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[Powered by Google Translate] Nate HARDISON: F'dan il-video fuq binarju, nuru kif

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jirrappreżentaw is-sett ta 'numri sħaħ, minn żero fuq up,

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bl-użu biss l-ċifri żero u wieħed.

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F'dan il-video, aħna qed tmur għall-użu notazzjoni binarji biex

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jirrappreżentaw, ittri test u bħal dawn, kif ukoll.

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>> Għaliex kieku aħna jolqot biex jagħmlu dan?

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Ukoll, taħt il-barnuża, kompjuter biss verament

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jifhem żero u dawk, l-ċifri binarju, peress li dawn

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jistgħu jkunu rappreżentati faċilment ma 'affarijiet elettromanjetiċi.

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>> Per eżempju, think tal-memorja tal-kompjuter tiegħek bħal twil

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sensiela ta 'bozoz tad-dawl, fejn kull bozza individwali

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jirrappreżenta żero jekk huwa mitfi, u waħda

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jekk huwa mdawwar fuq.

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Minflok tuża mazz ta 'bozoz tad-dawl, xi moderna

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memorja ma dan bl-użu kapaċitaturi li jkollhom baxx

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ħlas li jirrappreżentaw żero u ħlas għoli

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li jirrappreżentaw wieħed.

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>> Hemm tekniki oħrajn ukoll.

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Xorta waħda, sabiex taħżen xejn fil-memorja, għandna bżonn li

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1 jissarfu fi ħaġa li tista 'tkun fil-fatt

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rappreżentati fil-hardware fiżiċi.

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Mela ejja jaħsbu dwar kif nistgħu jirrappreżentaw ittri ma

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notazzjoni binarja.

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Bl-Ingliż, konna ltqajna 26-ittri fil-alfabetiku, A,

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>> B, Ċ, D, u l-bqija, sa permezz Z. Aħna tista 'tassenja kull wieħed u waħda

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dawn Numru ta ', ngħidu aħna żero sa 25, u mbagħad tuża

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notazzjoni binarja, nistgħu jirrappreżentaw kull numru bħala

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sekwenza ta 'żero u dawk.

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Li mhux wisq ħżiena.

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Madankollu, dan mhuwiex ser ikun biżżejjed.

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Ma 'din is-sistema, ma nistgħux verament jiddistingwi bejn

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ittri ta 'fuq u zghar.

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Jekk irridu kompjuter tagħna li tkun tista 'tiddistingwi bejn

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iż-żewġ kawżi, allura għandna bżonn addizzjonali 26 numri.

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U xi ngħidu dwar perjodi, virgoli, u

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marki oħra punteġġjatura?

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>> Fuq it-tastiera tiegħi, stajt ltqajna 32 ta 'dawn, inkluż kollha ta' l-

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karattri speċjali bħall-caret u l-ampersand.

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Li mhux inklużi l-karattri ċifri, żero permezz ta 'disa,

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peress li aħna xorta jridu jkunu jistgħu tip numri deċimali

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notazzjoni fuq il-kompjuter, anki jekk il-kompjuter biss verament

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jifhem notazzjoni binarja taħt il-barnuża.

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>> U fl-aħħarnett, aħna ser bżonn li jirrappreżenta karattru spazju hekk

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li Bar Ispazju tagħna xogħlijiet.

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Allura jidhru kif biex jirrappreżenta test fuq il-kompjuter

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jieħu ftit aktar minn nistgħu ħsibt inizjalment.

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Barra minn hekk, jassumi aħna mbagħad toħroġ bi kodifikazzjoni tagħna stess

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iskema biex jirrappreżentaw karattri bħala numri.

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Madankollu aħna jiddeċiedu li jikkodifikaw karattri inevitabbilment se jkunu

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arbitrarja, kif rajna preċedentement meta tkellimna dwar l-użu tal-

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numri żero sa 25 biex jirrappreżentaw l-ittri A

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permezz Z. Għaliex ma jużawx 10 permezz 35 sabiex inkunu tista 'tiffranka

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żero permezz ta 'disa għall-karattri ċifra?

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>> M'hemm l-ebda raġuni vera, aħna biss għażlet kwalunkwe deher

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aħjar għalina.

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Lura fl-1960ijiet kmieni, din kienet problema reali.

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Manifatturi ta 'kompjuters differenti kienu qed jużaw

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skemi differenti kodifikazzjoni, u dan ta 'komunikazzjoni magħmula

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bejn magni differenti ta 'kompitu diffiċli ħafna.

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L-American Istandards Istitut Nazzjonali, ANSI,

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ffurmat kumitat biex tiżviluppa skema komuni.

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U fl-1963, il-Kodiċi Standard Amerikana għall-Informazzjoni

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Interchange, aktar komunement magħrufa bħala ASCII, twieled.

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>> ASCII ġie maħsub bħala kodifikazzjoni 7-bit, li

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ifisser li kull karattru hija rrapreżentata minn kombinazzjoni

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ta 'seba' żerijiet u dawk.

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Ma 'dawk iż-żewġ valuri possibbli, żero jew wieħed, għal kull

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tal-bits 7, hemm żewġ għas-7 jew 128

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karattri li jistgħu jiġu rrappreżentati bil-ASCII

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kodifikazzjoni iskema.

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Allura 128 karattri ħsejjes simili ħafna, id-dritt?

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Ukoll, ftakar li hemm 26-ittri lowercase fil

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Ingliż, ieħor ittri majjuskoli ta 'kulur 26, 10 karattri ċifri,

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32 punteġġjatura u karattri speċjali,

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u l-karattru spazju wieħed.

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>> Li tpoġġi us fi 95, hekk aħna jkollhom ieħor 33 karattri li aħna

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tista 'tirrappreżenta.

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>> Allura dak ix-xellug?

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Ukoll, fil-jiem ta 'l-iżvilupp ta' ASCII, teletype

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magni, li huma tajprajters li jintużaw biex

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jibagħtu messaġġi permezz ta 'network, kienu mifruxa.

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U dawn il-magni kellhom il-karattri addizzjonali wżati biex

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kkontrollati, per eżempju, li jgħidulhom meta jiċċaqalqu l-

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print head down linja, l-għalf linja jew ċavetta linja l-ġdida,

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meta jimxu lejn l-marġini tax-xellug, il-ġarr ritorn,

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jew sempliċement lura ewlenin, u meta jmorru lura spazju wieħed, il-

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karattru backspace, u l-bqija.

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>> Dawn il-karattri huma msejħa karattri kontroll, u huma

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jikkostitwixxu l-bqija tas-sett ASCII.

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Mela jekk inħarsu lejn tabella ASCII, naraw li l-ewwel

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32 numri, żero permezz 31, huma riservati għall-kontroll

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karattri.

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Iżda aħna biss qal li kien hemm karattri kontroll 33.

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X'hemm-jittrattaw?

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Ukoll, in-numru żero u 127, l-ewwel u l-aħħar ta 'l-

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Sett ASCII, ikollhom xejriet bit speċjali, kollha żerijiet u kull

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dawk, rispettivament.

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>> Il-disinjaturi ta ASCII iddeċieda, għalhekk, biex

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tippreserva dawn in-numri ta 'karattri speċjali żejda,

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jiġifieri l-karattru null u l-karattru DEL.

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Null u DEL kienu intiżi għall-editjar tejp tal-karta, li użat

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li jkun mod komuni ta 'ħażna tad-data.

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Tejp tal-karta kien litteralment biss strixxa twila ta 'karta, u fi

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f'intervalli regolari dwar it-tejp, youd punch

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toqob li jaħżen id-data.

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Jiddependi fuq il-wisa 'tat-tejp, kull kolonna tkun

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jistgħu jakkomodaw 5, 6, 7, jew 8 bits.

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>> Li tirrappreżenta ftit żero, youd tagħmel xejn għall-tejp, youd

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biss tħalli spazju vojt.

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Għal daqsxejn waħda, youd punch toqba.

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Il-karattru null kien biss tħalli kolonna vojta,

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jindika l-żerijiet.

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U l-karattru DEL se punch kolonna sħiħa ta 'toqob

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permezz tejp tiegħek.

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Bħala riżultat, inti tista 'tuża l-karattru DEL li jitħassar

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informazzjoni.

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Immaġina teħid ta 'vot elezzjoni mimlija-out u mbagħad

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ippanċjar kollha toqob unpunched.

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>> Inti tinvalida l-vot għaliex dan huwa impossibbli li

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tgħid x'inhuma l-voti oriġinali kienu.

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Filwaqt li l-karattru DEL għadu jintuża huwa l-moderna

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Ħassar ewlenin, il-karattru null beda jiġi użat bħala l-

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karattru terminazzjoni ta 'sekwenzi C u

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xi formati oħra ta 'data.

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Inti tista 'taf il-karattru żero backslash,

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peress li kif aħna jirrappreżentaw bil-miktub.

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Allura lura għall-mejda ASCII tagħna.

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Wara l-ewwel karattri kontroll 32 jidħlu l-95

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karattri printable.

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>> Hemm koppja deċiżjonijiet jibred disinn li jiswew

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jitkellem dwar hawn.

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L-ewwel, il-karattri ċifra deċimali, żero permezz ta 'disa,

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jikkorrispondu għan-numri 48 permezz 57, li jidher

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tispikkax sakemm aħna nħarsu lejn in-numri 48 permezz 57

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miktuba fl-notazzjoni binarja.

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Jekk nagħmlu dan, allura naraw li l-ċifri karattru,

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żero, jikkorrispondi għal 0110000, 1 mapep għall 0110001, tnejn biex

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0110010, u l-bqija.

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Ara l-mudell?

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Kull karattru ċifri huwa fassal biex korrispondenti tiegħu

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ekwivalenti fil-notazzjoni binarju, prefissi bil 011.

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Issa jmiss, tinnota li l-ittri majjuskoli ta 'kulur tibda fil 65,

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ma uppercase A, iżda l-ittri lowercase

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ma jibda qabel 97.

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Allura hemm 32-ispazji bejniethom.

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Dan jidher stramb.

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Huma biss 26 ittri fil-alfabett.

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>> Għaliex maqsuma minnhom up bħal din?

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Għal darb'oħra, jekk inħarsu lejn ir-rappreżentazzjonijiet ta 'żewġ fibri, nistgħu

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tara mudell.

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Uppercase A huwa rappreżentat minn 1000001, u zghar a hija

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rappreżentat minn 1100001.

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Uppercase B huwa rappreżentat minn 1000010, u b zghar huwa

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rappreżentat minn 1100010.

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Tista 'tgħidli x'inhu għaddej hawn?

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Il-ftit li l-tieni mix-xellug, fiż-żewġ l-

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minn ħamsa, għall-pożizzjoni 32ths, huwa 0 għall kollha tal-uppercase

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ittri, u 1 għal kulħadd ta 'l-ittri lowercase.

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>> Dan ifisser konverżjoni minn uppercase zghar sa, u

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viċi versa, hija kwistjoni ta 'flip daqsxejn sempliċi.

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Allura li iwassalna għall-aħħar tat-tabella ASCII.

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Tista 'taħseb ta' xi ħaġa li aħna stajt minsija?

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Ukoll, dak dwar il-enye Spanjol, jew il-

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Grieg jew Ċirilliku alfabeti?

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U kif madwar Ċiniż karattri?

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Hemm ħafna li kien tħalliet barra mill ASCII.

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Madankollu, ieħor Unicode istandard jissejjaħ kien

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żviluppati biex ikopru kollha ta 'dawn

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karattri u ħafna aktar.

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>> Imma dak suġġett għall-ieħor żmien.

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Jisimni Nate Hardison.

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Dan huwa CS50.