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>> [Daqq tal-mużika]

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>> DAVID J. Malan: Kull dritt.

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>> [Daħk]

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>> Merħba lura.

5
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Dan huwa CS50.

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U dan l-aħħar ta 'ħames ġimgħa.

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U sa issa, aħna ħadthom pretty ħafna
ilhom jieħdu għal mogħtija li hemm

8
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teżisti din kompilatur, clang, li inti ħadthom
ġew invokazzjoni permezz ta 'dan

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għodda oħra msejħa Agħmel li b'xi mod
magically tikkonverti source code tiegħek

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fis kodiċi oġġett, l-żerijiet u dawk
li l-kompjuters CPU tiegħek, ċentrali

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unit ta 'proċessar, fil-fatt jifhem.

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Iżda jirriżulta hemm numru li l-
għaddejjin taħt il-barnuża fl

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bejn input u output.

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>> U nixtieq li tipproponi li aħna laħam
li fid ftit aktar dettall fis

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dawn l-erba passi, ikollhom xi ħaġa imsejħa
qabel l-ipproċessar, xi ħaġa

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imsejħa kompilazzjoni, li rajna,
xi ħaġa imsejħa assemblaġġ, u

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xi ħaġa imsejħa jgħaqqdu.

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Allura sa issa, f'xi tagħna
programmi, aħna kellna sharp jinkludi.

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Aktar reċentement aħna kellna xi sharp
tiddefinixxi għall kostanti.

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Għalhekk jirriżulta li dawk l-affarijiet li
huma prefissi bil-simbolu hash jew

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is-simbolu lira huma pre-proċessur
direttivi.

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Li jinsab biss mod fancy ta 'tgħid huwa
linja ta 'kodiċi li attwalment

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maqluba xi ħaġa oħra quddiem il-
kompjuter saħansitra jippruvaw li jikkonvertu tiegħek

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Programm tiġi żero u dawk.

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>> Per eżempju, qawwi tinkludi l-istandard
I / O. H, pretty ħafna biss ifisser jmorru

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quddiem, grab-kontenut tal-fajls
stdio.h u paste minnhom hemm dritt.

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Sabiex l-ebda żero u dawk
f'dak il-punt għadu.

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Huwa verament ftit sostituzzjoni.

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U li sar matul l-hekk imsejħa
istadju ta 'qabel l-ipproċessar, meta inti

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tmexxi effettivament clang jew speċifikament
Jagħmlu f'ħafna każijiet.

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Allura dan kollu kien jiġri
ewwel awtomatikament s'issa.

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>> Imbagħad jiġi l-pass kumpilazzjoni.

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Iżda aħna kont qed eżaġerat
kumpilazzjoni.

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Kumpilazzjoni programm verament ifisser li
teħodha minn xi ħaġa bħal C, il-

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kodiċi tas-sors konna ġie miktub, down
għal xi ħaġa imsejħa assemblaġġ.

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Lingwa assemblaġġ huwa livell aktar baxx
lingwa li, Thankfully, aħna mhux se

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għandhom ħafna okkażjoni biex
tikteb dan is-semestru.

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Iżda huwa fil-livell l-aktar baxx fil-
sens li inti litteralment tibda bil-miktub

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żid u naqqas u jimmultiplikaw u t-tagħbija
mill-memorja u jiffrankaw l-memorja, il-

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istruzzjonijiet bażika ħafna li l-kompjuter,
taħt il-barnuża,

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jifhem effettivament.

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>> Fl-aħħar nett, assemblaġġ jieħu dik il-lingwa
għall-żero u dawk li aħna kont qed

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jiddeskrivi s'issa.

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U verament fl-aħħarnett, hemm l-hekk imsejħa
jgħaqqdu fażi, li aħna ser

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tara fi ftit mument, li jgħaqqad
żerijiet tiegħek u dawk biż-żeri u

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dawk nies oħra qabel
għandek maħluqa.

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>> Għalhekk tikkunsidra dan il-programm sempliċi super.

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Kien minn Ġimgħa 1.

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Huwa biss qal, Hello World,
fuq l-iskrin.

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Aħna dam dan permezz clang.

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Jew aħna dam permezz Agħmel
li dam clang.

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U outputted fil-ħin fejn
xi żero u dawk.

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Iżda jirriżulta hemm
pass intermedju.

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Jekk immur hawn fuq - oops, ma
trid tara lilu s'issa.

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Jekk I jmorru fuq hawn biex appliance tiegħi
u I jiftħu hello.c, hawnhekk

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huwa l-istess programm.

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U dak li jien ser tagħmel terminal tiegħi
tieqa hawnhekk huwa jien ser

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run clang pjuttost milli Kun, li
automates l-erba '

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dawk il-passi għalina.

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U jien ser tagħmel clang-S u
imbagħad hello.c u mbagħad tidħol.

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>> U niġi pront Teptip
għal darb'oħra, li hija tajba.

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U issa fil-tieqa kemmxejn akbar,
Jien ser jiftħu gedit fil hawn.

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U jien ser tiftaħ fajl li,
jirriżulta, huwa hello.s sejjaħ din

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jkollu dak lingwa assemblaġġ
I imsemmi qabel.

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U dan huwa dak li sejjaħ assemblaġġ
lingwa, livell pjuttost baxx

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istruzzjonijiet li CPU Intel tiegħek
jew kwalunkwe huwa li l-ġewwa

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jifhem.

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U mov huwa għall-pass. sejħa hija għal
ssejjaħ, funzjoni livell baxx ħafna.

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sub huwa għall naqqas.

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>> Allura meta jkollok CPU partikolari ġewwa
tal-kompjuter tiegħek, dak li jagħmilha

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CPUs distinti, kontra ieħor fuq il-
suq, tkun li l-istruzzjonijiet li

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jifhem u spiss kif effiċjenti huwa
huwa, kif fast huwa fil eżekuzzjoni f'xi

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ta 'dawk l-istruzzjonijiet.

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Issa għal aktar fuq dan, inti tista 'tieħu
CS61 Fall jmiss fil-kulleġġ.

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Iżda hawnhekk għandna, per eżempju, ftit
identifikaturi li tista 'tidher familjari.

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hello.c huwa l-isem tal-programm.

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>> . Test -

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hemm Ma tantx ta 'interess hemm
biss issa, ifakkar li t-test

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segment, bħala tat-Tnejn, huwa fejn fl
memorja program tiegħek fil-fatt jispiċċa.

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Allura dak inqas vagament
familjari hemmhekk.

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Hawnhekk, naturalment, huwa referenza
tal-funzjoni prinċipali tagħna.

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Scrolling, dawn jirreferu għall-affarijiet
imsejħa reġistri, biċċiet żgħar ħafna tal-

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ġewwa memorja ta 'CPU tiegħek attwali.

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U jekk I iscroll anke
ulterjuri, nara xi tip

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aċċenn indirett ta 'ASCII.

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U hemm, tabilħaqq, hija li string,
hello, comma, dinja.

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>> Allura storja twila fil-qosor, dan kien
jiġri għalik, awtomatikament,

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taħt il-barnuża kollha ta 'dan iż-żmien.

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U dak li kien jiġri huwa verament darba
inti stajt run clang, jew permezz ta '

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Tagħmel, int jkollna l-ewwel,
mill-kodiċi sors, il-

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hekk imsejħa lingwa assemblaġġ.

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Imbagħad clang qiegħda taqleb din l-assemblea
lingwa isfel sa żero u dawk.

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U dan huwa l-slide li bdejna
diskussjoni tagħna fil-Ġimgħa 0 fuq -

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u mbagħad Ġimgħa 1 fuq.

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U mbagħad finalment, dawk żero u dawk
huma kkombinati ma 'l-żero u dawk

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minn dawk libreriji aħna kont qed tieħu
għall mogħtija bħal Standard I / O jew il-

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Librerija String jew saħansitra
il-librerija CS50.

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>> Allura biex żebgħa din l-istampa aktar
viżwalment, għandna hello.c.

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U, naturalment, tuża l-printf
jiffunzjonaw jiġifieri, bonjour dinja.

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Il-pass kumpilazzjoni tieħu l-isfel għal
dan il-fajl aħna biss raw hello.s, anke

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għalkemm thats tipikament mħassra
awtomatikament għalik.

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Iżda li l-kodiċi assemblaġġ
fil-pass tan-nofs.

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U allura meta aħna jiġbor l-assemblaġġ
lingwa, biex ngħidu hekk, li meta inti

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tikseb dawk żero u dawk.

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Allura aħna ħadthom żżomjati effettiv llum fuq
dak li aħna kont qed tieħu għall mogħtija,

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ifisser li jmorru kodiċi tas-sors
li toġġezzjona kodiċi.

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>> Iżda fl-aħħar, issa dak l-istess stampa -
ejja shove dan matul

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naħa tax-xellug.

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U jinnota li fil-quċċata hemm
Semmejt stdio.h.

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Li l-fajl li konna inklużi
fi kważi kollha tal-

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programmi konna bil-miktub.

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U li l-fajl li l-kontenut
nikseb kopja pasted,

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effettivament atop kodiċi tiegħek.

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Iżda jirriżulta li, fuq il-kompjuter
sistema x'imkien, hemm preżumibbilment

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fajl stdio.c li xi ħadd kiteb snin
ilu li timplimenta kollha ta 'l-

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funzjonijiet li kienu ddikjarati
fl stdio.h.

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>> Issa fir-realtà huwa probabbilment mhux fuq
Mac tiegħek jew PC tiegħek jew anke fil-

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CS50 appliance huwa kodiċi C prima.

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Xi ħadd diġà miġbura dan u inkluda
. Fajl għall-kodiċi oġġett jew o. A

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fajl, li tirreferi għal librerija maqsuma
li kien installat minn qabel u

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pre-ikkumpilata għalik.

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Iżda jissoponi li hemm tabilħaqq jeżisti
fuq stdio.c kompjuter tagħna b'mod parallel

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ma clang.

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Kodiċi tiegħek l-jiġu kkompilati
u mmuntati.

125
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kodiċi tal stdio.c qed tkun miġbura u
immuntati, b'tali mod li dan l-aħħar ħafna

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pass, stabbiliti hawn, irridu b'xi mod
link, biex ngħidu hekk, żerijiet tiegħek u dawk

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b'żero tiegħu jew tagħha u dawk f'waħda
programm sempliċi li, finalment, huwa

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imsejħa biss Hello.

129
00:06:20,540 --> 00:06:23,340
>> Allura li kollox tal-magic li l-
kien jiġri s'issa.

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00:06:23,340 --> 00:06:26,430
U se tkompli tieħu dawn
proċessi għall mogħtija, imma tirrealizza

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hemm ħafna ta 'dettalji mmerraq
għaddejjin taħt hemmhekk.

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U dan huwa dak li jagħmel tiegħek
kompjuter ma 'Intel ġewwa

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partikolarment distinti.

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>> Allura fuq din in-nota, jekk inti tixtieq li
jingħaqdu magħna għall-ikel nhar il-Ġimgħa, do go

135
00:06:37,020 --> 00:06:41,570
għall-cs50.net/rsvp post tas-soltu,
13:15 nhar il-Ġimgħa.

136
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U issa ftit avviżi ftit.

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00:06:43,400 --> 00:06:44,670
Allura aħna għandna xi aħbar tajba.

138
00:06:44,670 --> 00:06:45,970
U aħna għandna xi aħbar ħażina.

139
00:06:45,970 --> 00:06:47,260
Tibda bl xi aħbar tajba hawn.

140
00:06:47,260 --> 00:06:52,038

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>> [Miżgħuda]

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>> Kull dritt.

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Ukoll, huwa teknikament festa, hekk
mhuwiex tant rigal minna.

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Imma mbagħad l-aħbar ħażina tal-kors.

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00:06:58,030 --> 00:07:00,550

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00:07:00,550 --> 00:07:01,880
>> [Miżgħuda]

147
00:07:01,880 --> 00:07:03,530
>> I qattgħu ħafna ħin
fuq dawn animazzjonijiet.

148
00:07:03,530 --> 00:07:04,690
>> [Daħk]

149
00:07:04,690 --> 00:07:07,000
>> Se jkun hemm sessjoni ta 'reviżjoni
din ġejjin Tnejn.

150
00:07:07,000 --> 00:07:08,340
Huwa ser tkun fil PM 05:30.

151
00:07:08,340 --> 00:07:11,210
Aħna se infakkarkom ta 'dawn id-dettalji kollha
permezz ta 'email fuq li l-kors

152
00:07:11,210 --> 00:07:13,470
website biss fi ftit ta 'żmien jiem.

153
00:07:13,470 --> 00:07:16,610
Din se tkun iffilmjati u magħmula disponibbli
ftit wara.

154
00:07:16,610 --> 00:07:19,200
Hekk jekk inti ma tistax tagħmel dan it-tnejn
slot lejl, tinkwetax.

155
00:07:19,200 --> 00:07:22,270
Taqsimiet din il-ġimgħa li ġejjin se wkoll
tiffoka fuq ir-reviżjoni għall-kwizz.

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00:07:22,270 --> 00:07:25,670
Jekk taqsima tiegħek huwa nhar it-Tnejn, li huwa
tabilħaqq vaganzi università, aħna se

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jibqa 'jissodisfa fit-taqsima.

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00:07:26,920 --> 00:07:28,890
Jekk inti sempliċiment ma tistax tagħmel dan
taqsima għaliex inti qed tmur

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00:07:28,890 --> 00:07:29,860
bogħod, li l-multa.

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00:07:29,860 --> 00:07:33,710
Jattendu Ħadd jew is-sezzjoni it-Tlieta jew
tixgħel-in għat-taqsima Jason, li huwa

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disponibbli online.

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>> Allura, aktar aħbarijiet ħżiena.

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00:07:37,490 --> 00:07:41,960
Allura skond il-sillabu,
għandna lecture tnejn li jmiss.

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Iżda l-aħbar tajba -

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b'mod ċar, I jintefqu wisq ħin fuq dan.

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>> [Daħk]

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00:07:45,280 --> 00:07:47,140
>> Aħna ser tikkanċella jmiss nhar il-Ġimgħa lectures.

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Allura li se jkun rigal għalina, sabiex inti
tista 'verament ikollhom respite sabiħa

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00:07:50,590 --> 00:07:52,990
bejn din il-ġimgħa u ġimgħatejn għalhekk.

170
00:07:52,990 --> 00:07:57,460
Allura l-ebda lectures ġimgħa d-dieħla, biss ċkejkna
ftit kwizz, li għalihom inti għandek tkun

171
00:07:57,460 --> 00:07:59,030
jkollna dejjem aktar eċċitati.

172
00:07:59,030 --> 00:08:03,870
>> Mela ejja issa tagħti attenzjoni tagħna biex
xi ħaġa li huwa tabilħaqq aktar viżwali

173
00:08:03,870 --> 00:08:06,990
u aktar eċċitanti u li tiffissa l-istadju
għal dak li għaddej biex tkun fuq l-orizzont

174
00:08:06,990 --> 00:08:08,420
biss fi ftit ġimgħat ħin.

175
00:08:08,420 --> 00:08:12,160
Wara l-ewwel kwizz, aħna ser inbiddlu l-
tiffoka ta 'settijiet problema tagħna għall-ieħor

176
00:08:12,160 --> 00:08:16,710
problema speċifika dominju, dak ta '
forensiċi jew sigurtà b'mod aktar ġenerali.

177
00:08:16,710 --> 00:08:19,550
>> Fil-fatt, it-tradizzjoni ma 'din il-problema
sett huwa għalija waħda mill-

178
00:08:19,550 --> 00:08:24,850
tagħlim sħabi jew CAs li jimxu madwar
kampus tieħu xi ritratti ta '

179
00:08:24,850 --> 00:08:29,450
nies ovvji identifikabbli iżda mhux,
postijiet, jew affarijiet, allura kull sena I

180
00:08:29,450 --> 00:08:34,520
b'xi jirnexxilhom aċċidentalment iħassru
jew korrotti-karta tal-midja diġitali

181
00:08:34,520 --> 00:08:35,720
li l-ġewwa tal-kamera tagħna.

182
00:08:35,720 --> 00:08:36,860
Imma l-ebda big deal.

183
00:08:36,860 --> 00:08:39,200
I tista 'tmur quddiem u plagg
li fis-kompjuter tiegħi.

184
00:08:39,200 --> 00:08:43,010
I tista 'tagħmel immaġini forensika ta' dan, sabiex
biex jitkellmu, billi jikkopja l-żerijiet u

185
00:08:43,010 --> 00:08:46,830
dawk off ta 'dik il-karta tal-memorja, kemm jekk
karta SD tagħha jew flash card kompatti jew

186
00:08:46,830 --> 00:08:48,100
tkun xi tkun int familjari magħhom.

187
00:08:48,100 --> 00:08:49,300
U allura nistgħu idejn li out.

188
00:08:49,300 --> 00:08:53,190
>> U għalhekk l-isfida li għandna quddiemna, fost oħrajn
affarijiet għalik, se jkun li tikteb

189
00:08:53,190 --> 00:08:58,630
Kodiċi C li jirkupra mazz sħiħ ta '
JPEGs għalija u żvela se jkun

190
00:08:58,630 --> 00:09:00,190
dawk in-nies, postijiet, jew affarijiet.

191
00:09:00,190 --> 00:09:03,340
U aħna ser nitkellmu wkoll, din il-problema
iffissati u fil-jiem li ġejjin, dwar

192
00:09:03,340 --> 00:09:04,440
grafika aktar ġenerali.

193
00:09:04,440 --> 00:09:06,140
Imxejna użati minnhom, kors,
għal break out.

194
00:09:06,140 --> 00:09:09,080
Imma inti ħadthom tip ta 'tittieħed bħala fatta
teżisti dawn il-kunċetti ta 'livell għoli

195
00:09:09,080 --> 00:09:10,680
ta rettangoli u ovali.

196
00:09:10,680 --> 00:09:12,450
Iżda taħt il-barnuża
hemm pixels.

197
00:09:12,450 --> 00:09:14,370
U inti kellhom jibdew
jaħsbu dwar dawk.

198
00:09:14,370 --> 00:09:18,800
Jew inti se għal p-set 4 taħseb
dwar id-differenza bejn briks tiegħek, kif

199
00:09:18,800 --> 00:09:21,990
malajr int ballun miexja madwar
l-iskrin għal break out.

200
00:09:21,990 --> 00:09:24,830
Għalhekk hemm dan il-kunċett tal-
tikek fuq l-iskrin tiegħek li l-

201
00:09:24,830 --> 00:09:26,290
jidħlu fis-seħħ diġà.

202
00:09:26,290 --> 00:09:29,430
>> Issa dak li tara, għalkemm, huwa dak
ikollok fuq skrin tal-kompjuter.

203
00:09:29,430 --> 00:09:33,680
Jekk inti stajt qatt jarah xi tajba jew
TV ħażin, odds huma dawn pretty ħafna

204
00:09:33,680 --> 00:09:36,280
jikkura l-udjenza simili technophobes
li ma verament

205
00:09:36,280 --> 00:09:37,630
jafu ħafna dwar kompjuters.

206
00:09:37,630 --> 00:09:40,840
U għalhekk huwa faċli ħafna għall-pulizija
ditektif jiġifieri, tista 'inti

207
00:09:40,840 --> 00:09:41,710
tindif li sa għalija?

208
00:09:41,710 --> 00:09:42,710
Jew itejbu, id-dritt?

209
00:09:42,710 --> 00:09:45,550
Tittejjeb huwa bħall-kelma buzz fl
aktar kwalunkwe juru relatata magħha.

210
00:09:45,550 --> 00:09:49,240
U r-realtà hija jekk inti tieħu ħafna
stampa blurry ta 'suspett li jagħmlu

211
00:09:49,240 --> 00:09:51,620
xi ħaġa ħażina, inti ma tistax
biss ittejjeb dan.

212
00:09:51,620 --> 00:09:53,080
Inti ma tistax zoom infinitament.

213
00:09:53,080 --> 00:09:56,350
Inti ma tistax tara fl-glint ta 'xi ħadd
għajn li jkun ikkommetta dan

214
00:09:56,350 --> 00:09:59,860
kriminalità partikolarment, minkejja l-
prevalenza ta 'dan fuq it-TV.

215
00:09:59,860 --> 00:10:04,110
>> U hekk ma 'dak ejja jimmotivaw li
problema li jmiss stabbiliti ma idea fil

216
00:10:04,110 --> 00:10:05,765
xi turi li magħhom inti
jista 'jkun familjari.

217
00:10:05,765 --> 00:10:06,500
>> [Daqq video]

218
00:10:06,500 --> 00:10:07,835
>> -OK.

219
00:10:07,835 --> 00:10:09,956
Issa, ejja tikseb ħarsa tajba lejn inti.

220
00:10:09,956 --> 00:10:17,060

221
00:10:17,060 --> 00:10:17,766
>> -Żomm dan.

222
00:10:17,766 --> 00:10:18,658
Mexxi l lura.

223
00:10:18,658 --> 00:10:19,550
>> -Stenna minuta.

224
00:10:19,550 --> 00:10:21,580
Mur dritt.

225
00:10:21,580 --> 00:10:21,800
>> -Hemm.

226
00:10:21,800 --> 00:10:22,690
Jiffriżaw dik.

227
00:10:22,690 --> 00:10:23,692
>> Iskrin Full.

228
00:10:23,692 --> 00:10:23,846
>> -OK.

229
00:10:23,846 --> 00:10:24,154
Jiffriżaw dik.

230
00:10:24,154 --> 00:10:25,140
>> Jagħmel iktar iebsa fuq dik, se ya?

231
00:10:25,140 --> 00:10:27,090
>> -Vector fil dwar li Guy
mir-rota lura.

232
00:10:27,090 --> 00:10:29,730
>> Zoom fl-dritt hawn fuq dan il-post.

233
00:10:29,730 --> 00:10:33,700
>> -Bil-apparat dritt, il-imaged
jistgħu jiġu mkabbra u inċiżiv.

234
00:10:33,700 --> 00:10:34,490
>> -X'hemm li?

235
00:10:34,490 --> 00:10:35,870
>> -Huwa ta 'titjib programm.

236
00:10:35,870 --> 00:10:36,793
>> Tista 'ċara li kwalunkwe up?

237
00:10:36,793 --> 00:10:38,560
>> -I do not know.

238
00:10:38,560 --> 00:10:39,090
Ejja ittejjeb dan.

239
00:10:39,090 --> 00:10:41,690
>> Tittejjeb-taqsima A-6.

240
00:10:41,690 --> 00:10:43,510
>> -I msaħħa l-dettall u -

241
00:10:43,510 --> 00:10:44,456
>> -I think hemm biżżejjed biex itejbu.

242
00:10:44,456 --> 00:10:45,402
Jgħadduha lill-iskrin tiegħi.

243
00:10:45,402 --> 00:10:47,300
>> Tittejjeb il-riflessjoni fl-għajnejn tagħha.

244
00:10:47,300 --> 00:10:49,330
>> -Ejja run dan permezz
titjib video.

245
00:10:49,330 --> 00:10:50,340
>> -Edgar, inti tista ttejjeb dan?

246
00:10:50,340 --> 00:10:52,320
>> -Tistrieħ fuq.

247
00:10:52,320 --> 00:10:54,290
>> -I've ilhom jaħdmu fuq din ir-riflessjoni.

248
00:10:54,290 --> 00:10:55,560
>> Xi ħadd-riflessjoni tal.

249
00:10:55,560 --> 00:10:56,440
>> -Riflessjoni.

250
00:10:56,440 --> 00:10:57,940
>> -Hemm riflessjoni
ta 'wiċċ tar-raġel.

251
00:10:57,940 --> 00:10:58,860
>> -Il-riflessjoni.

252
00:10:58,860 --> 00:10:59,710
>> -Hemm riflessjoni.

253
00:10:59,710 --> 00:11:00,900
>> -Zoom fl fuq il-mera.

254
00:11:00,900 --> 00:11:03,500
>> Tista 'tara riflessjoni.

255
00:11:03,500 --> 00:11:04,700
>> Tista 'jsaħħu d-dehra minn hawn?

256
00:11:04,700 --> 00:11:05,700
>> Tista 'ttejjeb lilu dritt hawn?

257
00:11:05,700 --> 00:11:06,500
>> Tista 'ittejjeb dan?

258
00:11:06,500 --> 00:11:07,380
>> Tista 'ittejjeb dan?

259
00:11:07,380 --> 00:11:08,190
>> -Nistgħu itejbu dan?

260
00:11:08,190 --> 00:11:08,940
>> Tista 'ittejjeb dan?

261
00:11:08,940 --> 00:11:10,280
>> Żomm 'fuq it-tieni, jien ser itejbu.

262
00:11:10,280 --> 00:11:11,570
>> -Zoom fl fuq il-bieb.

263
00:11:11,570 --> 00:11:12,180
>> -X10.

264
00:11:12,180 --> 00:11:13,052
>> -Zoom.

265
00:11:13,052 --> 00:11:13,197
>> [Daħk]

266
00:11:13,197 --> 00:11:14,360
>> Nimxu-pulzieri

267
00:11:14,360 --> 00:11:15,100
>> -Stenna, stop.

268
00:11:15,100 --> 00:11:15,740
>> -Stop.

269
00:11:15,740 --> 00:11:16,290
>> -Nieqaf.

270
00:11:16,290 --> 00:11:19,390
>> -Jduru madwar 75 gradi
il vertikali jekk jogħġbok.

271
00:11:19,390 --> 00:11:19,886
>> [Daħk]

272
00:11:19,886 --> 00:11:24,350
>> -Stop, u lura lill-parti
dwar il-bieb għal darb'oħra.

273
00:11:24,350 --> 00:11:26,330
>> Ghandek-enhancer immaġni
li jistgħu Bitmap?

274
00:11:26,330 --> 00:11:28,990
>> Forsi-nistgħu nużaw il-Sen Pradeep
metodu biex tara fil-twieqi.

275
00:11:28,990 --> 00:11:30,680
>> -Dan is-software huwa state of the art.

276
00:11:30,680 --> 00:11:31,676
>> -Il-valur ikona huwa off.

277
00:11:31,676 --> 00:11:34,166
>> -Bil-kombinazzjoni
ta 'algoritmi.

278
00:11:34,166 --> 00:11:38,399
>> -Hu meħuda algoritmi illuminazzjoni li
il-livell li jmiss u I jistgħu jużawhom biex

279
00:11:38,399 --> 00:11:38,648
jsaħħu din ritratt.

280
00:11:38,648 --> 00:11:42,050
>> -Lock fuq u tkabbar l-assi z.

281
00:11:42,050 --> 00:11:42,760
>> Tittejjeb-.

282
00:11:42,760 --> 00:11:43,060
>> Tittejjeb-.

283
00:11:43,060 --> 00:11:43,760
>> Tittejjeb-.

284
00:11:43,760 --> 00:11:45,010
>> -Jiffriżaw u jtejbu.

285
00:11:45,010 --> 00:11:47,470

286
00:11:47,470 --> 00:11:47,910
>> [Daqq video END]

287
00:11:47,910 --> 00:11:51,470
>> DAVID J. Malan: So Set Problem
5 huwa dak li jinsab quddiem hemmhekk.

288
00:11:51,470 --> 00:11:55,260
Allura aħna ser dalwaqt nikseb għarfien aħjar
ta 'meta u għaliex inti tista'

289
00:11:55,260 --> 00:11:57,300
u tagħna ma jistgħu jtejbu il-mod.

290
00:11:57,300 --> 00:12:00,090
Iżda l-ewwel, ejja terġa 'lura l-attenzjoni tagħna
xi wħud mill-blokki tal-bini Aħna ser

291
00:12:00,090 --> 00:12:02,250
jeħtieġu li jkunu kapaċi li tgħid li l-istorja.

292
00:12:02,250 --> 00:12:05,580
>> Allura ifakkar li fassalna din l-istampa fuq
It-tnejn u xi ftit aħħar ġimgħa.

293
00:12:05,580 --> 00:12:09,970
U dan jiddeskrivi l-format ta 'affarijiet
fil-memorja tal-kompjuter tiegħek meta

294
00:12:09,970 --> 00:12:11,000
taħdem xi program.

295
00:12:11,000 --> 00:12:14,310
Il-segment teknoloġija top up, recall, jirreferi
għall-żerijiet attwali u dawk

296
00:12:14,310 --> 00:12:16,000
li jikkomponu programm tiegħek.

297
00:12:16,000 --> 00:12:19,340
Hemm, taħt dak, xi initialized jew
data uninitialized, li tipikament

298
00:12:19,340 --> 00:12:22,910
jirreferi għal affarijiet simili kostanti jew
kordi jew varjabbli globali li jkollhom

299
00:12:22,910 --> 00:12:24,200
ġew iddikjarati bil-quddiem.

300
00:12:24,200 --> 00:12:26,500
Hemm il-borġ, imma aħna ser jaslu
lura għal dak fil-bit.

301
00:12:26,500 --> 00:12:27,410
>> U allura hemm il-munzell.

302
00:12:27,410 --> 00:12:30,660
Ħafna bħal munzell ta 'dixxijiet fil-
kafetterija, dan huwa fejn memorja gets

303
00:12:30,660 --> 00:12:33,610
ub'saffi u ub'saffi kull meta
inti tagħmel dak fi programm?

304
00:12:33,610 --> 00:12:36,380

305
00:12:36,380 --> 00:12:37,730
X'inhu l-użu munzell għall?

306
00:12:37,730 --> 00:12:39,320
>> Yeah?

307
00:12:39,320 --> 00:12:40,000
>> Sejħa tal-funzjoni.

308
00:12:40,000 --> 00:12:42,890
Kwalunkwe ħin li inti sejħa funzjoni, huwa
mogħtija lill sliver ta 'memorja għall tagħha

309
00:12:42,890 --> 00:12:45,020
varjazzjonijiet lokali jew parametri tagħha.

310
00:12:45,020 --> 00:12:48,810
U pictorially, naraw li ma 'kull
funzjoni suċċessivi imsejħa, meta A

311
00:12:48,810 --> 00:12:52,520
sejħiet B C sejħiet sejħiet D, huma
nikseb ub'saffi fuq il-munzell.

312
00:12:52,520 --> 00:12:55,630
U fi ħdan kull wieħed minn dawk flieli ta '
memorja huwa essenzjalment ambitu uniku

313
00:12:55,630 --> 00:12:58,590
għal dik il-funzjoni, li, naturalment,
huwa problematiku jekk inti tixtieq li idejn

314
00:12:58,590 --> 00:13:01,850
minn funzjoni għall-oħra Biċċa
ta 'data li inti tixtieq li

315
00:13:01,850 --> 00:13:03,500
li jindiblu jew bidla.

316
00:13:03,500 --> 00:13:08,060
>> Allura dak li kien soluzzjoni tagħna biex jippermetti
Funzjoni rappreżentat minn munzell wieħed

317
00:13:08,060 --> 00:13:11,390
jinkwadra li jibdlu l-memorja ġewwa
ta 'ieħor frame munzell?

318
00:13:11,390 --> 00:13:14,590
Kif tagħmel dawn iż-żewġ jitkellmu ma 'xulxin?

319
00:13:14,590 --> 00:13:18,510
Hekk billi terġa 'pointers jew indirizzi,
li, għal darb'oħra, biss jiddeskrivu fejn fil

320
00:13:18,510 --> 00:13:22,280
memorja, permezz ta 'proċedura speċifika
numru gidma, il-partikolari

321
00:13:22,280 --> 00:13:23,830
valur jista 'jinstab.

322
00:13:23,830 --> 00:13:26,860
Allura recall aħħar darba wisq komplejna
l-istorja u kkunsidrat

323
00:13:26,860 --> 00:13:28,280
pjuttost program Buggy.

324
00:13:28,280 --> 00:13:32,900
U dan il-programm huwa Buggy għal ftit
raġunijiet, iżda l-aktar waħda tħassib huwa

325
00:13:32,900 --> 00:13:34,620
minħabba li ma jiċċekkjaw liema?

326
00:13:34,620 --> 00:13:39,111

327
00:13:39,111 --> 00:13:40,450
>> Yeah, jonqos biex jiċċekkja l-input.

328
00:13:40,450 --> 00:13:41,870
Jiddispjacini?

329
00:13:41,870 --> 00:13:43,880
>> Jekk huwa aktar minn 12-il karattru.

330
00:13:43,880 --> 00:13:47,260
Allura ħafna smartly, meta jċemplu memcopy,
li, kif tissuġġerixxi l-isem, biss

331
00:13:47,260 --> 00:13:50,630
kopji memorja mit-tieni argument tagħha
fis ewwel argument tagħha.

332
00:13:50,630 --> 00:13:54,730
It-tielet argument, ħafna smartly, huwa
kkontrollati sabiex jiġi żgurat li inti ma

333
00:13:54,730 --> 00:13:59,400
aktar minn kopja, f'dan il-każ, it-tul
ta 'bar, numru ta' karattri,

334
00:13:59,400 --> 00:14:03,810
fil-destinazzjoni, li hija din
array C. Iżda l-problema hija li dak

335
00:14:03,810 --> 00:14:07,230
jekk C innifsu mhuwiex kbir biżżejjed
biex jimmaniġġaw dan?

336
00:14:07,230 --> 00:14:09,900
Int ser kopja l-għadd ta '
bytes li inti stajt ġew mogħtija.

337
00:14:09,900 --> 00:14:13,040
Imma dak li inti fil-fatt ikollhom aktar
bytes milli għandek spazju għall?

338
00:14:13,040 --> 00:14:16,770
>> Ukoll, dan il-programm ħafna foolishly biss
addoċċ tipproċedi biex jieħdu kwalunkwe huwa

339
00:14:16,770 --> 00:14:20,650
partikolari, bonjour backslash 0 huwa
kbir jekk string huwa qasir

340
00:14:20,650 --> 00:14:22,040
biżżejjed, bħal ħames Chars.

341
00:14:22,040 --> 00:14:26,470
Imma jekk huwa attwalment 12-il karattru jew
1,200 karattri, rajna aħħar darba

342
00:14:26,470 --> 00:14:29,380
li int biss ser kompletament
jissostitwixxu memorja li

343
00:14:29,380 --> 00:14:30,470
ma jappartjenix lilek.

344
00:14:30,470 --> 00:14:34,390
U l-agħar każ, jekk inti jissostitwixxu dik
porzjon aħmar hemmhekk li aħna imsejjaħ il-

345
00:14:34,390 --> 00:14:35,380
ritorn indirizz -

346
00:14:35,380 --> 00:14:38,370
dan huwa biss fejn il-kompjuter
awtomatikament, għalik, wara l-

347
00:14:38,370 --> 00:14:43,130
xeni, tucks bogħod valur 32-bit li
ifakkar li dak indirizz suppost

348
00:14:43,130 --> 00:14:47,080
ritorn meta foo, din il-funzjoni l-oħra,
isir esekuzzjoni.

349
00:14:47,080 --> 00:14:49,320
Huwa Frak ħobż ta 'tipi
li dan jirritorna.

350
00:14:49,320 --> 00:14:52,490
Jekk inti jissostitwixxu li, potenzjalment,
jekk int l-Guy ħażina, jista tista

351
00:14:52,490 --> 00:14:54,750
potenzjalment tieħu f'idejha
kompjuter ta 'xi ħadd.

352
00:14:54,750 --> 00:14:58,020
U inti ser aktar żgur
tiġrifa huwa f'ħafna każijiet.

353
00:14:58,020 --> 00:15:01,690
>> Issa din il-problema ġiet aggravata biss
kif bdejna nitkellmu memorja

354
00:15:01,690 --> 00:15:03,010
ġestjoni aktar ġenerali.

355
00:15:03,010 --> 00:15:07,150
U malloc, għall-allokazzjoni tal-memorja, huwa
funzjoni li nistgħu nużaw biex jallokaw

356
00:15:07,150 --> 00:15:11,260
memorja meta ma nafux bil-quddiem
li nistgħu bżonn xi.

357
00:15:11,260 --> 00:15:13,960
Għalhekk, per eżempju, jekk immur lura
l-appliance hawn.

358
00:15:13,960 --> 00:15:21,010
U I jiftħu mill-aħħar hello2.c żmien,
ifakkar dan il-programm hawn, li ħares

359
00:15:21,010 --> 00:15:23,500
ftit xi ħaġa bħal din,
biss tliet linji -

360
00:15:23,500 --> 00:15:27,940
jiddikjara ismek, allura isem string,
fuq ix-xellug ugwali getstring.

361
00:15:27,940 --> 00:15:29,690
U allura aħna ipprintjaha,
isem l-utent.

362
00:15:29,690 --> 00:15:31,170
>> Allura dan kien programm sempliċi super.

363
00:15:31,170 --> 00:15:34,870
Biex ikunu ċari, let me imorru quddiem
u jagħmlu bonjour-2.

364
00:15:34,870 --> 00:15:36,680
Jien ser tagħmel dot mmejla bonjour-2.

365
00:15:36,680 --> 00:15:37,750
Iddikjara l-isem tiegħek -

366
00:15:37,750 --> 00:15:38,140
David.

367
00:15:38,140 --> 00:15:38,840
Ikteb.

368
00:15:38,840 --> 00:15:39,540
Hello David.

369
00:15:39,540 --> 00:15:41,060
Jidher li jaħdem OK.

370
00:15:41,060 --> 00:15:43,140
Imma x'inhu verament għaddej
taħt barnuża hawn?

371
00:15:43,140 --> 00:15:44,670
Ewwel ejja qaxxar wħud mis-saffi.

372
00:15:44,670 --> 00:15:48,380
String huwa biss sinonimu konna
realizzati għal liema?

373
00:15:48,380 --> 00:15:49,110
Star Char.

374
00:15:49,110 --> 00:15:52,740
Mela ejja jagħmilha ftit aktar arcane
iżda aktar teknikament korrett li din

375
00:15:52,740 --> 00:15:55,570
hija stilla char, li jfisser li
isem, iva, hija varjabbli.

376
00:15:55,570 --> 00:15:59,920
Imma dak ħwienet isem huwa l-indirizz ta '
a char, li jħoss ftit stramba

377
00:15:59,920 --> 00:16:01,050
għaliex jien jkollna lura string.

378
00:16:01,050 --> 00:16:03,580
Jien jkollna lura multipli
Chars mhux char.

379
00:16:03,580 --> 00:16:07,400
>> Iżda naturalment, għandek bżonn biss l-ewwel
indirizz char biex tiftakar fejn l-

380
00:16:07,400 --> 00:16:08,870
sekwenza sħiħa hija għaliex għaliex?

381
00:16:08,870 --> 00:16:12,700
Kif inti figura fejn l-aħħar ta '
l-sekwenza huwa li jkunu jafu l-bidu?

382
00:16:12,700 --> 00:16:13,630
Il żero backslash.

383
00:16:13,630 --> 00:16:17,260
Allura ma dawk iż-żewġ ħjiel inti figura
qabel il-bidu u t-tmiem ta '

384
00:16:17,260 --> 00:16:20,280
kwalunkwe string huma, sakemm dawn qed
iffurmat tajjeb ma 'dik null

385
00:16:20,280 --> 00:16:22,110
terminatur, li backslash żero.

386
00:16:22,110 --> 00:16:24,520
>> Iżda dan qed titlob getstring.

387
00:16:24,520 --> 00:16:28,020
U jirriżulta li getstring
dan il-ħin kien tip ta '

388
00:16:28,020 --> 00:16:28,820
qerq għalina.

389
00:16:28,820 --> 00:16:32,460
Huwa qed tagħmel dan ix-xogħol, biex tkun ċert,
jkollna string mill-utent.

390
00:16:32,460 --> 00:16:34,580
Iżda fejn jgħid li memorja
kienu ġejjin minn?

391
00:16:34,580 --> 00:16:38,440
Jekk immorru lura għall-istampa hawn u
japplikaw id-definizzjoni minn ftit

392
00:16:38,440 --> 00:16:42,610
mument ilu, li l-munzell huwa fejn
memorja tmur meta l-funzjonijiet huma msejħa,

393
00:16:42,610 --> 00:16:45,370
billi li l-loġika, meta inti sejħa getstring,
u mbagħad I tip

394
00:16:45,370 --> 00:16:50,900
D-A-V-I-D Ikteb, meta hija D-A-V-I-D
backslash żero maħżuna, ibbażati fuq il-

395
00:16:50,900 --> 00:16:53,480
istorja konna qalulna s'issa?

396
00:16:53,480 --> 00:16:55,190
>> Jidher li jkun
il-munzell, id-dritt?

397
00:16:55,190 --> 00:16:58,120
Meta inti sejħa tikseb string ikollok
ftit porzjon tal-memorja fuq il-munzell.

398
00:16:58,120 --> 00:17:01,630
Għalhekk stands għal raġuni li D-A-V-I-D
backslash żero hija maħżuna

399
00:17:01,630 --> 00:17:02,770
hemm fil-ċmieni.

400
00:17:02,770 --> 00:17:07,680
Imma stenna minuta, getstring prospetti
li string, biex ngħidu hekk, li jfisser

401
00:17:07,680 --> 00:17:11,700
huwa trej mill-kafetterija
tittieħed off-munzell.

402
00:17:11,700 --> 00:17:14,560
U aħna qal aħħar darba li malli
prospetti funzjoni, u inti tieħu li

403
00:17:14,560 --> 00:17:20,109
trej, biex ngħidu hekk, off-munzell, liema
inti tista 'tassumi dwar il-fdalijiet ta'

404
00:17:20,109 --> 00:17:21,819
li l-memorja?

405
00:17:21,819 --> 00:17:25,160
I sort tal redrew minnhom bħala trade marks in kwistjoni
għaliex effettivament issir

406
00:17:25,160 --> 00:17:26,250
Valuri mhux magħruf.

407
00:17:26,250 --> 00:17:29,500
Huma jistgħu jerġgħu jintużaw meta xi
funzjoni li jmiss huwa msejjaħ.

408
00:17:29,500 --> 00:17:31,870
>> Fi kliem ieħor, jekk aħna jiġri
li tkun ħażna -

409
00:17:31,870 --> 00:17:34,350
I ser tfassal stampa ta 'malajr
hawn tal-munzell.

410
00:17:34,350 --> 00:17:38,690
Jekk aħna jiġri li tinġibed l-qiegħ
ta 'segment memorja tiegħi, u aħna ser ngħidu

411
00:17:38,690 --> 00:17:42,230
li dan huwa l-post tal-memorja
okkupati minn prinċipali u forsi arg c u

412
00:17:42,230 --> 00:17:46,790
arg vs u kull ħaġa oħra fil-programm,
meta getstring tissejjaħ,

413
00:17:46,790 --> 00:17:51,120
preżumibbilment getstring gets
blokki ta 'memorja hawn.

414
00:17:51,120 --> 00:17:53,940
U mbagħad D-A-V-I-D b'xi
jispiċċa fil din il-funzjoni.

415
00:17:53,940 --> 00:17:55,320
U jien ser oversimplify.

416
00:17:55,320 --> 00:18:00,050
Imma ejja nassumu li tagħha D-A-V-I-D
backslash żero.

417
00:18:00,050 --> 00:18:03,500
Allura dan ħafna bytes huma użati fil-
l-qafas għall-getstring.

418
00:18:03,500 --> 00:18:08,270
>> Iżda hekk kif prospetti getstring, aħna
qal aħħar darba li dan il-memorja fuq

419
00:18:08,270 --> 00:18:11,340
hawn kollha isir - Woops! -

420
00:18:11,340 --> 00:18:14,270
kollha isir mħassra b'mod effettiv.

421
00:18:14,270 --> 00:18:17,220
U aħna tista 'taħseb dan issa bħala kwistjoni
marks minħabba li jaf

422
00:18:17,220 --> 00:18:18,720
x'inhu għaddej li ssir ta 'dak memorja.

423
00:18:18,720 --> 00:18:22,130
Tabilħaqq, I ħafna drabi jsejħu funzjonijiet
għajr getstring.

424
00:18:22,130 --> 00:18:24,750
U malli I call xi oħra
funzjoni minn getstring, forsi mhux

425
00:18:24,750 --> 00:18:28,860
dan il-programm partikolari aħna biss ħares
lejn iżda xi oħrajn, żgur xi oħra

426
00:18:28,860 --> 00:18:34,180
funzjoni tista 'tispiċċa li tingħata
dan il-post li jmiss fil-ċmieni.

427
00:18:34,180 --> 00:18:39,410
>> Allura ma jistax ikun li l-ħwienet getstring
D-A-V-I-D fuq il-munzell minħabba I kieku

428
00:18:39,410 --> 00:18:41,040
immedjatament jitilfu l-aċċess għaliha.

429
00:18:41,040 --> 00:18:43,720
Imma nafu li getstring
biss prospetti liema?

430
00:18:43,720 --> 00:18:47,220
Mhuwiex jirritornaw lejn
me sitt karattri.

431
00:18:47,220 --> 00:18:51,090
X'inhu verament jirritorna ma
aħna nikkonkludu aħħar darba?

432
00:18:51,090 --> 00:18:52,480
L-indirizz ta 'l-ewwel.

433
00:18:52,480 --> 00:18:56,650
Allura b'xi, meta inti imsejħa getstring,
huwa allokazzjoni ta 'blokki ta' memorja għall-

434
00:18:56,650 --> 00:18:59,620
l-sekwenza li t-tip u l-utenti
indirizz allura jirritornaw minnu.

435
00:18:59,620 --> 00:19:02,930
U jirriżulta li meta inti tixtieq li
jiffunzjonaw talloka memorja f'dan

436
00:19:02,930 --> 00:19:08,390
mod u r-ritorn lill-persuna li tissejjaħ
dik il-funzjoni, l-indirizz ta '

437
00:19:08,390 --> 00:19:11,870
li blokki ta 'memorja, inti assolutament
ma tista 'tqiegħed fil-ċmieni fil-

438
00:19:11,870 --> 00:19:14,750
qiegħ, għaliex funzjonalment huwa biss
ser jsirux tiegħek ħafna

439
00:19:14,750 --> 00:19:17,800
malajr, sabiex inti tista 'probabbilment raden fejn
aħna qed probabbilment se toss

440
00:19:17,800 --> 00:19:20,130
minflok, il-borġ hekk imsejħa.

441
00:19:20,130 --> 00:19:25,290
>> Allura bejn il-qiegħ ta 'l-memorja tiegħek
tqassim u l-quċċata ta 'l-memorja tiegħek

442
00:19:25,290 --> 00:19:26,820
tqassim huma mazz sħiħ ta 'segmenti.

443
00:19:26,820 --> 00:19:29,270
Wieħed huwa l-munzell, u d-dritt
hawn fuq huwa l-borġ.

444
00:19:29,270 --> 00:19:33,680
U borġ huwa biss blokki differenti ta '
memorja li mhuwiex użat għall-funzjonijiet

445
00:19:33,680 --> 00:19:34,770
meta jkunu qed jissejjaħ.

446
00:19:34,770 --> 00:19:38,100
Huwa użat għall-memorja fit-tul, meta
inti tixtieq funzjoni waħda li grab xi

447
00:19:38,100 --> 00:19:42,700
memorja u tkun tista 'tistrieħ fuq dan
mingħajr ma jitilfu l-kontroll fuqha.

448
00:19:42,700 --> 00:19:45,550
>> Issa inti tista 'forsi immedjatament
tara li dan mhux

449
00:19:45,550 --> 00:19:48,060
neċessarjament disinn perfetta.

450
00:19:48,060 --> 00:19:51,350
Kif program tiegħek memorja allokat fuq
l-munzell, jew kif inti sejħa aktar u

451
00:19:51,350 --> 00:19:55,540
funzjonijiet aktar, jew kif inti jallokaw
memorja fuq il-borġ ma malloc off bħala

452
00:19:55,540 --> 00:20:00,690
getstring qed tagħmel, dak li b'mod ċar
jidher li jkun problema inevitabbli?

453
00:20:00,690 --> 00:20:00,860
>> Dritt.

454
00:20:00,860 --> 00:20:03,150
Bħall-fatt li dawn vleġeġ
huma tipponta lejn xulxin

455
00:20:03,150 --> 00:20:04,380
ma bode ukoll.

456
00:20:04,380 --> 00:20:08,630
U fil-fatt, nistgħu malajr ħafna crash
programm fi kwalunkwe numru ta 'modi.

457
00:20:08,630 --> 00:20:12,050
Fil-fatt, I think we jista 'jkollhom
għamlu dan aċċidentalment darba.

458
00:20:12,050 --> 00:20:14,020
Jew jekk le, ejja tagħmel dan
deliberatament issa.

459
00:20:14,020 --> 00:20:21,330
Let me imorru quddiem u jiktbu super malajr
programm imsejjaħ dontdothis.c.

460
00:20:21,330 --> 00:20:26,730
U issa I ser imorru fil hawn u
do sharp jinkludu stdio.h.

461
00:20:26,730 --> 00:20:32,620
Ejja tiddikjara funzjoni foo jieħu
ebda argumenti, li hija

462
00:20:32,620 --> 00:20:34,040
denotat kif ukoll mill nulli.

463
00:20:34,040 --> 00:20:37,830
>> U l-unika ħaġa foo se tagħmel huwa
sejħa foo, li probabbilment mhuwiex il-

464
00:20:37,830 --> 00:20:39,100
idea smartest, iżda dan ikun hekk.

465
00:20:39,100 --> 00:20:40,490
Ent null prinċipali.

466
00:20:40,490 --> 00:20:45,270
Issa l-unika ħaġa prinċipali huwa għaddej
tagħmel huwa sejħa foo ukoll.

467
00:20:45,270 --> 00:20:51,050
U biss għall kicks, jien se jmorru
quddiem hawn u jgħidu printf "Hello minn

468
00:20:51,050 --> 00:20:52,340
foo. "

469
00:20:52,340 --> 00:20:52,890
>> OK.

470
00:20:52,890 --> 00:21:00,160
Mela jekk jien ma tagħmel xi żbalji,
Kun dontdothis dot mmejla.

471
00:21:00,160 --> 00:21:01,960
U ejja tagħmel dan fil-tieqa akbar -

472
00:21:01,960 --> 00:21:03,210
dot mmejla, dontdothis.

473
00:21:03,210 --> 00:21:07,590

474
00:21:07,590 --> 00:21:08,840
Come fuq.

475
00:21:08,840 --> 00:21:10,940

476
00:21:10,940 --> 00:21:11,890
Uh oh.

477
00:21:11,890 --> 00:21:13,100
Apparentement, inti tista 'tagħmel dan.

478
00:21:13,100 --> 00:21:15,190
Kkritikat dan.

479
00:21:15,190 --> 00:21:16,190
OK.

480
00:21:16,190 --> 00:21:16,580
Stenna.

481
00:21:16,580 --> 00:21:17,370
Stand mill.

482
00:21:17,370 --> 00:21:18,270
Did we -

483
00:21:18,270 --> 00:21:20,110
Aħna ma tuża bl Kun.

484
00:21:20,110 --> 00:21:22,050
>> [Sighs]

485
00:21:22,050 --> 00:21:25,110
>> Naf imma I think we
biss li imħassar.

486
00:21:25,110 --> 00:21:28,410
Uh, yeah.

487
00:21:28,410 --> 00:21:30,660
Kkritikat dan.

488
00:21:30,660 --> 00:21:32,640
Issolvi din Rob.

489
00:21:32,640 --> 00:21:34,678
What?

490
00:21:34,678 --> 00:21:35,928
Huwa sempliċi ħafna.

491
00:21:35,928 --> 00:21:43,820

492
00:21:43,820 --> 00:21:47,360
Yeah, aħna mdawrin ottimizzazzjoni off.

493
00:21:47,360 --> 00:21:48,970
OK, stand bye.

494
00:21:48,970 --> 00:21:49,950
Issa inħoss aħjar.

495
00:21:49,950 --> 00:21:51,390
OK.

496
00:21:51,390 --> 00:21:51,780
Kull dritt.

497
00:21:51,780 --> 00:21:53,430
>> Mela ejja recompile dan -

498
00:21:53,430 --> 00:21:55,880
Tagħmel inti dontdothis.

499
00:21:55,880 --> 00:22:00,090
Inti jista 'jkollok li tibdel isem dan
dothis.c fi ftit mument.

500
00:22:00,090 --> 00:22:00,710
Hemm immorru.

501
00:22:00,710 --> 00:22:01,240
Grazzi.

502
00:22:01,240 --> 00:22:02,050
OK.

503
00:22:02,050 --> 00:22:05,480
Allura l-fatt li I kien istampar
xi ħaġa kienet attwalment biss

504
00:22:05,480 --> 00:22:08,150
jonqos il-proċess li permezz tiegħu aħna
kien laħaq dak il-punt.

505
00:22:08,150 --> 00:22:08,510
OK.

506
00:22:08,510 --> 00:22:08,870
Phew!

507
00:22:08,870 --> 00:22:11,180
>> Allura dak li huwa attwalment jiġri?

508
00:22:11,180 --> 00:22:14,440
Ir-raġuni hemm, biss bħala twarrib, huwa
tagħmel xejn f'termini ta 'input u

509
00:22:14,440 --> 00:22:17,270
output għandu tendenza li jkun aktar bil-mod għaliex inti
għandek tikteb karattri għall-

510
00:22:17,270 --> 00:22:18,600
screen, Kien li tiskrollja.

511
00:22:18,600 --> 00:22:21,720
Allura storja twila fil-qosor, kellhom I attwalment
ġara hekk paċenzja, rridu naraw

512
00:22:21,720 --> 00:22:23,260
raw dan ir-riżultat finali wkoll.

513
00:22:23,260 --> 00:22:26,220
Issa li sibt ride ta 'l-istampar-ups,
naraw dan id-dritt bogħod.

514
00:22:26,220 --> 00:22:28,410
Allura għaliex qed jiġri dan.

515
00:22:28,410 --> 00:22:31,300
Ukoll, l-ispjegazzjoni sempliċi, naturalment,
hija li foo probabbilment m'għandux

516
00:22:31,300 --> 00:22:32,500
jiġu ssejjaħ lilha nnifisha.

517
00:22:32,500 --> 00:22:34,470
>> Issa f'termini ġenerali,
dan huwa recursion.

518
00:22:34,470 --> 00:22:36,970
U ħsibna ftit ġimgħat
ilu jirrikorri hija tajba.

519
00:22:36,970 --> 00:22:40,330
Recursion huwa b'dan il-mod maġika ta '
tesprimi lilek innifsek super konċiż.

520
00:22:40,330 --> 00:22:41,400
U hija biss xogħlijiet.

521
00:22:41,400 --> 00:22:45,060
Iżda hemm fattur ewlieni ta 'kollha ta'
l-programmi rikursivi konna tkellem

522
00:22:45,060 --> 00:22:48,260
dwar u ħares lejn s'issa, li
kienet li kellhom dak?

523
00:22:48,260 --> 00:22:52,610
A każ ta 'bażi, li kien xi hard coded
każ li qal f'xi sitwazzjonijiet

524
00:22:52,610 --> 00:22:56,210
ma sejħa foo, li huwa b'mod ċar
mhuwiex il-każ hawnhekk.

525
00:22:56,210 --> 00:22:58,920
>> Allura dak li hu verament jiġri
f'termini ta 'din l-istampa?

526
00:22:58,920 --> 00:23:01,790
Ukoll, meta prinċipali jitlob foo, huwa
jieħu biċċa ta 'memorja.

527
00:23:01,790 --> 00:23:04,150
Meta foo foo jitlob, jiġrilha
porzjon ta 'memorja.

528
00:23:04,150 --> 00:23:06,430
Meta foo foo jitlob, jiġrilha porzjon.

529
00:23:06,430 --> 00:23:07,080
Jiġrilha porzjon.

530
00:23:07,080 --> 00:23:08,120
Jiġrilha porzjon.

531
00:23:08,120 --> 00:23:09,460
Minħabba foo hija qatt lura.

532
00:23:09,460 --> 00:23:12,160
Aħna qatt tħassir wieħed minn dawk
frames mill-munzell.

533
00:23:12,160 --> 00:23:15,930
Allura aħna qed blowing permezz tal-borġ, mhux
nsemmux li jaf x'iktar, u

534
00:23:15,930 --> 00:23:19,600
aħna qed taqbeż il limiti ta 'tagħna
hekk imsejħa segment ta 'memorja.

535
00:23:19,600 --> 00:23:21,790
ERROR jmorru segmentazzjoni falza.

536
00:23:21,790 --> 00:23:24,110
>> Sabiex is-soluzzjoni hemm
b'mod ċar ma tagħmel dan.

537
00:23:24,110 --> 00:23:28,830
Iżda l-implikazzjoni akbar huwa li, iva,
hemm assolutament xi limitu,

538
00:23:28,830 --> 00:23:32,470
anki jekk mhuwiex definit sew, kif
bosta funzjonijiet tista 'ċċempel fil-

539
00:23:32,470 --> 00:23:34,970
programm, kif ħafna drabi funzjoni
tista 'sejħa nnifisha.

540
00:23:34,970 --> 00:23:38,430
Allura anke jekk aħna ma jippridkaw recursion
kif dan il-ħaġa potenzjalment maġika a

541
00:23:38,430 --> 00:23:41,870
Koppja ta 'ġimgħat ilu għall-sigma
funzjoni, u meta aħna tikseb l-informazzjoni

542
00:23:41,870 --> 00:23:45,270
istrutturi u CS50, tkun taf tara oħra
applikazzjonijiet għal dan, mhuwiex

543
00:23:45,270 --> 00:23:46,500
neċessarjament l-aħjar ħaġa.

544
00:23:46,500 --> 00:23:50,070
Għaliex jekk funzjoni jitlob huwa stess,
jitlob huwa stess, anki jekk ikun hemm bażi

545
00:23:50,070 --> 00:23:54,860
każ, jekk inti ma hit li każ bażi
għal 1,000 sejħiet jew 10,000 sejħiet, billi

546
00:23:54,860 --> 00:23:58,800
ħin li inti jista 'jkollok jispiċċaw tal-kamra
fuq l-hekk imsejħa munzell tiegħek u hit

547
00:23:58,800 --> 00:24:00,400
xi partijiet oħra ta 'memorja.

548
00:24:00,400 --> 00:24:03,950
Allura wisq huwa disinn trade-off
bejn eleganti u bejn

549
00:24:03,950 --> 00:24:06,920
robustezza ta partikulari tiegħek
implimentazzjoni.

550
00:24:06,920 --> 00:24:10,780
>> Allura hemm tnaqqis ieħor jew
gotcha ieħor għal dak li aħna ħadthom

551
00:24:10,780 --> 00:24:11,720
qed tagħmel s'issa.

552
00:24:11,720 --> 00:24:12,980
Meta I imsejħa getstring -

553
00:24:12,980 --> 00:24:15,120
let me jmorru lura fis bonjour-2.

554
00:24:15,120 --> 00:24:18,170
Avviż li jien ssejjaħ getstring,
li huwa jirritorna l-indirizz.

555
00:24:18,170 --> 00:24:20,730
U aħna jsostnu li llum indirizz
hija mill-borġ.

556
00:24:20,730 --> 00:24:24,480
U issa I am istampar l-
string f'dak l-indirizz.

557
00:24:24,480 --> 00:24:27,000
Imma aħna qatt ma stajt imsejjaħ il-
oppost ta 'getstring.

558
00:24:27,000 --> 00:24:30,850
Imxejna qatt kellu CALLL funzjoni simili
ungetstring, fejn inti idejn lura

559
00:24:30,850 --> 00:24:31,610
li l-memorja.

560
00:24:31,610 --> 00:24:33,250
Iżda franchement aħna probabbilment
kellu jkun.

561
00:24:33,250 --> 00:24:37,390
Għaliex jekk inżommu titlob lill-kompjuter
għall-memorja, permezz ta 'xi ħadd bħal

562
00:24:37,390 --> 00:24:40,830
getstring iżda qatt ma jagħtu lura, żgur
li wisq huwa marbut li jwassal għal

563
00:24:40,830 --> 00:24:42,970
problemi li biha aħna jispiċċaw ta 'memorja.

564
00:24:42,970 --> 00:24:46,140
>> U fil-fatt, nistgħu nħarsu għal dawn
problemi bl-għodda l-ġdida li l-użu

565
00:24:46,140 --> 00:24:47,640
huwa cryptic ftit għat-tip.

566
00:24:47,640 --> 00:24:50,960
Iżda let me imorru quddiem u tixrid it up
fuq l-iskrin fi ftit mument.

567
00:24:50,960 --> 00:24:56,940
Jien ser jimxi 'l quddiem u run Valgrind
ma parametru li l-ewwel kmand

568
00:24:56,940 --> 00:25:00,260
argument linja huwa l-isem
ta 'dak il-programm bonjour-2.

569
00:25:00,260 --> 00:25:02,650
U sfortunatament huwa
output huwa atrociously

570
00:25:02,650 --> 00:25:04,290
kumplessi għall-ebda raġuni tajba.

571
00:25:04,290 --> 00:25:06,280
Allura naraw dak kollu li mess.

572
00:25:06,280 --> 00:25:07,530
David huwa jiddikjara l-isem tiegħi.

573
00:25:07,530 --> 00:25:09,760
Allura dak il-programm
attwalment taħdem.

574
00:25:09,760 --> 00:25:11,180
U issa irridu jiksbu dan ir-riżultat.

575
00:25:11,180 --> 00:25:13,400
>> Allura Valgrind huwa simili
fl-ispirtu li GDB.

576
00:25:13,400 --> 00:25:14,950
Mhuwiex debugger per se.

577
00:25:14,950 --> 00:25:16,270
Imma hija kontrollur memorja.

578
00:25:16,270 --> 00:25:20,140
Huwa programm li se jimxu tiegħek
programm u jgħidlek jekk inti tlabt a

579
00:25:20,140 --> 00:25:23,860
kompjuter għall-memorja u qatt mogħtija li
lura, u b'hekk li jfisser li inti għandek

580
00:25:23,860 --> 00:25:24,570
nixxija memorja.

581
00:25:24,570 --> 00:25:26,240
U tnixxijiet memorja tendenza li tkun ħażina.

582
00:25:26,240 --> 00:25:29,120
U inti huwa l-utenti ta 'kompjuters għandhom
probabbilment jinħass dan, jekk għandek

583
00:25:29,120 --> 00:25:30,300
Mac jew PC.

584
00:25:30,300 --> 00:25:33,730
Qatt użati kompjuter tiegħek għall-
filwaqt u mhux fasslu f'diversi

585
00:25:33,730 --> 00:25:36,820
jum, jew inti ħadthom biss ltqajna lott ta '
programmi li jibda, u l-ħaġa kkritikat

586
00:25:36,820 --> 00:25:42,360
inaqqas biex jieqaf tħin, jew għall-inqas
huwa super annoying għall-użu, minħabba

587
00:25:42,360 --> 00:25:44,350
kollox biss ltqajna super bil-mod.

588
00:25:44,350 --> 00:25:46,260
>> Issa li jista 'jkun kull numru ta' raġunijiet.

589
00:25:46,260 --> 00:25:49,600
Dan jista 'jkun loop infinita, bug
kodiċi ta 'xi ħadd, jew, aktar sempliċi,

590
00:25:49,600 --> 00:25:53,250
jista 'jfisser li inti qed tuża aktar
memorja, jew jippruvaw, minn tiegħek

591
00:25:53,250 --> 00:25:54,920
kompjuter attwalment għandha.

592
00:25:54,920 --> 00:25:57,770
U forsi hemm bug f'xi programm
li jżommu tistaqsi għall-memorja.

593
00:25:57,770 --> 00:26:02,480
Browsers għas-snin kienu notorji għal
dan, titlob għall-memorja aktar u aktar

594
00:26:02,480 --> 00:26:03,870
iżda qatt għoti lura.

595
00:26:03,870 --> 00:26:07,220
Żgur, jekk inti biss għandek finite
ammont tal-memorja, inti ma tistax titlob

596
00:26:07,220 --> 00:26:09,990
infinitament ħafna drabi għall-
xi wħud li l-memorja.

597
00:26:09,990 --> 00:26:13,070
>> U għalhekk dak li tara hawn, anke jekk
darb'oħra output Valgrind huwa

598
00:26:13,070 --> 00:26:17,490
kumplikat bla bżonn li t'għajn lejn
ewwel, dan huwa l-parti interessanti.

599
00:26:17,490 --> 00:26:18,890
Borġ -

600
00:26:18,890 --> 00:26:20,060
fl-użu fil-ħruġ.

601
00:26:20,060 --> 00:26:22,810
Allura hawnhekk kemm memorja kienet
fl-użu fil-borġ fil-

602
00:26:22,810 --> 00:26:24,300
ħin tal-programm tiegħi ħareġ -

603
00:26:24,300 --> 00:26:27,280
apparentement sitt bytes fir blokka waħda.

604
00:26:27,280 --> 00:26:28,710
Hekk jien ser mewġa idejn tiegħi
lejn dak blokk huwa.

605
00:26:28,710 --> 00:26:31,270
Jaħsbu li huwa biss blokki, aktar
kelma teknika għall blokki.

606
00:26:31,270 --> 00:26:33,140
Iżda sitt bytes -

607
00:26:33,140 --> 00:26:36,870
liema huma l-sitt bytes li
kienu għadhom fl-użu?

608
00:26:36,870 --> 00:26:37,390
>> Eżattament.

609
00:26:37,390 --> 00:26:41,520
D-A-V-I-D backslash żero, ħamsa ittra
isem flimkien mal-terminatur null.

610
00:26:41,520 --> 00:26:46,350
Allura dan il-programm Valgrind ndunat li jien
talab għal sitt bytes, apparentement, billi

611
00:26:46,350 --> 00:26:48,950
mod ta getstring, iżda qatt ma
tawhom lura.

612
00:26:48,950 --> 00:26:52,030
U fil-fatt, dan jista 'ma jkunx hekk
ovvja jekk programm tiegħi ma 'tliet

613
00:26:52,030 --> 00:26:53,590
linji, iżda huwa 300 linji.

614
00:26:53,590 --> 00:26:56,920
Allura nistgħu ngħidu jagħtu kmand ieħor
argument linja li Valgrind li

615
00:26:56,920 --> 00:26:58,290
jagħmilha aktar verbose.

616
00:26:58,290 --> 00:26:59,760
Huwa ftit annoying li wieħed jiftakru.

617
00:26:59,760 --> 00:27:01,580
Imma jekk I do -

618
00:27:01,580 --> 00:27:01,930
ejja ara.

619
00:27:01,930 --> 00:27:03,540
Nixxija -

620
00:27:03,540 --> 00:27:05,030
Ma kien nixxija -

621
00:27:05,030 --> 00:27:07,580
anke I ma tiftakarx
dak li huwa off-idejn.

622
00:27:07,580 --> 00:27:08,550
>> - Leakage-verifika ugwali sħiħa.

623
00:27:08,550 --> 00:27:10,180
Yep, nirringrazzjak.

624
00:27:10,180 --> 00:27:12,520
- Leakage-verifika ugwali sħiħa.

625
00:27:12,520 --> 00:27:13,800
Ikteb.

626
00:27:13,800 --> 00:27:14,940
Istess programm qed taħdem.

627
00:27:14,940 --> 00:27:16,180
Tip David darb'oħra.

628
00:27:16,180 --> 00:27:17,660
Issa nara ftit aktar dettall.

629
00:27:17,660 --> 00:27:20,890
Iżda taħt is-sommarju borġ, li
hija identika għal erba - ah,

630
00:27:20,890 --> 00:27:22,120
dan huwa tip ta 'sbieħ.

631
00:27:22,120 --> 00:27:25,460
Issa Valgrind huwa attwalment tfittex
ftit diffiċli fil-kodiċi tiegħi.

632
00:27:25,460 --> 00:27:29,580
U huwa qal li, apparentement,
malloc fil-linja -

633
00:27:29,580 --> 00:27:30,580
aħna zoom out.

634
00:27:30,580 --> 00:27:31,980
Fil line -

635
00:27:31,980 --> 00:27:32,930
ma naraw liema linja huwa.

636
00:27:32,930 --> 00:27:35,110
Iżda malloc hija l-ewwel ħati.

637
00:27:35,110 --> 00:27:38,630
Hemm blog malloc.

638
00:27:38,630 --> 00:27:39,810
>> Kull dritt?

639
00:27:39,810 --> 00:27:40,450
OK, l-ebda.

640
00:27:40,450 --> 00:27:40,940
Dritt?

641
00:27:40,940 --> 00:27:42,520
I imsejħa getstring.

642
00:27:42,520 --> 00:27:44,460
getstring apparentement jitlob malloc.

643
00:27:44,460 --> 00:27:47,800
Allura dak linja tal-kodiċi hija apparentement
tort talli

644
00:27:47,800 --> 00:27:49,050
allokat dan il-memorja?

645
00:27:49,050 --> 00:27:51,560

646
00:27:51,560 --> 00:27:55,540
Ejja nassumu li kull min kiteb malloc
kien madwar twil biżżejjed li huwa

647
00:27:55,540 --> 00:27:56,390
mhux tort tagħhom.

648
00:27:56,390 --> 00:27:57,520
Allura huwa probabbilment minjiera.

649
00:27:57,520 --> 00:28:02,000
getstring fil cs50.c - b'tali mod li l-
fajl x'imkien fuq il-kompjuter -

650
00:28:02,000 --> 00:28:05,210
fil-linja 286 jidher li jkun il-ħati.

651
00:28:05,210 --> 00:28:08,140
Issa ejja nassumu li cs50 kien
madwar għal ammont deċenti ta 'żmien, sabiex

652
00:28:08,140 --> 00:28:09,720
aħna wisq huma infallibbli.

653
00:28:09,720 --> 00:28:14,080
U dan huwa probabbilment mhux getstring
li l-bug tinsab, iżda pjuttost fil-

654
00:28:14,080 --> 00:28:17,810
linja bonjour-2.c 18.

655
00:28:17,810 --> 00:28:20,670
>> Mela ejja tagħti ħarsa lejn
dak li linja 18 kien.

656
00:28:20,670 --> 00:28:21,130
Oh.

657
00:28:21,130 --> 00:28:27,130
B'xi din il-linja mhux neċessarjament
buggy, per se, iżda huwa r-raġuni

658
00:28:27,130 --> 00:28:28,630
wara li l-memorja tnixxija.

659
00:28:28,630 --> 00:28:32,140
Allura super sempliċi, dak li kieku intuwittivament
jkun is-soluzzjoni hawn?

660
00:28:32,140 --> 00:28:34,710
Jekk aħna qed tistaqsi għall-memorja, qatt ma kienu
tagħtiha lura, u li jidher li jkun

661
00:28:34,710 --> 00:28:37,940
problema għaliex matul iż-żmien tal-kompjuter tiegħi
tista jispiċċaw ta 'memorja, jista bil-mod

662
00:28:37,940 --> 00:28:42,110
isfel, affarijiet ħżiena jista 'jiġri, ukoll,
x'hemm-soluzzjoni intuwittivi sempliċi?

663
00:28:42,110 --> 00:28:43,140
Just tagħtiha lura.

664
00:28:43,140 --> 00:28:44,770
>> Kif inti tillibera li l-memorja?

665
00:28:44,770 --> 00:28:49,970
Ukoll, Thankfully huwa pjuttost sempliċi
li biss jgħidu isem ħielsa.

666
00:28:49,970 --> 00:28:51,260
U aħna stajt qatt sar qabel dan.

667
00:28:51,260 --> 00:28:55,890
Iżda int tista 'essenzjalment taħseb
ħielsa kif l-oppost ta malloc.

668
00:28:55,890 --> 00:28:58,030
ħieles huwa l-oppost ta '
allokazzjoni memorja.

669
00:28:58,030 --> 00:28:59,540
Allura issa let me recompile dan.

670
00:28:59,540 --> 00:29:02,050
Kun bonjour-2.

671
00:29:02,050 --> 00:29:04,620
Let me run mill-ġdid. bonjour-2 David.

672
00:29:04,620 --> 00:29:07,290
Għalhekk jidher li jaħdem fil-
bl-istess mod.

673
00:29:07,290 --> 00:29:11,180
Imma jekk immur lura għall Valgrind u jerġa 'jsir
l-istess kmand ġodda tiegħi

674
00:29:11,180 --> 00:29:14,720
miġbura programm, ittajpjar
fl-isem tiegħi bħal qabel -

675
00:29:14,720 --> 00:29:15,370
sbieħ.

676
00:29:15,370 --> 00:29:16,760
Sommarju borġ -

677
00:29:16,760 --> 00:29:17,740
fl-użu fil-ħruġ -

678
00:29:17,740 --> 00:29:19,370
żero bytes fi blokki żero.

679
00:29:19,370 --> 00:29:21,840
U dan huwa super sbieħ, kollha
blokki borġ kienu meħlusa.

680
00:29:21,840 --> 00:29:23,480
Ebda tnixxijiet huma possibbli.

681
00:29:23,480 --> 00:29:27,200
>> Allura ġejjin up, mhux ma Problem Set 4,
iżda ma Problema Set 5, l-forensika

682
00:29:27,200 --> 00:29:30,740
u 'l quddiem, dan ukoll se ssir
miżura tal-korrettezza tal tiegħek

683
00:29:30,740 --> 00:29:33,630
programm, jekk jew le inti għandek
jew ma jkollhomx tnixxijiet memorja.

684
00:29:33,630 --> 00:29:36,900
Iżda Thankfully, mhux biss tista 'raġuni
permezz tagħhom intuwittivament, li

685
00:29:36,900 --> 00:29:40,430
hija, forsi, faċli għall-programmi żgħar
iżda diffiċli għal programmi akbar,

686
00:29:40,430 --> 00:29:43,860
Valgrind, għal dawk il-programmi akbar,
jistgħu jgħinuk tidentifika

687
00:29:43,860 --> 00:29:45,360
il-problema partikolari.

688
00:29:45,360 --> 00:29:47,500
>> Iżda hemm problema waħda oħra
li jistgħu jinqalgħu.

689
00:29:47,500 --> 00:29:51,245
Let me tiftaħ dan il-fajl hawn, li hija,
għal darb'oħra, eżempju kemmxejn sempliċi.

690
00:29:51,245 --> 00:29:53,760
Imma ejja tiffoka fuq dak
dan il-programm ma.

691
00:29:53,760 --> 00:29:55,190
Din tissejjaħ memory.c.

692
00:29:55,190 --> 00:29:58,380
Aħna ser post dan illum aktar tard fil-
zip ta 'source code tal-lum.

693
00:29:58,380 --> 00:30:01,610
U tinnota li għandi funzjoni msejħa
f li jieħu l-ebda argumenti u

694
00:30:01,610 --> 00:30:02,800
prospetti xejn.

695
00:30:02,800 --> 00:30:07,240
F'konformità 20, jien apparentement tiddikjara
pointer għal int u ssejjaħ dan x.

696
00:30:07,240 --> 00:30:09,570
Jien tassenja huwa r-ritorn
valur tal malloc.

697
00:30:09,570 --> 00:30:14,590
U biss li tkun ċara, kemm bytes am
I probabbilment jkollna lura minn malloc

698
00:30:14,590 --> 00:30:17,080
f'din is-sitwazzjoni?

699
00:30:17,080 --> 00:30:18,040
>> Probabbilment 40.

700
00:30:18,040 --> 00:30:18,840
Fejn tista 'tikseb dan minn?

701
00:30:18,840 --> 00:30:22,410
Ukoll, jekk inti recall li int spiss
4 bytes, għall-inqas huwa fl-

702
00:30:22,410 --> 00:30:25,110
appliance, 10 darbiet 4 hija ovvjament 40.

703
00:30:25,110 --> 00:30:28,920
Allura malloc huwa jirritorna l-indirizz ta '
blokki ta 'memorja u l-ħażna li

704
00:30:28,920 --> 00:30:30,800
jindirizzaw finalment x.

705
00:30:30,800 --> 00:30:32,570
Allura biex tkun ċara, liema
allura qed jiġri?

706
00:30:32,570 --> 00:30:34,990
Well, let me jaqilbu lura
li stampa tagħna hawn.

707
00:30:34,990 --> 00:30:38,150
Let me mhux biss jiġbed l-qiegħ tal tiegħi
memorja tal-kompjuter, let me imorru quddiem u

708
00:30:38,150 --> 00:30:42,990
jiġbed l-rettangolu kollu li
jirrappreżenta kollha RAM tiegħi.

709
00:30:42,990 --> 00:30:44,790
>> Aħna ser ngħidu li l-munzell
huwa fuq il-qiegħ.

710
00:30:44,790 --> 00:30:47,010
U hemm segment test
id-dejta uninitialized.

711
00:30:47,010 --> 00:30:49,880
Imma jien biss se astratt dawk
affarijiet oħra bogħod bħala dot, dot dot.

712
00:30:49,880 --> 00:30:53,470
Jien biss ser jirreferi għal dan
bħala l-borġ fil-quċċata.

713
00:30:53,470 --> 00:30:57,070
U mbagħad fil-qiegħ ta 'din l-istampa,
biex jirrappreżentaw prinċipali, jien ser

714
00:30:57,070 --> 00:30:59,880
biex tagħtiha memorja flieli
fuq il-munzell.

715
00:30:59,880 --> 00:31:03,150
Għal f, jien ser tagħtiha porzjon
tal-memorja fuq il-munzell.

716
00:31:03,150 --> 00:31:05,140
Issa, I ltqajna biex tikkonsulta tiegħi
kodiċi tas-sors mill-ġdid.

717
00:31:05,140 --> 00:31:07,170
X'inhuma l-varjazzjonijiet lokali għall ewlieni?

718
00:31:07,170 --> 00:31:10,710
Apparentement xejn, sabiex dak il-porzjon huwa
effettivament vojta jew lanqas bħala kbar

719
00:31:10,710 --> 00:31:11,600
kif stajt irtirat hu.

720
00:31:11,600 --> 00:31:15,730
Iżda fil-f, I jkollhom varjabbli lokali,
li tissejjaħ x.

721
00:31:15,730 --> 00:31:20,410
Hekk jien ser jimxi 'l quddiem u jagħti f
blokki ta 'memorja, ssejjaħ dan x.

722
00:31:20,410 --> 00:31:24,680
>> U issa malloc 10 darbiet 4,
Allura malloc 40, fejn jgħid li

723
00:31:24,680 --> 00:31:25,430
memorja ġejjin minn?

724
00:31:25,430 --> 00:31:27,530
Imxejna ma tfasslux stampa
bħal dan qabel.

725
00:31:27,530 --> 00:31:31,140
Imma ejja nassumu li huwa effettiv
ġejjin minn hawn, hekk wieħed,

726
00:31:31,140 --> 00:31:33,170
tnejn, tlieta, erba ', ħames.

727
00:31:33,170 --> 00:31:34,680
U issa I bżonn 40 ta 'dawn.

728
00:31:34,680 --> 00:31:37,540
So I ser biss tagħmel dot, dot, dot li tissuġġerixxi
li hemm saħansitra aktar memorja

729
00:31:37,540 --> 00:31:39,350
ġejjin lura mill-borġ.

730
00:31:39,350 --> 00:31:40,710
Issa x'inhu l-indirizz?

731
00:31:40,710 --> 00:31:42,620
Ejja jagħżlu arbitrarja tagħna
tindirizza kif dejjem -

732
00:31:42,620 --> 00:31:46,310
Ox123, anki jekk huwa probabbilment se
li hija xi ħaġa kompletament differenti.

733
00:31:46,310 --> 00:31:50,420
Dik hija l-indirizz tal-ewwel byte fl
memorja li jien tistaqsi malloc għall.

734
00:31:50,420 --> 00:31:53,630
>> Għalhekk fil-qosor, linja darba 20 tesegwixxi,
dak li hu litteralment

735
00:31:53,630 --> 00:31:57,170
maħżuna ġewwa ta 'x hawn?

736
00:31:57,170 --> 00:31:58,730
Ox123.

737
00:31:58,730 --> 00:32:00,370
Ox123.

738
00:32:00,370 --> 00:32:01,550
U l-OX huwa uninteresting.

739
00:32:01,550 --> 00:32:03,200
Dan ifisser biss Heres
numru hexadeċimali.

740
00:32:03,200 --> 00:32:06,490
Imma x'hemm importanti hu li dak li stajt maħżen
fl x, li huwa varjabbli lokali.

741
00:32:06,490 --> 00:32:10,260
Iżda tip tad-data tiegħu, għal darb'oħra,
huwa indirizz ta 'int.

742
00:32:10,260 --> 00:32:12,710
Well, jien ser taħżen Ox123.

743
00:32:12,710 --> 00:32:16,610
Iżda għal darb'oħra, jekk dan huwa ftit wisq
komplikati żżejjed, jekk I iscroll

744
00:32:16,610 --> 00:32:21,490
lura, nistgħu astratt dan bogħod pjuttost
raġonevolment u biss jgħidu li x hija

745
00:32:21,490 --> 00:32:23,910
pointer għal dak blokki ta 'memorja.

746
00:32:23,910 --> 00:32:24,070
>> OK.

747
00:32:24,070 --> 00:32:26,230
Issa l-kwistjoni fil-idejn
huwa dan li ġej -

748
00:32:26,230 --> 00:32:29,910
linja 21, jirriżulta, huwa Buggy.

749
00:32:29,910 --> 00:32:31,160
Għaliex?

750
00:32:31,160 --> 00:32:34,890

751
00:32:34,890 --> 00:32:36,930
>> Jiddispjacini?

752
00:32:36,930 --> 00:32:38,640
Huwa ma jkollu -

753
00:32:38,640 --> 00:32:40,390
jgħidu li darba aktar.

754
00:32:40,390 --> 00:32:41,240
Ukoll, ma ħielsa.

755
00:32:41,240 --> 00:32:42,350
Allura dak tat-tieni imma.

756
00:32:42,350 --> 00:32:45,000
Allura hemm waħda oħra biss, speċifikament
fil-linja 21.

757
00:32:45,000 --> 00:32:49,480

758
00:32:49,480 --> 00:32:50,040
>> Eżattament.

759
00:32:50,040 --> 00:32:54,980
Din il-linja sempliċi ta 'kodiċi hija biss
overflow buffer, overrun buffer.

760
00:32:54,980 --> 00:32:57,050
A buffer ifisser biss blokki ta 'memorja.

761
00:32:57,050 --> 00:33:01,520
Imma dak blokki ta 'memorja huwa ta' daqs
10, 10 interi, li jfisser li jekk irridu

762
00:33:01,520 --> 00:33:05,350
indiċi ġewwa fiha billi tuża z-zokkor sintattika
ta 'notazzjoni array, il-kwadru

763
00:33:05,350 --> 00:33:09,220
parentesi, ikollok aċċess għall-
x bracket 0 x 1 x bracket,

764
00:33:09,220 --> 00:33:10,390
bracket dot, dot, dot.

765
00:33:10,390 --> 00:33:13,270
x bracket 9 hija l-akbar wieħed.

766
00:33:13,270 --> 00:33:17,680
Mela jekk nagħmel x bracket 10, fejn
Jien attwalment għaddejjin fil-memorja?

767
00:33:17,680 --> 00:33:19,120
>> Ukoll, jekk ikolli 10 int -

768
00:33:19,120 --> 00:33:21,070
ejja fil-fatt jiġbed kollha
minn dawn hawn.

769
00:33:21,070 --> 00:33:22,700
Allura li kienet l-ewwel ħamsa.

770
00:33:22,700 --> 00:33:24,660
Hawn il-ħames ints oħra.

771
00:33:24,660 --> 00:33:29,580
Allura x bracket 0 huwa hawnhekk. x bracket 1 huwa
hawn. x bracket 9 huwa hawnhekk. x bracket

772
00:33:29,580 --> 00:33:37,960
10 huwa hawnhekk, li jfisser I am javżak,
fil-linja 21, il-kompjuter li jpoġġi l-

773
00:33:37,960 --> 00:33:39,400
Numru fejn?

774
00:33:39,400 --> 00:33:42,010
In-numru 0 fejn?

775
00:33:42,010 --> 00:33:43,380
Ukoll, huwa 0, iva.

776
00:33:43,380 --> 00:33:45,460
Iżda biss l-fatt li 0 tagħha
huwa tip ta 'koinċidenza.

777
00:33:45,460 --> 00:33:47,140
Dan jista 'jkun in-numru
50, għal kulħadd aħna kura.

778
00:33:47,140 --> 00:33:50,480
Iżda aħna qed tipprova tqiegħed lilha fuq x bracket
10, li huwa fejn dan

779
00:33:50,480 --> 00:33:53,700
trade mark in kwistjoni huwa mfassal, li
mhix ħaġa tajba.

780
00:33:53,700 --> 00:33:57,070
Dan il-programm jista 'tajjeb ħafna
crash bħala riżultat.

781
00:33:57,070 --> 00:33:59,400
>> Issa, ejja imorru quddiem u ara jekk dan
huwa, tabilħaqq, dak li jiġri.

782
00:33:59,400 --> 00:34:02,600
Jagħmlu memorja, peress li l-fajl
huwa msejjaħ memory.c.

783
00:34:02,600 --> 00:34:05,950
Ejja imorru quddiem u run
il-memorja programm.

784
00:34:05,950 --> 00:34:08,239
Allura aħna ltqajna xxurtjati, fil-fatt, jidher.

785
00:34:08,239 --> 00:34:09,340
Sirna xxurtjati.

786
00:34:09,340 --> 00:34:11,060
Imma ejja ara jekk irridu issa run Valgrind.

787
00:34:11,060 --> 00:34:14,170
Ewwel daqqa t'għajn, programm tiegħi jista
jidhru li huma perfettament korretta.

788
00:34:14,170 --> 00:34:18,010
Iżda let me run Valgrind mal-
- Leakage-verifika ugwali sħiħa fuq il-memorja.

789
00:34:18,010 --> 00:34:20,110
>> U issa meta I run dan -

790
00:34:20,110 --> 00:34:21,030
interessanti.

791
00:34:21,030 --> 00:34:26,800
Invalid jiktbu ta 'daqs 4 fi
linja 21 ta memory.c.

792
00:34:26,800 --> 00:34:29,284
Linja 21 ta memory.c huwa li wieħed?

793
00:34:29,284 --> 00:34:30,340
Oh, interessanti.

794
00:34:30,340 --> 00:34:31,080
Imma stenna.

795
00:34:31,080 --> 00:34:32,389
Daqs 4, dak hu li jirreferu għall?

796
00:34:32,389 --> 00:34:34,969
I biss ma wieħed jikteb,
iżda huwa ta 'daqs 4.

797
00:34:34,969 --> 00:34:36,889
Għaliex huwa 4?

798
00:34:36,889 --> 00:34:39,280
Huwa għaliex dan huwa int, li
huwa, għal darb'oħra, erba bytes.

799
00:34:39,280 --> 00:34:42,510
Allura Valgrind sabet bug li I,
glancing fil-kodiċi tiegħi, ma.

800
00:34:42,510 --> 00:34:45,040
U forsi TF tiegħek kieku jew ma.

801
00:34:45,040 --> 00:34:48,469
What Iżda Valgrind għal dak żgur sabet
ħadna żball hemm, anke

802
00:34:48,469 --> 00:34:52,719
jekk aħna ltqajna xxurtjati, u l-kompjuter
iddeċieda, eh, jien mhux ser crash

803
00:34:52,719 --> 00:34:57,470
sempliċiment għaliex inti mimsus byte wieħed, waħda
jiswew int ta 'memorja li inti ma

804
00:34:57,470 --> 00:34:58,550
attwalment stess.

805
00:34:58,550 --> 00:35:00,380
>> Well, x'iktar huwa Buggy hawn.

806
00:35:00,380 --> 00:35:01,180
Indirizz -

807
00:35:01,180 --> 00:35:03,190
dan huwa indirizz crazy tfittex
f'hexadecimal.

808
00:35:03,190 --> 00:35:06,890
Dan ifisser biss x'imkien fil-borġ huwa
żero bytes wara blokk ta 'daqs 40

809
00:35:06,890 --> 00:35:07,620
huwa allokat.

810
00:35:07,620 --> 00:35:10,610
Let me zoom out hawn u ara jekk
dan huwa xi ftit aktar utli.

811
00:35:10,610 --> 00:35:11,410
Interessanti.

812
00:35:11,410 --> 00:35:15,600
40 bytes huma definittivament mitlufa
fir-rekord telf 1 ta '1.

813
00:35:15,600 --> 00:35:17,840
Għal darb'oħra, kliem aktar milli huwa utli hawn.

814
00:35:17,840 --> 00:35:21,350
Iżda bbażata fuq il-linji indikati,
fejn għandi probabbilment tiffoka tiegħi

815
00:35:21,350 --> 00:35:24,070
attenzjoni għall bug ieħor?

816
00:35:24,070 --> 00:35:26,570
Qisu linja 20 ta memory.c.

817
00:35:26,570 --> 00:35:30,990
>> Hekk jekk immorru lura għal-linja 20, dak l-
wieħed li inti identifikat aktar kmieni.

818
00:35:30,990 --> 00:35:33,030
U huwa mhux neċessarjament buggy.

819
00:35:33,030 --> 00:35:35,160
Imma aħna għandna dan maqluba effetti tiegħu.

820
00:35:35,160 --> 00:35:38,790
Allura kif nista korretta mill-inqas
wieħed minn dawk l-iżbalji?

821
00:35:38,790 --> 00:35:42,240
Liema jista 'nagħmel wara linja 21?

822
00:35:42,240 --> 00:35:47,110
I jistgħu jagħmlu mingħajr x, għalhekk hija
li jagħtu lura li l-memorja.

823
00:35:47,110 --> 00:35:49,230
U kif nista jiffissaw dan bug?

824
00:35:49,230 --> 00:35:52,120
I għandek definittivament tmur
aktar il-bogħod minn 0.

825
00:35:52,120 --> 00:35:53,670
So let me jippruvaw u jerġa 'jsir dan.

826
00:35:53,670 --> 00:35:56,080
Jiddispjacini, definittivament jmorru
aktar il-bogħod minn 9.

827
00:35:56,080 --> 00:35:57,510
Għamla memorja.

828
00:35:57,510 --> 00:36:00,650
Let me terġa Valgrind
fil-tieqa akbar.

829
00:36:00,650 --> 00:36:01,580
U issa tfittex.

830
00:36:01,580 --> 00:36:02,250
Nizza.

831
00:36:02,250 --> 00:36:03,270
Kollha blokki borġ kienu meħlusa.

832
00:36:03,270 --> 00:36:04,270
Ebda tnixxijiet huma possibbli.

833
00:36:04,270 --> 00:36:07,520
U sa hawn fuq hawn, hemm l-ebda referenza
kwalunkwe aktar tad-dritt invalida.

834
00:36:07,520 --> 00:36:09,820
>> Just biex jiksbu greedy, u ejja
ara jekk demostrazzjoni oħra

835
00:36:09,820 --> 00:36:11,050
ma jmurx kif maħsub -

836
00:36:11,050 --> 00:36:12,560
I ma jiksbu xxurtjati mument ilu.

837
00:36:12,560 --> 00:36:15,530
U l-fatt li dan huwa 0 huwa forsi
qarrieqa bla bżonn.

838
00:36:15,530 --> 00:36:20,650
Ejja biss tagħmel 50, kemmxejn arbitrarja
numru, għamla memorja memorja dot mmejla -

839
00:36:20,650 --> 00:36:21,410
xorta jiksbu xxurtjati.

840
00:36:21,410 --> 00:36:22,510
Xejn s jiġġarrfu.

841
00:36:22,510 --> 00:36:26,150
Ejja ngħidu I biss tagħmel xi ħaġa verament
foolish, u I do 100.

842
00:36:26,150 --> 00:36:30,360
Let me remake memorja,
dot mmejla memorja -

843
00:36:30,360 --> 00:36:31,075
ltqajna xxurtjati darb'oħra.

844
00:36:31,075 --> 00:36:32,800
Kif madwar 1,000?

845
00:36:32,800 --> 00:36:35,370
ints lil hinn, bejn wieħed u ieħor,
fejn I għandhom ikunu?

846
00:36:35,370 --> 00:36:37,410
Għamla memorja -

847
00:36:37,410 --> 00:36:38,570
kkritikat dan.

848
00:36:38,570 --> 00:36:39,920
>> [Daħk]

849
00:36:39,920 --> 00:36:41,270
>> OK.

850
00:36:41,270 --> 00:36:43,920
Ejja ma mess madwar aktar.

851
00:36:43,920 --> 00:36:45,120
Terġa 'ssir memorja.

852
00:36:45,120 --> 00:36:45,840
Hemm immorru.

853
00:36:45,840 --> 00:36:46,410
Kull dritt.

854
00:36:46,410 --> 00:36:52,500
Allura apparentement inti indiċi 100.000 ints
lil hinn fejn għandek ilhom

855
00:36:52,500 --> 00:36:54,410
memorja, affarijiet ħżiena jiġri.

856
00:36:54,410 --> 00:36:56,430
Allura dan huwa ovvjament mhux
a hard, regola fast.

857
00:36:56,430 --> 00:36:58,190
I kien tip ta 'użu ta' prova
u żball biex naslu s'hemm.

858
00:36:58,190 --> 00:37:02,230
Iżda dan huwa minħabba, storja twila fil-qosor,
memorja tal-kompjuter tiegħek huwa maqsum ukoll

859
00:37:02,230 --> 00:37:03,580
fis-dawn l-affarijiet imsejħa segmenti.

860
00:37:03,580 --> 00:37:07,260
U xi kultant, il-kompjuter fil-fatt
tak ftit aktar memorja

861
00:37:07,260 --> 00:37:08,400
milli inti titlob.

862
00:37:08,400 --> 00:37:12,170
Iżda għall-effiċjenza, huwa biss aktar faċli biex
tikseb aktar memorja, iżda biss jgħidlek

863
00:37:12,170 --> 00:37:13,780
li int jkollna porzjon ta 'dan.

864
00:37:13,780 --> 00:37:16,370
>> U jekk ikollok xortik tajba kultant,
Għalhekk, inti tista 'tkun tista' tmiss

865
00:37:16,370 --> 00:37:17,795
memorja li ma jappartjenix lilek.

866
00:37:17,795 --> 00:37:21,860
Inti għandek l-ebda garanzija li dak il-valur
inti tpoġġi hemm se jibqgħu hemm, għaliex

867
00:37:21,860 --> 00:37:25,080
il-kompjuter xorta jaħseb mhuwiex
tiegħek, iżda mhux neċessarjament għaddej

868
00:37:25,080 --> 00:37:29,910
li tolqot taqsima oħra ta 'memorja fil-
kompjuter u jinduċi żball bħal

869
00:37:29,910 --> 00:37:31,710
dan wieħed hawn.

870
00:37:31,710 --> 00:37:32,060
Kull dritt.

871
00:37:32,060 --> 00:37:37,240
Kwalunkwe mistoqsijiet imbagħad fuq memorja?

872
00:37:37,240 --> 00:37:37,590
>> Kull dritt.

873
00:37:37,590 --> 00:37:40,610
Ejja tagħti ħarsa hawn, imbagħad, fil-
xi ħaġa li aħna kont qed tieħu għal

874
00:37:40,610 --> 00:37:48,361
mogħti għal żmien pjuttost twil, li
Huwa f'dan inkartament imsejjaħ cs50.h.

875
00:37:48,361 --> 00:37:49,420
Allura dan huwa fajl.

876
00:37:49,420 --> 00:37:51,130
Dawn huma biss mazz sħiħ
ta 'kummenti up top.

877
00:37:51,130 --> 00:37:53,900
U inti jista 'jkollok ħares lejn dan jekk
inti poked madwar fuq l-appliance.

878
00:37:53,900 --> 00:37:57,000
Iżda jirriżulta li l-ħin kollu,
meta aħna użati biex jużaw string bħala

879
00:37:57,000 --> 00:38:01,130
sinonimu, il-mezzi li bihom aħna ddikjarat
li sinonimu kien ma 'dan

880
00:38:01,130 --> 00:38:03,990
keyword typedef, għal definizzjoni tip.

881
00:38:03,990 --> 00:38:07,500
U aħna qed essenzjalment tgħid, tagħmel
string sinonimu għal star char.

882
00:38:07,500 --> 00:38:11,190
Li l-mezzi li bihom il-munzell
maħluqa dawn ir-roti ta 'taħriġ magħrufa bħala

883
00:38:11,190 --> 00:38:12,040
l-sekwenza.

884
00:38:12,040 --> 00:38:14,830
>> Issa hawn biss prototip
għall getchar.

885
00:38:14,830 --> 00:38:17,350
Aħna tista raw qabel, iżda li
tabilħaqq dak li tagħmel. getchar

886
00:38:17,350 --> 00:38:19,070
jieħu ebda argumenti, jirritorna char.

887
00:38:19,070 --> 00:38:21,340
getdouble jieħu ebda argumenti,
jirritorna doppja.

888
00:38:21,340 --> 00:38:24,440
getfloat jieħu ebda argumenti, prospetti
a float, u oħrajn.

889
00:38:24,440 --> 00:38:27,270
getint huwa fil hawn. getlonglong
huwa fil hawn.

890
00:38:27,270 --> 00:38:28,820
U getstring huwa fil hawn.

891
00:38:28,820 --> 00:38:29,420
U li hu.

892
00:38:29,420 --> 00:38:33,080
Din il-linja vjola huwa Preprocessor ieħor
Direttiva minħabba

893
00:38:33,080 --> 00:38:35,550
hashtag fil-bidu ta 'dan.

894
00:38:35,550 --> 00:38:35,870
>> Kull dritt.

895
00:38:35,870 --> 00:38:38,380
Allura issa let me jmorru fil cs50.c.

896
00:38:38,380 --> 00:38:40,400
U aħna mhux se jitkellmu twil wisq dwar dan.

897
00:38:40,400 --> 00:38:43,280
Iżda biex jagħtuk idea ta 'x'hemm
ilu għaddej dan kollu

898
00:38:43,280 --> 00:38:46,434
ħin, let me go għal -

899
00:38:46,434 --> 00:38:48,250
ejja do getchar.

900
00:38:48,250 --> 00:38:51,050
Allura getchar huwa l-aktar kummenti.

901
00:38:51,050 --> 00:38:52,060
Iżda jidher qisu dan.

902
00:38:52,060 --> 00:38:54,800
Allura dan huwa l-funzjoni effettiva
getchar li aħna kont qed

903
00:38:54,800 --> 00:38:56,055
tieħu għall mogħtija jeżisti.

904
00:38:56,055 --> 00:38:59,370
U anke jekk aħna ma jużaw dan wieħed
li spiss, jekk qatt, huwa inqas

905
00:38:59,370 --> 00:39:00,470
relattivament sempliċi.

906
00:39:00,470 --> 00:39:02,580
Allura huwa min jieħu
ħarsa lejn hawn.

907
00:39:02,580 --> 00:39:06,540
>> Allura getchar għandha loop infinita,
deliberatament hekk apparentement.

908
00:39:06,540 --> 00:39:10,050
Imbagħad jitlob - u dan huwa tip ta '
użu mill-ġdid sbieħ ta 'kodiċi aħna lilna nfusna kiteb.

909
00:39:10,050 --> 00:39:11,220
Huwa jappella getstring.

910
00:39:11,220 --> 00:39:12,460
Minħabba dak ma
jfissirx li tikseb char?

911
00:39:12,460 --> 00:39:14,730
Ukoll, inti tista 'ukoll tipprova tikseb
linja kollha ta 'test mill-utent u

912
00:39:14,730 --> 00:39:16,940
imbagħad biss ħarsa lejn wieħed
ta 'dawk il-karattri.

913
00:39:16,940 --> 00:39:19,170
F'konformità 60, hawn ftit
daqsxejn ta 'verifika sanità.

914
00:39:19,170 --> 00:39:21,610
Jekk getstring lura null,
ejja ma tipproċedi.

915
00:39:21,610 --> 00:39:22,820
Xi ħaġa li marret ħażin.

916
00:39:22,820 --> 00:39:28,120
>> Issa dan huwa kemmxejn tedjanti iżda
konvenzjonali C. char max probabbilment

917
00:39:28,120 --> 00:39:29,960
jirrappreżenta biss dak li
ibbażata fuq l-isem tagħha?

918
00:39:29,960 --> 00:39:31,670
Huwa kostanti.

919
00:39:31,670 --> 00:39:36,040
Huwa bħall-valur numeriku tal-
akbar char inti tista 'tirrappreżenta ma

920
00:39:36,040 --> 00:39:40,370
wieħed gidma, li huwa probabbilment l-
255, li hija l-akbar numru li

921
00:39:40,370 --> 00:39:42,720
jirrappreżentaw tmien bits,
jibdew minn żero.

922
00:39:42,720 --> 00:39:47,460
Allura stajt jużaw dan, f'dan il-funzjoni, meta
miktub dan il-kodiċi, biss minħabba

923
00:39:47,460 --> 00:39:51,753
jekk xi ħaġa tmur ħażin fil getchar iżda
l-għan tagħha fil-ħajja huwa li jirritornaw

924
00:39:51,753 --> 00:39:54,830
char, inti jeħtieġ li b'xi mod ikunu jistgħu
li sinjal lill-utent li

925
00:39:54,830 --> 00:39:55,840
xi ħaġa li marret ħażin.

926
00:39:55,840 --> 00:39:56,970
Aħna ma jkunux jistgħu jirritornaw null.

927
00:39:56,970 --> 00:39:58,480
Jirriżulta li null hija pointer.

928
00:39:58,480 --> 00:40:01,030
U għal darb'oħra, getchar għandha
jirritornaw char.

929
00:40:01,030 --> 00:40:04,760
>> Allura l-konvenzjoni, jekk xi ħaġa tmur
ħażina, huwa inti, l-programmer, jew

930
00:40:04,760 --> 00:40:08,160
F'dan il-każ, mal-librerija me, I kellha
a biss tiddeċiedi arbitrarju, jekk

931
00:40:08,160 --> 00:40:12,230
xi ħaġa tmur ħażin, jien ser
jirritorna l-għadd 255, li huwa verament

932
00:40:12,230 --> 00:40:17,240
jfisser li nistgħu ma, l-utent ma jistax tip
il-karattru rappreżentata mill-

933
00:40:17,240 --> 00:40:21,410
numru 255 għaliex kellna steal
bħala hekk imsejħa valur Sentinel

934
00:40:21,410 --> 00:40:23,410
jirrappreżentaw problema.

935
00:40:23,410 --> 00:40:27,010
Issa jirriżulta li l-karattru 255
mhix xi ħaġa inti tista tip fuq

936
00:40:27,010 --> 00:40:28,380
keyboard tiegħek, dan huwa no big deal.

937
00:40:28,380 --> 00:40:30,910
L-utent ma avviż li
Stajt misruqa dan il-karattru.

938
00:40:30,910 --> 00:40:34,620
Imma jekk inti qatt tara fil-paġni bniedem fuq
sistema tal-kompjuter xi referenza għal

939
00:40:34,620 --> 00:40:38,560
tappijiet kollha kostanti bħal din li jgħid,
f'każijiet ta 'żbalji Dan jista' kostanti

940
00:40:38,560 --> 00:40:42,720
jiġu rritornati, li kollox xi bniedem ma
snin ilu kien arbitrarjament iddeċidiet li

941
00:40:42,720 --> 00:40:45,680
jirritorna dan il-valur speċjali u
sejħa hija kostanti fil-każ

942
00:40:45,680 --> 00:40:46,840
xi ħaġa tmur ħażin.

943
00:40:46,840 --> 00:40:48,580
>> Issa l-magic jiġri stabbiliti hawn.

944
00:40:48,580 --> 00:40:52,600
L-ewwel, jien tiddikjara f'konformità 67
żewġ karattri, C1 u C2.

945
00:40:52,600 --> 00:40:57,080
U mbagħad fil-linja 68, hemm attwalment
linja ta 'kodiċi li l-reminixxenti tal

946
00:40:57,080 --> 00:41:01,140
ħabib tagħna printf, peress li
ma jkollu mija Cs fil-kwotazzjonijiet.

947
00:41:01,140 --> 00:41:06,490
Imma avviż dak li qed jiġri hawn.
sscanf ifisser scan string -

948
00:41:06,490 --> 00:41:11,690
ifisser skanja ifformattjat
spag, sscanf Ergo.

949
00:41:11,690 --> 00:41:12,590
X'ifisser dan?

950
00:41:12,590 --> 00:41:16,310
Dan ifisser li inti tgħaddi għal sscanf string.

951
00:41:16,310 --> 00:41:18,420
U l-linja hija tkun xi tkun
it-tipi utent pulzieri

952
00:41:18,420 --> 00:41:23,520
Inti tgħaddi għal sscanf string format simili
dan li tg scanf liema huma

953
00:41:23,520 --> 00:41:25,870
inti bit-tama l-utent ikun ittajpjat pulzieri

954
00:41:25,870 --> 00:41:29,730
Inti mbagħad jgħaddu fil-indirizzi ta 'tnejn
biċċiet ta 'memorja, f'dan il-każ,

955
00:41:29,730 --> 00:41:31,150
għaliex għandi żewġ placeholders.

956
00:41:31,150 --> 00:41:34,610
Hekk jien ser jagħti dan l-indirizz
tal C1 u l-indirizz tal C2.

957
00:41:34,610 --> 00:41:37,700
>> U tfakkar li inti tagħti funzjoni tal-
indirizz ta 'xi varjabbli, x'hemm

958
00:41:37,700 --> 00:41:38,950
l-implikazzjoni?

959
00:41:38,950 --> 00:41:41,400

960
00:41:41,400 --> 00:41:45,050
X'jista 'dik il-funzjoni jagħmlu bħala riżultat
li jagħtiha l-indirizz ta '

961
00:41:45,050 --> 00:41:48,170
varjabbli, għall-kuntrarju
il-varjabbli innifsu?

962
00:41:48,170 --> 00:41:49,450
Hija tista 'bidla, id-dritt?

963
00:41:49,450 --> 00:41:53,250
Jekk kellek xi ħadd mappa lil fiżika
indirizz, jistgħu jmorru hemm u tagħmel

964
00:41:53,250 --> 00:41:54,750
kull ma jixtiequ f'dak l-indirizz.

965
00:41:54,750 --> 00:41:55,800
Istess idea hawn.

966
00:41:55,800 --> 00:41:59,950
Jekk aħna jgħaddu lill sscanf, l-indirizz ta 'żewġ
biċċiet ta 'memorja, anke dawn ċkejkna

967
00:41:59,950 --> 00:42:03,585
biċċiet ftit ta 'memorja, C1 u C2, iżda
aħna għid l-indirizz minnhom,

968
00:42:03,585 --> 00:42:05,170
sscanf tista 'bidla.

969
00:42:05,170 --> 00:42:08,530
>> Allura iskop sscanf fil-ħajja, jekk naqraw
il-paġna bniedem, huwa li jaqra dak li l-

970
00:42:08,530 --> 00:42:13,420
utent ittajpjat fil, tama għall-utent li
ittajpjat fil karattru u forsi

971
00:42:13,420 --> 00:42:16,470
karattru ieħor, u tkun xi tkun l-utent
ittajpjat, l-ewwel karattru tmur

972
00:42:16,470 --> 00:42:19,310
hawn, it-tieni karattru tmur hawn.

973
00:42:19,310 --> 00:42:22,470
Issa, bħala twarrib, dan, u inti
biss jafu dan mid-dokumentazzjoni,

974
00:42:22,470 --> 00:42:25,570
il-fatt li nressaq spazju vojt hemm
ifisser biss li jien ma kura jekk

975
00:42:25,570 --> 00:42:28,440
l-utent hits-bar-ispazju ftit
drabi qabel ma hu jew hi tieħu

976
00:42:28,440 --> 00:42:30,400
karattru, jien ser jinjora
kull spazju abjad.

977
00:42:30,400 --> 00:42:32,510
Allura li, naf mill-
id-dokumentazzjoni.

978
00:42:32,510 --> 00:42:36,570
>> Il-fatt li hemm tieni% a c
segwit minn spazju abjad huwa attwalment

979
00:42:36,570 --> 00:42:37,410
intenzjonat.

980
00:42:37,410 --> 00:42:41,190
I jridu jkunu kapaċi li jikxfu jekk l-utent
invitat up inkella ma kkooperawx.

981
00:42:41,190 --> 00:42:45,630
Hekk jien bit-tama li l-utent ittajpjat biss
fil-karattru wieħed, għalhekk jien bit-tama

982
00:42:45,630 --> 00:42:50,640
li sscanf huwa biss se jirritorna l-
valur ta '1 minħabba li, għal darb'oħra, jekk Naqra

983
00:42:50,640 --> 00:42:55,400
id-dokumentazzjoni, l-iskop sscanf fl
ħajja huwa li jirritornaw għall-għadd ta '

984
00:42:55,400 --> 00:42:59,170
varjabbli li ġew mimlija
b'kontribut utent.

985
00:42:59,170 --> 00:43:02,270
>> I għaddew f'żewġ varjabbli
indirizzi, C1 u C2.

986
00:43:02,270 --> 00:43:06,420
Jien bit-tama, madankollu, li wieħed biss mill-
minnhom gets maqtula għaliex jekk sscanf

987
00:43:06,420 --> 00:43:11,130
prospetti 2, x'hemm preżumibbilment
l-implikazzjoni loġikament?

988
00:43:11,130 --> 00:43:14,600
Li l-utent ma biss jagħtu me waħda
karattru bħal I told lilu jew lilha.

989
00:43:14,600 --> 00:43:17,860
Huma probabbilment ittajpjat fil
inqas żewġ karattri.

990
00:43:17,860 --> 00:43:22,430
Mela jekk jien minflok ma kellhomx it-tieni
% C, I biss kellhom wieħed, li

991
00:43:22,430 --> 00:43:25,370
franchement tkun aktar intuwittivi
approċċ, I think-ewwel daqqa t'għajn,

992
00:43:25,370 --> 00:43:30,220
int mhux se tkun kapaċi li jikxfu
jekk l-utent ikun ġie jagħtik aktar

993
00:43:30,220 --> 00:43:31,780
input minn inti fil-fatt riedu.

994
00:43:31,780 --> 00:43:34,100
Allura dan huwa forma impliċita
ta 'verifika żball.

995
00:43:34,100 --> 00:43:35,640
>> Imma dak I do avviż hawn.

996
00:43:35,640 --> 00:43:39,970
Ladarba jien ċert li l-utent tatni waħda
karattru, I tilliberalizza l-linja, tagħmel

997
00:43:39,970 --> 00:43:44,450
l-oppost ta 'getstring, li mbagħad
użi malloc, u mbagħad I lura

998
00:43:44,450 --> 00:43:51,030
C1, il-karattru li I ttamat l-
utent sakemm u sakemm biss.

999
00:43:51,030 --> 00:43:54,680
Allura a quick glimpsed biss, imma
xi mistoqsijiet dwar getchar?

1000
00:43:54,680 --> 00:43:57,450

1001
00:43:57,450 --> 00:43:59,590
Aħna ser jiġu lura uħud mill-oħrajn.

1002
00:43:59,590 --> 00:44:03,770
>> Well, let me imorru quddiem u tagħmel dan -
jissoponi issa, biss biex jimmotivaw tagħna

1003
00:44:03,770 --> 00:44:08,910
diskussjoni fil-ġimgħa plus ħin, dan
huwa fajl imsejjaħ structs.h.

1004
00:44:08,910 --> 00:44:11,440
U għal darb'oħra, dan huwa biss togħma
ta 'xi ħaġa li tinsab quddiem.

1005
00:44:11,440 --> 00:44:13,090
Iżda avviż li ħafna
ta 'dan huwa kummenti.

1006
00:44:13,090 --> 00:44:17,440
So let me jenfasizzaw biss il-
parti interessanti għal issa.

1007
00:44:17,440 --> 00:44:18,020
typedef -

1008
00:44:18,020 --> 00:44:19,700
hemm l-istess keyword mill-ġdid.

1009
00:44:19,700 --> 00:44:23,100
typedef nużaw biex tiddikjara string
bħala tip ta 'data speċjali.

1010
00:44:23,100 --> 00:44:27,490
Tista 'tuża typedef biex joħolqu marka ġdida
tipi ta 'data li ma kinux jeżistu meta

1011
00:44:27,490 --> 00:44:28,570
C ġiet ivvintata.

1012
00:44:28,570 --> 00:44:32,520
Per eżempju, int jiġi ma C. char
jiġi ma C. doppja tiġi ma C. Iżda

1013
00:44:32,520 --> 00:44:34,000
hemm l-ebda kunċett ta 'student.

1014
00:44:34,000 --> 00:44:37,230
And yet jkun pjuttost utli biex ikun
kapaċi jikteb programm li taħżen

1015
00:44:37,230 --> 00:44:40,440
fil-varjabbli, għadd ID ta 'student,
isem tagħhom, u d-dar tagħhom.

1016
00:44:40,440 --> 00:44:42,890
Fi kliem ieħor, tliet biċċiet
ta 'data, bħal int u

1017
00:44:42,890 --> 00:44:44,420
spag u ieħor spaga.

1018
00:44:44,420 --> 00:44:48,220
>> Bil typedef, x'hemm pretty qawwija
dwar dan u l-sturct keyword għal

1019
00:44:48,220 --> 00:44:53,660
istruttura, inti, l-programmer fl-2013,
jistgħu attwalment tiddefinixxi stess l tiegħek

1020
00:44:53,660 --> 00:44:57,530
tipi ta 'data li ma kinux jeżistu snin
ilu iżda li jaqdu skopijiet tiegħek.

1021
00:44:57,530 --> 00:45:01,910
U hekk hawn, fil-linji 13 permezz 19,
aħna qed tiddikkjara tip ta 'data ġdida, bħall-

1022
00:45:01,910 --> 00:45:04,320
l int, iżda ssejjaħ dan student.

1023
00:45:04,320 --> 00:45:09,310
U ġewwa ta 'din il-varjabbli se
jkun ta 'tliet affarijiet - l INT, string,

1024
00:45:09,310 --> 00:45:09,930
u string.

1025
00:45:09,930 --> 00:45:13,040
Allura inti tista 'taħseb x'hemm verament
ġara hawn, anke jekk din hija

1026
00:45:13,040 --> 00:45:17,160
daqsxejn ta 'simplifikazzjoni għal-lum,
student essenzjalment se

1027
00:45:17,160 --> 00:45:19,450
biex teżamina bħal dan.

1028
00:45:19,450 --> 00:45:22,580
Tagħha ser tkun blokki ta '
memorja ma 'ID, isem

1029
00:45:22,580 --> 00:45:25,580
qasam, u qasam dar.

1030
00:45:25,580 --> 00:45:30,670
U aħna ser ikunu jistgħu jużaw dawk biċċiet ta '
memorja u l-aċċess għalihom kif ġej.

1031
00:45:30,670 --> 00:45:38,870
>> Jekk immur fis struct0.c, hawnhekk hija
relattivament twil, iżda wara

1032
00:45:38,870 --> 00:45:42,630
mudell, tal-kodiċi li
tuża dan trick ġdid.

1033
00:45:42,630 --> 00:45:45,790
Allura l-ewwel, let me niġbidlek l-attenzjoni
għall-partijiet interessanti top up.

1034
00:45:45,790 --> 00:45:49,670
Sharp jiddefinixxi istudenti 3, tiddikjara
imsejħa istudenti kostanti u assenjati

1035
00:45:49,670 --> 00:45:53,450
huwa arbitrarjament-numru 3, biss
so I jkollhom tliet studenti li jużaw

1036
00:45:53,450 --> 00:45:54,830
dan il-programm għal issa.

1037
00:45:54,830 --> 00:45:55,960
Hawnhekk tidħol Main.

1038
00:45:55,960 --> 00:45:58,860
U avviż, kif nista niddikjara
firxa ta 'studenti?

1039
00:45:58,860 --> 00:46:00,480
Well, I biss tuża l-istess sintassi.

1040
00:46:00,480 --> 00:46:02,110
L-istudent kelma hija ovvjament ġdid.

1041
00:46:02,110 --> 00:46:04,790
Iżda studenti, klassi, l-istudenti parentesi.

1042
00:46:04,790 --> 00:46:06,720
>> Allura sfortunatament hemm ħafna
ta 'użu mill-ġdid ta' termini hawn.

1043
00:46:06,720 --> 00:46:07,660
Dan huwa biss numru.

1044
00:46:07,660 --> 00:46:09,040
Allura dan huwa simili qal tlieta.

1045
00:46:09,040 --> 00:46:11,430
Klassi huwa biss dak li nixtieq
li jsejħu l-varjabbli.

1046
00:46:11,430 --> 00:46:12,840
I jistgħu sejħa hija istudenti.

1047
00:46:12,840 --> 00:46:15,880
Iżda klassi, din mhix klassi fi
oġġett orjentati Java tip ta 'mod.

1048
00:46:15,880 --> 00:46:17,220
Huwa biss klassi ta 'studenti.

1049
00:46:17,220 --> 00:46:20,590
U t-tip tad-data ta 'kull element
f'dak array huwa student.

1050
00:46:20,590 --> 00:46:23,040
Allura dan huwa xi ftit differenti
u minn tgħid xi ħaġa

1051
00:46:23,040 --> 00:46:25,250
bħal dan, huwa biss -

1052
00:46:25,250 --> 00:46:29,500
Jien qal jagħtu me tliet studenti
u sejħa dik il-klassi array.

1053
00:46:29,500 --> 00:46:29,800
>> Kull dritt.

1054
00:46:29,800 --> 00:46:30,680
Issa hawn loop erbgħa.

1055
00:46:30,680 --> 00:46:33,480
Familjari Dan Guy - jtenni
minn żero fuq sa tlieta.

1056
00:46:33,480 --> 00:46:35,160
U hawnhekk l-biċċa ġdida ta 'sintassi.

1057
00:46:35,160 --> 00:46:37,710
Il-programm għaddej biex iwassluni,
il-bniedem, biex tagħtiha student

1058
00:46:37,710 --> 00:46:39,200
ID, li hija int.

1059
00:46:39,200 --> 00:46:44,650
U hawnhekk l-sintassi li magħhom inti tista '
jaħżnu xi ħaġa fil-qasam ID fi

1060
00:46:44,650 --> 00:46:48,630
klassi post bracket I. So
dan sintassi mhix xi ħaġa ġdida.

1061
00:46:48,630 --> 00:46:51,450
Dan ifisser biss jagħtu me-tmien
student fil-klassi.

1062
00:46:51,450 --> 00:46:52,940
Iżda dan is-simbolu huwa ġdid.

1063
00:46:52,940 --> 00:46:56,320
Sa issa, aħna ħadthom ma tistax tintuża dot,
inqas fil-kodiċi bħal dan.

1064
00:46:56,320 --> 00:47:01,490
Dan ifisser mur l-Struct magħruf bħala
student u xi ħaġa hemmhekk.

1065
00:47:01,490 --> 00:47:05,670
Bl-istess mod, f'dan il-linja li jmiss, 31, go
quddiem u tpoġġi kwalunkwe tipi l-utent

1066
00:47:05,670 --> 00:47:10,530
għal isem hawn u dak li jagħmlu għal
house, l-istess ħaġa, imorru quddiem u

1067
00:47:10,530 --> 00:47:13,230
poġġih fil. house.

1068
00:47:13,230 --> 00:47:15,955
>> Allura dak li ma dan il-programm
finalment do?

1069
00:47:15,955 --> 00:47:17,220
Tista 'tara teaser ftit hemmhekk.

1070
00:47:17,220 --> 00:47:24,780
Let me imorru quddiem u do jagħmlu structs 0
dot mmejla Struct 0, ID istudent 1,

1071
00:47:24,780 --> 00:47:28,250
jgħidu David Mather, student ID 2.

1072
00:47:28,250 --> 00:47:32,070
Rob Kirkland, student ID 3.

1073
00:47:32,070 --> 00:47:35,010
Lauren Leverit -

1074
00:47:35,010 --> 00:47:38,380
u l-unika ħaġa dan il-programm ma,
li huwa biss kompletament arbitrarja, huwa

1075
00:47:38,380 --> 00:47:40,980
Jien ridt li tagħmel xi ħaġa ma din id-data,
issa li stajt mgħallma us kif

1076
00:47:40,980 --> 00:47:43,450
użu structs, huwa I biss kellhom
dan loop extra hawn.

1077
00:47:43,450 --> 00:47:45,260
I jtenni fuq il-firxa ta 'studenti.

1078
00:47:45,260 --> 00:47:49,170
I użati, ħabib forsi issa familjari tagħna,
string iqabblu, stircomp li

1079
00:47:49,170 --> 00:47:53,780
verifika huwa d-dar 8 istudent
daqs Mather?

1080
00:47:53,780 --> 00:47:56,760
U jekk iva, biss print xi ħaġa
arbitrarju simili, iva, huwa.

1081
00:47:56,760 --> 00:47:59,430
Iżda għal darb'oħra, biss jagħtu me opportunitajiet
għall-użu u użu mill-ġdid u

1082
00:47:59,430 --> 00:48:02,270
użu mill-ġdid dan dot notazzjoni ġdida.

1083
00:48:02,270 --> 00:48:03,250
>> Allura quién, right?

1084
00:48:03,250 --> 00:48:06,270
Ġejjin bi programm istudent ikun
kemmxejn arbitrarja, iżda jirriżulta

1085
00:48:06,270 --> 00:48:09,800
li nistgħu nagħmlu affarijiet utli ma
dan, per eżempju kif ġej.

1086
00:48:09,800 --> 00:48:14,600
Din hija Struct ħafna aktar ikkumplikat
fl C. Huwa ltqajna tużżana jew aktar oqsma,

1087
00:48:14,600 --> 00:48:15,880
kemmxejn cryptically jismu.

1088
00:48:15,880 --> 00:48:20,110
Imma jekk inti stajt qatt semgħu ta 'grafika
format tal-fajl imsejħa Bitmap, BMP, huwa

1089
00:48:20,110 --> 00:48:22,830
Jirriżulta li l-format tal-fajl Bitmap
pretty ħafna qisu li dan.

1090
00:48:22,830 --> 00:48:24,200
Huwa wiċċ stupid Smiley ftit.

1091
00:48:24,200 --> 00:48:27,840
Huwa image żgħira li stajt żżomjati
fuq pretty big hekk li I tista 'tara kull

1092
00:48:27,840 --> 00:48:30,410
tal-tikek individwali jew pixels.

1093
00:48:30,410 --> 00:48:33,800
Issa, jirriżulta nistgħu jirrappreżentaw
dot iswed, ngħidu aħna, in-numru 0.

1094
00:48:33,800 --> 00:48:35,520
U dot abjad bin-numru 1.

1095
00:48:35,520 --> 00:48:39,140
>> Allura fi kliem ieħor, jekk inti tixtieq li tiġbed
Wiċċ smiley u ħlief li l-immaġni fil-

1096
00:48:39,140 --> 00:48:42,680
kompjuter, huwa biżżejjed li jaħżen żerijiet u
dawk li jixbhu dan, fejn,

1097
00:48:42,680 --> 00:48:45,250
għal darb'oħra, dawk huma bojod
u żerijiet huma suwed.

1098
00:48:45,250 --> 00:48:48,290
U flimkien, jekk inti effettivament ikollhom
a gird ta dawk żerijiet, inti għandek

1099
00:48:48,290 --> 00:48:51,030
grid ta 'pixels, u jekk inti jistabbilixxu
out, inti għandek ħelu

1100
00:48:51,030 --> 00:48:52,560
ftit wiċċ Smiley.

1101
00:48:52,560 --> 00:48:58,150
Issa, format tal-fajl Bitmap, BMP, huwa
effettivament li taħtha il-barnuża,

1102
00:48:58,150 --> 00:49:00,970
iżda b'aktar pixels Sot li inti
jistgħu attwalment jirrappreżentaw kuluri.

1103
00:49:00,970 --> 00:49:05,170
>> Imma meta jkollok aktar sofistikati
formati tal-fajl bħal BMP u JPEG u GIF

1104
00:49:05,170 --> 00:49:09,360
li magħhom inti tista 'tkun familjari, dawk
fajls fuq disk tipikament mhux biss

1105
00:49:09,360 --> 00:49:13,760
jkollhom żero u dawk għall-pixels, imma
għandhom xi metadata kif ukoll -

1106
00:49:13,760 --> 00:49:16,960
meta fis-sens li mhuwiex verament
data iżda huwa utli li jkollhom.

1107
00:49:16,960 --> 00:49:21,370
Allura dawn l-oqsma huma hawn jimplika, u
aħna ser tara dan f'aktar dettall fil P-set

1108
00:49:21,370 --> 00:49:25,810
5, li qabel l-żero u dawk li
jirrappreżentaw l-pixels fi immaġini,

1109
00:49:25,810 --> 00:49:29,110
hemm mazz ta 'metadata bħal
id-daqs tal-immaġni u l-

1110
00:49:29,110 --> 00:49:30,250
wisa 'tal-immaġini.

1111
00:49:30,250 --> 00:49:32,910
U tinnota jien tnittif off xi
affarijiet arbitrarji hawn -

1112
00:49:32,910 --> 00:49:34,260
wisa 'u għoli.

1113
00:49:34,260 --> 00:49:36,160
Għadd bit u xi affarijiet oħra.

1114
00:49:36,160 --> 00:49:37,840
Allura hemm xi metadata fil-fajl.

1115
00:49:37,840 --> 00:49:41,470
>> Iżda billi wieħed jifhem kif il-fajls huma stabbiliti
out b'dan il-mod, inti tista 'attwalment

1116
00:49:41,470 --> 00:49:45,890
imbagħad jimmanipulaw immaġini, jirkupraw immaġini
minn disk, resize immaġini.

1117
00:49:45,890 --> 00:49:47,560
Imma inti ma tistax neċessarjament
itejbu lilhom.

1118
00:49:47,560 --> 00:49:48,480
I meħtieġa ritratt.

1119
00:49:48,480 --> 00:49:52,840
So I marru lura għal RJ hawn, li inti raw
fuq l-iskrin pjuttost xi żmien ilu.

1120
00:49:52,840 --> 00:49:57,160
U jekk I jiftħu Keynote hawn, dan huwa
x'jiġri jekk inti tipprova li zoom u

1121
00:49:57,160 --> 00:49:59,380
itejbu RJ.

1122
00:49:59,380 --> 00:50:01,480
Huwa ma jkollna xi aħjar verament.

1123
00:50:01,480 --> 00:50:06,240
Issa Keynote huwa tip ta ċajpir hu
ftit, biss biex tleqqija fuq il-

1124
00:50:06,240 --> 00:50:11,040
fatt li RJ ma jiksbu partikolarment
msaħħa meta inti zoom pulzieri

1125
00:50:11,040 --> 00:50:13,310
U jekk tagħmel dan il-mod,
tara l-kwadri?

1126
00:50:13,310 --> 00:50:15,490
Yeah, inti tista 'definittivament tara
il-kwadri fuq projector.

1127
00:50:15,490 --> 00:50:17,690
>> Dan huwa dak ikollok meta inti ittejjeb.

1128
00:50:17,690 --> 00:50:22,570
Iżda fil-fehim kif RJ tagħna jew l-
Smiley wiċċ hija implimentata se let us

1129
00:50:22,570 --> 00:50:24,950
attwalment jikteb il-kodiċi li jimmanipula
dawn l-affarijiet.

1130
00:50:24,950 --> 00:50:29,970
U ħsibt I d tintemm fit din in-nota, ma
55 sekondi ta 'jtejjbu dik l-

1131
00:50:29,970 --> 00:50:31,230
I DARE, ngħidu aħna pjuttost qarrieqa.

1132
00:50:31,230 --> 00:50:32,990
>> [Daqq video]

1133
00:50:32,990 --> 00:50:34,790
>> -Hu tinsab.

1134
00:50:34,790 --> 00:50:38,310
Dwar dak, I do not know.

1135
00:50:38,310 --> 00:50:41,200
>> Allura dak li-nafu?

1136
00:50:41,200 --> 00:50:45,280
>> Li fil-09:15 Ray Santoya
kien fil-ATM.

1137
00:50:45,280 --> 00:50:47,830
>> Għalhekk il-kwistjoni-huwa dak
kien hu tagħmel fi 9:16?

1138
00:50:47,830 --> 00:50:50,750
>> -Isparar-disa millimeter
fuq xi ħaġa.

1139
00:50:50,750 --> 00:50:52,615
Forsi hu ra l-sniper.

1140
00:50:52,615 --> 00:50:54,760
>> -Or kien jaħdem miegħu.

1141
00:50:54,760 --> 00:50:56,120
>> Stenna-.

1142
00:50:56,120 --> 00:50:57,450
Mur lura waħda.

1143
00:50:57,450 --> 00:50:58,700
>> Liema taħseb?

1144
00:50:58,700 --> 00:51:05,530

1145
00:51:05,530 --> 00:51:09,490
>> Wassal-wiċċ tiegħu up, full screen.

1146
00:51:09,490 --> 00:51:09,790
>> Tiegħu-nuċċalijiet.

1147
00:51:09,790 --> 00:51:11,040
>> -Hemm riflessjoni.

1148
00:51:11,040 --> 00:51:21,790

1149
00:51:21,790 --> 00:51:23,520
>> -Dik hija l-tim tal-baseball Neuvitas.

1150
00:51:23,520 --> 00:51:24,530
C'est logo tagħhom.

1151
00:51:24,530 --> 00:51:27,040
>> -U hu jitkellem lil min hu
liebes ġakketta li.

1152
00:51:27,040 --> 00:51:27,530
>> [Daqq video END]

1153
00:51:27,530 --> 00:51:29,180
>> DAVID J. Malan: Dan se
jkun Problema Set 5.

1154
00:51:29,180 --> 00:51:30,720
Aħna se tara inti ġimgħa d-dieħla.

1155
00:51:30,720 --> 00:51:32,330
>> SPEAKER MALE: Fl-CS50 jmiss.

1156
00:51:32,330 --> 00:51:39,240
>> [Crickets chirping]

1157
00:51:39,240 --> 00:51:41,270
>> [Daqq tal-mużika]