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[Powered by Google Translate] JORDAN JOZWIAK: Aina akitoa, kwa maana rahisi, ni

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njia ya kubadilisha tafsiri ya kompyuta ya baadhi ya data na

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implicitly au waziwazi kubadilisha data zake aina.

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Kama vile kubadilisha int kwa kuelea, au kinyume chake.

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Kuelewa aina akitoa, tunahitaji

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kuanza na shemu -

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data aina wenyewe.

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Katika lugha ya kompyuta kama C, kila vigezo na aina fulani

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ya data aina kwamba huamua jinsi ya kompyuta, na vivyo hivyo

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user, anatafsiri kwamba kutofautiana.

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Namba data aina kama vile int kuelea, muda mrefu, na

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mara mbili, wote wana sifa zao za kipekee na ni

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kutumika kwa bayana maadili ya tofauti kati na usahihi.

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Aina akitoa inaruhusu sisi kuchukua hatua floating idadi kama

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3.14 na kupata sehemu kabla decimal, 3 katika kesi hii,

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na akitoa kwa int.

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Hebu chukua mfano kutoka lugha ya Kiingereza kwa kifupi

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mapitio ya aina, na kuona jinsi akitoa aina inaweza kubadilika

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njia ya sisi kutafsiri kipande cha data.

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Kwa data, hebu kuchukua alama hapa.

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Mimi tu rejea mistari haya kwa makini configured kama

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ishara, lakini kama mtu ambaye anajua lugha ya Kiingereza,

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wewe mara kutambua kwamba wao ni, kwa kweli, barua.

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Wewe implicitly kueleweka aina data.

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Kuangalia hii kamba ya barua tunaweza kuona wawili

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tofauti ya maneno, kila na maana yake mwenyewe.

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Kuna nomino, upepo, kama katika upepo unavuma nje.

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Na kuna kitenzi, upepo, kama katika nahitaji

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upepo zamu yangu ya analogi.

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Huu ni mfano kuvutia, kwa sababu tunaweza kuona

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jinsi ya aina ya kwamba sisi hawawajui data zetu, kama nomino au

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verb, mabadiliko jinsi tunavyotumia data kwamba -

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kama upepo neno au upepo.

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Ingawa kompyuta hajali kuhusu sarufi na sehemu

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ya hotuba ya Kiingereza, sawa kanuni ya msingi inatumika.

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Hiyo ni, tunaweza kubadilisha tafsiri ya halisi

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sawa data kuhifadhiwa katika kumbukumbu kwa kifupi akitoa kwa

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aina tofauti.

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Hapa ni ukubwa wa aina ya kawaida juu ya 32-bit

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mfumo wa uendeshaji.

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Tuna Char saa 1 int Byte, na kuelea katika ka 4, kwa muda mrefu

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muda mrefu na mara mbili katika ka 8.

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Kwa sababu int inachukua hadi ka 4, itachukua up bits 32

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wakati ni kuhifadhiwa katika kumbukumbu kama mfululizo binary

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ya zeros na ndio.

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Muda mrefu kama variable yetu bado kama int aina,

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kompyuta daima kubadilisha wale wale na zeros kutoka

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binary katika idadi ya awali.

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Hata hivyo, tunaweza kinadharia kutupwa wale 32

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bits katika mfululizo wa aina Boolean.

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Na kisha kompyuta itakuwa hakuna tena kuona idadi, lakini

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badala ya ukusanyaji wa zeros na ndio.

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Tunaweza pia kujaribu kusoma data kwamba kama numeric tofauti

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aina, au hata kama kamba ya herufi nne.

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Wakati wa kushughulika na idadi katika akitoa, ni lazima kuzingatia jinsi

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usahihi wa thamani yako itakuwa walioathirika.

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Kumbuka kwamba usahihi inaweza kukaa sawa,

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au unaweza kupoteza usahihi, lakini unaweza kamwe kupata usahihi.

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Hebu kupitia kwa njia tatu ya kawaida kwamba unaweza

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kupoteza usahihi.

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Akitoa kuelea kwa int kusababisha truncation wa kila kitu

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baada ya uhakika decimal, hivyo wewe ni kushoto

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na namba nzima.

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Kama sisi kuchukua x kuelea ambayo itakuwa sawa 3.7, tunaweza kutupwa

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this x variable kwa int kwa kifupi kuandika int katika

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mabano.

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Kila mara sisi kutumia muda huu haki hapa, tutaweza kwa ufanisi

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kutumia thamani tatu kwa sababu tumekuwa truncated

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kila kitu baada ya uhakika decimal.

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Tunaweza pia kubadilisha muda mrefu int, ambayo itakuwa

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vile vile kusababisha hasara ya bits high-utaratibu.

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muda mrefu inachukua hadi ka 8, au bits 64 katika kumbukumbu.

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Hivyo wakati sisi kuwatupia int ambayo tu ana ka 4, au 32

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bits, sisi ni kimsingi chopping off bits wote kwamba

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kuwakilisha maadili binary juu.

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Unaweza pia kutupa mara mbili kwa kuelea, ambayo nitakupa

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wewe kuelea karibu inawezekana mara mbili bila

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lazima rounding yake.

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Sawa na muda wetu kwa muda mrefu kwa uongofu int, hasara katika

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usahihi ni kwa sababu mbili ina data zaidi.

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mbili itawawezesha kuhifadhi 53 bits muhimu,

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takribani 16 muhimu tarakimu.

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Wakati kuelea tu kuruhusu kuhifadhi 24

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muhimu bits, takribani saba muhimu tarakimu.

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Katika kesi hizi mbili za mwisho, inaweza kuwa na manufaa kwa kufikiria

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aina akitoa kama resizing picha.

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Wakati wewe kwenda kutoka kawaida kubwa kwa kawaida ndogo, huwezi kuona

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mambo kama wazi kwa sababu wewe kupoteza data

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katika fomu ya saizi.

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Aina akitoa pia inaweza kusababisha matatizo wakati sisi

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kutupwa ints kwa inaelea.

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Tangu ikifungwa kwenye mashine ya 32-bit tu kuwa 24

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bits muhimu, hawawezi usahihi kuwakilisha maadili

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zaidi ya 2 kwa nguvu ya 24, au 16,777,217.

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Sasa hebu majadiliano juu akitoa wazi na thabiti.

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Akitoa wazi ni wakati sisi kuandika aina katika mabano

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kabla ya jina kutofautiana.

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Kama mfano, kabla ya sisi aliandika int katika mabano kabla yetu

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kuelea x kutofautiana.

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Kwa njia hii, sisi kupata thamani int,

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truncated thamani ya 3.7 -

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3.

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Kinachojitokeza ni wakati akitoa compiler moja kwa moja changes

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sawa aina kwa aina super, au hufanya baadhi ya aina nyingine ya

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akitoa bila kuhitaji mtumiaji kuandika

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yoyote code ya ziada.

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Kwa mfano, wakati sisi kuongeza 5 na 1.1, maadili yetu tayari kuwa na

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aina kuhusishwa na wao.

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5 ni int, ambapo 1.1 ni kuelea.

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Ili kuongeza yao, kompyuta Anamfukuza 5 ndani ya kuelea,

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ambayo ingekuwa kitu sawa kama kuandika 5.0 katika

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nafasi ya kwanza.

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Lakini kwa njia hii sisi kusema kuelea 5, au 5.0, pamoja na kile ilikuwa tayari

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kuelea, 1.1, na kutoka hapo tunaweza kweli kuongeza hizi

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maadili na kupata thamani 6.1.

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Akitoa Kinachojitokeza pia inaruhusu sisi hawawajui vigezo ya

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aina tofauti kwa kila mmoja.

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Tunaweza daima hawawajui aina chini sahihi katika zaidi

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sahihi moja.

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Kwa mfano, kama tuna x mara mbili, na y int -

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na haya inaweza kuwa na maadili yoyote kwamba sisi akawaweka -

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tunaweza kusema x sawa y.

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Kwa sababu mara mbili ana zaidi kuliko usahihi int, hivyo sisi

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si kupoteza taarifa yoyote.

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Kwa upande mwingine, ingekuwa siyo lazima kuwa sahihi kusema

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y sawa x, kwa sababu mbili anaweza kuwa na thamani kubwa kuliko

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integer.

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Na hivyo integer wanaweza kuwa na uwezo wa kushikilia wote

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taarifa iliyohifadhiwa katika mbili.

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Akitoa Kinachojitokeza ni pia kutumika katika waendeshaji kulinganisha kama

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kubwa zaidi kuliko, chini ya, au operator usawa.

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Njia hii tunaweza kusema kama 5.1 ni kubwa kuliko 5, na sisi kupata

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kusababisha kweli.

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Kwa sababu ni int 5, lakini itabidi kutupwa kwa kuelea ili

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kuwa ikilinganishwa na kuelea 5.1, tunatarajia kusema 5.1 ni

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kubwa kuliko 5.0.

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Huyo ni kweli na kusema iwapo 2.0 sawa sawa na 2.

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Tunatarajia pia kupata kweli, kwa sababu kompyuta atamtupia

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integer 2 kwa kuelea na kisha kusema 2.0 sawa sawa na 2.0,

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hii ni kweli.

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Usisahau kwamba tunaweza pia kutupwa kati ya ints na chars,

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au ASCII maadili.

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Chars pia haja ya kupunguzwa kwa binary, ambayo ni kwa nini

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urahisi kubadili kati ya chars na husika yao

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ASCII maadili.

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Ili kujifunza zaidi kuhusu hili, angalia video wetu juu ya ASCII.

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Wakati wewe kuchukua muda kufikiria jinsi data imehifadhiwa,

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inaanza kufanya mengi ya akili.

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Ni kama tu tofauti kati ya upepo na upepo.

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data ni sawa, lakini aina inaweza kubadili jinsi sisi

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kuifasiri.

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Jina langu ni Jordan Jozwiak, hii cs50.