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[Powered by Google Translate] DAVID DICIURCIO: Hivyo dhana muhimu kufahamu katika

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programu hii ni dhana ya upeo.

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Wigo unaweza kuelezwa kama mazingira ambayo kutofautiana ni

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inayoonekana au kupatikana.

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Kwa mfano, hebu kusema sisi kuwa na kazi, kuu, kwamba ni

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zinatakiwa kuongezwa variable, x, kutoka moja mpaka mbili.

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Kama tunavyoona, kuu initializes x kwa moja, Prints

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nje Nakala baadhi, kisha anaendesha increment kazi, kabla ya

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uchapishaji zaidi maandishi.

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Kama kazi hii walikuwa kuendesha usahihi, ingekuwa

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magazeti nje x kama 2.

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Hebu jaribu hilo.

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>> Hivyo, kama unaweza kuona, kuu hafanyi kile sisi inatarajiwa.

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Ni anarudi thamani 1, badala

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kuliko 2 tulivyotarajia.

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Sababu ya mdudu hii inaweza kuelezwa na upeo.

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Katika kazi, kuu, sisi initialized x

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tu ndani ya kazi.

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Kwa maneno mengine, x variable ni alitangaza ndani ya nchi ndani

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kazi, kuu, na si kupatikana

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nje ya kazi.

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Tu kuu wanaweza kupata x katika hali hii.

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Wakati sisi kuwaita increment hatuwezi kupita x kama pembejeo, lakini

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tu nakala ya x.

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Kama matokeo ya hili, increment kazi tu anaongeza

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thamani 1 kwa nakala ya thamani ya x.

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Lakini si kwa X yenyewe.

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Wakati sisi kurudi kuu, x yenyewe hajabadilika wakati wote.

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Hivyo uchapishaji nje x tu mavuno thamani ya 1.

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>> Naam, basi, kwamba majani ya swali: jinsi lazima sisi kurekebisha

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kazi hii?

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Moja ufumbuzi ni kuwa na increment kurudi thamani.

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Kwa njia hii, increment kazi mapenzi

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kutupatia nyuma integer.

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Hivyo hapa ni code yetu upya kwa

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mbadala increment kazi.

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Hapa, sisi badala akarudi x + 1, badala ya mwisho tu

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na x kuwa sawa na x + 1.

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Pia, kuchukua taarifa kwamba sisi badala ya pato la

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increment, awali tupu, na int, na kusema kuwa

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increment sasa kupita nyuma thamani integer.

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Sasa, baada ya anaendesha increment, itakuwa kurejea kwa thamani ya

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2, hasa kama sisi lengo.

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>> Mwingine hali ambayo inaonyesha umuhimu wa upeo

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ni katika scopeloop.c.

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Katika kanuni hii, tuna kwa kitanzi ambayo variable

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jumla ni initialized wakati kila hatua.

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Kwa bahati mbaya, code hii haina kukusanya.

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Hii ni kwa sababu jumla variable kweli haipo

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nje kwa kitanzi.

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Vigezo alitangaza ndani ya matanzi tu lipo ndani ya

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kitanzi yenyewe na ni alionyesha katika makosa yetu

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ujumbe, jumla Undeclared.

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jumla ya variable bado kuwa alitangaza ndani ya wigo

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ya kazi kuu.

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Aidha, wakati kila iteration wa wetu kwa kitanzi, sisi

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ni reinitializing jumla wetu kwa 0.

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Hii yenyewe haina kuweka code kutoka kuandaa, lakini

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ingeweza kuzuia jumla kutoka milele summing kwa thamani 1 uliopita.

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>> Tena nini ni njia bora ya kutatua tatizo hili?

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Moja ya njia rahisi ni pamoja na kufanya jumla ya mitaa

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kazi, kuu, badala ya kitanzi yenyewe.

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Hii jumla ya kweli increment, na hatimaye,

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kuruhusu kuwa kuchapishwa baada ya kitanzi.

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Mbinu nyingine kwamba mimi itabidi tu kwa ufupi muhtasari ingekuwa

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kuwa matumizi ya vigezo kimataifa.

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Vigezo Global ni vigezo kwamba ni alitangaza kabla kuu

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kwamba kudumisha thamani zao katika mpango mzima.

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Bila shaka, kazi inaweza kubadilika thamani ya kimataifa,

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lakini hawana kwenda nje ya wigo kama vigezo mitaa.

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Hata hivyo, kwa kutumia vigezo kimataifa huelekea kipaji

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juu kama kubuni mbaya, kwa vile kuna njia bora ya

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kubadilishana data miongoni mwa kazi.

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Kwa mfano, kwa kutumia kuyatumia.

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Lakini zaidi juu ya kwamba wakati mwingine.

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>> Hatimaye, ni muhimu kuwa na ufahamu wa upeo

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katika muktadha wa kumbukumbu ya kompyuta, au RAM.

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Wakati sisi nitafanya mpango, mitaa vigezo na majukumu

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ni aliongeza kwa mahali maalum katika

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RAM aitwaye stack.

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Kama kurudi kazi, muafaka stack ya vigezo ni

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ufanisi kuondolewa kutoka stack kumkomboa up kumbukumbu zaidi.

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Hivyo wakati marekebisho upeo, hakikisha unakumbuka hizi tatu

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muhimu pointi.

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Moja, upeo inaweza kuwa ama ndani au wa kimataifa.

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Ni inategemea ambapo variable ni alitangaza.

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Mbili, vigezo alitangaza au initialized katika kazi ni

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mitaa kwa kazi hiyo na haiwezi kubadilishwa kwa wengine

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kazi, angalau si bila kutumia kuyatumia.

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Hatimaye, vigezo ni pia mitaa matanzi kwamba ni

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alitangaza ndani.

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vigezo si kupatikana

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nje ya kitanzi.

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>> Hayo ni yote kwa sasa juu ya upeo.

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Shukrani kwa ajili ya kuangalia.