na sanduku bluu.

202
00:10:23,666 --> 00:10:27,290
Lakini mimi daima kusema, kama mimi nina kujenga
sanduku kwamba wanaweza kushikilia integers

203
00:10:27,290 --> 00:10:28,950
sanduku kwamba ni rangi ya kijani.

204
00:10:28,950 --> 00:10:33,020
Na mimi kuchukua marker wa kudumu
na mimi kuandika k upande wa hayo.

205
00:10:33,020 --> 00:10:37,590
Hivyo nina sanduku aitwaye k,
ndani ambayo siwezi kuweka integers.

206
00:10:37,590 --> 00:10:41,070
Hivyo wakati mimi kusema int k, hiyo ni
nini kinatokea katika kichwa changu.

207
00:10:41,070 --> 00:10:43,140
Kama mimi kusema k ni sawa na tano, je, Mimi kufanya?

208
00:10:43,140 --> 00:10:45,110
Naam, mimi nina kuweka tano
katika sanduku, haki.

209
00:10:45,110 --> 00:10:48,670
Hii ni pretty moja kwa moja, kama
Nasema int k, kujenga sanduku aitwaye k.

210
00:10:48,670 --> 00:10:52,040
Kama mimi kusema k ni sawa na 5,
kuweka tano katika eneo la hatari.

211
00:10:52,040 --> 00:10:53,865
Ni matumaini kwamba si sana ya leap.

212
00:10:53,865 --> 00:10:55,990
Hapa ni ambapo mambo kwenda
kidogo ya kuvutia ingawa.

213
00:10:55,990 --> 00:11:02,590
Kama mimi kusema int * pk, vizuri hata kama mimi si
kujua jambo hili lazima maana,

214
00:11:02,590 --> 00:11:06,150
ni wazi got kitu
cha kufanya na integer.

215
00:11:06,150 --> 00:11:08,211
Hivyo nina kwenda kwa rangi
sanduku hii ya kijani-ish,

216
00:11:08,211 --> 00:11:10,210
Najua ni got kitu
cha kufanya na integer,

217
00:11:10,210 --> 00:11:13,400
lakini siyo integer yenyewe,
kwa sababu ni nyota int.

218
00:11:13,400 --> 00:11:15,390
Kuna kitu kidogo
mbalimbali kuhusu suala hilo.

219
00:11:15,390 --> 00:11:17,620
Hivyo integer ya kushiriki,
lakini vinginevyo ni

220
00:11:17,620 --> 00:11:19,830
si mno tofauti na
nini tulikuwa kuzungumza juu.

221
00:11:19,830 --> 00:11:24,240
Ni sanduku, got wake studio,
ni amevaa studio pk,

222
00:11:24,240 --> 00:11:27,280
na ni uwezo wa kufanya
nyota int, chochote wale ni.

223
00:11:27,280 --> 00:11:29,894
Wana kitu cha kufanya
kwa integers, ni wazi kuwa.

224
00:11:29,894 --> 00:11:31,060
Hapa ni mstari wa mwisho ingawa.

225
00:11:31,060 --> 00:11:37,650
Kama mimi kusema pk = & k, Ho,
nini ilitokea tu, sawa?

226
00:11:37,650 --> 00:11:41,820
Hivyo hii namba kubahatisha, inaonekana random
idadi, anapata kutupwa ndani ya boksi hapo.

227
00:11:41,820 --> 00:11:44,930
Wote yaani, ni pk
anapata pepe ya k.

228
00:11:44,930 --> 00:11:52,867
Hivyo mimi nina sticking ambapo k anaishi katika kumbukumbu,
anwani yake, anwani ya ka yake.

229
00:11:52,867 --> 00:11:55,200
Wote mimi nina kufanya ni mimi kusema
thamani kwamba ni nini mimi kwenda

230
00:11:55,200 --> 00:11:59,430
kuweka ndani ya boksi yangu aitwaye pk.

231
00:11:59,430 --> 00:12:02,080
Na kwa sababu mambo haya ni
kuyatumia, na kwa sababu kuangalia

232
00:12:02,080 --> 00:12:04,955
katika kamba kama sifuri x
nane sifuri c saba nne nane

233
00:12:04,955 --> 00:12:07,790
mbili sifuri pengine ni
si ya maana sana.

234
00:12:07,790 --> 00:12:12,390
Wakati sisi ujumla taswira kuyatumia,
sisi kwa kweli kufanya hivyo kama kuyatumia.

235
00:12:12,390 --> 00:12:17,000
Pk inatupa habari
tunahitaji kupata k katika kumbukumbu.

236
00:12:17,000 --> 00:12:19,120
Hivyo kimsingi pk ina mshale ndani yake.

237
00:12:19,120 --> 00:12:21,670
Na kama sisi kutembea urefu
ya kwamba mshale, fikiria

238
00:12:21,670 --> 00:12:25,280
ni kitu unaweza kutembea juu ya, kama sisi
kutembea pamoja urefu wa mshale,

239
00:12:25,280 --> 00:12:29,490
katika ncha sana ya kwamba mshale, sisi
utapata mahali katika kumbukumbu

240
00:12:29,490 --> 00:12:31,390
ambapo k anaishi.

241
00:12:31,390 --> 00:12:34,360
Na kwamba ni kweli muhimu
kwa sababu mara moja tunajua ambapo k anaishi,

242
00:12:34,360 --> 00:12:37,870
tunaweza kuanza kufanya kazi na data
ndani ya kwamba kumbukumbu eneo.

243
00:12:37,870 --> 00:12:40,780
Ingawa sisi ni kupata teeny
kidogo mbele ya sisi wenyewe kwa sasa.

244
00:12:40,780 --> 00:12:42,240
>> Kwa hiyo kile ni pointer?

245
00:12:42,240 --> 00:12:45,590
Pointer ni bidhaa ambazo data
thamani ya kumbukumbu ya mahali.

246
00:12:45,590 --> 00:12:49,740
Hiyo ilikuwa ni kwamba sifuri x nane sifuri mambo
kinachoendelea, ambayo ilikuwa kumbukumbu ya mahali.

247
00:12:49,740 --> 00:12:52,060
Hiyo ilikuwa ni eneo katika kumbukumbu.

248
00:12:52,060 --> 00:12:55,080
Na aina ya pointer
inaeleza aina

249
00:12:55,080 --> 00:12:56,930
wa takwimu utapata katika
kwamba kumbukumbu ya mahali.

250
00:12:56,930 --> 00:12:58,810
Hivyo kuna int nyota sehemu ya haki.

251
00:12:58,810 --> 00:13:03,690
Kama mimi kufuata mshale, ni
kwenda risasi mimi eneo.

252
00:13:03,690 --> 00:13:06,980
Na eneo hilo, kile
utapata huko katika mfano wangu,

253
00:13:06,980 --> 00:13:08,240
ni kijani rangi sanduku.

254
00:13:08,240 --> 00:13:12,650
Ni integer, kwamba ni nini mimi
utapata nikienda kwa anwani hiyo.

255
00:13:12,650 --> 00:13:14,830
Aina ya data ya
pointer inaeleza nini

256
00:13:14,830 --> 00:13:17,936
utapata katika kumbukumbu ya mahali.

257
00:13:17,936 --> 00:13:19,560
Hivyo hapa ni kitu kweli ya baridi ingawa.

258
00:13:19,560 --> 00:13:25,090
Kuyatumia kuruhusu sisi kupita
vigezo kati ya majukumu.

259
00:13:25,090 --> 00:13:28,520
Na kwa kweli kupita vigezo
na kupita nakala za kwao.

260
00:13:28,520 --> 00:13:32,879
Kwa sababu kama sisi kujua hasa ambapo
katika kumbukumbu kupata kutofautiana,

261
00:13:32,879 --> 00:13:35,670
hatuna haja ya kufanya nakala ya
hilo, tunaweza tu kwenda eneo hilo

262
00:13:35,670 --> 00:13:37,844
na kufanya kazi na kwamba kutofautiana.

263
00:13:37,844 --> 00:13:40,260
Hivyo katika kuyatumia kiini aina
ya kufanya mazingira ya kompyuta

264
00:13:40,260 --> 00:13:42,360
mengi zaidi kama ulimwengu halisi, haki.

265
00:13:42,360 --> 00:13:44,640
>> Hivyo hapa ni mfano.

266
00:13:44,640 --> 00:13:48,080
Hebu kusema kwamba nina daftari,
haki, na ni kamili ya maelezo.

267
00:13:48,080 --> 00:13:50,230
Na napenda wewe kwa taarifa hiyo.

268
00:13:50,230 --> 00:13:53,960
Wewe ni kazi ambayo
updates maelezo, haki.

269
00:13:53,960 --> 00:13:56,390
Kwa njia tumekuwa
kazi hadi sasa, kile

270
00:13:56,390 --> 00:14:02,370
ikitokea ni utachukua daftari wangu,
utasikia kwenda dukani nakala,

271
00:14:02,370 --> 00:14:06,410
itabidi kufanya Xerox nakala ya
kila ukurasa wa daftari.

272
00:14:06,410 --> 00:14:09,790
Wewe itabidi kuondoka daftari yangu nyuma
juu ya dawati yangu wakati wewe ni kosa,

273
00:14:09,790 --> 00:14:14,600
utasikia kwenda na kuvuka nje mambo katika wangu
daftari ambayo ni nje ya tarehe au makosa,

274
00:14:14,600 --> 00:14:19,280
na kisha utasikia kupita nyuma
mimi mkusanyiko wa kurasa Xerox

275
00:14:19,280 --> 00:14:22,850
kuwa ni replica ya daftari yangu na
mabadiliko ambayo umefanya na hiyo.

276
00:14:22,850 --> 00:14:27,040
Na katika hatua hiyo, ni juu yangu kama
wito kazi, kama mpigaji,

277
00:14:27,040 --> 00:14:30,582
kwa kuamua kuchukua maelezo yako na
kuunganisha yao nyuma katika daftari yangu.

278
00:14:30,582 --> 00:14:32,540
Hivyo kuna mengi ya hatua
waliohusika hapa, hivi.

279
00:14:32,540 --> 00:14:34,850
Kama sivyo kuwa bora
kama mimi tu kusema, hey, unaweza wewe

280
00:14:34,850 --> 00:14:38,370
kuboresha daftari yangu kwa
yangu, mkono wewe daftari wangu,

281
00:14:38,370 --> 00:14:40,440
na wewe kuchukua mambo na
halisi kuvuka yao nje

282
00:14:40,440 --> 00:14:42,810
na kuboresha maelezo yangu katika daftari yangu.

283
00:14:42,810 --> 00:14:45,140
Na kisha nipe daftari yangu nyuma.

284
00:14:45,140 --> 00:14:47,320
Hiyo ni aina ya nini
kuyatumia kuruhusu sisi kufanya,

285
00:14:47,320 --> 00:14:51,320
wao kufanya mazingira haya mengi
zaidi kama jinsi sisi kazi katika hali halisi.

286
00:14:51,320 --> 00:14:54,640
>> Haki zote hivyo kwamba ni nini
pointer ni, hebu majadiliano

287
00:14:54,640 --> 00:14:58,040
kuhusu jinsi ya kuyatumia kazi katika C, na
jinsi gani tunaweza kuanza kufanya kazi pamoja nao.

288
00:14:58,040 --> 00:15:02,550
Hivyo kuna pointer rahisi sana
katika C aitwaye pointer null.

289
00:15:02,550 --> 00:15:04,830
Null pointi pointer chochote.

290
00:15:04,830 --> 00:15:08,310
Hii pengine inaonekana kana kwamba ni
kweli si jambo muhimu sana,

291
00:15:08,310 --> 00:15:10,500
lakini kama tutaweza kuona
kidogo baadaye, ukweli

292
00:15:10,500 --> 00:15:15,410
kwamba hii pointer null ipo
kweli kweli wanaweza kuja katika Handy.

293
00:15:15,410 --> 00:15:19,090
Na wakati wowote kujenga pointer, na
huna kuweka thamani yake immediately-

294
00:15:19,090 --> 00:15:21,060
mfano wa kuweka
thamani yake mara moja

295
00:15:21,060 --> 00:15:25,401
Itakuwa slides michache nyuma
ambapo nilivyosema pk sawa na & k,

296
00:15:25,401 --> 00:15:28,740
pk anapata k ya mitaani, kama
tutaweza kuona nini maana,

297
00:15:28,740 --> 00:15:32,990
tutaweza kuona jinsi ya kanuni kwamba shortly-
kama hatuwezi kuweka thamani yake kwa kitu

298
00:15:32,990 --> 00:15:35,380
maana mara moja,
unapaswa daima

299
00:15:35,380 --> 00:15:37,480
kuweka pointer yako kwa uhakika kwa null.

300
00:15:37,480 --> 00:15:40,260
Unapaswa kuweka kwa uhakika na kitu chochote.

301
00:15:40,260 --> 00:15:43,614
>> Hiyo ni tofauti sana kuliko
tu kuacha thamani kama ilivyo

302
00:15:43,614 --> 00:15:45,530
na kisha kutangaza
pointer na kuchukua tu

303
00:15:45,530 --> 00:15:48,042
ni null sababu hiyo ni mara chache kweli.

304
00:15:48,042 --> 00:15:50,000
Hivyo unapaswa daima kuweka
thamani ya pointer

305
00:15:50,000 --> 00:15:55,690
kwa null kama huna kuweka thamani yake
kwa kitu ya maana mara moja.

306
00:15:55,690 --> 00:15:59,090
Unaweza kuangalia kama thamani pointer ya
ni batili kwa kutumia alama usawa

307
00:15:59,090 --> 00:16:05,450
(==), Tu kama wewe kulinganisha integer yoyote
maadili au maadili tabia kwa kutumia (==)

308
00:16:05,450 --> 00:16:06,320
vilevile.

309
00:16:06,320 --> 00:16:10,994
Ni aina maalum ya mara kwa mara
thamani uweze kutumia mtihani.

310
00:16:10,994 --> 00:16:13,160
Ili kwamba ilikuwa rahisi sana
pointer, pointer null.

311
00:16:13,160 --> 00:16:15,320
Njia nyingine ya kujenga
pointer ni ya kutafuta

312
00:16:15,320 --> 00:16:18,240
pepe ya kutofautiana
umefanya tayari umba,

313
00:16:18,240 --> 00:16:22,330
na wewe kufanya hivyo kwa kutumia &
alama anuani ya uchimbaji.

314
00:16:22,330 --> 00:16:26,720
Ambayo tumekuwa tayari kuona awali
katika kwanza mchoro mfano mimi ilionyesha.

315
00:16:26,720 --> 00:16:31,450
Hivyo kama x ni kutofautiana kwamba tumekuwa
tayari umba ya aina integer,

316
00:16:31,450 --> 00:16:35,110
kisha & x ni pointer integer.

317
00:16:35,110 --> 00:16:39,810
& x ni- kumbuka, & ni kwenda kutafuta
pepe ya kitu juu ya haki.

318
00:16:39,810 --> 00:16:45,350
Na kwa kuwa pointer ni ya mitaani,
kuliko & x ni pointer integer

319
00:16:45,350 --> 00:16:48,560
thamani ambao ni wapi katika kumbukumbu x maisha.

320
00:16:48,560 --> 00:16:50,460
Ni x ya mahali.

321
00:16:50,460 --> 00:16:53,296
Hivyo & x ni anuani ya x.

322
00:16:53,296 --> 00:16:55,670
Hebu kuchukua hatua hii moja
kuungana na kitu zaidi na

323
00:16:55,670 --> 00:16:58,380
Mimi alluded katika video kabla.

324
00:16:58,380 --> 00:17:06,730
Kama arr ni safu ya mara mbili, kisha
& arr mraba mabano i ni pointer

325
00:17:06,730 --> 00:17:08,109
maradufu.

326
00:17:08,109 --> 00:17:08,970
SAWA.

327
00:17:08,970 --> 00:17:12,160
ARR mraba mabano i, ikiwa
arr ni safu ya mara mbili,

328
00:17:12,160 --> 00:17:19,069
kisha ARR mraba mabano i ni
i-th kipengele cha kwamba safu,

329
00:17:19,069 --> 00:17:29,270
na & ARR mraba mabano i ni wapi katika
kumbukumbu i-th kipengele cha arr lipo.

330
00:17:29,270 --> 00:17:31,790
>> Hivyo nini maana hapa?

331
00:17:31,790 --> 00:17:34,570
Jina arrays, maana
ya jambo hili zima,

332
00:17:34,570 --> 00:17:39,290
ni kwamba jina safu ya ni
kweli yenyewe pointer.

333
00:17:39,290 --> 00:17:41,170
Tumekuwa kazi
na kuyatumia wote pamoja

334
00:17:41,170 --> 00:17:45,290
kila wakati kwamba umetumia safu.

335
00:17:45,290 --> 00:17:49,090
Kumbuka kutokana na mfano
juu ya wigo kutofautiana,

336
00:17:49,090 --> 00:17:53,420
karibu na mwisho wa video Mimi sasa
mfano ambapo tuna kazi

337
00:17:53,420 --> 00:17:56,890
aitwaye seti int na a
kazi kuitwa seti safu.

338
00:17:56,890 --> 00:18:00,490
Na changamoto yako kuamua
iwapo au la, au nini

339
00:18:00,490 --> 00:18:03,220
maadili ambayo sisi kuchapishwa
Mwisho wa kazi,

340
00:18:03,220 --> 00:18:05,960
mwishoni mwa mpango kuu.

341
00:18:05,960 --> 00:18:08,740
>> Kama unakumbuka kutokana na mfano kwamba
au kama wameweza watched video,

342
00:18:08,740 --> 00:18:13,080
unajua kwamba wakati wewe-wito kwa
kuweka int ufanisi hana kitu.

343
00:18:13,080 --> 00:18:16,390
Lakini mwito wa kuweka safu gani.

344
00:18:16,390 --> 00:18:19,280
Na mimi aina ya glossed juu kwa nini
hivyo ndivyo ilivyo wakati huo.

345
00:18:19,280 --> 00:18:22,363
I just alisema, vizuri ni safu, ni
maalum, unajua, kuna sababu.

346
00:18:22,363 --> 00:18:25,020
Sababu ni kwamba safu ya
jina ni kweli tu pointer,

347
00:18:25,020 --> 00:18:28,740
na kuna hii maalum
Mabano ya mraba syntax kwamba

348
00:18:28,740 --> 00:18:30,510
kufanya mambo mengi nicer kufanya kazi pamoja.

349
00:18:30,510 --> 00:18:34,410
Na wao kufanya wazo la
pointer mengi kidogo vitisho,

350
00:18:34,410 --> 00:18:36,800
na hii ndiyo sababu wao ni aina
ya kuwasilishwa katika njia hiyo.

351
00:18:36,800 --> 00:18:38,600
Lakini kwa kweli arrays ni kuyatumia tu.

352
00:18:38,600 --> 00:18:41,580
Na hii ndiyo maana wakati sisi
alifanya mabadiliko kwa safu,

353
00:18:41,580 --> 00:18:44,880
wakati sisi kupita safu kama parameter
kwa kazi au kama hoja

354
00:18:44,880 --> 00:18:50,110
kwa kazi, yaliyomo ya safu
kweli iliyopita katika wawili callee

355
00:18:50,110 --> 00:18:51,160
na katika mpigaji.

356
00:18:51,160 --> 00:18:55,846
Ambayo kwa kila aina nyingine ya
kutofautiana tuliona haikuwa hivyo.

357
00:18:55,846 --> 00:18:58,970
Hivyo hiyo ni kitu cha kushika katika
akili wakati wewe ni kufanya kazi na kuyatumia,

358
00:18:58,970 --> 00:19:01,610
ni kwamba jina la
safu kweli pointer

359
00:19:01,610 --> 00:19:04,750
kwa kipengele kwanza ya safu hiyo.

360
00:19:04,750 --> 00:19:08,930
>> OK hivyo sasa tuna haya yote
ukweli, hebu kuendelea, haki.

361
00:19:08,930 --> 00:19:11,370
Kwa nini sisi huduma ya juu
ambapo kitu anaishi.

362
00:19:11,370 --> 00:19:14,120
Naam kama nilivyosema, ni pretty
muhimu kujua ambapo kitu anaishi

363
00:19:14,120 --> 00:19:17,240
hivyo unaweza kwenda huko na mabadiliko hayo.

364
00:19:17,240 --> 00:19:19,390
Kazi pamoja na kweli
na kitu ambacho wewe

365
00:19:19,390 --> 00:19:23,710
wanataka kufanya kwa kuwa kuchukua athari kutofautiana,
na si kuchukua athari kwenye baadhi nakala yake.

366
00:19:23,710 --> 00:19:26,150
Hii inaitwa dereferencing.

367
00:19:26,150 --> 00:19:28,690
Sisi kwenda kwa kumbukumbu na
sisi mabadiliko ya thamani pale.

368
00:19:28,690 --> 00:19:32,660
Hivyo kama tuna pointer na ni kuitwa
pc, na inaelekeza katika tabia,

369
00:19:32,660 --> 00:19:40,610
basi tunaweza kusema * pc na * pc ni
jina la kile tutaweza kupata kama tukienda

370
00:19:40,610 --> 00:19:42,910
kwa anwani pc.

371
00:19:42,910 --> 00:19:47,860
Nini tutaweza kupata huko ni tabia na
* pc ni jinsi sisi rejea data wakati huo

372
00:19:47,860 --> 00:19:48,880
eneo.

373
00:19:48,880 --> 00:19:54,150
Hivyo tunaweza kusema kitu kama
* pc = D au kitu kama hicho,

374
00:19:54,150 --> 00:19:59,280
na hiyo ina maana kwamba kila
ilikuwa kumbukumbu anuani pc,

375
00:19:59,280 --> 00:20:07,040
chochote tabia awali alikuwa
huko, sasa ni D, kama sisi kusema * pc = D.

376
00:20:07,040 --> 00:20:10,090
>> Hivyo hapa sisi kwenda tena kwa
baadhi C mambo weird, haki.

377
00:20:10,090 --> 00:20:14,560
Hivyo tumeona * awali kama kuwa
namna fulani ni sehemu ya aina data,

378
00:20:14,560 --> 00:20:17,160
na sasa ni kuwa kutumika katika
mazingira tofauti kidogo

379
00:20:17,160 --> 00:20:19,605
kupata data katika eneo.

380
00:20:19,605 --> 00:20:22,480
Najua ni utata kidogo na
hiyo ni kweli sehemu ya yote hii

381
00:20:22,480 --> 00:20:25,740
kama, kwa nini kuyatumia na mythology hii
inayowazunguka kama kuwa hivyo tata,

382
00:20:25,740 --> 00:20:28,250
ni aina ya tatizo syntax, uaminifu.

383
00:20:28,250 --> 00:20:31,810
Lakini * hutumika katika mazingira yote miwili,
wote kama sehemu ya jina aina,

384
00:20:31,810 --> 00:20:34,100
na tutaweza kuona kidogo
baadaye kitu kingine, pia.

385
00:20:34,100 --> 00:20:36,490
Na hivi sasa ni
dereference operator.

386
00:20:36,490 --> 00:20:38,760
Hivyo huenda kwa kumbukumbu,
ni wanapata data

387
00:20:38,760 --> 00:20:43,000
katika eneo la pointer, na
utapata kuendesha katika mapenzi.

388
00:20:43,000 --> 00:20:45,900
>> Sasa hii ni sawa na
kutembelea jirani yako, haki.

389
00:20:45,900 --> 00:20:48,710
Kama unajua nini yako
jirani anaishi, uko

390
00:20:48,710 --> 00:20:50,730
si kunyongwa nje na jirani yako.

391
00:20:50,730 --> 00:20:53,510
Unajua kutokea kwa
kujua wapi wanaishi,

392
00:20:53,510 --> 00:20:56,870
lakini hiyo haina maana kwamba kwa
mujibu wa kuwa na maarifa kwamba

393
00:20:56,870 --> 00:20:59,170
wewe ni mazungumzo pamoja nao.

394
00:20:59,170 --> 00:21:01,920
Kama unataka kuingiliana nao,
una kwenda kwa nyumba zao,

395
00:21:01,920 --> 00:21:03,760
una kwenda kwa wanakoishi.

396
00:21:03,760 --> 00:21:07,440
Na mara moja kufanya hivyo,
basi unaweza kuingiliana

397
00:21:07,440 --> 00:21:09,420
nao tu kama wewe d wanataka.

398
00:21:09,420 --> 00:21:12,730
Na vile vile na vigezo,
unahitaji kwenda kwa anuani wao

399
00:21:12,730 --> 00:21:15,320
kama unataka kiutendaji yao,
huwezi kujua mahali.

400
00:21:15,320 --> 00:21:21,495
Na njia ya kwenda kwa anwani ni
kutumia *, dereference operator.

401
00:21:21,495 --> 00:21:23,620
Je, unafikiri hutokea
kama sisi kujaribu dereference na

402
00:21:23,620 --> 00:21:25,260
pointer ambao thamani ni batili?

403
00:21:25,260 --> 00:21:28,470
Kumbuka kwamba null
pointer anazungumzia kitu.

404
00:21:28,470 --> 00:21:34,110
Hivyo kama wewe kujaribu dereference na
kitu au kwenda kwa anwani kitu,

405
00:21:34,110 --> 00:21:36,800
unafikiri nini hufanyika?

406
00:21:36,800 --> 00:21:39,630
Vizuri kama wewe guessed segmentation
kosa, wewe d kuwa na haki.

407
00:21:39,630 --> 00:21:41,390
Kama wewe kujaribu na dereference
pointer null,

408
00:21:41,390 --> 00:21:43,140
kuteseka segmentation
kosa. Lakini kusubiri,

409
00:21:43,140 --> 00:21:45,820
hakuwa nawaambia, kwamba
kama wewe si kwenda

410
00:21:45,820 --> 00:21:49,220
kuweka thamani yako ya yako
pointer kwa kitu ya maana,

411
00:21:49,220 --> 00:21:51,000
unapaswa kuweka kwa null?

412
00:21:51,000 --> 00:21:55,290
Nilifanya na kwa kweli segmentation
kosa ni aina ya tabia nzuri.

413
00:21:55,290 --> 00:21:58,680
>> Umewahi alitangaza kutofautiana na
si kupewa thamani yake mara moja?

414
00:21:58,680 --> 00:22:02,680
Hivyo wewe tu kusema int x; huna
kweli hawawajui kwa kitu chochote

415
00:22:02,680 --> 00:22:05,340
na kisha baadaye katika kanuni yako,
wewe magazeti nje thamani ya x,

416
00:22:05,340 --> 00:22:07,650
kuwa bado si
kupewa kwa kitu chochote.

417
00:22:07,650 --> 00:22:10,370
Mara kwa mara utasikia kupata
sifuri, lakini wakati mwingine

418
00:22:10,370 --> 00:22:15,000
ili kupata baadhi ya idadi random, na
hawana wazo ilikotoka.

419
00:22:15,000 --> 00:22:16,750
Vile vile anaweza mambo
kutokea na kuyatumia.

420
00:22:16,750 --> 00:22:20,110
Wakati kutangaza pointer
int * pk kwa mfano,

421
00:22:20,110 --> 00:22:23,490
na huna hawawajui kwa thamani,
kupata ka nne kwa kumbukumbu.

422
00:22:23,490 --> 00:22:25,950
Chochote ka nne ya
kumbukumbu ya mfumo Unaweza

423
00:22:25,950 --> 00:22:28,970
kupata kwamba kuwa na baadhi ya thamani ya maana.

424
00:22:28,970 --> 00:22:31,760
Na kuna uwezekano kuwa
kitu tayari pale kwamba

425
00:22:31,760 --> 00:22:34,190
ni hawahitaji tena na mwingine
kazi, hivyo wewe tu na

426
00:22:34,190 --> 00:22:35,900
chochote data alikuwa huko.

427
00:22:35,900 --> 00:22:40,570
>> Nini kama wewe alijaribu kufanya dereference
baadhi anwani hiyo wewe don't- kulikuwa na

428
00:22:40,570 --> 00:22:43,410
Tayari ka na habari katika
kuna, hiyo ni sasa katika pointer yako.

429
00:22:43,410 --> 00:22:47,470
Kama wewe kujaribu na dereference kwamba pointer,
unaweza kuwa messing na baadhi ya kumbukumbu

430
00:22:47,470 --> 00:22:49,390
kwamba hakuwa na nia
kwa fujo na hayo yote.

431
00:22:49,390 --> 00:22:51,639
Na kwa kweli unaweza kufanya
kitu kweli kutisha,

432
00:22:51,639 --> 00:22:54,880
kama kuvunja mpango mwingine,
au kuvunja kazi nyingine,

433
00:22:54,880 --> 00:22:58,289
au kufanya kitu malicious kwamba
wewe hakuwa na nia ya kufanya wakati wote.

434
00:22:58,289 --> 00:23:00,080
Na hivyo ndiyo sababu ni
kweli wazo nzuri

435
00:23:00,080 --> 00:23:04,030
kuweka kuyatumia yako kwa null ikiwa
si kuweka yao kwa kitu ya maana.

436
00:23:04,030 --> 00:23:06,760
Ni pengine bora katika
Mwisho wa siku kwa mpango wako

437
00:23:06,760 --> 00:23:09,840
ajali kisha kwa ajili yake kufanya
kitu ambacho screws up

438
00:23:09,840 --> 00:23:12,400
Mpango mwingine au kazi nyingine.

439
00:23:12,400 --> 00:23:15,207
Tabia ambayo pengine ni hata
chini bora kuliko crashing tu.

440
00:23:15,207 --> 00:23:17,040
Na hivyo ndiyo sababu ni
kweli tabia nzuri

441
00:23:17,040 --> 00:23:20,920
kupata katika kuweka kuyatumia yako
kwa null kama huna kuwaweka

442
00:23:20,920 --> 00:23:24,540
kwa maana thamani
mara moja, thamani kwamba unajua

443
00:23:24,540 --> 00:23:27,260
na kwamba unaweza salama dereference.

444
00:23:27,260 --> 00:23:32,240
>> Basi hebu kurudi sasa na tuangalie
katika syntax unaonyesha hali halisi.

445
00:23:32,240 --> 00:23:37,400
Kama mimi kusema int * p ;, nini mimi tu kosa gani?

446
00:23:37,400 --> 00:23:38,530
Kile nimepata kufanyika ni hii.

447
00:23:38,530 --> 00:23:43,290
Najua thamani ya p ni anwani
kwa sababu kuyatumia yote ni tu

448
00:23:43,290 --> 00:23:44,660
anwani.

449
00:23:44,660 --> 00:23:47,750
Naweza dereference p
kutumia * operator.

450
00:23:47,750 --> 00:23:51,250
Katika hali hii hapa, saa sana
juu kukumbuka * ni sehemu ya aina.

451
00:23:51,250 --> 00:23:53,510
* Int ni aina data.

452
00:23:53,510 --> 00:23:56,150
Lakini siwezi dereference
p kutumia * operator,

453
00:23:56,150 --> 00:24:01,897
na kama mimi kufanya hivyo, kama mimi kwenda kwa anwani hiyo,
nini mimi kupata katika anwani hiyo?

454
00:24:01,897 --> 00:24:02,855
Mimi utapata integer.

455
00:24:02,855 --> 00:24:05,910
Hivyo int * p kimsingi ni
akisema, s ni mahali.

456
00:24:05,910 --> 00:24:09,500
Naweza dereference p na kama
Mimi kufanya, mimi utapata integer

457
00:24:09,500 --> 00:24:11,920
wakati huo kumbukumbu eneo.

458
00:24:11,920 --> 00:24:14,260
>> OK hivyo mimi alisema kulikuwa na mwingine
Jambo annoying na nyota

459
00:24:14,260 --> 00:24:17,060
na hapa ndipo kwamba
Jambo annoying na nyota ni.

460
00:24:17,060 --> 00:24:21,640
Umewahi walijaribu kutangaza
vigezo mbalimbali ya aina moja

461
00:24:21,640 --> 00:24:24,409
juu ya mstari huo wa kanuni?

462
00:24:24,409 --> 00:24:27,700
Hivyo kwa mara ya pili, kujifanya kuwa mstari,
kificho mimi kweli kuwa kuna katika kijani

463
00:24:27,700 --> 00:24:29,366
si huko na ni haki anasema int x, y, z ;.

464
00:24:29,366 --> 00:24:31,634

465
00:24:31,634 --> 00:24:34,550
Gani kwamba kufanya ni kweli kujenga
tatu integer vigezo kwa ajili yenu,

466
00:24:34,550 --> 00:24:36,930
mtu mmoja aitwaye x, yeye anayeitwa
y, na mtu mmoja aitwaye z.

467
00:24:36,930 --> 00:24:41,510
Ni njia ya kufanya hivyo bila
kuwa na mgawanyiko kwenye mistari mitatu.

468
00:24:41,510 --> 00:24:43,890
>> Hapa ni wapi nyota kupata
annoying tena ingawa,

469
00:24:43,890 --> 00:24:49,200
kwa sababu * ni kweli sehemu
wa wote jina aina na sehemu

470
00:24:49,200 --> 00:24:50,320
jina la kutofautiana.

471
00:24:50,320 --> 00:24:56,430
Na hivyo kama mimi kusema int * px, py, PZ, nini mimi
kweli kupata ni pointer integer

472
00:24:56,430 --> 00:25:01,650
aitwaye px na integers mbili, py na PZ.

473
00:25:01,650 --> 00:25:04,950
Na kwamba pengine si kile
tunataka, hilo si jambo zuri.

474
00:25:04,950 --> 00:25:09,290
>> Hivyo kama nataka kujenga kuyatumia nyingi
juu ya mstari huo, wa aina moja,

475
00:25:09,290 --> 00:25:12,140
na nyota, kile kwa kweli wanahitaji
kufanya ni kusema int * pa, * AS, * pc.

476
00:25:12,140 --> 00:25:17,330

477
00:25:17,330 --> 00:25:20,300
Sasa baada tu alisema kuwa
na sasa nawaambia hii,

478
00:25:20,300 --> 00:25:22,170
pengine kamwe kufanya hivyo.

479
00:25:22,170 --> 00:25:25,170
Na pengine ni jambo jema kwa uaminifu,
kwa sababu waweza inadvertently

480
00:25:25,170 --> 00:25:26,544
saza nyota, kitu kama hicho.

481
00:25:26,544 --> 00:25:29,290
Pengine ni bora kwa labda kutangaza
kuyatumia juu ya mistari ya mtu binafsi,

482
00:25:29,290 --> 00:25:31,373
lakini ni mwingine tu moja
wale syntax annoying

483
00:25:31,373 --> 00:25:35,310
mambo na nyota kwamba kufanya
kuyatumia vigumu kufanya kazi pamoja.

484
00:25:35,310 --> 00:25:39,480
Kwa sababu ni tu kisintaksia hii
fujo una kazi kupitia.

485
00:25:39,480 --> 00:25:41,600
Pamoja na mazoezi ni gani
kweli kuwa asili ya pili.

486
00:25:41,600 --> 00:25:45,410
Mimi bado kufanya makosa na bado
baada programu kwa miaka 10,

487
00:25:45,410 --> 00:25:49,630
hivyo si kuwa upset kama kitu kinachotokea
na wewe, ni pretty kawaida kwa uaminifu.

488
00:25:49,630 --> 00:25:52,850
Ni kweli aina ya
flaw ya syntax.

489
00:25:52,850 --> 00:25:54,900
>> OK hivyo mimi aina ya ahadi
kwamba tunataka upya

490
00:25:54,900 --> 00:25:59,370
Dhana ya jinsi kubwa ni kamba.

491
00:25:59,370 --> 00:26:02,750
Vizuri kama niliwaambieni kwamba
kamba, tumekuwa kweli aina ya

492
00:26:02,750 --> 00:26:04,140
wamekuwa uongo na wewe wakati wote.

493
00:26:04,140 --> 00:26:06,181
Hakuna aina data inayoitwa
kamba, na kwa kweli mimi

494
00:26:06,181 --> 00:26:09,730
zilizotajwa hii katika moja ya yetu
video mwanzo juu ya aina ya data,

495
00:26:09,730 --> 00:26:13,820
kamba iliyokuwa aina data kwamba
iliundwa kwa ajili yenu katika CS50.h.

496
00:26:13,820 --> 00:26:17,050
Una # ni pamoja na
CS50.h ili kuitumia.

497
00:26:17,050 --> 00:26:19,250
>> Naam kamba ni kweli tu
vinginevyo kwa kitu

498
00:26:19,250 --> 00:26:23,600
aitwaye * Char,
pointer kwa tabia.

499
00:26:23,600 --> 00:26:26,010
Vizuri kuyatumia, kukumbuka,
ni anazungumzia tu.

500
00:26:26,010 --> 00:26:28,780
Kwa hiyo kile ni ukubwa
katika ka wa kamba?

501
00:26:28,780 --> 00:26:29,796
Naam ni nne au nane.

502
00:26:29,796 --> 00:26:32,170
Na sababu nasema nne au
nane ni kwa sababu ni kweli

503
00:26:32,170 --> 00:26:36,730
inategemea mfumo, Kama unatumia
CS50 ide, * Char ni ukubwa wa Char

504
00:26:36,730 --> 00:26:39,340
* Ni nane, ni mfumo 64-bit.

505
00:26:39,340 --> 00:26:43,850
Kila address katika kumbukumbu ni 64 bits kwa muda mrefu.

506
00:26:43,850 --> 00:26:48,270
Kama unatumia appliance CS50
au kutumia yoyote mashine 32-bit,

507
00:26:48,270 --> 00:26:51,640
na wewe Nimesikia kwamba muda 32-bit
mashine, ni nini 32-bit mashine?

508
00:26:51,640 --> 00:26:56,090
Vizuri tu ina maana kwamba kila
anwani katika kumbukumbu ni 32 bits kwa muda mrefu.

509
00:26:56,090 --> 00:26:59,140
Na hivyo bits 32 ni ka nne.

510
00:26:59,140 --> 00:27:02,710
Hivyo * Char ni nne au nane
ka kutegemea mfumo wako.

511
00:27:02,710 --> 00:27:06,100
Na hakika aina yoyote data,
na pointer data yoyote

512
00:27:06,100 --> 00:27:12,030
aina, tangu kuyatumia yote ni tu
anwani, ni ka nne au nane.

513
00:27:12,030 --> 00:27:14,030
Basi hebu kupitia upya hii
mchoro na hebu kuhitimisha

514
00:27:14,030 --> 00:27:18,130
video hii na zoezi kidogo hapa.

515
00:27:18,130 --> 00:27:21,600
Hivyo hapa ni mchoro sisi kushoto mbali na
mwanzoni mwa video.

516
00:27:21,600 --> 00:27:23,110
Hivyo kile kinachotokea sasa kama mimi kusema * pk = 35?

517
00:27:23,110 --> 00:27:26,370

518
00:27:26,370 --> 00:27:30,530
Hivyo ni nini maana wakati mimi kusema, * pk = 35?

519
00:27:30,530 --> 00:27:32,420
Kuchukua pili.

520
00:27:32,420 --> 00:27:34,990
* pk.

521
00:27:34,990 --> 00:27:39,890
Katika mazingira hapa, * ni
dereference operator.

522
00:27:39,890 --> 00:27:42,110
Hivyo wakati dereference
alama ni kutumika,

523
00:27:42,110 --> 00:27:48,520
twende kwa anwani alisema kwa
na pk, na sisi kubadili kile tunaona.

524
00:27:48,520 --> 00:27:55,270
Hivyo * pk = 35 kwa ufanisi
gani hii kwa picha.

525
00:27:55,270 --> 00:27:58,110
Hivyo ni kimsingi syntactically
kufanana na ya Baada ya kusema k = 35.

526
00:27:58,110 --> 00:28:00,740

527
00:28:00,740 --> 00:28:01,930
>> Moja zaidi.

528
00:28:01,930 --> 00:28:05,510
Kama mimi kusema int m, mimi kujenga
kutofautiana mpya iitwayo m.

529
00:28:05,510 --> 00:28:08,260
Sanduku mpya, ni sanduku ya kijani kwa sababu
itakuja kushikilia integer,

530
00:28:08,260 --> 00:28:09,840
na ni kinachoitwa m.

531
00:28:09,840 --> 00:28:14,960
Kama mimi kusema m = 4, mimi kuweka
integer ndani ya boksi hilo.

532
00:28:14,960 --> 00:28:20,290
Kama kusema pk = & m, jinsi gani
mabadiliko haya mchoro?

533
00:28:20,290 --> 00:28:28,760
Pk = & m, je unakumbuka kile
& Operator gani au ni wito?

534
00:28:28,760 --> 00:28:34,430
Kumbuka kwamba baadhi & jina kutofautiana
ni pepe ya jina kutofautiana.

535
00:28:34,430 --> 00:28:38,740
Kwa hiyo kile sisi ni kusema ni
pk anapata pepe ya m.

536
00:28:38,740 --> 00:28:42,010
Na hivyo kwa ufanisi kile kinachotokea
mchoro ni kwamba PK pointi tena

537
00:28:42,010 --> 00:28:46,420
kwa k, lakini pointi kwa m.

538
00:28:46,420 --> 00:28:48,470
>> Tena kuyatumia ni sana
gumu kufanya kazi na

539
00:28:48,470 --> 00:28:50,620
na wao kuchukua mengi ya
mazoezi, lakini kwa sababu

540
00:28:50,620 --> 00:28:54,150
ya uwezo wao wa kuruhusu
kupita data kati ya kazi

541
00:28:54,150 --> 00:28:56,945
na kwa kweli kuwa wale
mabadiliko kuchukua athari,

542
00:28:56,945 --> 00:28:58,820
kupata kichwa yako karibu
ni kweli ni muhimu.

543
00:28:58,820 --> 00:29:02,590
Pengine ni ngumu zaidi
mada sisi kujadili katika CS50,

544
00:29:02,590 --> 00:29:05,910
lakini thamani kwamba
kupata kutoka kwa kutumia kuyatumia

545
00:29:05,910 --> 00:29:09,200
mbali outweighs matatizo
kwamba kuja kutoka kujifunza kwao.

546
00:29:09,200 --> 00:29:12,690
Hivyo Napenda bora wa
Bahati kujifunza kuhusu kuyatumia.

547
00:29:12,690 --> 00:29:15,760
Mimi nina Doug Lloyd, hii ni CS50.

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