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>> [Daqq ta mużika]

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DAVID J. Malan: Kull dritt.

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Dan huwa CS50, u dan
hija t-tmiem tal-Ġimgħa Erba.

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U wieħed mis-suġġetti llum
hija li tal-forensiċi diġitali,

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l-arti ta 'rkupru informazzjoni.

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U fil-fatt, anki jekk
int fil-midst

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dritt issa tal-Paċi fi Three
u tbegħid, ġimgħa d-dieħla,

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l-enfasi se tkun fuq
preċiżament dan id-dominju.

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>> Allura wieħed mill-impjiegi coolest I qatt
kellhom kien lura fl-iskola gradwati,

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I meta kien qed jaħdem għall-popolazzjonijiet lokali
Middlesex County District Attorney tal

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uffiċċju, forensika tagħmel xogħol.

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Allura essenzjalment, il Massachusetts
Pulizija Stat, f'okkażjoni,

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meta jaħdmu fuq il-każijiet se
jġibu affarijiet simili hard drives

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u floppy disks u
karti tal-memorja u simili.

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U dawn se jgħadduhom
lili u mentor tiegħi,

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u l-għan tagħna kien li ssib evidenza,
jekk kienx hemm xi, fuq dawn il-mezzi.

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Glimpses Issa, inti tista raw
din id-dinja tal-forensiċi

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fil-midja, TV u films.

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Imma l-impjieg kelli, u
daresay li dinja,

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mhuwiex pjuttost simili inti tara dan.

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Ejja tagħti ħarsa lejn dak
inti ħadthom probabbilment jidhru.

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[Daqq ta 'video]

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OK.

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Issa, ejja tikseb ħarsa tajba lejn inti.

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>> [Daqq ta mużika]

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>> -Hold Dan.

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Mexxi dik lura.

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>> -Wait Minuta.

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Mur dritt.

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-Hemm.

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Jiffriżaw dik.

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Full-iskrin.

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>> OK.

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Jiffriżaw dik.

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-Tighten Up fuq li, se inti?

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>> -Vector Fl fuq dak
Guy mill-rota lura.

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>> -Zoom Fl-dritt hawn fuq dan il-post.

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>> -Bil L-apparat dritt, il-
image jistgħu jiġu mkabbra u inċiżiv.

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>> Liema-li?

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>> -Hija S programm titjib.

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>> -Jista Inti ċar li up kwalunkwe?

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>> -I Ma jafux.

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Ejja ittejjeb dan.

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>> -Enhance Taqsima A6.

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I msaħħa l-dettall, and--

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-I Think hemm biżżejjed biex itejbu.

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Jgħadduha lill-iskrin tiegħi.

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>> -I Msaħħa r-riflessjoni fil-għajn tagħha.

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-Let S imexxu dan permezz
video titjib.

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>> -Edgar, Inti tista ttejjeb dan?

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>> Hang fuq.

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>> -I've Ilhom jaħdmu fuq din ir-riflessjoni.

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>> Riflessjoni ta 'xi ħadd -Hemm tal.

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>> -Reflection.

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-Hemm S riflessjoni tal-wiċċ tar-raġel.

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>> Riflessjoni -Il!

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-Hemm L riflessjoni.

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-Zoom Fuq il-mera.

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Tista 'tara riflessjoni.

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>> -Jista Inti jtejbu l-immaġini minn hawn?

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-Jista Inti ittejjeb dan?

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-Jista Inti ittejjeb dan?

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-Jista Aħna ittejjeb dan?

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-Jista Inti ittejjeb dan?

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-Hold Fuq it-tieni.

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I ser itejbu.

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-Zoom Fl fuq il-bieb.

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-Times 10.

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-Zoom.

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-Move Fil.

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-Aktar.

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-Wait, Stop.

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-Stop.

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-Pause Dan.

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Dawwar us 75 gradi
madwar il-vertikali, jekk jogħġbok.

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>> -Stop.

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Mur lura għall-parti
dwar il-bieb għal darb'oħra.

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>> -Got Enhancer immaġni li jistgħu Bitmap?

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>> -Maybe Nistgħu nużaw l Singh Pradeep
metodu biex tara fil-twieqi.

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>> -Il Software huwa l-istat ta 'l-arti.

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>> -Il Eigenvalue huwa off.

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>> -Bil-Dritt
kombinazzjoni ta 'algorithms--

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>> Meħuda illuminazzjoni -He tal
algoritmi għal-livell li jmiss,

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u nista jużawhom biex
jsaħħu din ritratt.

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>> Lock fuq u tkabbar l-assi-z.

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>> -Enhance.

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Tittejjeb.

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-Enhance.

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-Freeze U jtejbu.

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[END daqq ta 'video]

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DAVID J. Malan: Allura dawn huma
kliem kollha, imma dawn ma kienux

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użat fil-sentenzi korrett.

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U fil-fatt fil-futur, kwalunkwe ħin,
jekk jogħġbok, inti tisma xi ħadd jgħid l-kelma,

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"Ittejjeb," chuckle biss ftit.

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Għaliex meta inti tipprova biex ittejjeb,
per eżempju, dan huwa dak li jiġri.

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>> Allura hawnhekk ritratt sabiħ ħafna.

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Dan huwa Daven CS50 stess.

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U jissoponi li aħna riedu
tiffoka fuq il-Twinkle fl-għajnejn tiegħu,

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jew l-riflessjoni tal-
Guy ħżiena li kienet b'mod ċar

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maqbud mill-kameras tas-sigurtà.

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Dan huwa dak li jiġri meta
inti zoom fl fuq xbieha li

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għandha biss numru finit
ta 'bits assoċjati magħha.

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>> Dan huwa dak li inti se tikseb.

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U fil-fatt, fl-għajnejn Daven tal
huwa iżda erba, forsi sitt pixels

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li jikkomponu eżattament dak
kien glimmering hemmhekk.

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Allura Problema Set Erba finalment se jkollhom
inti tesplora din id-dinja, partikolarment

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min-natura ta 'xi ħaġa
nitolbu i file / o, fejn

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i / o huwa biss mod fancy ta '
qal input u output.

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>> Allura s'issa, kollha ta 'l-interazzjonijiet
aħna kellna ma 'kompjuter

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kienu ġeneralment bil tiegħek
keyboard u l-iskrin,

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iżda mhux daqshekk mal-hard disk,
jew iffrankar ta 'fajls lil hinn mill-dawk li inti

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yourself jiktbu.

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Programmi tiegħek s'issa jkollhom
ma kien joħloq, u l-iffrankar,

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u l-aġġornament fajls tagħhom stess.

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>> Ukoll, x'hemm fajl?

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Ukoll, xi ħaġa bħal JPEG.

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Din hija immaġni inti tista
għandhom jew upload biex Facebook,

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jew tara kullimkien fuq il-web.

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Tabilħaqq, li ritratt aħna biss
raw ta Daven kien JPEG.

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U x'hemm interessanti
dwar fajls simili JPEGs

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huwa li jkunu jistgħu jiġu identifikati,
tipikament, minn ċerti mudelli ta 'bits.

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>> Fi kliem ieħor, dak huwa li
jiddistingwi JPEG minn GIF

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minn Ping minn Word
dokument ta 'xi fajl Excel?

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Ukoll, huwa biss differenti
mudelli ta 'bits.

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U dawk mudelli differenti huma
normalment fil-bidu ta 'dawn il-fajls.

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>> Allura li meta l-kompjuter tiegħek tiftaħ Word
doc, jew meta kompjuter tiftaħ JPEG,

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jidher tipikament fil-
ewwel diversi bits fil-fajl.

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U jekk huwa jirrikonoxxi mudell,
jgħid, oh, din hija immaġni.

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Let me juru li
l-utent bħala grafika.

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Jew, oh, dan qisu doc ​​Word.

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Let me juru lill-utent bħala esej.

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>> Allura per eżempju, JPEGs,
jirriżulta, huma

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pjuttost sofistikati
taħt il-barnuża.

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Iżda l-ewwel tliet bytes fil aktar minn darba kull
JPEG tibda bil dawn it-tliet numri.

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Allura byte żero, wieħed, u tnejn huma, fil-
aktar minn darba kull JPEG, 255, allura n-numru

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216, allura n-numru 255.

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>> U dak li inti ser tkun kapaċi
biex tibda tagħmel ġimgħa d-dieħla

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huwa attwalment poking taħt
il-barnuża ta 'fajls simili JPEGs

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u bħal fajls Bitmap, u tara
x'hemm dejjem kien hemm sakemm

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kif inti kont qed tuża kompjuter.

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>> Imma x'hemm ma jkunx hemm tipikament
miktub bħal numri deċimali bħal dan.

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Xjenzjati tal-kompjuter ma
tendenza li jitkellmu fil deċimali.

150
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Huma ma verament jitkellmu fil binarja.

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Tipikament, meta rridu
li jesprimu numri,

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aħna attwalment jużaw hexadecimal,
li inti tista 'recall

153
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minn, ngħidu aħna, Problem Set
Wieħed, li kkontestat

154
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inti biex jaħsbu dwar sistema differenti.

155
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>> Aħna, naturalment, huma familjari
bi deċimali, żero permezz disa.

156
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Aħna tkellimna dwar binarja.

157
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U aħna ma verament ikollhom
għall-użu li ħafna hawn

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fuq barra, għaliex kompjuters se jużaw dak.

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Iżda programmaturi se ħafna
spiss, imma mhux dejjem,

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jużaw hexadecimal, li ifisser biss
għandek 16-ittri fil alfabett tiegħek,

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kif oppost għal tnejn jew 10.

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>> Allura kif taħseb li għodd sa ogħla
minn disa f'hexadecimal?

163
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Inti tmur 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
a, b, c, d, e, f, biss billi konvenzjoni.

164
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Imma x'hemm importanti hu li kull
minn dawn huwa simbolu wieħed.

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M'hemm l-ebda 10.

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M'hemm l-ebda 11, per se, għax kull
ta 'ċifri diġitali tiegħek, eżatt bħal fil-deċimali

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u eżatt bħal fil binarja, għandhom biss
jkun karattru wieħed, b'konvenzjoni.

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>> Allura li allura huwa l-alfabett li għandna
għad-dispożizzjoni tagħna għal hexadecimal.

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Allura dak li ma JPEG look like jekk inti
kellhom jiktbu out dawk l-ewwel tlieta

170
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bytes mhux bħala informazzjoni, iżda,
per eżempju, bħala hexadecimal?

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U għaliex hija hex anki dak kollu li utli?

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>> Well, ħarsa lejn eżempju.

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Mela jekk nikteb l-bits li
jirrappreżentaw dawn numbers-- deċimali

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dan jista 'jkun ftit Rusty
issa minn ftit ġimgħat lura,

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iżda l-waħda xellug u l-
dritt wieħed huma pjuttost faċli.

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255 kien in-numru akbar aħna
jista 'jirrappreżenta bi tmien bits.

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Kien dawk kollha.

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Allura l-unika waħda li kemmxejn
interessanti huwa l-waħda tan-nofs.

179
00:06:21,320 --> 00:06:24,700
U jekk inti tip ta 'do l-
matematika, inti ser jiġi dedott li, tabilħaqq,

180
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dak il-mudell ta 'wieħed u
żerijiet tirrappreżenta 216.

181
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Mela ejja biss jistipulaw għall
issa li dawn huma korretti.

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Iżda għaliex dan huwa interessanti?

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>> Well, byte, naturalment, huwa tmien bits.

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U jirriżulta li jekk taħseb
ta 'byte bħala żewġ biċċiet ta' erba 'bits,

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bħal dan.

186
00:06:39,500 --> 00:06:41,000
Let me biss żid xi spazju.

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Allura qabel, wara.

188
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Stajt biss miżjud xi spazju abjad
f'ġieħ viżwalizzazzjoni hawnhekk.

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Kif tista aħna issa jirrappreżentaw in,
jiġifieri, hexadeċimali kull quad ta 'bits,

190
00:06:51,840 --> 00:06:52,880
kull sett ta 'erba' bits?

191
00:06:52,880 --> 00:06:56,420
>> Allura per eżempju, fuq ix-xellug
issa, aħna għandna 1111 fil binarja.

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X'inhu dak in-numru fil-deċimali,
jekk inti tagħmel l-matematika?

193
00:07:00,420 --> 00:07:03,780
Inti għandek l-dawk post, il-post twos,
il-fours post, u l-post eights.

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>> UDJENZA: 15.

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00:07:04,341 --> 00:07:05,340
DAVID J. Malan: Huwa 15.

196
00:07:05,340 --> 00:07:08,340
Mela jekk nagħmlu tmien plus erba
flimkien ma 'tnejn plus wieħed, irridu jiksbu 15.

197
00:07:08,340 --> 00:07:11,790
So I tista 'tikteb isfel 15 hawn taħt
1111, imma l-punt kollu hawnhekk

198
00:07:11,790 --> 00:07:13,190
huwa hexadecimal, mhux Deċimali.

199
00:07:13,190 --> 00:07:17,310
Allura minflok kitba fl-15, 1-5,
Jien ser jikteb li fl hex,

200
00:07:17,310 --> 00:07:22,311
li jekk taħseb lura, jekk għandek
żero permezz f, x'inhu 15 se tkun?

201
00:07:22,311 --> 00:07:22,810
UDJENZA: f.

202
00:07:22,810 --> 00:07:24,434
DAVID J. Malan: Għalhekk jirriżulta li l f.

203
00:07:24,434 --> 00:07:29,140
U inti tista 'taħdem li minn billi qal,
ukoll, jekk huwa 10, imbagħad OK, f huwa 15.

204
00:07:29,140 --> 00:07:33,250
Allura fil-fatt, nistgħu jikteb
dan l-istess sett ta 'numri kif f f.

205
00:07:33,250 --> 00:07:35,750
U mbagħad jekk nagħmlu daqsxejn ta 'matematika,
aħna ser jiġi dedott li dan huwa d.

206
00:07:35,750 --> 00:07:38,650
Tmien huwa pjuttost faċli, għaliex aħna
jkollhom wieħed fil-post eights.

207
00:07:38,650 --> 00:07:40,620
U mbagħad, aħna għandna koppja aktar f f'S.

208
00:07:40,620 --> 00:07:44,669
>> Allura dak bnedmin tendenza li tagħmel permezz tal-konvenzjoni
meta jużaw hexadecimal huwa huma biss

209
00:07:44,669 --> 00:07:47,710
tikteb din ftit aktar konċiż,
jeħles ta 'ħafna ta' dak l-ispazju abjad.

210
00:07:47,710 --> 00:07:50,890
U biss li tkun super ċara li
qarrejja li dan huwa hexadecimal,

211
00:07:50,890 --> 00:07:54,670
il-konvenzjoni sempliċi fost
bnedmin qed tikteb żero

212
00:07:54,670 --> 00:07:58,000
x, li m'għandha l-ebda tifsira oħra
minn identifikatur viżwali ta ',

213
00:07:58,000 --> 00:07:59,590
hawn taqa 'numru hex.

214
00:07:59,590 --> 00:08:04,210
>> U mbagħad, inti tpoġġi l-żewġ numri, f
f f'dan il-każ, allura d a, imbagħad f f.

215
00:08:04,210 --> 00:08:06,700
Allura qasir storja twila,
hexadecimal biss tendenza

216
00:08:06,700 --> 00:08:11,990
li jkun utli għax kull wieħed tagħha
ċifri, żero permezz f, perfettament linji

217
00:08:11,990 --> 00:08:13,880
up bil-mudell ta 'erba' bits.

218
00:08:13,880 --> 00:08:18,080
>> Mela jekk għandek żewġ numri hexadecimal,
żero permezz F, għal darb'oħra u għal darb'oħra,

219
00:08:18,080 --> 00:08:20,256
li jagħtik perfettament
tmien bits jew byte wieħed.

220
00:08:20,256 --> 00:08:22,380
Allura hu għalhekk li għandha tendenza li
jkun konvenzjonalment utli.

221
00:08:22,380 --> 00:08:24,990
M'hemm l-ebda intellettwali
kontenut verament lil hinn minn dak,

222
00:08:24,990 --> 00:08:27,010
għajr utilità attwali tagħha.

223
00:08:27,010 --> 00:08:29,310
>> Issa JPEGs mhumiex l-unika
fajl formati għall-grafika.

224
00:08:29,310 --> 00:08:33,230
Inti tista 'tfakkar li hemm
files bħal dan fid-dinja,

225
00:08:33,230 --> 00:08:34,830
inqas minn ftit snin lura.

226
00:08:34,830 --> 00:08:37,580
>> Allura dan kien effettivament
installat fil-Windows XP

227
00:08:37,580 --> 00:08:39,960
fuq miljuni ta 'PCs madwar id-dinja.

228
00:08:39,960 --> 00:08:43,000
U dan kien fajl Bitmap, BMP.

229
00:08:43,000 --> 00:08:47,690
U fajl Bitmap, kif tkun taf tara li jmiss
ġimgħa, ifisser biss mudell ta 'tikek,

230
00:08:47,690 --> 00:08:51,710
pixels kif dawn qed imsejħa,
mappa fuq bits, verament.

231
00:08:51,710 --> 00:08:55,160
>> Allura x'hemm interessanti, għalkemm,
dwar dan il-format fajl, BMP, huwa

232
00:08:55,160 --> 00:08:58,590
li taħtha il-barnuża, dan
għandha aktar minn biss tliet bytes

233
00:08:58,590 --> 00:09:01,020
li jikkomponu header tagħha, hekk
li jitkellmu, l-ewwel ftit gdim.

234
00:09:01,020 --> 00:09:03,330
Hija fil-fatt jistenna ftit
ikkumplikat ewwel daqqa t'għajn.

235
00:09:03,330 --> 00:09:04,704
U tkun taf tara dan fil-P sett.

236
00:09:04,704 --> 00:09:06,810
U jkollna xi ħaġa
out partikolari ta 'dan issa

237
00:09:06,810 --> 00:09:10,720
ma jkunx daqshekk importanti, bħala biss il-fatt
li fil-bidu ta 'kull Bitmap

238
00:09:10,720 --> 00:09:13,823
fajl, format grafika,
hemm mazz sħiħ ta 'numri.

239
00:09:13,823 --> 00:09:14,980

240
00:09:14,980 --> 00:09:16,720
>> Issa Microsoft, il-
awtur ta 'dan il-format,

241
00:09:16,720 --> 00:09:18,820
tendenza li jsejħu dawk
l-affarijiet mhux ints u Chars

242
00:09:18,820 --> 00:09:22,259
u sufruni iżda kliem u d
kliem u twal u bytes.

243
00:09:22,259 --> 00:09:23,800
Allura dawn qed biss tipi differenti ta 'dejta.

244
00:09:23,800 --> 00:09:25,170
Huma qed ismijiet differenti
għall-istess ħaġa.

245
00:09:25,170 --> 00:09:26,740
Imma inti taf tara li fil Set Erba P.

246
00:09:26,740 --> 00:09:31,450
>> Iżda din hija biss li jgħidu li jekk bniedem
double-klikks xi fajl BMP fuq tiegħu

247
00:09:31,450 --> 00:09:35,015
jew hard drive tagħha, u tiftaħ tieqa
up juri lilu jew lilha li l-immaġni,

248
00:09:35,015 --> 00:09:38,500
li ġara minħabba li l-operattiva
sistema preżumibbilment ndunat mhux biss

249
00:09:38,500 --> 00:09:41,460
l-estensjoni fajl BMP
fl-isem fajl,

250
00:09:41,460 --> 00:09:45,010
iżda wkoll il-fatt li hemm xi
konvenzjoni għall-mudell ta 'bits

251
00:09:45,010 --> 00:09:47,490
fil-bidu nett
ta dan il-fajl Bitmap.

252
00:09:47,490 --> 00:09:50,270
>> Imma ejja issa jiffokaw fuq
tali file kkumplikata,

253
00:09:50,270 --> 00:09:52,120
iżda minflok fuq xi ħaġa bħal din.

254
00:09:52,120 --> 00:09:55,190
Ejja ngħidu hawn fil gedit, I
biss ikollhom l-bidu

255
00:09:55,190 --> 00:09:57,070
ta 'programm li pjuttost sempliċi.

256
00:09:57,070 --> 00:09:58,860
Stajt ltqajna xi jinkludi top up.

257
00:09:58,860 --> 00:10:02,120
# Jinkludu "structs.h" Issa stajt ltqajna iżda
I ser terga 'lura għal dik fil-mument.

258
00:10:02,120 --> 00:10:03,974
Iżda din hija utli għal issa.

259
00:10:03,974 --> 00:10:05,890
Allura dan huwa programm
li għaddej biex jimplimentaw

260
00:10:05,890 --> 00:10:07,335
bħall-database tar-Reġistratur.

261
00:10:07,335 --> 00:10:09,710
Allura database ta 'studenti,
u kull student fid-dinja

262
00:10:09,710 --> 00:10:13,190
għandha isem u dar u probabbilment xi
Jittieħed oħra, iżda aħna ser jżommha sempliċi.

263
00:10:13,190 --> 00:10:15,140
Kull student għandha isem u dar.

264
00:10:15,140 --> 00:10:17,700
>> Mela jekk jien ridt li jiktbu
programm li l-għan fil-ħajja

265
00:10:17,700 --> 00:10:19,860
kien biss li jtenni mill-
żero fuq sa tlieta,

266
00:10:19,860 --> 00:10:22,070
jekk hemm tliet studenti
fil-Harvard University.

267
00:10:22,070 --> 00:10:25,350
U jien biss trid li tikseb, bl-użu GetString,
isem u d-dar ta 'kull student,

268
00:10:25,350 --> 00:10:26,600
u mbagħad biss print dawk out.

269
00:10:26,600 --> 00:10:28,630
>> Dan huwa tip simili Week
Wieħed, Żewġ Week Jittieħed issa,

270
00:10:28,630 --> 00:10:30,810
fejn I nur die għal
loop jew xi ħaġa bħal dik.

271
00:10:30,810 --> 00:10:34,500
U nixtieq li sejħa GetString ftit
drabi, u mbagħad jistampaw f ftit drabi.

272
00:10:34,500 --> 00:10:37,340
Allura kif tista 'nagħmel dan, għalkemm,
meta kemm isem u dar

273
00:10:37,340 --> 00:10:39,070
huma involuti għal kull student?

274
00:10:39,070 --> 00:10:42,830
>> Allura l-ewwel istint tiegħi jista
jkun li tagħmel xi ħaġa bħal din.

275
00:10:42,830 --> 00:10:49,620
I jista ewwel ngħid, ukoll, jagħtu me,
jgħidu, firxa ta 'spag imsejħa ismijiet.

276
00:10:49,620 --> 00:10:51,530
U jien ma tridx hardcode tliet hawn.

277
00:10:51,530 --> 00:10:53,064
What do I tixtieq li tqiegħed hemmhekk?

278
00:10:53,064 --> 00:10:55,730
Allura STUDENTI, għaliex dan huwa biss
kostanti ddikjarat fil-quċċata,

279
00:10:55,730 --> 00:10:57,860
biss hekk I ma jkollhom hardcode
tlieta fil-postijiet multipli.

280
00:10:57,860 --> 00:11:00,859
Dan il-mod, I tista 'bidla f'post wieħed,
u din taffettwa bidla kullimkien.

281
00:11:00,859 --> 00:11:04,470
U mbagħad, I tista 'tagħmel
string djar STUDENTI.

282
00:11:04,470 --> 00:11:10,250
>> U issa, I tista 'tagħmel xi ħaġa simili
għall (i int = 0; i <STUDENTI; i ++.

283
00:11:10,250 --> 00:11:14,390
So jien ittajpjar malajr, iżda dan huwa
probabbilment sintassi familjari issa.

284
00:11:14,390 --> 00:11:17,030
>> U issa, dan kien aktar riċenti.

285
00:11:17,030 --> 00:11:22,890
Jekk I tixtieq li tqiegħed fil-i-th
isem istudent, I think I do dan.

286
00:11:22,890 --> 00:11:26,480
U mbagħad, mhux ismijiet
iżda djar parentesi i.

287
00:11:26,480 --> 00:11:29,930
I do dan, GetString, u ħallieh
me jmorru lura u tiffissa din il-linja.

288
00:11:29,930 --> 00:11:30,430
Jaqblu?

289
00:11:30,430 --> 00:11:31,200
Ma naqbilx?

290
00:11:31,200 --> 00:11:32,366
Mhuwiex ħafna faċli għall-utent.

291
00:11:32,366 --> 00:11:33,890
I ma qal lill-utent x'għandek tagħmel.

292
00:11:33,890 --> 00:11:36,520
>> Imma issa, jekk I wkoll
riedu aktar tard, ejja

293
00:11:36,520 --> 00:11:40,060
jiġifieri, jistampa dawn l-affarijiet
out-- hekk Todo aktar tard.

294
00:11:40,060 --> 00:11:42,330
Jien ser jagħmlu aktar
this-- dan forsi jiġifieri

295
00:11:42,330 --> 00:11:45,970
implimentazzjoni korretta ta '
jkollna l-ismijiet u djar, tliet

296
00:11:45,970 --> 00:11:48,870
minnhom totali ta 'kull, minn utent.

297
00:11:48,870 --> 00:11:51,280
>> Imma dan mhux disinn tajjeb ħafna, id-dritt?

298
00:11:51,280 --> 00:11:55,220
X'jiġri jekk student ikollu mhux biss l-isem
u dar, iżda wkoll numru ta 'identifikazzjoni,

299
00:11:55,220 --> 00:11:57,770
u numru tat-telefon,
u l-indirizz email,

300
00:11:57,770 --> 00:12:00,280
u forsi home page, u
forsi Twitter manku,

301
00:12:00,280 --> 00:12:03,730
u kull numru ta 'dettalji oħra
assoċjat ma 'student jew persuna,

302
00:12:03,730 --> 00:12:04,610
b'mod aktar ġenerali.

303
00:12:04,610 --> 00:12:07,720
Kif aħna jibdew żid
funzjonalità għal dan il-programm?

304
00:12:07,720 --> 00:12:14,080
>> Well, I jħossu bħall-eħfef mod jista
jkun li tagħmel xi ħaġa simili, ejja ngħidu,

305
00:12:14,080 --> 00:12:16,490
int STUDENTI ids.

306
00:12:16,490 --> 00:12:18,380
So I tista 'tpoġġi IDs kollha tagħhom fil hemmhekk.

307
00:12:18,380 --> 00:12:22,240
U mbagħad, għal xi ħaġa
bħal numri tat-telefon,

308
00:12:22,240 --> 00:12:24,400
M'inix ċert kif
jirrappreżenta dak għadha biss.

309
00:12:24,400 --> 00:12:30,280
Mela ejja imorru quddiem u biss sejħa
dan Twitters STUDENTI, li

310
00:12:30,280 --> 00:12:33,550
hija ftit stramba, but--
u mazz aktar oqsma.

311
00:12:33,550 --> 00:12:36,360
>> Stajt bdew b'mod effettiv
kopja u paste hawn.

312
00:12:36,360 --> 00:12:39,416
U dan se jikber pretty
dens pretty malajr, right?

313
00:12:39,416 --> 00:12:42,290
Ma Ikun sbieħ jekk kien hemm
fid-dinja struttura data magħrufa

314
00:12:42,290 --> 00:12:45,600
mhux bħala int jew string, imma xi ħaġa
livell ogħla, l-estrazzjoni, hekk

315
00:12:45,600 --> 00:12:47,570
biex jitkellmu, magħrufa bħala student?

316
00:12:47,570 --> 00:12:50,220
C ma jiġu mal built-in
funzjonalità għall-istudenti,

317
00:12:50,220 --> 00:12:52,260
imma dak jekk jien ridt li jagħtih din?

318
00:12:52,260 --> 00:12:55,640
>> Ukoll, jirriżulta, jien ser
tiftaħ fajl imsejjaħ structs.h hawn,

319
00:12:55,640 --> 00:12:57,090
u inti tista 'tagħmel eżattament dan.

320
00:12:57,090 --> 00:12:58,290
U aħna qed tmur biex tibda tagħmel dan issa.

321
00:12:58,290 --> 00:13:01,490
U taħtha l-hood tal Set Tliet P,
inti stajt diġà qed tagħmel dan issa.

322
00:13:01,490 --> 00:13:05,920
M'hemm l-ebda ħaġa bħal g rect jew
a g ovali fil-lingwa ta 'programmar C.

323
00:13:05,920 --> 00:13:10,570
>> Folks fil Stanford implimentati dawk
tipi ta 'data bl-użu dan l-approċċ hawnhekk,

324
00:13:10,570 --> 00:13:13,900
tiddikjara data ġdida tagħhom stess
tipi jużaw keyword ġdida

325
00:13:13,900 --> 00:13:16,744
imsejħa Struct u ieħor
wieħed imsejjaħ typedef.

326
00:13:16,744 --> 00:13:19,660
U fil-fatt, anki jekk l-sintassi
jistenna ftit differenti minn għalf

327
00:13:19,660 --> 00:13:23,550
Rajna qabel, fl
prinċipju, huwa super sempliċi.

328
00:13:23,550 --> 00:13:25,297
>> Dan ifisser biss "jiddefinixxi tip."

329
00:13:25,297 --> 00:13:27,255
Li għaddej biex tkun
istruttura, u struttura

330
00:13:27,255 --> 00:13:29,400
huwa biss bħal kontenitur
għal affarijiet multipli.

331
00:13:29,400 --> 00:13:31,780
U li l-istruttura li qed jiġri
li jkollhom string imsejjaħ isem,

332
00:13:31,780 --> 00:13:33,210
u string imsejjaħ house.

333
00:13:33,210 --> 00:13:37,520
U ejja sejħa, biss għall-konvenjenza,
dan l-istudent kollu struttura tad-data.

334
00:13:37,520 --> 00:13:40,320
>> Allura l-mument ikollok biex
l-virgola, inti għandek issa

335
00:13:40,320 --> 00:13:43,280
maħluqa data tiegħek stess
tip imsejħa student

336
00:13:43,280 --> 00:13:46,420
li issa stands flimkien int,
u float, u char, u string,

337
00:13:46,420 --> 00:13:50,270
u g rect, u g ovali, u kull numru
ta 'affarijiet oħra nies ivvintat.

338
00:13:50,270 --> 00:13:53,340
>> Allura x'hemm utli dwar dan
issa huwa li jekk immur lura

339
00:13:53,340 --> 00:13:57,430
li Struct 0 u jintemm dan
implimentazzjoni, li I kiteb

340
00:13:57,430 --> 00:14:02,080
bil-quddiem hawnhekk, avviż li kollha
tal-messiness inevitabbli li

341
00:14:02,080 --> 00:14:05,490
kienet waslet biex tibda jiġri bħala I miżjuda
numri tat-telefon u twitters u kollha

342
00:14:05,490 --> 00:14:07,370
dawn l-affarijiet oħra
definizzjoni ta 'student,

343
00:14:07,370 --> 00:14:11,810
issa huwa konċiż jitgeżwer
bħala wieħed biss firxa ta 'studenti.

344
00:14:11,810 --> 00:14:15,500
>> U kull wieħed minn dawk l-istudenti issa
għandha affarijiet multipli ġewwa ta 'dan.

345
00:14:15,500 --> 00:14:16,930
Allura li biss tħalli mistoqsija waħda.

346
00:14:16,930 --> 00:14:19,700
Kif tista 'tikseb fil-isem,
u l-dar, u l-ID,

347
00:14:19,700 --> 00:14:21,640
u kwalunkwe ħaġa oħra huwa
ġewwa tal-istudent?

348
00:14:21,640 --> 00:14:22,930
Super sempliċi, kif ukoll.

349
00:14:22,930 --> 00:14:25,730
Sintassi New, iżda idea sempliċi.

350
00:14:25,730 --> 00:14:29,239
>> Inti sempliċiment indiċi fil-firxa,
kif għamilna aħħar ġimgħa u dan.

351
00:14:29,239 --> 00:14:31,030
U x'hemm b'mod ċar l-
biċċa ġdida ta 'sintassi?

352
00:14:31,030 --> 00:14:32,590

353
00:14:32,590 --> 00:14:35,880
Just., Li tfisser "go ġewwa l-
istruttura u x-qasam msejħa

354
00:14:35,880 --> 00:14:39,030
isem, jiksbu l-qasam imsejħa dar,
jiksbu l-qasam imsejħa istudent. "

355
00:14:39,030 --> 00:14:41,940
>> Għalhekk fl Set Tliet P, jekk int
għadhom jaħdmu fuq li,

356
00:14:41,940 --> 00:14:44,020
u folks aktar għadhom
huma, jirrealizzaw li kif inti

357
00:14:44,020 --> 00:14:46,130
tibda tuża affarijiet simili
g rects u G ovali

358
00:14:46,130 --> 00:14:50,201
u affarijiet oħra li ma jidhirx li
ġejjin minn Week Zero, One, jew tnejn,

359
00:14:50,201 --> 00:14:52,950
jirrealizzaw li dan għaliex Stanford
iddikjarata xi tipi ġodda ta 'dejta.

360
00:14:52,950 --> 00:14:56,160
>> U fil-fatt, dan huwa eżattament dak li aħna ser
do, kif ukoll, fir Set Erba P, meta

361
00:14:56,160 --> 00:14:59,880
nibdew biex jittrattaw ma 'affarijiet
bħal stampi, bitmaps, u aktar.

362
00:14:59,880 --> 00:15:02,882
Allura li jinsab biss teaser u
mudell mentali għal dak li huwa li ġejjin.

363
00:15:02,882 --> 00:15:04,590
Issa, I procrastinated
daqsxejn dalgħodu.

364
00:15:04,590 --> 00:15:09,560
I kien tip ta 'kurjużi biex tara dak
l-wallpaper Microsoft attwalment

365
00:15:09,560 --> 00:15:10,310
Dehra illum.

366
00:15:10,310 --> 00:15:15,200
U jirriżulta xi ħadd fl-2006
attwalment marret għal kważi preċiżament

367
00:15:15,200 --> 00:15:19,210
l-istess post li r-ritratt fir-realtà
dak qisu li dawn il-jiem.

368
00:15:19,210 --> 00:15:21,380
Il-qasam issa huwa xi ftit overgrown.

369
00:15:21,380 --> 00:15:24,850
>> Allura jitkellem issa 'immaġini,
ejja iġibu lura Daven hawn

370
00:15:24,850 --> 00:15:26,890
fuq l-iskrin u Nicholas,
u biss infakkarkom

371
00:15:26,890 --> 00:15:30,540
li jekk inti tixtieq li jingħaqdu magħna għall-ikel
dan Ġimgħa, ras għal URL tas-soltu tagħna

372
00:15:30,540 --> 00:15:31,440
hawn.

373
00:15:31,440 --> 00:15:33,530
>> Għalhekk, fejn ma we leave off nhar it-Tnejn?

374
00:15:33,530 --> 00:15:35,140
Aħna introdotti din il-problema, id-dritt?

375
00:15:35,140 --> 00:15:37,610
Dan kien apparentement a korretta
implimentazzjoni ta 'tpartit,

376
00:15:37,610 --> 00:15:40,460
fejn inti tieħu żewġ ints,
wieħed imsejjaħ, wieħed imsejjaħ b,

377
00:15:40,460 --> 00:15:44,130
tpartit minnhom, bħad Laura għamlet hawn
fuq il-palk mal-ħalib u l-ilma,

378
00:15:44,130 --> 00:15:46,820
bl-użu ta temporanju
varjabbli, jew tazza vojta,

379
00:15:46,820 --> 00:15:50,540
sabiex inkunu tista 'tpoġġi b fil u fl
b mingħajr ma tagħmel mess ta 'affarijiet.

380
00:15:50,540 --> 00:15:51,560
We użati varjabbli.

381
00:15:51,560 --> 00:15:52,870
Huwa sejjaħ temp.

382
00:15:52,870 --> 00:15:55,520
>> Imma dak kien il-fundamentali
problema ma dan il-kodiċi nhar it-Tnejn?

383
00:15:55,520 --> 00:15:57,700

384
00:15:57,700 --> 00:15:58,870
Liema kienet l-problema hawn?

385
00:15:58,870 --> 00:16:00,106

386
00:16:00,106 --> 00:16:00,605
Yeah.

387
00:16:00,605 --> 00:16:01,970
>> UDJENZA: Huwa jieħu aktar spazju.

388
00:16:01,970 --> 00:16:04,719
>> DAVID J. Malan: Jieħu up aktar
ispazju, għaliex jien jużaw varjabbli,

389
00:16:04,719 --> 00:16:05,400
u li OK.

390
00:16:05,400 --> 00:16:07,300
Dan huwa veru, imma jien
se ngħid li l-OK.

391
00:16:07,300 --> 00:16:10,030
Huwa biss 32 bits fil-grand
iskema ta 'affarijiet, hekk mhux big deal.

392
00:16:10,030 --> 00:16:10,655
Ħsibijiet oħra?

393
00:16:10,655 --> 00:16:12,572
UDJENZA: Huwa biss tpartit
il-varjabbli lokalment.

394
00:16:12,572 --> 00:16:13,571
DAVID J. Malan: Eżattament.

395
00:16:13,571 --> 00:16:15,090
Hija biss tpartit-varjabbli lokalment.

396
00:16:15,090 --> 00:16:18,173
Minħabba kwalunkwe ħin inti sejħa function--
meta kelli l-trejs mill Annenberg

397
00:16:18,173 --> 00:16:19,840
aħħar darba, inti għandek prinċipali fuq il-qiegħ.

398
00:16:19,840 --> 00:16:23,560
Hekk kif inti sejħa funzjoni msejħa
tpartit, tpartit ma jiksbu x uy,

399
00:16:23,560 --> 00:16:24,400
il-valuri oriġinali.

400
00:16:24,400 --> 00:16:26,392
X'jagħmel get swap, ma aħna jsostnu?

401
00:16:26,392 --> 00:16:27,100
Udjenza: Kopji.

402
00:16:27,100 --> 00:16:28,090
DAVID J. Malan: Allura kopji tagħhom.

403
00:16:28,090 --> 00:16:31,120
Allura jiġrilha wieħed u tnejn, jekk inti
mfakkra l-eżempju mill-aħħar darba,

404
00:16:31,120 --> 00:16:34,730
iżda kopja ta 'wieħed u tnejn
li huma skambjati b'suċċess.

405
00:16:34,730 --> 00:16:38,550
Iżda sfortunatament fl-aħħar,
dawk il-valuri għadhom l-istess.

406
00:16:38,550 --> 00:16:41,880
Allura nistgħu naraw dan mal tagħna
ħabib ġdid, wieħed jittama GDB,

407
00:16:41,880 --> 00:16:45,180
li inti jew il-TFS u l Ca jkollhom
ġew gwida li inti lejn kif ġej.

408
00:16:45,180 --> 00:16:51,210
>> Allura l-ebda irtirar swap jistenna like-- ejja
jiftħu this-- tidher bħal dan.

409
00:16:51,210 --> 00:16:54,160
Aħna initialized x għal wieħed, y għal tnejn.

410
00:16:54,160 --> 00:16:55,620
Kieku mazz ta 'print f'S.

411
00:16:55,620 --> 00:16:58,080
Iżda mbagħad, is-sejħa ċavetta
hawn kien li tpartit, li

412
00:16:58,080 --> 00:17:00,260
huwa eżattament l-kodiċi we
biss raw mument ilu.

413
00:17:00,260 --> 00:17:03,180
Liema hija korretta fl-ewwel
t'għajn, iżda funzjonalment,

414
00:17:03,180 --> 00:17:06,800
dan il-programm ma taħdimx, għaliex
dan ma tpartit permanenti xuy.

415
00:17:06,800 --> 00:17:10,190
>> Mela ejja ara dan, warm quick
up hawn ma GDB, a ./noswap.

416
00:17:10,190 --> 00:17:11,867

417
00:17:11,867 --> 00:17:15,200
A mazz ta 'informazzjoni kbira li
I ser teħles minn mal Kontroll L għal issa.

418
00:17:15,200 --> 00:17:17,516
U issa, jien se
imorru quddiem u run.

419
00:17:17,516 --> 00:17:19,349
U sfortunatament, li
ma kienet li utli.

420
00:17:19,349 --> 00:17:22,355
Hija dam il-programm ġewwa ta 'dan
programm imsejjaħ GDB, debugger,

421
00:17:22,355 --> 00:17:23,730
iżda hija ma let me poke madwar.

422
00:17:23,730 --> 00:17:26,229
>> Allura kif nista attwalment nieqaf
eżekuzzjoni ġewwa dan il-programm?

423
00:17:26,229 --> 00:17:27,410

424
00:17:27,410 --> 00:17:28,329
Allura break.

425
00:17:28,329 --> 00:17:32,340
UI jistgħu jiksru fuq kwalunkwe
numru, wieħed, 10, 15 linja.

426
00:17:32,340 --> 00:17:35,530
Imma I tista 'wkoll break simbolikament
billi qal break prinċipali.

427
00:17:35,530 --> 00:17:38,980
U li għaddej biex jistabbilixxu pawża
punt, apparentement fil-linja 16 prinċipali.

428
00:17:38,980 --> 00:17:40,050
U fejn huwa linja 16?

429
00:17:40,050 --> 00:17:42,960
Ejja ħa mmorru sal-kodiċi
u jitla 'sa noswap.

430
00:17:42,960 --> 00:17:46,930
U fil-fatt, linja 16 hija l-
ewwel ħafna fil-programm.

431
00:17:46,930 --> 00:17:52,130
>> Allura issa, jekk I jimxi 'l quddiem u t-tip
run dan iż-żmien, Ikteb, dan waqfa qasira.

432
00:17:52,130 --> 00:17:53,080
Mela ejja poke madwar.

433
00:17:53,080 --> 00:17:55,716
Stampa x-- għaliex huwa x żero?

434
00:17:55,716 --> 00:17:56,705

435
00:17:56,705 --> 00:17:57,830
U jinjora l-sinjal dollaru.

436
00:17:57,830 --> 00:17:59,725
Li jinsab biss għal fancier
użu tal-programm.

437
00:17:59,725 --> 00:18:00,780

438
00:18:00,780 --> 00:18:03,140
Għaliex hija x żero fil-mument?

439
00:18:03,140 --> 00:18:03,640
Yeah.

440
00:18:03,640 --> 00:18:07,061
>> UDJENZA: Huwa waqfa qasira dritt qabel
linja 16, ma attwalment fuq il-linja 16.

441
00:18:07,061 --> 00:18:08,060
DAVID J. Malan: Eżattament.

442
00:18:08,060 --> 00:18:11,630
GDB, kontumaċja, kien waqfa qasira
eżekuzzjoni eżatt qabel il-linja 16.

443
00:18:11,630 --> 00:18:14,820
Għalhekk ma jkunx eżegwit, li
ifisser x hija ta 'xi valur mhux magħruf.

444
00:18:14,820 --> 00:18:17,150
U aħna ltqajna xxurtjati li huwa
xi ħaġa nadif bħal żero.

445
00:18:17,150 --> 00:18:20,310
Allura issa jekk I tip li jmiss,
issa esegwiti 16.

446
00:18:20,310 --> 00:18:22,000
Huwa stennija għalija li tesegwixxi 17.

447
00:18:22,000 --> 00:18:23,400
Let me imorru quddiem u print x.

448
00:18:23,400 --> 00:18:24,094
Huwa wieħed.

449
00:18:24,094 --> 00:18:25,260
Let me imorru quddiem u y istampar.

450
00:18:25,260 --> 00:18:26,176
X'għandi I tara issa?

451
00:18:26,176 --> 00:18:27,660

452
00:18:27,660 --> 00:18:28,560
>> UDJENZA: [inaudible]

453
00:18:28,560 --> 00:18:29,165
>> DAVID J. Malan: A louder ftit.

454
00:18:29,165 --> 00:18:30,040
>> UDJENZA: [inaudible]

455
00:18:30,040 --> 00:18:30,537

456
00:18:30,537 --> 00:18:32,120
DAVID J. Malan: Mhux pjuttost konsensus.

457
00:18:32,120 --> 00:18:34,760
Allura iva, naraw xi valur żibel.

458
00:18:34,760 --> 00:18:37,862
Issa, y hija 134514064 hemmhekk.

459
00:18:37,862 --> 00:18:39,320
Ukoll, huwa biss xi valur żibel.

460
00:18:39,320 --> 00:18:41,350
Programm My użi RAM
għal skopijiet differenti.

461
00:18:41,350 --> 00:18:42,350
Hemm funzjonijiet oħra.

462
00:18:42,350 --> 00:18:44,040
Nies oħra kiteb ġewwa kompjuter tiegħi.

463
00:18:44,040 --> 00:18:46,789
Allura dawk bits ġew użati għall-
valuri oħra, u dak li jien jaraw

464
00:18:46,789 --> 00:18:49,470
huwa l-fdalijiet ta 'xi
użu minn qabel ta 'dak l-memorja.

465
00:18:49,470 --> 00:18:53,350
>> Allura l-ebda big deal, għaliex malli
tip I kif jmiss u mbagħad jistampaw y,

466
00:18:53,350 --> 00:18:55,640
huwa initialized li
il-valur li nixtieq.

467
00:18:55,640 --> 00:18:57,400
Allura issa, ejja imorru quddiem ftit aktar mgħaġġel.

468
00:18:57,400 --> 00:18:58,540
N għal li jmiss.

469
00:18:58,540 --> 00:18:59,570
Ejja nagħmlu dan mill-ġdid.

470
00:18:59,570 --> 00:19:00,530
Ejja nagħmlu dan mill-ġdid.

471
00:19:00,530 --> 00:19:02,404
Imma ma rridx li hit
hawnhekk, għaliex jekk I

472
00:19:02,404 --> 00:19:05,110
trid tara x'inhu għaddej ġewwa
tal tpartit, x'inhu l-kmand?

473
00:19:05,110 --> 00:19:05,520
>> UDJENZA: passi.

474
00:19:05,520 --> 00:19:06,436
>> DAVID J. Malan: passi.

475
00:19:06,436 --> 00:19:09,800
Allura dan passi me fi
funzjoni, minflok fuqha.

476
00:19:09,800 --> 00:19:12,270
U issa, huwa ftit cryptic
onestament, iżda din hija biss

477
00:19:12,270 --> 00:19:14,581
javżak me jien fil-linja 33 issa.

478
00:19:14,581 --> 00:19:15,580
U ejja tagħmel dan mill-ġdid.

479
00:19:15,580 --> 00:19:16,080
Temperatura Stampa.

480
00:19:16,080 --> 00:19:17,129

481
00:19:17,129 --> 00:19:20,170
Valur Żibel, negattiv dan iż-żmien,
iżda li biss għadu valur żibel.

482
00:19:20,170 --> 00:19:22,810
Mela ejja do jmiss, temperatura print.

483
00:19:22,810 --> 00:19:27,130
Huwa initialized għal 1, li
kien il-valur ta 'x, aka a.

484
00:19:27,130 --> 00:19:29,110
>> Issa, fejn huma tagħna u X li ġejjin minn?

485
00:19:29,110 --> 00:19:32,510
Ukoll, avviż fil prinċipali, aħna
imsejħa dawn x valuri u y.

486
00:19:32,510 --> 00:19:34,740
Aħna mbagħad għadda minnhom li tpartit kif ġej.

487
00:19:34,740 --> 00:19:37,010
X daħal ewwel, y comma.

488
00:19:37,010 --> 00:19:40,020
U mbagħad, swap tista jsejħulhom xuy.

489
00:19:40,020 --> 00:19:42,630
Iżda għaċ-ċarezza, huwa
ssejjaħ minnhom u b.

490
00:19:42,630 --> 00:19:45,970
Iżda aub issa ser ikunu
kopji ta 'xuy, rispettivament.

491
00:19:45,970 --> 00:19:50,660
>> Mela jekk jien jmorru lura għall GDB, temperatura
issa huwa wieħed u issa huwa wieħed.

492
00:19:50,660 --> 00:19:56,130
Imma jekk I do jmiss u issa do print
a, a diġà ġie mċaqalqa.

493
00:19:56,130 --> 00:20:00,030
Il-ħalib ġie jitferra 'l-ewwel
ħġieġ meraq tal-larinġ li, jew viċi versa.

494
00:20:00,030 --> 00:20:04,750
>> U jekk jien tagħmel li jmiss darb'oħra, u issa
jekk I jistampa bħala verifika sanità,

495
00:20:04,750 --> 00:20:07,687
a huwa għadu tnejn, iżda b issa huwa wieħed.

496
00:20:07,687 --> 00:20:08,770
Franchement, huwa għadu hemm.

497
00:20:08,770 --> 00:20:10,670
I ma 'kura dak temperatura hu.

498
00:20:10,670 --> 00:20:16,850
Imma malli I issa tip, ejja ngħidu,
tkompli tmur lura, issa jien fl-aħħar

499
00:20:16,850 --> 00:20:17,480
il-programm.

500
00:20:17,480 --> 00:20:20,730
U sfortunatament, x hija
xorta waħda u y għadu tnejn.

501
00:20:20,730 --> 00:20:22,272
>> Allura dak li kien l-utilità ta 'GDB hemmhekk?

502
00:20:22,272 --> 00:20:23,980
Hija ma għinni jiffissaw
il-problema per se,

503
00:20:23,980 --> 00:20:26,265
iżda nisperaw għinni
jifhimha bit-twettiq

504
00:20:26,265 --> 00:20:30,000
li iva, il-loġika tiegħi huwa dritt, iżda
kodiċi tiegħi mhix finalment li

505
00:20:30,000 --> 00:20:31,450
impatt permanenti.

506
00:20:31,450 --> 00:20:34,570
Allura li hija problema aħna qed
ser issa isolvu llum.

507
00:20:34,570 --> 00:20:37,870
>> Imma ejja nikseb hemm permezz ta 'dan.

508
00:20:37,870 --> 00:20:39,230
String huwa gidba.

509
00:20:39,230 --> 00:20:41,860
Hija, wisq, mhux tip data
li teżisti fl C. Huwa

510
00:20:41,860 --> 00:20:44,750
kien sinonimu għal xi
żmien għal xi ħaġa oħra,

511
00:20:44,750 --> 00:20:47,300
u nistgħu jiżvelaw li kif ġej.

512
00:20:47,300 --> 00:20:53,282
>> Let me imorru quddiem u tiftaħ
programm imsejjaħ jqabblu-0.

513
00:20:53,282 --> 00:20:56,240
U minflok tip dan wieħed out,
aħna ser tibda biex jimxu permezz tal-kodiċi

514
00:20:56,240 --> 00:20:58,040
I diġà kiteb, imma
huwa biss ftit linji.

515
00:20:58,040 --> 00:20:59,570
Allura dan huwa jqabblu-0.

516
00:20:59,570 --> 00:21:02,380
U l-ewwel ħaġa li qed nagħmel
huwa jkollna linja tat-test.

517
00:21:02,380 --> 00:21:05,610
>> Imma liema avviż jien
tagħmel għall-ewwel darba.

518
00:21:05,610 --> 00:21:07,910
X'inhu differenti b'mod ċar dwar il-linja 21?

519
00:21:07,910 --> 00:21:10,020

520
00:21:10,020 --> 00:21:11,402
Attwalment, stenna minuta.

521
00:21:11,402 --> 00:21:12,110
Dan huwa tnejn kopja.

522
00:21:12,110 --> 00:21:13,568
Dan lanqas ma huwa l-programm dritt.

523
00:21:13,568 --> 00:21:14,780
Kull dritt, twissija ISPOILER.

524
00:21:14,780 --> 00:21:16,890
Kull dritt, hekk qatt f'moħħhom dik.

525
00:21:16,890 --> 00:21:18,520
Dik hija l-risposta għal mistoqsija futur.

526
00:21:18,520 --> 00:21:21,450
>> Hawnhekk huwa iqabblu-0, u jien
dwar li tikseb linja ta 'test.

527
00:21:21,450 --> 00:21:22,435
Tal Program ferm aktar sempliċi.

528
00:21:22,435 --> 00:21:23,560
Allura dan huwa sempliċi.

529
00:21:23,560 --> 00:21:28,070
Dan huwa simili One Week, Week Żewġ Jittieħed
fil-mument. string s = GetString.

530
00:21:28,070 --> 00:21:29,700
Issa, jien ngħid mill-ġdid stabbiliti hawn.

531
00:21:29,700 --> 00:21:31,830
string t = GetString.

532
00:21:31,830 --> 00:21:35,300
U mbagħad, l-aħħar ħaġa f'dan
programm, kif ismu jissuġġerixxi,

533
00:21:35,300 --> 00:21:37,090
huwa jien ser jippruvaw biex iqabblu lilhom.

534
00:21:37,090 --> 00:21:40,709
>> Mela jekk i, l-ewwel string,
ugwali = t, allura jien

535
00:21:40,709 --> 00:21:42,250
se ngħid inti tip l-istess ħaġa.

536
00:21:42,250 --> 00:21:44,291
Else, jien ser ngħid
inti tip affarijiet differenti.

537
00:21:44,291 --> 00:21:45,880
Mela ejja tiġbor u tmexxi dan il-programm.

538
00:21:45,880 --> 00:21:48,481
Sabiex tagħmel jqabblu żero.

539
00:21:48,481 --> 00:21:48,980
Jistenna tajba.

540
00:21:48,980 --> 00:21:50,490
Ebda żbalji kumpilazzjoni.

541
00:21:50,490 --> 00:21:52,386
>> Let me imorru quddiem issa
u t-tip ./compare-0.

542
00:21:52,386 --> 00:21:55,230

543
00:21:55,230 --> 00:21:59,220
Let me imorru quddiem u jgħidu xi ħaġa
: Daven u xi ħaġa: Rob.

544
00:21:59,220 --> 00:22:00,450
U jien tip affarijiet differenti.

545
00:22:00,450 --> 00:22:01,250
S'issa, hekk tajjeb.

546
00:22:01,250 --> 00:22:02,680
Programm jidher li tkun korretta.

547
00:22:02,680 --> 00:22:03,880
>> Imma ejja run mill-ġdid.

548
00:22:03,880 --> 00:22:05,800
Say xi ħaġa: Gabe.

549
00:22:05,800 --> 00:22:07,140
Say xi ħaġa: Gabe.

550
00:22:07,140 --> 00:22:08,520

551
00:22:08,520 --> 00:22:09,020
Kull dritt.

552
00:22:09,020 --> 00:22:10,851
Maybe I hit l-ispazju bar
jew xi ħaġa funky.

553
00:22:10,851 --> 00:22:11,600
Ejja nagħmlu dan mill-ġdid.

554
00:22:11,600 --> 00:22:13,020
Allura Zamyla.

555
00:22:13,020 --> 00:22:13,970

556
00:22:13,970 --> 00:22:14,470
Zamyla.

557
00:22:14,470 --> 00:22:15,740

558
00:22:15,740 --> 00:22:17,330
Affarijiet differenti.

559
00:22:17,330 --> 00:22:19,430
Allura dak li qed jiġri?

560
00:22:19,430 --> 00:22:23,200
>> Allura aħna għandna dawn iż-żewġ linji ta '
kodiċi, GetString qed jissejjaħ darbtejn.

561
00:22:23,200 --> 00:22:25,760
U mbagħad, jien sempliċiment
jippruvaw iqabblu s u t.

562
00:22:25,760 --> 00:22:28,370
Imma dak li verament mbagħad qed jiġri?

563
00:22:28,370 --> 00:22:31,180
Well, kalligrafija tiegħi waslet biex
biċċier dan l-eżempju kemmxejn.

564
00:22:31,180 --> 00:22:34,630
U ejja attwalment tarmi
dan up hawn fuq, kif ukoll.

565
00:22:34,630 --> 00:22:37,390

566
00:22:37,390 --> 00:22:45,712
>> Allura għandna linja bħal
string s = GetString.

567
00:22:45,712 --> 00:22:48,295
Allura dak sempliċement l-ewwel
linja interessanti minn dak il-programm.

568
00:22:48,295 --> 00:22:49,920

569
00:22:49,920 --> 00:22:52,974
Imma dak li dan il-ħin kien
tmur fuq taħt il-barnuża?

570
00:22:52,974 --> 00:22:55,890
Ukoll, fuq il-naħa tax-xellug ġenb huwa string,
li hija xi tip ta 'varjabbli,

571
00:22:55,890 --> 00:22:56,785
u huwa msejjaħ s.

572
00:22:56,785 --> 00:23:00,019
So I taf li dan qed tuża memorja,
jew RAM, fil-kompjuter tiegħi b'xi.

573
00:23:00,019 --> 00:23:02,060
So I m ser astratt
jiġbed li bħala kwadru.

574
00:23:02,060 --> 00:23:04,820
32 bits, jirriżulta, iżda
aktar fuq li fil-futur.

575
00:23:04,820 --> 00:23:06,410
U mbagħad, x'inhu għaddej hawn?

576
00:23:06,410 --> 00:23:08,700
>> Well, GetString ovvjament
gets string mill-utent.

577
00:23:08,700 --> 00:23:11,360
U GetString ltqajna
Zamyla jew Gabe jew Daven.

578
00:23:11,360 --> 00:23:14,640
Mela ejja jagħżlu l-ewwel
ta 'dawk, li kien Daven.

579
00:23:14,640 --> 00:23:19,174
Allura effettiv, liema GetString ltqajna
me f'dik ewwel każ kien-D a-vs-e-n.

580
00:23:19,174 --> 00:23:22,690

581
00:23:22,690 --> 00:23:25,045
U mbagħad, x'iktar għamilt
it tagħti me segretament?

582
00:23:25,045 --> 00:23:25,920
UDJENZA: [inaudible]

583
00:23:25,920 --> 00:23:28,720
DAVID J. Malan: Yeah,
l / 0 jew null karattru.

584
00:23:28,720 --> 00:23:30,550
Għalhekk effettivament tatni string.

585
00:23:30,550 --> 00:23:34,550
Iżda aħna diġà jafu minn qabel
jistenna li string huwa biss firxa

586
00:23:34,550 --> 00:23:37,895
ta 'karattri, u huwa mitmum minn
dan il-karattru sentinella speċjali, / 0.

587
00:23:37,895 --> 00:23:39,220

588
00:23:39,220 --> 00:23:42,310
>> Imma jekk dan huwa minnu
u dan huwa kwadru,

589
00:23:42,310 --> 00:23:44,160
dan huwa b'mod ċar rettangolu ħafna akbar.

590
00:23:44,160 --> 00:23:46,830
U fil-fatt, dan huwa,
I jsostnu, biss 32 bits.

591
00:23:46,830 --> 00:23:49,500
U dan huwa b'mod ċar aktar minn 32
bits, għaliex dan huwa probabbilment

592
00:23:49,500 --> 00:23:51,583
tmienja plus tmienja plus tmienja
plus tmienja plus tmienja,

593
00:23:51,583 --> 00:23:53,320
biss minħabba bytes fil ASCII.

594
00:23:53,320 --> 00:23:57,030
Kif l-Heck aħna se tajbin
Daven fis din il-kaxxa ftit hawn?

595
00:23:57,030 --> 00:23:59,880
>> Ukoll, dak li huwa GetString fatt jagħmlu?

596
00:23:59,880 --> 00:24:03,680
Ukoll, dan grid hawn tirrappreżenta
memorja tal-kompjuter tiegħi jew RAM.

597
00:24:03,680 --> 00:24:07,564
Mela ejja arbitrarju ngħid li jekk
kull wieħed minn dawn jirrappreżenta byte,

598
00:24:07,564 --> 00:24:09,730
allura nistgħu naħsbu ta 'kull
byte bħala li għandhom l-indirizz,

599
00:24:09,730 --> 00:24:13,830
bħal 33 Oxford Street, jew 34
Oxford Street, jew 35 Oxford Street.

600
00:24:13,830 --> 00:24:16,700
>> Hekk biss bħal djar ikollhom indirizzi
u l-bini jkollhom indirizzi,

601
00:24:16,700 --> 00:24:19,810
so do bytes individwali ta '
memorja jkollhom indirizzi jew numri

602
00:24:19,810 --> 00:24:21,042
li jidentifika unikament minnhom.

603
00:24:21,042 --> 00:24:22,000
Issa, dan huwa arbitrarju.

604
00:24:22,000 --> 00:24:25,370
Iżda biex jżommha sempliċi, jien ser
użu hexadecimal biss b'konvenzjoni,

605
00:24:25,370 --> 00:24:28,200
iżda l-0x mezzi xejn oħra
minn "dan huwa hexadecimal."

606
00:24:28,200 --> 00:24:31,030
u jien ser jsostnu li l-
"D" jispiċċa fil Byte Wieħed fil-memorja.

607
00:24:31,030 --> 00:24:34,210
>> I ltqajna xejn għaddejjin fil
memorja, hekk Daven ltqajna l-ewwel post

608
00:24:34,210 --> 00:24:35,509
fil Byte One.

609
00:24:35,509 --> 00:24:36,800
Dan, imbagħad, se tkun 0x2.

610
00:24:36,800 --> 00:24:37,831

611
00:24:37,831 --> 00:24:38,705
Dan se 0x3.

612
00:24:38,705 --> 00:24:39,840

613
00:24:39,840 --> 00:24:41,800
Dan se jkun 0x4.

614
00:24:41,800 --> 00:24:43,025
Dan se 0x5.

615
00:24:43,025 --> 00:24:44,025
Dan se jkun 0x6.

616
00:24:44,025 --> 00:24:45,560

617
00:24:45,560 --> 00:24:48,290
>> Imma ladarba inti tibda taħseb
dwar dak Nagħmlu l-kompjuter

618
00:24:48,290 --> 00:24:50,710
taħt il-barnuża,
inti tista 'tibda biex jiddeduċu

619
00:24:50,710 --> 00:24:54,960
kif inti, xi snin ilu, kieku
implimentaw C innifsu.

620
00:24:54,960 --> 00:24:58,360
X'inhu GetString probabbilment
returning-- minħabba li

621
00:24:58,360 --> 00:25:00,946
iħoss bhalu mhuwiex
jirritornaw Daven, per se,

622
00:25:00,946 --> 00:25:03,320
għaliex hu żgur mhux se
li jitwaħħal f'dan box-- ftit

623
00:25:03,320 --> 00:25:05,090
Allura x'inhi GetString probabbilment jirritorna?

624
00:25:05,090 --> 00:25:07,958

625
00:25:07,958 --> 00:25:08,920
>> UDJENZA: [inaudible]

626
00:25:08,920 --> 00:25:10,540
>> DAVID J. Malan: Il-lokazzjoni tal Daven.

627
00:25:10,540 --> 00:25:12,770
U huwa qed tagħmel dan
qatt peress One Week.

628
00:25:12,770 --> 00:25:16,150
Dak GetString huwa verament
jirritornaw mhix string, per se.

629
00:25:16,150 --> 00:25:17,780
Din kienet waħda mir-jinsab ftit abjad.

630
00:25:17,780 --> 00:25:22,520
Huwa jirritorna l-indirizz tal-
string fil-memorja, l-indirizz uniku.

631
00:25:22,520 --> 00:25:24,820
Daven jgħix fi 33 Oxford Street.

632
00:25:24,820 --> 00:25:29,310
Iżda aktar konċiż, Gavin jgħix
fil 0x1, Indirizz Numru Wieħed.

633
00:25:29,310 --> 00:25:32,280
>> Allura dak gets tpoġġi f'dan
kaxxa ftit imbagħad, tkun ċara,

634
00:25:32,280 --> 00:25:35,930
huwa biss l-indirizz ta 'dak string.

635
00:25:35,930 --> 00:25:38,110
Allura dan il-ħin, dan
ilu għaddej.

636
00:25:38,110 --> 00:25:41,650
Imma dak li din jagħti x'wieħed jifhem li
issa hija li jekk kollox i għandha

637
00:25:41,650 --> 00:25:44,710
huwa numru ġewwa ta 'dan, li l-
biex int tieqaf, l-programmer,

638
00:25:44,710 --> 00:25:47,970
milli jpoġġu kull numru fil
kwalunkwe varjabbli u biss jaqbeż

639
00:25:47,970 --> 00:25:49,080
għal dak blokki ta 'memorja?

640
00:25:49,080 --> 00:25:51,320
U fil-fatt, aħna ser tara
thats theddida ħin li jmiss.

641
00:25:51,320 --> 00:25:53,500
>> Iżda għal issa, dan iħoss insuffiċjenti.

642
00:25:53,500 --> 00:25:55,630
Jekk I say, nikseb me a
string, inti tagħti me Daven.

643
00:25:55,630 --> 00:25:57,230
Imma inti ma verament jagħtu me Daven.

644
00:25:57,230 --> 00:25:59,310
Kulma għandek tagħti me huwa l-indirizz Daven tal.

645
00:25:59,310 --> 00:26:04,310
Kif do I imbagħad jaf fiż-żgur
fejn Daven jibda u ends--

646
00:26:04,310 --> 00:26:07,140
l-istorja tal jkollna weird--
fejn Daven jibda u jispiċċa,

647
00:26:07,140 --> 00:26:10,435
u mbagħad, l-li jmiss
string fil-memorja jibda?

648
00:26:10,435 --> 00:26:11,520

649
00:26:11,520 --> 00:26:13,620
>> Ukoll, jekk int għoti
me-bidu ta 'Daven,

650
00:26:13,620 --> 00:26:17,230
essenzjalment, kif inkun naf
fejn it-tmiem ta 'ismu hu?

651
00:26:17,230 --> 00:26:20,550
Dan il-karattru null speċjali, li
huwa aktar u aktar importanti issa

652
00:26:20,550 --> 00:26:23,040
jekk kordi taħtha l-
hood huma sempliċiment identifikati

653
00:26:23,040 --> 00:26:25,820
unikament mill-post tagħhom fil-memorja.

654
00:26:25,820 --> 00:26:28,130
Allura dan il-ħin, li l-
dak li kien għaddej.

655
00:26:28,130 --> 00:26:32,470
>> Allura meta nħarsu issa fil
il-kodiċi hawn, jispjegaw

656
00:26:32,470 --> 00:26:35,790
jekk inti l-bug fil-linja 26.

657
00:26:35,790 --> 00:26:39,560
Għaliex hija Zamyla u Zamyla differenti?

658
00:26:39,560 --> 00:26:41,330
Għaliex hija Gabe u Gabe differenti?

659
00:26:41,330 --> 00:26:42,154
Yeah, fid-dahar.

660
00:26:42,154 --> 00:26:43,390
>> UDJENZA: Huma għandhom indirizzi differenti.

661
00:26:43,390 --> 00:26:45,931
>> DAVID J. Malan: Sempliċement minħabba
huma għandhom indirizzi differenti.

662
00:26:45,931 --> 00:26:48,820
Għaliex meta inti sejħa GetString
darb'oħra, li jiena ser tagħmel malajr hawn,

663
00:26:48,820 --> 00:26:52,870
jekk dan huwa l-tieni linja, spag
t, kif għamilt f'dak il-programm,

664
00:26:52,870 --> 00:26:55,030
ugwali sejħa oħra għall GetString.

665
00:26:55,030 --> 00:26:56,370

666
00:26:56,370 --> 00:26:58,670
Il-ħin li jmiss I call
GetString, jien ser

667
00:26:58,670 --> 00:27:00,190
biex tikseb blokki differenti ta 'memorja.

668
00:27:00,190 --> 00:27:02,220
>> GetString huwa permess
li titlob lill-operattiva

669
00:27:02,220 --> 00:27:03,800
sistema għall-memorja aktar u aktar.

670
00:27:03,800 --> 00:27:07,894
Huwa mhux se jerġa 'jintuża l-istess
sitt bytes kull wieħed ħin.

671
00:27:07,894 --> 00:27:09,810
Huwa ser tikseb ġdida
blokki ta 'memorja, li

672
00:27:09,810 --> 00:27:12,780
ifisser t hija se tikseb
xi valur ta 'hawn fuq.

673
00:27:12,780 --> 00:27:15,380
>> Allura meta I do i ugwali =
t, int ma jitqabblu

674
00:27:15,380 --> 00:27:17,880
D kontra dan u A kontra
dan u V kontra dan.

675
00:27:17,880 --> 00:27:19,588
Inti jqabbel dan
kontra dan, li

676
00:27:19,588 --> 00:27:24,020
franchement huwa useless-- pretty useful--
hija pjuttost inutli, minħabba li verament

677
00:27:24,020 --> 00:27:25,830
jimpurtaha fejn il-kordi huma fil-memorja?

678
00:27:25,830 --> 00:27:26,850
>> U fil-fatt, aħna ma.

679
00:27:26,850 --> 00:27:28,980
U aħna mhux qed tmur biex
jibdew partikolarment kura.

680
00:27:28,980 --> 00:27:34,180
Biss sal-punt li jistgħu jinqalgħu bugs
u theddid għas-sigurtà jistgħu jinqalgħu rieda

681
00:27:34,180 --> 00:27:36,100
aħna attwalment jibdew għall-kura dwar dan.

682
00:27:36,100 --> 00:27:37,230
Mela ejja tiffissa din il-problema.

683
00:27:37,230 --> 00:27:39,650
Jirriżulta, inti tiffissa lilha super sempliċiment.

684
00:27:39,650 --> 00:27:42,600
>> U ejja fil-fatt, qabel I
juru li għal darb'oħra, dak li kieku

685
00:27:42,600 --> 00:27:47,170
you do jekk fi klassi CS50,
u inti kellhom jimplimentaw

686
00:27:47,170 --> 00:27:48,600
paragun kontra żewġ kordi.

687
00:27:48,600 --> 00:27:51,440
Inti b'mod ċar ma tistax sempliċement tuża s ugwali = t.

688
00:27:51,440 --> 00:27:54,090
Iżda biss loġikament, kemm
kieku inti tqabbel din is-sekwenza

689
00:27:54,090 --> 00:27:56,370
kontra din is-sekwenza jużaw kodiċi C?

690
00:27:56,370 --> 00:27:56,880
Yeah.

691
00:27:56,880 --> 00:27:58,780
>> UDJENZA: Just jagħmlu l-
għall loop [inaudible]

692
00:27:58,780 --> 00:28:00,670

693
00:28:00,670 --> 00:28:01,670
DAVID J. Malan: Perfect.

694
00:28:01,670 --> 00:28:02,900
UDJENZA: [inaudible]

695
00:28:02,900 --> 00:28:03,310
DAVID J. Malan: Yeah.

696
00:28:03,310 --> 00:28:05,390
Just jużaw għal loop jew
filwaqt loop jew ikun x'ikun.

697
00:28:05,390 --> 00:28:08,710
Iżda biss tapplika l-idea bażika li jekk
dan huwa blokki ta 'memorja jew firxa

698
00:28:08,710 --> 00:28:11,590
u dan huwa, jtenni fuq
kemm fl-istess ħin.

699
00:28:11,590 --> 00:28:12,960
U biss jqabblu l-ittri.

700
00:28:12,960 --> 00:28:14,260
>> U inti ħadthom ltqajna biex tkun
ftit attenti, għaliex inti

701
00:28:14,260 --> 00:28:16,247
ma jridux finger wieħed
li jmorru passat l-oħra

702
00:28:16,247 --> 00:28:18,080
għaliex string wieħed huwa
itwal mill-oħra.

703
00:28:18,080 --> 00:28:21,380
Allura int tmur jridu sabiex jikkontrolla għal
dan il-valur speċjali fl-aħħar, null.

704
00:28:21,380 --> 00:28:24,017
Imma huwa verament, fil-
aħħar, sempliċi bħal dik.

705
00:28:24,017 --> 00:28:26,100
U franchement, aħna m'għandekx bżonn
biex jivvinta dik ir-rota.

706
00:28:26,100 --> 00:28:27,960
Hawnhekk huwa Version Żewġ.

707
00:28:27,960 --> 00:28:32,910
U dak li jien se ngħid hawnhekk hija li
minflok jitqabblu s ugwali = t,

708
00:28:32,910 --> 00:28:38,964
Jien minflok se ngħid, jekk string
paragun ta 'virgola s t ugwali = 0.

709
00:28:38,964 --> 00:28:40,130
Issa, dak li huwa string jqabblu?

710
00:28:40,130 --> 00:28:43,046
>> Jirriżulta, huwa funzjoni li
tiġi ma C, li l-iskop fil-ħajja

711
00:28:43,046 --> 00:28:44,650
huwa li jitqabblu żewġ kordi.

712
00:28:44,650 --> 00:28:48,300
U ħawwad jqabblu, jekk naqraw tagħha
paġna bniedem jew dokumentazzjoni jew CS50

713
00:28:48,300 --> 00:28:50,630
referenza, li se
sempliċiment jgħidlek li ħawwad

714
00:28:50,630 --> 00:28:55,730
jqabblu prospetti jew negattivi
Numru jew numru pożittiv jew żero,

715
00:28:55,730 --> 00:28:57,660
fejn zero ifisser li qed indaqs.

716
00:28:57,660 --> 00:28:58,570
>> Hekk biss konġettura.

717
00:28:58,570 --> 00:29:00,390
Liema jista jfisser jekk
ħawwad prospetti jqabblu

718
00:29:00,390 --> 00:29:02,110
valur negattiv jew il-valur pożittiv?

719
00:29:02,110 --> 00:29:02,785

720
00:29:02,785 --> 00:29:04,285
UDJENZA: Aktar minn jew inqas minn.

721
00:29:04,285 --> 00:29:05,570
DAVID J. Malan: Yeah,
akbar minn jew inqas minn.

722
00:29:05,570 --> 00:29:08,640
Mela jekk int riedu biex issolvi kollu
mazz ta 'kordi fil dictionary--

723
00:29:08,640 --> 00:29:12,975
kif aħna se eventwalment tistabbilixxi l-road--
funzjoni perfetta għall-użu potenzjalment,

724
00:29:12,975 --> 00:29:15,850
minħabba li għaddej biex tagħmel dan
paragun ta 'kordi għalik, u għid

725
00:29:15,850 --> 00:29:20,060
inti tagħmel jasal quddiem b, jew ma
b come qabel alfabetikament.

726
00:29:20,060 --> 00:29:21,490
Nistgħu nagħmlu eżattament dan.

727
00:29:21,490 --> 00:29:23,620
>> U avviż Jien għamilt waħda oħra
ħaġa f'dan l-eżempju.

728
00:29:23,620 --> 00:29:26,870
X'iktar nbidel ogħla
up f'dan funzjoni ewlenija?

729
00:29:26,870 --> 00:29:28,500

730
00:29:28,500 --> 00:29:29,350
Char *.

731
00:29:29,350 --> 00:29:31,150
U dan huwa dak gidba abjad ieħor.

732
00:29:31,150 --> 00:29:33,750
Dan il-ħin, meta inti stajt
ġie kitba string,

733
00:29:33,750 --> 00:29:38,350
aħna ġew segretament riskrittura
string bħala char * hekk li clang attwalment

734
00:29:38,350 --> 00:29:39,270
jifhem inti.

735
00:29:39,270 --> 00:29:42,450
>> Fi kliem ieħor, fil CS50.h
u kif aħna ser eventwalment tara,

736
00:29:42,450 --> 00:29:45,950
għamilna sinonimu imsejjaħ string
dak l-istess ħaġa bħat char *.

737
00:29:45,950 --> 00:29:49,910
U għal issa, biss jafu li l-
*, F'dan il-kuntest, għall-inqas,

738
00:29:49,910 --> 00:29:51,286
ifisser-indirizz.

739
00:29:51,286 --> 00:29:52,210
>> L-indirizz ta 'dak?

740
00:29:52,210 --> 00:29:56,390
Ukoll, il-fatt li għidt
char *, u mhux int * jew float *,

741
00:29:56,390 --> 00:30:00,820
ifisser li char * hija
l-indirizz ta 'char.

742
00:30:00,820 --> 00:30:06,770
Allura din il-kaxxa ftit hawn, aka
string, huwa verament ta 'tip char *,

743
00:30:06,770 --> 00:30:10,490
li huwa sempliċiment mezz fancy ta 'tgħid,
f'din il-kaxxa se jmorru indirizz.

744
00:30:10,490 --> 00:30:12,430
U dak li ma l-indirizz jirreferu għall?

745
00:30:12,430 --> 00:30:13,780
Apparentement, char.

746
00:30:13,780 --> 00:30:16,410
>> Iżda nistgħu assolutament
jkollhom int * u affarijiet oħra.

747
00:30:16,410 --> 00:30:20,790
Iżda għal issa, char * huwa verament l-aktar
sempliċi u waħda ta 'interess.

748
00:30:20,790 --> 00:30:23,310
Allura din il-problema li qed jiġri
jogħlew, għalkemm, għal darb'oħra.

749
00:30:23,310 --> 00:30:24,830
>> Ejja ngħidu I jiftħu dan il-programm.

750
00:30:24,830 --> 00:30:27,670
Ejja ara jekk issa nistgħu jbassru
x'hemm ħażin ma 'dan il-kodiċi.

751
00:30:27,670 --> 00:30:31,140
Allura f'dan il-programm, kopja-0, jien
se jmorru 'l quddiem u għal darb'oħra sejħa

752
00:30:31,140 --> 00:30:34,190
GetString u jaħżnu l-valur fl-i.

753
00:30:34,190 --> 00:30:38,800
>> U mbagħad, għaliex jien tagħmel dan,
biss bħala tfakkira minn ġimgħat passat?

754
00:30:38,800 --> 00:30:40,960
Aħna ma jgħidu li GetString
kultant prospetti null.

755
00:30:40,960 --> 00:30:42,793
Xi jfisser jekk
GetString prospetti null?

756
00:30:42,793 --> 00:30:45,040

757
00:30:45,040 --> 00:30:46,034
Xi ħaġa li marret ħażin.

758
00:30:46,034 --> 00:30:48,950
Huwa probabbilment tfisser il-sekwenza huwa wisq
big, out tal-kompjuter ta 'memorja.

759
00:30:48,950 --> 00:30:51,724
Dan jiġri super, super, super
rarament, iżda jista 'jiġri.

760
00:30:51,724 --> 00:30:53,890
Aħna rridu li jikkontrolla għal dan,
u li kollox li aħna qed tagħmel.

761
00:30:53,890 --> 00:30:57,910
>> Għaliex aħna ser tara issa, jekk inti ma
tibda iċċekkjar abitwalment għal affarijiet

762
00:30:57,910 --> 00:31:00,870
bħal null, inti tista
attwalment jibdew imorru

763
00:31:00,870 --> 00:31:03,106
indirizzi fil-memorja li huma invalidi.

764
00:31:03,106 --> 00:31:05,980
U int ser tibda inducing
aktar u aktar difetti segmentazzjoni.

765
00:31:05,980 --> 00:31:08,360
Jew fi Mac jew PC, just
jikkawżaw kompjuter li hang

766
00:31:08,360 --> 00:31:10,340
jew programm 'ffriżar, potenzjalment.

767
00:31:10,340 --> 00:31:14,930
>> Allura issa, I talba f'kopja-0.c, li jien
vais kopja dawn kordi permezz

768
00:31:14,930 --> 00:31:15,685
tal-linja 28.

769
00:31:15,685 --> 00:31:16,850

770
00:31:16,850 --> 00:31:18,750
U mbagħad, jien ser
li titlob fil-qiegħ

771
00:31:18,750 --> 00:31:21,430
hawnhekk li jien ser
jbiddel wieħed minnhom.

772
00:31:21,430 --> 00:31:22,330
>> Allura avviż dan.

773
00:31:22,330 --> 00:31:24,370
Jien ssejjaħ strlen tagħna ħabib antik.

774
00:31:24,370 --> 00:31:28,960
U biss jispjegaw bl-Ingliż
liema din il-linja 34 qed tagħmel?

775
00:31:28,960 --> 00:31:32,480
X'tagħmel t bracket 0
jirrappreżentaw fuq ix-xellug.

776
00:31:32,480 --> 00:31:32,980
Yeah.

777
00:31:32,980 --> 00:31:34,339
>> UDJENZA: L-ewwel karattru ta 't?

778
00:31:34,339 --> 00:31:35,880
DAVID J. Malan: L-ewwel karattru ta 't.

779
00:31:35,880 --> 00:31:36,379
Li dan.

780
00:31:36,379 --> 00:31:40,024
Ewwel karattru ta 't, nixtieq
li jassenja l-verżjoni uppercase

781
00:31:40,024 --> 00:31:41,190
ta 'l-ewwel karattru f't.

782
00:31:41,190 --> 00:31:43,200
Allura dan huwa kapitalizzazzjoni
l-ewwel ittra.

783
00:31:43,200 --> 00:31:46,340
U mbagħad, il-ħafna aħħar ħaġa I do
f'dan il-programm huwa nitlob hawn

784
00:31:46,340 --> 00:31:50,340
l-oriġinali, i, u hawnhekk l-kopja, t.

785
00:31:50,340 --> 00:31:54,610
>> Iżda bbażata fuq l-istorja aħna biss
qal dwar liema kordi verament huma,

786
00:31:54,610 --> 00:31:57,520
dak li hu linja 28 verament
tagħmel, u dak li huwa

787
00:31:57,520 --> 00:31:59,405
l-bug jirriżultaw għaddej
li tkun fuq l-iskrin?

788
00:31:59,405 --> 00:32:01,300

789
00:32:01,300 --> 00:32:03,500
>> Allura l-ewwel, l-ewwel domanda, 28.

790
00:32:03,500 --> 00:32:09,040
X'inhu = string t i verament tagħmel?

791
00:32:09,040 --> 00:32:16,430
Jekk għandna fuq il-naħa tax-xellug
ġenb hawn = string t s;

792
00:32:16,430 --> 00:32:19,400
li tagħti me kaxxa waħda
hawn u kaxxa waħda hawn.

793
00:32:19,400 --> 00:32:25,530
U jissoponi dan l-indirizz huwa 0x,
ejja ngħidu, 50 dan iż-żmien, b'mod arbitrarju.

794
00:32:25,530 --> 00:32:28,847
X'jagħmel = string t s
do taħt il-barnuża?

795
00:32:28,847 --> 00:32:30,340
>> UDJENZA: [inaudible]

796
00:32:30,340 --> 00:32:34,100
>> DAVID J. Malan: Taħżen l-memorja
jindirizzaw hemmhekk, sabiex 0x50 tmur hemmhekk.

797
00:32:34,100 --> 00:32:37,980
Allura jekk issa, I mur l-ewwel
karattru f't u uppercase dan,

798
00:32:37,980 --> 00:32:39,535
dak li jien effettivament jagħmlu biex i?

799
00:32:39,535 --> 00:32:41,300

800
00:32:41,300 --> 00:32:43,450
Ninsab verament tagħmel l-istess ħaġa, id-dritt?

801
00:32:43,450 --> 00:32:47,680
Għaliex jekk 0x50-- Indirizz u biss, I
m'għandhomx wisq spazju fuq il-bord hawn,

802
00:32:47,680 --> 00:32:51,750
iżda jassumi li dan huwa 0x50 stabbiliti hawn,
x'imkien fil-memorja tal-kompjuter tiegħi.

803
00:32:51,750 --> 00:32:55,825
>> U jien, per eżempju, Gabe
fl zghar hawn, bħal dan.

804
00:32:55,825 --> 00:32:57,120

805
00:32:57,120 --> 00:33:01,980
U għidt bracket t
0 gets kapitalizzat.

806
00:33:01,980 --> 00:33:04,860
Ukoll, t parentesi 0 hija
l-ewwel ittra f't.

807
00:33:04,860 --> 00:33:07,840
Allura ftit g va
jsiru G. big Iżda l-problema

808
00:33:07,840 --> 00:33:09,410
huwa, dak ma s wkoll il-punt li?

809
00:33:09,410 --> 00:33:10,300
>> UDJENZA: L-istess.

810
00:33:10,300 --> 00:33:11,841
>> DAVID J. Malan: L-istess ħaġa eżatt.

811
00:33:11,841 --> 00:33:16,342
Allura spjegazzjoni sempliċi forsi,
anki jekk il-sintassi hija ftit stramb.

812
00:33:16,342 --> 00:33:17,050
Mela ejja tagħmel dan.

813
00:33:17,050 --> 00:33:20,210
Make-kopja 0 u mbagħad ./copy-0.

814
00:33:20,210 --> 00:33:21,820

815
00:33:21,820 --> 00:33:24,110
Say xi ħaġa: Gabe.

816
00:33:24,110 --> 00:33:26,760
U sfortunatament, it-tnejn
minnhom issa ġew kapitalizzat,

817
00:33:26,760 --> 00:33:29,500
iżda għal dak sottostanti
raġuni li aħna qed sempliċiment

818
00:33:29,500 --> 00:33:32,350
issa jittrattaw indirizzi.

819
00:33:32,350 --> 00:33:36,470
>> Allura kif nistgħu jibdew
address-- no pun intended--

820
00:33:36,470 --> 00:33:39,270
kif nistgħu tibda tindirizza
din il-problema partikolari?

821
00:33:39,270 --> 00:33:44,400
Ukoll, fil-copy1.c, affarijiet sejrin
biex tikseb ftit aktar kumplikata.

822
00:33:44,400 --> 00:33:49,310
Imma nixtieq tippretendi
Soluzzjoni kunċettwalment sempliċi.

823
00:33:49,310 --> 00:33:50,852
>> Allura diffiċli biex jiksbu ewwel daqqa t'għajn.

824
00:33:50,852 --> 00:33:53,560
Mhux se tkun faċli għall-ewwel
ħin inti tip out, forsi,

825
00:33:53,560 --> 00:33:57,440
iżda jekk il-problema hija li
sempliċiment tagħmel = t i biss

826
00:33:57,440 --> 00:33:59,694
kopji-indirizz, liema,
ġdid jekk I tista 'pick fuqek,

827
00:33:59,694 --> 00:34:02,110
se tkun is-soluzzjoni
għal fatt ikkupjar string?

828
00:34:02,110 --> 00:34:04,906

829
00:34:04,906 --> 00:34:06,770
>> UDJENZA: Aħna ser probabbilment
tuża loop darb'oħra.

830
00:34:06,770 --> 00:34:06,890
>> DAVID J. Malan: Yeah.

831
00:34:06,890 --> 00:34:08,390
Allura aħna qed tmur biex bżonn loop darb'oħra.

832
00:34:08,390 --> 00:34:11,800
U għaliex jekk aħna tixtieq li kopja
string s fis string ieħor,

833
00:34:11,800 --> 00:34:14,120
aħna probabbilment tixtieq li tagħmel dan
karattru mill-karattru.

834
00:34:14,120 --> 00:34:17,199
Iżda l-problema hija, jekk
dan huwa oriġinarjament s,

835
00:34:17,199 --> 00:34:22,159
issa għandna bżonn biex tibda espliċitu
allokazzjoni memorja għal t.

836
00:34:22,159 --> 00:34:24,320
>> Fi kliem ieħor, ejja
tiġbed dan għall-aħħar darba.

837
00:34:24,320 --> 00:34:28,659
Jekk dan huwa string s = GetString.

838
00:34:28,659 --> 00:34:30,956

839
00:34:30,956 --> 00:34:32,455
U ejja tpoġġi dan up here, kif ukoll.

840
00:34:32,455 --> 00:34:36,639

841
00:34:36,639 --> 00:34:37,420
Dan huwa GetString.

842
00:34:37,420 --> 00:34:39,070

843
00:34:39,070 --> 00:34:43,860
U mbagħad, l-istampa għal xi ħaġa
bħal dik se tkun bħal qabel,

844
00:34:43,860 --> 00:34:44,360
g-a-b e / 0.

845
00:34:44,360 --> 00:34:47,294

846
00:34:47,294 --> 00:34:48,960
Li jistenna ftit xi ħaġa bħal din.

847
00:34:48,960 --> 00:34:53,650
U s għalhekk, nagħmlu sejħa dan 0x50,
u li għaddej biex tkun 51, 52.

848
00:34:53,650 --> 00:34:54,409
>> Allura dan huwa 0x50.

849
00:34:54,409 --> 00:34:55,679

850
00:34:55,679 --> 00:34:59,690
U mbagħad, I do string t.

851
00:34:59,690 --> 00:35:02,450
Fil-memorja, li jinsab biss se
tagħti me ftit kwadru bħal dan.

852
00:35:02,450 --> 00:35:04,080
Allura x'inhu l-pass ewlieni issa?

853
00:35:04,080 --> 00:35:09,870
Jekk I tixtieq li kopja s fis t, liema
vojt għandna bżonn biex timla hawn?

854
00:35:09,870 --> 00:35:12,050
Jew dak li għandna bżonn li
do fuq livell għoli?

855
00:35:12,050 --> 00:35:14,101

856
00:35:14,101 --> 00:35:14,600
Yeah?

857
00:35:14,600 --> 00:35:16,200

858
00:35:16,200 --> 00:35:17,020
Xi ħadd?

859
00:35:17,020 --> 00:35:17,690
Yeah.

860
00:35:17,690 --> 00:35:19,214
>> UDJENZA: Għandna bżonn li [inaudible].

861
00:35:19,214 --> 00:35:21,380
DAVID J. Malan: Yeah, aħna
bżonn timla dan il-vojt.

862
00:35:21,380 --> 00:35:24,340
I ma tista 'kopja u mbagħad
kapitalizzazzjoni isem Gabe tal

863
00:35:24,340 --> 00:35:28,120
sal I titlob lill-sistema operattiva
għall chunk ieħor ta 'memorja

864
00:35:28,120 --> 00:35:30,640
li l-inqas kemm kbar kif l-oriġinali.

865
00:35:30,640 --> 00:35:32,130
Allura li tħalli us bil-kwistjoni.

866
00:35:32,130 --> 00:35:36,080
>> Kif nista titlob lill-sistema operattiva ma
biss għal Pointer ftit sempliċi

867
00:35:36,080 --> 00:35:38,530
kif din tissejjaħ, ta
indirizz, l-Pointer ma

868
00:35:38,530 --> 00:35:40,980
għal ftit kaxxa sempliċi
bħal din tissejjaħ string?

869
00:35:40,980 --> 00:35:44,200
Kif nista titlob lill-operattiva
sistema għal blokki kbar ta 'memorja?

870
00:35:44,200 --> 00:35:48,430
S'issa, stajt biss gotten li back
indirettament billi ċċempel GetString.

871
00:35:48,430 --> 00:35:50,740
Allura kif huwa GetString
anki jkollna memorja tiegħu?

872
00:35:50,740 --> 00:35:53,430
>> Ukoll, jirriżulta li hemm
din il-funzjoni oħra hawn

873
00:35:53,430 --> 00:35:55,160
li aħna issa ser tibda tuża.

874
00:35:55,160 --> 00:35:59,780
Issa, dan jistenna than-- b'mod aktar cryptic
u jiena l-unika waħda li tista 'tara it--

875
00:35:59,780 --> 00:36:03,150
din il-linja jistenna b'mod aktar cryptic
allura għandu fl-ewwel daqqa t'għajn.

876
00:36:03,150 --> 00:36:04,650
Imma ejja tease l barra.

877
00:36:04,650 --> 00:36:07,950
>> Fuq in-naħa tax-xellug, I jkollhom char * t.

878
00:36:07,950 --> 00:36:13,280
Allura bl-Ingliż, ejja nibdew biex jifformulaw
sentenzi xierqa fil jargon tekniku.

879
00:36:13,280 --> 00:36:19,757
Allura dan huwa allokazzjoni ta '
varjabbli ta 'char tip * t imsejħa.

880
00:36:19,757 --> 00:36:21,090
Issa, dak li verament ma jfisser?

881
00:36:21,090 --> 00:36:23,881
>> Ukoll, dan ifisser, dak li jien ser
biex tistabbilixxi dan il-varjabbli imsejħa t?

882
00:36:23,881 --> 00:36:24,780

883
00:36:24,780 --> 00:36:26,402
An-indirizz ta 'char.

884
00:36:26,402 --> 00:36:28,360
Allura li jinsab biss l-aktar sempliċi,
aktar mod raġonevoli

885
00:36:28,360 --> 00:36:29,930
jiddeskrivi in-naħa tax-xellug.

886
00:36:29,930 --> 00:36:32,890
Allura li toħloq din il-kaxxa hawn biss.

887
00:36:32,890 --> 00:36:34,760
Allura l-naħa tal-lemin,
preżumibbilment, huwa għaddej

888
00:36:34,760 --> 00:36:37,170
li jalloka li akbar
blokki ta 'memorja kif?

889
00:36:37,170 --> 00:36:38,340
Mela ejja tease dan apparti.

890
00:36:38,340 --> 00:36:41,131
>> Huwa enormi fl-ewwel daqqa t'għajn,
imma x'inhu għaddej ġewwa hawn?

891
00:36:41,131 --> 00:36:43,740
L-ewwel, hemm malloc, li
hija apparentement ħabib ġdid tagħna,

892
00:36:43,740 --> 00:36:45,450
"Memorja jalloka."

893
00:36:45,450 --> 00:36:49,560
Allura dan huwa l-argument qed ikunu mgħoddija
fis dan, dan huwa argument pretty big.

894
00:36:49,560 --> 00:36:50,970
Mela ejja tease dan apparti.

895
00:36:50,970 --> 00:36:53,410
>> strlen ta 'i, naturalment, jirrappreżenta the--

896
00:36:53,410 --> 00:36:54,142

897
00:36:54,142 --> 00:36:55,600
UDJENZA: In-numru ta 'karattri.

898
00:36:55,600 --> 00:36:56,710
DAVID J. Malan: Biss il-
numru ta 'karattri fit s.

899
00:36:56,710 --> 00:36:59,040
Allura l-tul ta 'i, il-string oriġinali.

900
00:36:59,040 --> 00:37:00,350
Allura-G a-b-e.

901
00:37:00,350 --> 00:37:02,320
Allura huwa probabbilment erba f'dan il-każ.

902
00:37:02,320 --> 00:37:05,485
Why am I tagħmel +1 wara
ssejjaħ strlen ta s?

903
00:37:05,485 --> 00:37:06,360
UDJENZA: [inaudible]

904
00:37:06,360 --> 00:37:07,590
DAVID J. Malan: Għal dak
karattru speċjali null.

905
00:37:07,590 --> 00:37:11,260
Jekk inti titlob lili x'inhu l-tul ta '
Isem Gabe, jiena vais ngħid erbgħa.

906
00:37:11,260 --> 00:37:14,480
Taht il-barnuża, għalkemm, I bżonn
li ħames byte għall-karattru null.

907
00:37:14,480 --> 00:37:16,100
Allura hu għalhekk li jien tagħmel l +1.

908
00:37:16,100 --> 00:37:21,730
>> Issa biss fil-każ li inti taħdem dan
programm fuq il-kompjuter minbarra, say,

909
00:37:21,730 --> 00:37:24,610
l-appliance CS50,
fejn id-daqs ta 'char

910
00:37:24,610 --> 00:37:26,350
jista 'jkun differenti
minn computer-- tiegħi stess

911
00:37:26,350 --> 00:37:30,590
Jirriżulta li nista 'sejħa dan
sizeof operatur, staqsi il-kompjuter,

912
00:37:30,590 --> 00:37:32,870
x'inhu d-daqs ta '
char fuq dan il-kompjuter?

913
00:37:32,870 --> 00:37:37,400
>> U billi timmultiplika ħamsa f'dan
pereżempju bl-daqs ta 'char, li

914
00:37:37,400 --> 00:37:40,440
fuq kompjuters aktar se
jkun biss wieħed, malloc

915
00:37:40,440 --> 00:37:44,830
se talloka għalija dan big
blokki ta 'memorja fuq hawn fuq il-lemin.

916
00:37:44,830 --> 00:37:47,140
U li għaddej biex return--
huwa function-- hekk huwa

917
00:37:47,140 --> 00:37:48,265
ser jirritornaw għall lili dak?

918
00:37:48,265 --> 00:37:50,914

919
00:37:50,914 --> 00:37:51,830
UDJENZA: L-indirizz?

920
00:37:51,830 --> 00:37:53,709
DAVID J. Malan: L-indirizz ta 'dak?

921
00:37:53,709 --> 00:37:55,250
UDJENZA: Tal il-memorja huwa allokat?

922
00:37:55,250 --> 00:37:56,450
DAVID J. Malan: Tal il
memorja huwa allokat.

923
00:37:56,450 --> 00:37:59,189
So I jkollhom l-ebda idea, franchement,
fejn dan ikun ser jispiċċaw.

924
00:37:59,189 --> 00:38:01,480
Jien ser tipproponi li
li għaddej biex jispiċċaw fil 0x88.

925
00:38:01,480 --> 00:38:02,770

926
00:38:02,770 --> 00:38:06,009
Kompletament arbitrarja, iżda
x'imkien ieħor għajr 0x50,

927
00:38:06,009 --> 00:38:08,800
għaliex is-sistema operattiva, liema
Windows u Mac OS tagħmel għalija, huwa

928
00:38:08,800 --> 00:38:11,230
kun żgur li huwa jagħti
me biċċiet differenti ta 'RAM.

929
00:38:11,230 --> 00:38:14,210
>> Allura dan huwa l-valur, fejn dan
blokki ta 'memorja tista' tispiċċa.

930
00:38:14,210 --> 00:38:16,060
Allura dan huwa dak jispiċċa fil hawn, 0x88.

931
00:38:16,060 --> 00:38:17,480

932
00:38:17,480 --> 00:38:21,570
Allura issa b'mod ċar, I jistgħu jifhmu
li dan mhuwiex l-istess bħal dan,

933
00:38:21,570 --> 00:38:23,960
għaliex qed tipponta lejn
biċċiet differenti ta 'memorja.

934
00:38:23,960 --> 00:38:29,980
Mela jekk jien issa fil-fatt tixtieq li kopja din
fil, ejja do soluzzjoni proposta tiegħek.

935
00:38:29,980 --> 00:38:36,870
>> Ejja biss jmorru, joħolqu għal loop,
u jagħmlu bracket t i gets bracket s i.

936
00:38:36,870 --> 00:38:39,760
Minħabba issa I jistgħu jużaw
dan-array like notazzjoni,

937
00:38:39,760 --> 00:38:43,390
għaliex anki jekk malloc ħafna
ġeneriku jalloka me memorja,

938
00:38:43,390 --> 00:38:45,290
memorja huwa bytes biss kontigwi.

939
00:38:45,290 --> 00:38:47,240
Byte, byte, byte, lura lura biex lura.

940
00:38:47,240 --> 00:38:50,030
>> I jista 'żgur bħala programmer
titratta dan bħala firxa, li

941
00:38:50,030 --> 00:38:55,090
tfisser I jistgħu jużaw dan finalment familjari
notazzjoni tal biss xi parentesi kwadri.

942
00:38:55,090 --> 00:38:56,462

943
00:38:56,462 --> 00:39:00,020
>> So let me nieqaf hemm, għaliex
dan huwa ħafna kollha f'daqqa, anke

944
00:39:00,020 --> 00:39:03,530
għalkemm l-idea bażika li terġa
hija li string, dan il-ħin,

945
00:39:03,530 --> 00:39:05,550
mhix tip ta 'dejta ġdid per se.

946
00:39:05,550 --> 00:39:10,150
Huwa biss hekk imsejħa pointer,
indirizz ta 'karattru,

947
00:39:10,150 --> 00:39:12,650
li ifisser biss huwa numru
li permezz tal-konvenzjoni tal-bniedem

948
00:39:12,650 --> 00:39:15,350
għandna t-tendenza li tikteb bħala 0x xi ħaġa.

949
00:39:15,350 --> 00:39:18,590
>> Iżda huwa biss numru,
bħal 33 Oxford Street,

950
00:39:18,590 --> 00:39:20,530
li jiġri li jkun l-
Indirizz bini CS tal.

951
00:39:20,530 --> 00:39:22,000

952
00:39:22,000 --> 00:39:23,545
Kwalunkwe mistoqsijiet dwar dawn id-dettalji?

953
00:39:23,545 --> 00:39:24,790

954
00:39:24,790 --> 00:39:25,289
Yeah?

955
00:39:25,289 --> 00:39:28,530
>> UDJENZA: Għalfejn nagħmlu check
għal t ugwali għal nulla?

956
00:39:28,530 --> 00:39:30,740
>> DAVID J. Malan: Għalfejn nagħmlu
iċċekkja għal t ugwali għal nulla?

957
00:39:30,740 --> 00:39:33,250
Jekk naqraw il-documentation--
question-- kbira għall malloc,

958
00:39:33,250 --> 00:39:37,020
li għaddej biex ngħid fil-istampar multa,
kultant malloc tista 'ritorn null,

959
00:39:37,020 --> 00:39:38,080
bħad GetString.

960
00:39:38,080 --> 00:39:41,820
U fil-fatt, GetString prospetti nulli
jekk, imbagħad, malloc prospetti nulli,

961
00:39:41,820 --> 00:39:43,130
minħabba GetString użi malloc.

962
00:39:43,130 --> 00:39:46,400
>> U li jista 'jiġri jekk il-OS,
Mac OS, Windows, ikun x'ikun, huwa sempliċiment

963
00:39:46,400 --> 00:39:48,130
out ta 'memorja għalik.

964
00:39:48,130 --> 00:39:49,820
Allura dan huwa dak li ġara hemmhekk.

965
00:39:49,820 --> 00:39:52,910
>> U let me jiżvelaw ħaġa waħda oħra
li jistgħu biss blow moħħok

966
00:39:52,910 --> 00:39:55,100
jew kompletament tkun wisq fuq il-linja.

967
00:39:55,100 --> 00:39:59,770
Imma let me pull up il-
istess għall loop għall-ikkupjar,

968
00:39:59,770 --> 00:40:05,480
li mument ilu, recall kien
dan. bracket t i gets bracket s i.

969
00:40:05,480 --> 00:40:06,740
>> Nizza u faċli għall-utent.

970
00:40:06,740 --> 00:40:09,330
Iħoss bħal Week Żewġ darb'oħra.

971
00:40:09,330 --> 00:40:14,920
Iżda din il-verżjoni attwalment jista 'jkun
miktuba mill-ġdid bħala dan, li tidher cryptic.

972
00:40:14,920 --> 00:40:18,280
Huwa ta 'teknika msejħa pointer
aritmetika, indirizz aritmetika.

973
00:40:18,280 --> 00:40:19,600
Iżda għaliex ma dan ix-xogħol?

974
00:40:19,600 --> 00:40:22,220
>> Issa annoyingly, il-
awturi ta 'C iddeċidew li jużaw

975
00:40:22,220 --> 00:40:25,070
is-simbolu * għal skopijiet differenti.

976
00:40:25,070 --> 00:40:29,020
Rajna hija użat darba diġà,
char *, li tfisser "tagħti me a varjabbli

977
00:40:29,020 --> 00:40:31,210
li għaddej biex fihom
l-indirizz ta 'char. "

978
00:40:31,210 --> 00:40:33,990
* Allura char f'dak il-kuntest
ifisser "tagħti me a varjabbli."

979
00:40:33,990 --> 00:40:40,050
>> Sfortunatament, jekk inti tuża l-* mingħajr
kelma quddiem ta 'dan, bħal char,

980
00:40:40,050 --> 00:40:41,905
huwa issa msejjaħ l-
operatur dereference.

981
00:40:41,905 --> 00:40:43,530
U aħna ser tara aktar ta 'dan qabel twil.

982
00:40:43,530 --> 00:40:44,930
Iżda dan ifisser biss "jmorru hemm."

983
00:40:44,930 --> 00:40:49,070
Huwa simili qal, jekk xi ħadd mogħtija lili
fuq biċċa karta "33 Oxford Street,"

984
00:40:49,070 --> 00:40:53,830
jekk I do "* Oxford Street 33," dan ifisser
"Go fl-triq għall-bini CS."

985
00:40:53,830 --> 00:40:57,220
>> Allura * ifisser biss jmorru hemm jekk
hemm l-ebda kelma quddiem ta 'dan.

986
00:40:57,220 --> 00:40:59,100
Allura dak li huwa t, li jkun ċar?

987
00:40:59,100 --> 00:41:03,250
t huwa l-indirizz tal-blokki ta '
memorja li ngħatat lura lili.

988
00:41:03,250 --> 00:41:06,650
i huwa l-indirizz ta 'dak li, biex tkun ċara,
fl-eżempju aħna kont qed tiddiskuti,

989
00:41:06,650 --> 00:41:07,500
tal Gabe zghar?

990
00:41:07,500 --> 00:41:08,990

991
00:41:08,990 --> 00:41:10,005
i huwa l-indirizz of--

992
00:41:10,005 --> 00:41:11,585

993
00:41:11,585 --> 00:41:12,460
UDJENZA: L-sekwenza.

994
00:41:12,460 --> 00:41:14,126
DAVID J. Malan: Of isem oriġinali Gabe tal.

995
00:41:14,126 --> 00:41:16,660
Allura huwa l-indirizz ta '
din blokki ta 'memorja.

996
00:41:16,660 --> 00:41:22,220
Mela jekk jien ngħid t + I-- i, avviż,
huwa biss ħabib antik tagħna.

997
00:41:22,220 --> 00:41:24,770
Huwa biss varjabbli indiċi
thats mtennija minn żero fuq up

998
00:41:24,770 --> 00:41:26,960
għat-tul tas-sekwenza s.

999
00:41:26,960 --> 00:41:30,367
Allura li għaddej biex tkun żero, allura wieħed,
imbagħad tnejn, imbagħad tlieta, imbagħad erba.

1000
00:41:30,367 --> 00:41:33,200
Mela ejja jimmuntaw dawn ġdida
Biċċiet puzzle scratch simili, jekk inti se,

1001
00:41:33,200 --> 00:41:36,140
anki jekk, għal darb'oħra, il-sintassi
huwa ferm aktar arcane minn Scratch.

1002
00:41:36,140 --> 00:41:39,522
Allura t huwa indirizz +
i huwa ser jagħti me

1003
00:41:39,522 --> 00:41:42,480
numru, minħabba li dawn huma kollha
numri li aħna kont qed tpinġija bħala hex.

1004
00:41:42,480 --> 00:41:43,560
Iżda dawn qed biss numri.

1005
00:41:43,560 --> 00:41:49,960
>> Mela jekk l-indirizz ta 't għidna
kien 0x88, x'hemm 0x88 plus żero.

1006
00:41:49,960 --> 00:41:51,564

1007
00:41:51,564 --> 00:41:53,980
Anke jekk int mhux komdu
ma hex għadhom, tieħu raden.

1008
00:41:53,980 --> 00:41:54,410
>> UDJENZA: L-oriġinal.

1009
00:41:54,410 --> 00:41:55,850
>> DAVID J. Malan: Still 0x88.

1010
00:41:55,850 --> 00:41:58,910
Allura dak li ma * 0x88 jfisser?

1011
00:41:58,910 --> 00:42:02,670
Dan ifisser, "jmorru hemm" li tfisser
effettivament, "iqiegħed subgħajh tiegħek hawn."

1012
00:42:02,670 --> 00:42:06,930
U issa fuq in-naħa tal-lemin tal
din l-espressjoni, * u mbagħad fl parens,

1013
00:42:06,930 --> 00:42:11,586
s + i jfisser i, li hija l-
jindirizzaw up here tal-g ftit.

1014
00:42:11,586 --> 00:42:16,220
i + 0 huwa, ovvjament, i, ikun x'ikun i huwa.

1015
00:42:16,220 --> 00:42:21,230
>> Allura issa, huwa * i, li bħad * 33
Oxford Street ifisser mur l-indirizz

1016
00:42:21,230 --> 00:42:22,010
s.

1017
00:42:22,010 --> 00:42:24,170
Allura hawnhekk dan saba, lemin.

1018
00:42:24,170 --> 00:42:26,050
Allura dak am I se kopja fil dak?

1019
00:42:26,050 --> 00:42:30,260
Il-ħaġa dwar id-dritt, li hija
Gabe, ftit g hawn, fis hawn.

1020
00:42:30,260 --> 00:42:32,750
>> U għalhekk l-effett ta 'dik
ewwel iterazzjoni tal-linja,

1021
00:42:32,750 --> 00:42:36,200
kif inti propost, anki jekk jidher
crazy aktar ikkumplikat minn kull ħaġa

1022
00:42:36,200 --> 00:42:42,110
konna rajna qabel, huwa sempliċiment tgħid
mur hawn u kopja dan il-karattru hawnhekk.

1023
00:42:42,110 --> 00:42:44,700
Huwa giving you mappa biex żewġ postijiet.

1024
00:42:44,700 --> 00:42:46,130
>> U aħna ser tara ħafna aktar ta 'dan.

1025
00:42:46,130 --> 00:42:50,600
Iżda għal issa, it-tama hi biss li
jintroduċu xi wħud minn dawn l-ideat bażiċi.

1026
00:42:50,600 --> 00:42:53,550
U fil-fatt, ejja nħarsu lejn
programm finali wieħed hawn,

1027
00:42:53,550 --> 00:42:57,480
u allura l-claymation imwiegħed,
li se tagħmel dak kollu dritt.

1028
00:42:57,480 --> 00:42:57,980
Kull dritt.

1029
00:42:57,980 --> 00:43:01,680
So let me tiftaħ up-- hemm immorru.

1030
00:43:01,680 --> 00:43:02,850

1031
00:43:02,850 --> 00:43:05,440
Mela ejja me-- aħna ser terga 'lura
li din l-istampa qabel twil.

1032
00:43:05,440 --> 00:43:08,360
Let me jiftħu dan l-eżempju finali hawn.

1033
00:43:08,360 --> 00:43:09,440

1034
00:43:09,440 --> 00:43:12,710
>> Allura hawnhekk huwa super, super
programm li accomplishes

1035
00:43:12,710 --> 00:43:15,050
xejn fil-ħajja li ma l-segwenti.

1036
00:43:15,050 --> 00:43:18,740
Hija l-ewwel jiddikjara żewġ varjabbli, x
u y, li mhumiex numri dan iż-żmien,

1037
00:43:18,740 --> 00:43:19,240
per se.

1038
00:43:19,240 --> 00:43:20,448
Huma qed mhux interi, per se.

1039
00:43:20,448 --> 00:43:22,899
Huma apparentament int *.

1040
00:43:22,899 --> 00:43:25,690
Allura biss xi ħadd, xi jfisser
jekk tip ta 'data tiegħek, varjabbli tiegħek,

1041
00:43:25,690 --> 00:43:26,860
huwa ta 'int tip * star?

1042
00:43:26,860 --> 00:43:30,240
Dik hija l-indirizz ta 'int.

1043
00:43:30,240 --> 00:43:31,990
>> So I stajt ebda idea fejn hu għadu.

1044
00:43:31,990 --> 00:43:35,150
Dan ifisser biss "mressaq, eventwalment,
l-indirizz ta 'int hawn. "

1045
00:43:35,150 --> 00:43:38,340
0x50, 0x88, kull fejn hija fil-
memorja, l-indirizz huwa għaddej hemmhekk.

1046
00:43:38,340 --> 00:43:40,200
U dan huwa dak y hija
ser ikunu, kif ukoll.

1047
00:43:40,200 --> 00:43:44,920
>> Jekk I issa ngħid x = malloc (sizeof (int)),
dan huwa mod fancy ta 'tgħid,

1048
00:43:44,920 --> 00:43:49,000
ħej sistema operattiva, permezz malloc,
tagħti me memorja biżżejjed għall-daqs

1049
00:43:49,000 --> 00:43:52,370
ta 'int, li huwa probabbilment
ser ikunu ta '32 bits jew erba bytes.

1050
00:43:52,370 --> 00:43:53,680
>> Allura dak li ma malloc ritorn?

1051
00:43:53,680 --> 00:43:55,250
Malloc jirritorna indirizz.

1052
00:43:55,250 --> 00:43:57,020
Allura x'inhu għaddej biex nikseb maħżuna fil x?

1053
00:43:57,020 --> 00:44:00,600
L-indirizz tal-blokki ta '
memorja, l-erba 'bytes, li malloc

1054
00:44:00,600 --> 00:44:03,360
biss sabu għalija billi tistaqsi
is-sistema operattiva.

1055
00:44:03,360 --> 00:44:08,240
>> Issa sadanittant, linja
erbgħa hawn, il-* x = 42.

1056
00:44:08,240 --> 00:44:09,990
Just biex tkun ċara,
x'inhu għaddej hemm isfel?

1057
00:44:09,990 --> 00:44:11,530
Fuq in-naħa tax-xellug, * x.

1058
00:44:11,530 --> 00:44:13,610
li simili * 33 Oxford Street.

1059
00:44:13,610 --> 00:44:15,523
Allura * x ifisser liema?

1060
00:44:15,523 --> 00:44:16,450
>> UDJENZA: Mur.

1061
00:44:16,450 --> 00:44:17,908
>> DAVID J. Malan: Mur f'dak l-indirizz.

1062
00:44:17,908 --> 00:44:20,466
Kull fejn dik blokki ta '
memorja huwa, mur għaliha.

1063
00:44:20,466 --> 00:44:21,979
U tpoġġi dak hemm, ovvjament?

1064
00:44:21,979 --> 00:44:22,520
UDJENZA: 42.

1065
00:44:22,520 --> 00:44:23,580
DAVID J. Malan: 42.

1066
00:44:23,580 --> 00:44:25,650
Kull dritt, y *, l-istess idea.

1067
00:44:25,650 --> 00:44:26,860
Mur fl-indirizz y.

1068
00:44:26,860 --> 00:44:31,740
Poġġi n-numru 13 hemmhekk,
imma dak li hu y fil-mument?

1069
00:44:31,740 --> 00:44:33,172

1070
00:44:33,172 --> 00:44:34,630
UDJENZA: M'hemm l-ebda memorja għall y.

1071
00:44:34,630 --> 00:44:35,710
DAVID J. Malan: M'hemm
l-ebda memorja għall y.

1072
00:44:35,710 --> 00:44:38,215
Allura dak li ma y probabbilment
fihom, kif aħna kont qed tgħid?

1073
00:44:38,215 --> 00:44:38,520
>> UDJENZA: Żibel.

1074
00:44:38,520 --> 00:44:39,480
>> DAVID J. Malan: Xi valur żibel.

1075
00:44:39,480 --> 00:44:41,320
Issa, il-valur żibel għadu numru.

1076
00:44:41,320 --> 00:44:43,160
Hija xorta jistgħu jiġu interpretati indirizz.

1077
00:44:43,160 --> 00:44:45,160
Huwa bħallikieku xi ħadd
mħarrbxa xi ħaġa isfel,

1078
00:44:45,160 --> 00:44:48,002
u I interpretawh b'mod inkorrett fis-sens
xi bini fl-triq.

1079
00:44:48,002 --> 00:44:50,460
U jekk inti biss tipprova li jmorru fis
xi bini inti ma proprji,

1080
00:44:50,460 --> 00:44:53,710
jew xi blokki ta 'memorja int ma
Kien mogħti, affarijiet ħżiena jista 'jiġri.

1081
00:44:53,710 --> 00:44:57,740
Computer jista crash, jew xi oħra
imġieba mhux determinat jista 'jiġri.

1082
00:44:57,740 --> 00:45:01,310
>> Allura l-intro, imbagħad, li Binky hija din.

1083
00:45:01,310 --> 00:45:04,290
I still remember, 20
xi snin bil-fard aktar tard,

1084
00:45:04,290 --> 00:45:07,200
fejn I kien meta I finalment
mifhum pointers.

1085
00:45:07,200 --> 00:45:09,520
>> Liema jiġifieri, jekk inti
leave hawn fi tliet minuti

1086
00:45:09,520 --> 00:45:12,170
u think I ma
jifhmu pointers, tirrealizza

1087
00:45:12,170 --> 00:45:14,410
Għandi mfakkar għall-20
snin għall xi raġuni crazy

1088
00:45:14,410 --> 00:45:17,140
meta u għaliex finalment għereq
fil, seduta bit-tagħlim tiegħi

1089
00:45:17,140 --> 00:45:19,501
sħabi, Nishat Mehta fil-
dahar tal Eliot Dining Hall.

1090
00:45:19,501 --> 00:45:21,250
Issa, stajt mfakkar
dan minħabba li dan kien

1091
00:45:21,250 --> 00:45:23,920
waħda mit-temi I, fil
partikolari, tħabtu ma.

1092
00:45:23,920 --> 00:45:26,470
U allura, finalment għafast,
bħal I DARE jgħidu ħafna ta 'suġġetti

1093
00:45:26,470 --> 00:45:27,460
eventwalment se.

1094
00:45:27,460 --> 00:45:32,590
U issa, biex jagħmlu li jħossu li l-
kuntenti u l-aktar konvinċenti,

1095
00:45:32,590 --> 00:45:35,360
ejja tagħti ħarsa finali tagħna
aħħar tliet minuti hawn fuq Binky,

1096
00:45:35,360 --> 00:45:37,675
minn ħabib tagħna, Nick
Parlante minn Stanford.

1097
00:45:37,675 --> 00:45:38,910

1098
00:45:38,910 --> 00:45:41,580
>> [Daqq ta 'video]

1099
00:45:41,580 --> 00:45:42,750
>> -Hey, Binky.

1100
00:45:42,750 --> 00:45:43,500
Wake up!

1101
00:45:43,500 --> 00:45:45,960
Wasal iż-żmien għall-gost pointer.

1102
00:45:45,960 --> 00:45:47,012
>> Liema-li?

1103
00:45:47,012 --> 00:45:48,723
Tgħallem dwar pointers?

1104
00:45:48,723 --> 00:45:50,580
Oh, Goody!

1105
00:45:50,580 --> 00:45:53,563
>> -Well, Biex tibda, I raden aħna qed
ser jeħtieġu koppja pointers.

1106
00:45:53,563 --> 00:45:54,390
>> OK.

1107
00:45:54,390 --> 00:45:57,930
Dan il-kodiċi jalloka żewġ pointers,
li jista 'jiġbed l interi.

1108
00:45:57,930 --> 00:45:58,430
OK.

1109
00:45:58,430 --> 00:46:02,140
Well, I tara l-żewġ pointers, iżda dawn
ma jidhirx li jkun tipponta lejn xi ħaġa.

1110
00:46:02,140 --> 00:46:02,980
>> -li-Dritt.

1111
00:46:02,980 --> 00:46:05,100
Inizjalment, pointers
ma jurux xejn.

1112
00:46:05,100 --> 00:46:08,030
L-affarijiet dawn jenfasizzaw huma msejħa
pointees, u meta dawn jitwaqqfu l

1113
00:46:08,030 --> 00:46:09,370
pass separat.

1114
00:46:09,370 --> 00:46:10,220
>> -OH, Id-dritt, id-dritt.

1115
00:46:10,220 --> 00:46:10,950
Jien kont naf li.

1116
00:46:10,950 --> 00:46:12,385
Il pointees huma separati.

1117
00:46:12,385 --> 00:46:14,315
Er, hekk kif taħseb li jallokaw pointee?

1118
00:46:14,315 --> 00:46:15,340

1119
00:46:15,340 --> 00:46:15,960
>> OK.

1120
00:46:15,960 --> 00:46:18,970
Ukoll, dan il-kodiċi jalloka
a pointee ġdid numru sħiħ,

1121
00:46:18,970 --> 00:46:20,950
u dan parti tistabbilixxi x-punt lilha.

1122
00:46:20,950 --> 00:46:22,050

1123
00:46:22,050 --> 00:46:23,230
>> -Hey, Li jistenna aħjar.

1124
00:46:23,230 --> 00:46:25,060
Sabiex tagħmel dan jagħmlu xi ħaġa.

1125
00:46:25,060 --> 00:46:25,990
>> OK.

1126
00:46:25,990 --> 00:46:30,455
I ser dereference il-pointer x biex
jaħżen numru 42 fis pointee tagħha.

1127
00:46:30,455 --> 00:46:32,830
Għal dan trick, I bzonn tiegħi
Magic Wand ta Dereferencing.

1128
00:46:32,830 --> 00:46:34,130

1129
00:46:34,130 --> 00:46:36,080
>> -Your Magic Wand ta Dereferencing?

1130
00:46:36,080 --> 00:46:37,357

1131
00:46:37,357 --> 00:46:38,190
That-- li l-kbir.

1132
00:46:38,190 --> 00:46:39,340

1133
00:46:39,340 --> 00:46:41,080
>> -Dan Huwa dak li l-kodiċi Dehra.

1134
00:46:41,080 --> 00:46:44,110
I ser biss twaqqaf in-numru, u [POP]

1135
00:46:44,110 --> 00:46:44,700
>> -Hey, Ħarsa.

1136
00:46:44,700 --> 00:46:46,140
Hemm din tmur.

1137
00:46:46,140 --> 00:46:50,980
>> -Allura Tagħmel dereference fuq x ġej
il-vleġġa għall-aċċess pointee tagħha.

1138
00:46:50,980 --> 00:46:53,160
F'dan il-każ, maħżen 42 fil hemmhekk.

1139
00:46:53,160 --> 00:46:57,710
Hey ipprova uża dan biex jaħżnu l-għadd
13 permezz tal-pointer oħra, y.

1140
00:46:57,710 --> 00:46:58,760
>> OK.

1141
00:46:58,760 --> 00:47:03,270
I ser biss jmorru fuq hawn biex y,
u jiksbu l-numru 13 set up.

1142
00:47:03,270 --> 00:47:07,930
U mbagħad, jieħdu l-Wand ta
Dereferencing u biss [BUZZ]

1143
00:47:07,930 --> 00:47:08,960
>> -OH!

1144
00:47:08,960 --> 00:47:09,500
>> -OH, Ħej!

1145
00:47:09,500 --> 00:47:11,090
Li ma ħadmux.

1146
00:47:11,090 --> 00:47:15,630
Say, Binky, ma naħsibx dereferencing
y hija idea tajba, għaliex inti taf,

1147
00:47:15,630 --> 00:47:17,850
twaqqif tal-pointee
huwa pass separat.

1148
00:47:17,850 --> 00:47:20,450
U jien ma naħsibx li aħna qatt ma kien.

1149
00:47:20,450 --> 00:47:21,480
>> Punt -Good.

1150
00:47:21,480 --> 00:47:21,980
-Yeah.

1151
00:47:21,980 --> 00:47:25,680
Aħna allokat il-y pointer, iżda aħna
qatt tistabbilixxi li jippuntaw lejn pointee.

1152
00:47:25,680 --> 00:47:27,190

1153
00:47:27,190 --> 00:47:28,616
>> -Very Attent.

1154
00:47:28,616 --> 00:47:30,240
-Hey, Qed tfittex tajba hemmhekk, Binky.

1155
00:47:30,240 --> 00:47:33,400
Inti tista 'tiffissa lilha hekk li l-punti y
għall-istess pointee bħala x?

1156
00:47:33,400 --> 00:47:34,000
>> -Sure.

1157
00:47:34,000 --> 00:47:36,780
I ser tuża Magic Wand tiegħi
ta 'Assenjament Pointer.

1158
00:47:36,780 --> 00:47:38,740
>> -Il Li għaddej biex tkun
problema bħal qabel?

1159
00:47:38,740 --> 00:47:39,240
-Nru.

1160
00:47:39,240 --> 00:47:40,660
Dan ma tmissx il-pointees.

1161
00:47:40,660 --> 00:47:44,450
Hija biss bidliet pointer wieħed biex
punt li l-istess ħaġa bħat ieħor.

1162
00:47:44,450 --> 00:47:45,450
>> -OH, Nara.

1163
00:47:45,450 --> 00:47:48,200
Issa punti Y-istess post bħall x.

1164
00:47:48,200 --> 00:47:48,910
Allura stenna.

1165
00:47:48,910 --> 00:47:49,950
Issa, y hija ffissata.

1166
00:47:49,950 --> 00:47:51,120
Hija għandha pointee.

1167
00:47:51,120 --> 00:47:54,510
Allura inti tista 'tipprova l-Wand ta
Dereferencing darb'oħra biex jibagħtu l-13 fuq.

1168
00:47:54,510 --> 00:47:56,510
>> -Uh, OK.

1169
00:47:56,510 --> 00:47:58,160
Hawnhekk tmur. [POP]

1170
00:47:58,160 --> 00:47:59,340
>> -Hey, Tħares lejn dak.

1171
00:47:59,340 --> 00:48:00,750
Issa dereferencing xogħlijiet fuq y.

1172
00:48:00,750 --> 00:48:04,991
U minħabba l-pointers huma qsim
li pointee wieħed, tnejn tara l-13.

1173
00:48:04,991 --> 00:48:05,490
-Yeah.

1174
00:48:05,490 --> 00:48:06,870
Qsim, ikun x'ikun.

1175
00:48:06,870 --> 00:48:08,820
Allura aħna se jaqilbu postijiet issa?

1176
00:48:08,820 --> 00:48:09,440
>> Oh, tħares.

1177
00:48:09,440 --> 00:48:10,830
We qed barra ta 'żmien.

1178
00:48:10,830 --> 00:48:11,570
>> -But--

1179
00:48:11,570 --> 00:48:13,530
>> Just ftakar-tliet regoli pointer.

1180
00:48:13,530 --> 00:48:16,560
Numru Wieħed, l-istruttura bażika
huwa li inti għandek pointer,

1181
00:48:16,560 --> 00:48:18,680
u punti fuq għal pointee.

1182
00:48:18,680 --> 00:48:20,640
Iżda l-pointer u
pointee huma separati,

1183
00:48:20,640 --> 00:48:22,610
u l-iżball komuni
huwa li jitwaqqaf pointer,

1184
00:48:22,610 --> 00:48:25,000
iżda li tinsa biex tagħtiha pointee.

1185
00:48:25,000 --> 00:48:28,170
>> Numru Tnejn, dereferencing pointer
jibda fil-pointer

1186
00:48:28,170 --> 00:48:31,050
u ssegwi vleġġa tiegħu fuq
għall-aċċess pointee tagħha.

1187
00:48:31,050 --> 00:48:33,400
Kif nafu lkoll, dan
jaħdem biss jekk ikun hemm

1188
00:48:33,400 --> 00:48:36,270
a pointee, liema tip ta '
gets lura għall-numru wieħed regola.

1189
00:48:36,270 --> 00:48:39,000
>> Numru Tliet, pointer
assenjazzjoni jieħu pointer waħda

1190
00:48:39,000 --> 00:48:42,320
u bidliet li punt li l-
istess pointee bħala pointer ieħor.

1191
00:48:42,320 --> 00:48:44,160
Allura wara l-assenjazzjoni,
iż-żewġ pointers

1192
00:48:44,160 --> 00:48:45,910
se jindika l-istess pointee.

1193
00:48:45,910 --> 00:48:47,990
Kultant, li sejjaħ qsim.

1194
00:48:47,990 --> 00:48:49,740
U li kollox hemm għaliha, verament.

1195
00:48:49,740 --> 00:48:50,277
Bye bye issa.

1196
00:48:50,277 --> 00:48:51,110
[END daqq ta 'video]

1197
00:48:51,110 --> 00:48:52,568
DAVID J. Malan: Li lilha għall CS50.

1198
00:48:52,568 --> 00:48:55,110
Aħna se tara int ġimgħa d-dieħla.

1199
00:48:55,110 --> 00:48:56,064