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>> DAVID Malan: Hello, u
merħba lura għall CS50.

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Allura dan huwa l-aħħar ta 'erba' ġimgħat.

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Just tħabbira wieħed ewwel.

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Allura l-hekk imsejjaħ ħames Tnejn tkun
ġejjin up dan it-tnejn li ġejjin.

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00:00:19,600 --> 00:00:22,800
Din hija l-opportunità għall-bidla minn
Sib / insodisfaċenti għal grad ittra, jew minn

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grad ittra SAT / insodisfaċenti.

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Annoyingly, dan il-proċess ma jeħtieġu
firma, għaliex inti għandek timla

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00:00:27,130 --> 00:00:28,770
out waħda ta 'dawk roża żid / qatra forom.

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>> Minħabba teknikament, l-SAT / insodisfaċenti
Verżjoni u l-verżjoni grad ittra

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jkollhom in-numri katalgu distinti.

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Imma l-ebda big deal.

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Just toħroġ lili jew lil Rob
jew Lauren fi kwalunkwe punt.

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Jew email us jekk inti ma jkollhom it-tip
ta 'burokrazija li għandek bżonn illum, u aħna

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se jkun żgur biex jgħinuk tieħu
ħsieb ta 'dak qabel it-Tnejn.

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>> Kull dritt, hekk illum -

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attwalment, hemm daqsxejn ta 'eku.

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Nistgħu tone me isfel daqsxejn?

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OK.

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Allura llum, aħna jintroduċu suġġett
magħrufa bħala pointers.

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U jien ser jammettu li dan huwa wieħed mill-
suġġetti aktar kumplessi li għandna t-tendenza li

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ikopru f'dan il-klassi, jew verament xi
kors ta 'introduzzjoni li juża C.

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>> Iżda tieħu kelma tiegħi għaliha, partikolarment
jekk moħħok iħoss bent ftit aktar

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llum u fil-ġimgħat li ġejjin.

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Mhuwiex rappreżentant ta 'inti jkollok
kwalunkwe agħar f'dan ifisser biss li

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huwa suġġett partikolarment sofistikat
li I wegħda, ftit ġimgħat

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għalhekk, se jidhru wisq impressjonanti
sempliċi retrospettivament.

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>> I still remember din il-ġurnata.

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I kien seduta fil Elliott Dining Hall,
seduta li jmiss TF Nishat tiegħi Mehta,

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li kien residenti ta 'Elliott dar.

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U għal xi raġuni, dan
suġġett biss klikks.

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Li huwa li jgħidu li jien wisq tħabtu
miegħu għal xi ammont ta 'żmien, iżda I

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se nagħmlu l-almu tiegħi biex jgħinu biex jiġu evitati kwalunkwe tali
ġlieda ma 'tema li finalment

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huwa pjuttost qawwija.

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>> Fil-fatt, waħda mit-temi aħna ser jiddiskutu
fil-ġimgħat li ġejjin huwa li

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ta 'sigurtà, u kif inti tista' fil-fatt
jisfruttaw magni b'modi

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li ma kinux intiżi.

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U dawk isfruttamenti huma tipikament
ir-riżultat ta 'bugs, żbalji li aħna

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nies jagħmlu billi ma fehim xi
tal-implimentazzjoni sottostanti

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Dettalji via liema programmi huma magħmula.

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>> Issa jagħmlu din jidhru l-aktar utenti
friendly, ħsibt I d jkollhom 10

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tieni preview ta 'claymation ftit
figura jismu Binky li ġie ppreżentat

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ħajja minn ħabib ta 'tagħna fil Stanford,
professur Nick Parlante.

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Allura ippermettuli li jtik din
teaser ta 'Binky hawn.

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>> [Daqq video]

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>> -Ħej, Binky.

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Wake up.

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Wasal iż-żmien għall-gost pointer.

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>> -X'hemm li?

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Tgħallem dwar pointers?

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Oh, goodie.

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>> [Daqq video END]

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>> DAVID Malan: Dan huwa Stanford
xjenza tal-kompjuter.

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Allura aktar fuq li li ġejjin.

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>> [Applause]

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>> DAVID Malan: Jiddispjacini, Nick.

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>> Allura ifakkar li l-aħħar darba aħna spiċċajna fuq
dan cliffhanger verament eċċitanti

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fejn din il-funzjoni
biss ma ħadmux.

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Mill-inqas intuwittivament, li ħass
bħal din għandha taħdem.

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Simply iskambji il-valuri
ta 'żewġ numri interi.

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Iżda tfakkar li meta aħna stampata tal-
Valuri oriġinali prinċipali, waħda u

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tnejn, kienu għadhom wieħed u
tnejn u mhux tnejn u wieħed.

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>> So let me attwalment jaqilbu
fuq l-appliance.

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U I kiteb up a bit tal-kodiċi skeletali fil
javvanzaw hawn, fejn I jsostnu li x

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se tkun l-1, y se jkun 2.

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I imbagħad jistampa tnejn tagħhom
Valuri li jistampa f.

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>> I imbagħad titlob stabbiliti hawn li
aħna qed tmur biex tpartit lilhom.

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I ħalla post vojt hawn għalina biex
timla llum ftit mument.

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Imbagħad, jien ser jsostnu li l-
żewġ varjabbli ġew skambjati.

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Imbagħad jien ser jistampaw
minnhom mill-ġdid.

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U għalhekk wieħed jittama, I għandha tara 1, 2.

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2, 1.

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Dik hija l-sempliċi super
għan dritt issa.

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>> Allura kif do we go dwar iskambji
żewġ varjabbli?

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Ukoll jekk nipproponi hawnhekk li dawn tazzi
jafu jirrappreżentaw memorja fil-kompjuter.

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Dan huwa ftit gdim, dan
hija ieħor ftit gdim.

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Jista għandna voluntier come fuq u '
ħallat us xi xarbiet, jekk familjari?

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Come fuq up.

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X'hemm isem tiegħek?

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>> JESS: Jess.

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>> DAVID Malan: Jess?

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Come on up, Jess.

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Jekk inti ma mind, għandna biex tpoġġi l-
Google ħġieġ fuq inti sabiex inkunu nistgħu

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immortalize dan.

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OK, ħġieġ.

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Jirreġistra video.

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U OK, aħna tajba li
jmorru ma Jess hawn.

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Kull dritt.

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Nizza li jissodisfaw inti.

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>> Allura dak li nixtieq li inti tagħmel hawn -
jekk inti tista ', pjuttost malajr -

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biss pours us nofs tazza larinġ
meraq u nofs tazza tal-ħalib,

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jirrappreżentaw b'mod effettiv in-numri 1
fl tazza waħda u 2 fit-tazza oħra.

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>> Din se tkun footage tajba.

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>> JESS: Jiddispjacini.

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>> DAVID Malan: No, no.

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Huwa OK.

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Nizza.

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Kull dritt, hekk għandna erba 'bytes
valur ta 'meraq tal-larinġ.

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Aħna ser imsejħa l-valur 1.

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Issa erba 'bytes ieħor li jiswew ta' ħalib.

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Se sejħa hija valur 2.

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Allura x u y, rispettivament.

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>> Kull dritt, hekk issa jekk il-ħidma fuq naħa -
għalik, Jess, quddiem ta 'kulħadd

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ta 'klassi tiegħek -

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huwa li tpartit l-valuri ta 'xuy bħal
li aħna rridu l-meraq tal-larinġ fil-

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tazza oħra u l-ħalib f'dan tazza, kif
jista inti - qabel ma attwalment tagħmel

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dan - tmur dwar kif isir dan?

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>> OK, għaqli deċiżjoni.

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Għalhekk ikollok bżonn ftit aktar memorja.

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Mela ejja jallokaw temporanju
tazza, jekk inti se.

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U issa tipproċedi biex tpartit xuy.

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>> Eċċellenti.

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Allura ħafna isir ukoll.

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Grazzi tant, Jess.

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Hawnhekk inti.

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A souvenir ftit.

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>> OK, hekk ovvjament, idea sempliċi super.

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Kompletament intuwittivi li għandna bżonn daqsxejn
aktar spazju għall-ħażna - f'din il-forma,

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tazza - jekk aħna fil-fatt tixtieq li
tpartit dawn iż-żewġ varjabbli.

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Mela ejja jagħmlu eżattament dan.

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Up hawn fl bejn fejn nitlob jien
se tkun qed twettaq xi iskambji, I ser

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imorru quddiem u tiddikjara temperatura.

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U jien ser twaqqaf it ugwali għal, per eżempju, x.

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>> Imbagħad jien ser jibdlu l-valur tal-
x bħad Jess ma hawn ma '

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ħalib u meraq tal-larinġ
li jkun ugwali għal y.

131
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U jien se jibdlu y li jkun ugwali
li ma x, għaliex issa aħna se jkunu

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staġnati f'ċirku, iżda pjuttost TEMP.

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Fejn I temporanjament - jew fejn Jess
temporanjament tpoġġi l-meraq tal-larinġ

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qabel clobbering li
tazza mal-ħalib.

135
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>> So let me aqbad issa u jagħmlu dan.

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Huwa sejjaħ noswap.c.

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U issa let me run ebda swap.

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U fil-fatt nara, jekk I jespandu l-
tieqa ftit, li

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x hija l-1, y huwa 2.

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U allura x hija 2, y hija l-1.

141
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>> Iżda tfakkar li nhar it-Tnejn għamilna affarijiet
ftit differenti fejn I

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minflok implimentati funzjoni helper,
jekk inti se, li kien attwalment null.

143
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I sejħitilha tpartit.

144
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I tatha żewġ parametri, u I imsejħa
minnhom u I imsejħa minnhom b.

145
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>> Franchement, I jistgħu jsejħulhom xuy.

146
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M'hemm xejn waqfien
me milli jagħmlu dan.

147
00:06:06,040 --> 00:06:08,140
Iżda nixtieq jargumentaw li huwa mbagħad
ftit ambigwa.

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Minħabba jfakkru għal It-tnejn li aħna
sostna li dawn il-parametri kienu

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kopji tal-valuri għaddew pulzieri

150
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Allura hija biss messijiet mal tiegħek
mind, I think, jekk tuża

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eżattament l-istess varjabbli.

152
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>> So I ser minflok jsejħulhom a
u b, biss għaċ-ċarezza.

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Iżda nistgħu jsejħulhom aktar
xejn irridu.

154
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U jien ser kopja u paste
effettivament dan il-kodiċi mill-up hemm

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isfel fil hawn.

156
00:06:27,170 --> 00:06:29,110
Minħabba I biss raw li taħdem.

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Allura dak fil-forma pjuttost tajba.

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U jien ser jibdlu x tiegħi għal, x tiegħi
għal, y tiegħi biex b uy tiegħi biex b.

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>> Allura fi kliem ieħor, l-istess loġika eżatt.

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L-istess ħaġa eżatt li Jess għamlet.

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U allura l-ħaġa waħda I għandek tagħmel up
hawn, naturalment, huwa issa jinvokaw din

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funzjoni, jew sejħa din il-funzjoni.

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So I se sejħa din il-funzjoni ma 'żewġ
inputs, u x y, u hit Save.

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>> Kull dritt, hekk fundamentalment
l-istess ħaġa.

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Fil-fatt, stajt probabbilment għamel il-programm
kumplessi bla bżonn billi

166
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kitba ta 'funzjoni li jinsab biss tieħu
xi sitt linji ta 'kodiċi billi I

167
00:07:00,820 --> 00:07:02,970
qabel kienu implimentaw
dan biss tlieta.

168
00:07:02,970 --> 00:07:06,230
>> So let me aqbad issa u remake
dan, jagħmlu l-ebda swap.

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Kull dritt, I invitat up here.

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Dan għandu jkun żball li inti tista '
tara aktar komunement bħala tiegħek

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programmi nikseb aktar kumplessi.

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Iżda hemm jiffissaw faċli.

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Let me iscroll back up here.

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>> U x'inhu l-ewwel żball jien jaraw?

175
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Dikjarazzjoni impliċita.

176
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Xi jfisser li tipikament jindika?

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00:07:21,466 --> 00:07:22,830
Oh, I nesa l-prototip.

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I nesa li jgħallmu l-kompilatur li tpartit
se jibqgħu jeżistu anke jekk huwa

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ma teżistix fil-bidu nett
tal-programm.

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Hekk jien biss se ngħid null, tpartit,
int, a b int, b'waqfa u virgola.

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>> Hekk jien mhux ser reimplement dan.

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Imma issa jaqbel x'hemm stabbiliti hawn.

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U avviż, in-nuqqas ta 'punt u virgola
hawnhekk, li ma tkunx meħtieġa meta

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implimentazzjoni.

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>> So let me remake dan, jagħmlu l-ebda swap.

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Forma ferm aħjar.

187
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Mexxi l-ebda swap.

188
00:07:48,130 --> 00:07:48,740
U kkritikat dan.

189
00:07:48,740 --> 00:07:51,650
Issa aħna qed lura fejn konna nhar it-Tnejn,
meta l-ħaġa ma tpartit.

190
00:07:51,650 --> 00:07:55,410
>> U x'inhu l-ispjegazzjoni intuwittivi
għal għaliex dan huwa l-każ?

191
00:07:55,410 --> 00:07:56,380
Yeah?

192
00:07:56,380 --> 00:07:57,630
>> STUDENT: [inaudible].

193
00:07:57,630 --> 00:08:04,140

194
00:08:04,140 --> 00:08:05,230
>> DAVID Malan: Eżattament.

195
00:08:05,230 --> 00:08:07,330
Allura aub huma kopji ta 'xuy.

196
00:08:07,330 --> 00:08:10,680
U fil-fatt, kull darba li inti kont qed
sejħa funzjoni s'issa li

197
00:08:10,680 --> 00:08:12,540
tgħaddi varjabbli bħall ints -

198
00:08:12,540 --> 00:08:14,470
daqstant swap qed tistenna hawn -

199
00:08:14,470 --> 00:08:16,270
inti guys kienu qed jittrasferixxu fl kopji.

200
00:08:16,270 --> 00:08:19,150
>> Issa li ifisser li jieħu xi ftit
ta 'żmien, qasma tat-tieni, għall-

201
00:08:19,150 --> 00:08:23,270
kompjuter li kopja tal-bits minn wieħed
varjabbli fl-bits ta 'ieħor.

202
00:08:23,270 --> 00:08:24,610
Iżda li mhux tali big deal.

203
00:08:24,610 --> 00:08:25,920
Iżda dawn qed madankollu kopja.

204
00:08:25,920 --> 00:08:30,020
>> U hekk issa, fil-kuntest ta 'tpartit,
I am fil-fatt b'suċċess

205
00:08:30,020 --> 00:08:31,180
tibdil ta 'u b.

206
00:08:31,180 --> 00:08:33,000
Fil-fatt, ejja do a quick
sanità check.

207
00:08:33,000 --> 00:08:36,830
Stampa f a huwa% i, linja ġdida.

208
00:08:36,830 --> 00:08:38,770
U plug ejja fil.

209
00:08:38,770 --> 00:08:41,830
Issa ejja jagħmlu l-istess ħaġa ma 'b.

210
00:08:41,830 --> 00:08:43,640
U ejja jagħmlu l-istess ħaġa hawn.

211
00:08:43,640 --> 00:08:47,260
>> U issa, let me kopja dawk l-istess linji
mill-ġdid fil-qiegħ tal-funzjoni

212
00:08:47,260 --> 00:08:51,250
wara tliet linji tiegħi ta 'interessanti
seta eżegwit, u

213
00:08:51,250 --> 00:08:53,270
tipprintja u b darb'oħra.

214
00:08:53,270 --> 00:08:56,030
Allura issa ejja jagħmlu dan, jagħmlu l-ebda swap.

215
00:08:56,030 --> 00:08:58,430
Let me jagħmlu l-tieqa terminal a
bit taller, sabiex inkunu jista 'jara

216
00:08:58,430 --> 00:08:59,520
aktar minnu f'daqqa.

217
00:08:59,520 --> 00:09:00,860
>> U run ebda swap.

218
00:09:00,860 --> 00:09:04,000
x hija l-1, y huwa 2. a huwa 1, b huwa 2.

219
00:09:04,000 --> 00:09:06,070
U mbagħad, a hija 2, b hija l-1.

220
00:09:06,070 --> 00:09:09,390
Għalhekk qed taħdem, bħad Jess
ma hawn ġewwa ta 'swap.

221
00:09:09,390 --> 00:09:13,090
Iżda naturalment, huwa li l-ebda effett
fuq l-varjabbli fil prinċipali.

222
00:09:13,090 --> 00:09:15,360
>> Allura rajna trick li biha aħna
jista jiffissaw dan, id-dritt?

223
00:09:15,360 --> 00:09:19,560
Meta inti qed iħabbtu wiċċhom ma 'dan scoping
kwistjoni, inti tista 'biss Punt u jagħmlu x

224
00:09:19,560 --> 00:09:22,400
uy liema tip ta 'varjabbli minflok?

225
00:09:22,400 --> 00:09:23,390
>> Inti jista 'jagħmilhom globali.

226
00:09:23,390 --> 00:09:27,560
Tpoġġihom fuq nett tal-fajl
kif għamilna, anki fil-logħba tal-15.

227
00:09:27,560 --> 00:09:28,890
Aħna nużaw varjabbli globali.

228
00:09:28,890 --> 00:09:32,420
Iżda fil-kuntest tal-logħba ta '15,
huwa raġonevoli li jkollhom globali

229
00:09:32,420 --> 00:09:37,170
varjabbli li jirrappreżenta l-bord, minħabba
l-intier ta '15.c hija kollha

230
00:09:37,170 --> 00:09:38,650
dwar implimentazzjoni din il-logħba.

231
00:09:38,650 --> 00:09:41,470
Dak hu l-fajl jeżisti tagħmel.

232
00:09:41,470 --> 00:09:44,170
>> Iżda f'dan il-każ hawnhekk, jien
sejħa swap funzjoni.

233
00:09:44,170 --> 00:09:45,380
Irrid li tpartit żewġ varjabbli.

234
00:09:45,380 --> 00:09:48,950
U għandu tibda tħossok ftit sloppy
jekk is-soluzzjoni kollha ta 'tagħna

235
00:09:48,950 --> 00:09:51,300
problemi meta aħna run fis ambitu
kwistjonijiet huwa jagħmilha globali.

236
00:09:51,300 --> 00:09:54,730
Minħabba malajr ħafna programm tagħna huwa
se ssir pjuttost mess.

237
00:09:54,730 --> 00:09:57,760
U aħna ma li kemxejn ħafna
bħala riżultat 15.c.

238
00:09:57,760 --> 00:10:00,470
>> Iżda jirriżulta hemm
mod aħjar għal kollox.

239
00:10:00,470 --> 00:10:05,600
Let me fatt imorru lura u tħassar il-
jistampa l-f, biss biex jissimplifikaw dan il-kodiċi.

240
00:10:05,600 --> 00:10:09,160
U let me jipproponu li
dan, fil-fatt, huwa ħażin.

241
00:10:09,160 --> 00:10:15,990
Imma jekk jien minflok iżidu f'xi asterisks
u stilel, I jista 'minflok jibdlu din

242
00:10:15,990 --> 00:10:18,670
funzjoni fis waħda li
attwalment operattiv.

243
00:10:18,670 --> 00:10:25,020
>> So let me jmorru lura hawn u jammettu qal
asteriski hija dejjem diffiċli,

244
00:10:25,020 --> 00:10:26,170
so I ser jgħidu istilel.

245
00:10:26,170 --> 00:10:27,660
I ser biss fess sa li wieħed.

246
00:10:27,660 --> 00:10:28,190
Kull dritt.

247
00:10:28,190 --> 00:10:30,190
U issa, dak li jien ser
biex tagħmel minflok?

248
00:10:30,190 --> 00:10:34,130
>> Allura l-ewwel nett, jien ser tispeċifika
li minflok jgħaddu minn int fis

249
00:10:34,130 --> 00:10:37,980
il-funzjoni tpartit, jien minflok
ta 'se ngħid star int.

250
00:10:37,980 --> 00:10:39,170
Issa, dak ma l-istilla jindika?

251
00:10:39,170 --> 00:10:41,970
Dan huwa dan il-kunċett ta 'pointer li
Binky, il-karattru claymation, kien

252
00:10:41,970 --> 00:10:43,465
jirreferu għall mument ilu.

253
00:10:43,465 --> 00:10:47,610
>> Allura jekk ngħidu star int, it-tifsira ta '
dan issa huwa li mhux se jkun

254
00:10:47,610 --> 00:10:49,110
għaddiet fl-valur tagħha.

255
00:10:49,110 --> 00:10:50,350
Huwa mhux se jiġu kkupjati pulzieri

256
00:10:50,350 --> 00:10:54,700
Pjuttost, l-indirizz ta 'huwa
se tiġi mgħoddija pulzieri

257
00:10:54,700 --> 00:10:57,840
>> Allura ifakkar li ġewwa tal-kompjuter tiegħek
huwa mazz sħiħ ta 'memorja, inkella

258
00:10:57,840 --> 00:10:58,760
magħrufa bħala RAM.

259
00:10:58,760 --> 00:11:00,520
U li RAM huwa biss
mazz sħiħ ta 'bytes.

260
00:11:00,520 --> 00:11:03,320
Hekk jekk Mac tiegħek jew PC tiegħek
żewġ gigabytes, inti għandek 2

261
00:11:03,320 --> 00:11:05,760
biljun bytes ta 'memorja.

262
00:11:05,760 --> 00:11:08,440
>> Issa ejja biss jissoponi li biss biex
żżomm affarijiet sbieħ u ordnat, aħna

263
00:11:08,440 --> 00:11:09,450
tassenja indirizz -

264
00:11:09,450 --> 00:11:10,170
numru -

265
00:11:10,170 --> 00:11:12,270
għal kull byte ta 'RAM fil-kompjuter tiegħek.

266
00:11:12,270 --> 00:11:15,410
L-ewwel byte ta 'dawk 2
biljun huwa billi numru żero.

267
00:11:15,410 --> 00:11:18,572
Il-wieħed li jmiss huwa numru byte wieħed, in-numru
tnejn, it-triq kollha fuq up, dot dot

268
00:11:18,572 --> 00:11:20,530
dot, għal madwar 2 biljuni.

269
00:11:20,530 --> 00:11:23,640
>> Allura inti tista 'numru ta' bytes
tal-memorja fil-kompjuter tiegħek.

270
00:11:23,640 --> 00:11:26,460
Mela ejja nassumu li dak hu
rridu nfissru minn indirizz.

271
00:11:26,460 --> 00:11:31,360
Allura meta nara int star a, x'inhu għaddej
għandhom jiġu mgħoddija fil swap issa huwa l-

272
00:11:31,360 --> 00:11:32,830
indirizz ta '.

273
00:11:32,830 --> 00:11:37,150
Mhux valur tagħha, iżda tkun xi tkun postali tagħha
indirizz huwa, biex ngħidu hekk -

274
00:11:37,150 --> 00:11:38,810
post tagħha fil RAM.

275
00:11:38,810 --> 00:11:41,250
>> U l-istess għall-b, jien ser
jiġifieri l-istess ħaġa.

276
00:11:41,250 --> 00:11:42,720
Int, star, b.

277
00:11:42,720 --> 00:11:46,350
Bħala twarrib, teknikament l-istilla
tista 'tmur f'postijiet oħra.

278
00:11:46,350 --> 00:11:50,140
Iżda aħna ser standardizzati fuq l-istilla qed
dritt li jmiss għall-tip data.

279
00:11:50,140 --> 00:11:54,080
>> Allura tpartit firma issa jfisser, agħti lili
l-indirizz ta 'int, u sejħa

280
00:11:54,080 --> 00:11:55,400
dak l-indirizz a.

281
00:11:55,400 --> 00:11:58,690
U jagħtu me indirizz ieħor ta '
int u sejħa li jindirizzaw b.

282
00:11:58,690 --> 00:12:01,120
>> Imma issa kodiċi tiegħi hawn għall-bidla.

283
00:12:01,120 --> 00:12:03,470
Għaliex jekk Niddikjara temperatura int -

284
00:12:03,470 --> 00:12:05,580
li għadu ta int tip -

285
00:12:05,580 --> 00:12:08,700
iżda I taħżen fiha ta ',
liema tip ta 'valur?

286
00:12:08,700 --> 00:12:12,870
Biex ikunu ċari, jien tqegħid ta 'a ma'
il-kodiċi kif miktub dritt issa?

287
00:12:12,870 --> 00:12:14,360
>> Jien tqegħid tal-post fil-.

288
00:12:14,360 --> 00:12:16,500
Imma jien ma jimpurtahom dwar il-
post issa, id-dritt?

289
00:12:16,500 --> 00:12:21,940
Temp jeżisti biss Jess "tielet tazza
jeżistu, għal liema skop?

290
00:12:21,940 --> 00:12:23,090
Li jaħżen valur.

291
00:12:23,090 --> 00:12:24,830
Ħalib jew meraq tal-larinġ.

292
00:12:24,830 --> 00:12:28,520
Mhux li attwalment jaħżnu l-indirizz ta '
waħda minn dawk l-affarijiet, li jħoss

293
00:12:28,520 --> 00:12:31,200
ftit tagħmel sens f'dan reali
kuntest dinji xorta waħda.

294
00:12:31,200 --> 00:12:34,990
>> Allura verament, dak li nixtieq li jitqiegħdu fil temperatura
mhuwiex l-indirizz ta ', iżda l-

295
00:12:34,990 --> 00:12:36,180
kontenut ta '.

296
00:12:36,180 --> 00:12:41,930
Mela jekk huwa numru bħal 123, dan huwa
l-byte 123 ta 'memorja li biss

297
00:12:41,930 --> 00:12:45,090
jiġri li jkun jokkupaw, li l-valur
fil-jiġri li jkun jokkupaw.

298
00:12:45,090 --> 00:12:49,040
>> Jekk Irrid immur għal dak l-indirizz,
I bżonn biex ngħid star a.

299
00:12:49,040 --> 00:12:52,610
Bl-istess mod, jekk I kellhom jibdlu x'hemm
fl-indirizz a, nibdel

300
00:12:52,610 --> 00:12:53,570
dan biex jibdew.

301
00:12:53,570 --> 00:12:58,185
Jekk irrid li jaħżen fil x'hemm fil-
post ta 'ma' dak l fil-post

302
00:12:58,185 --> 00:13:02,180
fil b, star b star.

303
00:13:02,180 --> 00:13:05,340
>> Għalhekk fil-qosor, anke jekk dan ikun pjuttost mhux
għarqa fil s'issa - u I ma jistennewx

304
00:13:05,340 --> 00:13:06,560
li dan iwassal tant mgħaġġel -

305
00:13:06,560 --> 00:13:11,100
tirrealizza li kollha qed nagħmel huwa prefiss
dawn il stilla għall-varjabbli tiegħi,

306
00:13:11,100 --> 00:13:13,350
qal ma grab il-valuri.

307
00:13:13,350 --> 00:13:14,520
Tbiddilx l-valuri.

308
00:13:14,520 --> 00:13:17,600
Iżda, mur dawk l-indirizzi
u jiksbu l-valur.

309
00:13:17,600 --> 00:13:21,430
Mur f'dak l-indirizz u l-bidla
il-valur hemmhekk.

310
00:13:21,430 --> 00:13:25,500
>> Allura issa let me iscroll lura sal-quċċata,
biss biex jiffissaw din il-linja hawn, biex

311
00:13:25,500 --> 00:13:27,690
jibdlu l-prototip biex jaqblu.

312
00:13:27,690 --> 00:13:30,280
Imma I issa jeħtieġ li jagħmlu ħaġa waħda oħra.

313
00:13:30,280 --> 00:13:35,500
Intuwittivament, jekk stajt mibdula-tipi
ta 'argumenti li l-iskambju qed tistenna,

314
00:13:35,500 --> 00:13:37,245
x'iktar għandi bżonn biex
bidla fil-kodiċi tiegħi?

315
00:13:37,245 --> 00:13:39,750

316
00:13:39,750 --> 00:13:40,840
>> Meta I call swap.

317
00:13:40,840 --> 00:13:43,340
Minħabba dritt issa, dak am
I tgħaddi li tpartit xorta?

318
00:13:43,340 --> 00:13:47,450
Il-valur x u l-valur ta 'y, jew
il-ħalib u l-meraq tal-larinġ.

319
00:13:47,450 --> 00:13:48,510
Imma jien ma trid tagħmel dan.

320
00:13:48,510 --> 00:13:51,060
I minflok jridu jgħaddu dak?

321
00:13:51,060 --> 00:13:53,050
Il-post ta 'x u
il-post ta 'y.

322
00:13:53,050 --> 00:13:55,300
X'inhuma indirizzi postali tagħhom,
biex ngħidu hekk.

323
00:13:55,300 --> 00:13:57,600
>> Allura biex tagħmel dan, hemm xi ampersand.

324
00:13:57,600 --> 00:13:59,260
Ampersand tip ta 'ħsejjes bħal indirizz.

325
00:13:59,260 --> 00:14:03,240
hekk n, ampersand, l-indirizz
ta 'x, u l-indirizz ta' y.

326
00:14:03,240 --> 00:14:06,790
Allura huwa intenzjonat li nużaw
ampersands meta ssejjaħ il-funzjoni,

327
00:14:06,790 --> 00:14:10,230
u stilel meta tiddikjara u meta
implimentazzjoni tal-funzjoni.

328
00:14:10,230 --> 00:14:14,220
>> U jaħsbu biss tal ampersand bħala l-
indirizz tal-operatur, u stilel kif l-

329
00:14:14,220 --> 00:14:15,490
jmorru hemm operatur -

330
00:14:15,490 --> 00:14:18,640
jew, b'mod aktar xieraq, l-
operatur dereference.

331
00:14:18,640 --> 00:14:23,480
Allura li l-lott kollu ta 'kliem biss biex
jgħidu li issa, wieħed jittama, swap va

332
00:14:23,480 --> 00:14:24,440
biex tkun korretta.

333
00:14:24,440 --> 00:14:26,550
>> Let me imorru quddiem u jagħmlu -

334
00:14:26,550 --> 00:14:30,940
ejja fil-fatt tibdel isem il-fajl, lest
dan il-programm għadu jissejjaħ ebda swap.

335
00:14:30,940 --> 00:14:33,240
I jsostnu li aħna ser sejħa hija swap.c issa.

336
00:14:33,240 --> 00:14:35,670
Sabiex tagħmel, tpartit.

337
00:14:35,670 --> 00:14:37,520
Dot, slash, tpartit.

338
00:14:37,520 --> 00:14:40,210
>> U issa fil-fatt, huwa x 1, y huwa 2.

339
00:14:40,210 --> 00:14:44,040
U mbagħad, x hija 2, y hija waħda.

340
00:14:44,040 --> 00:14:46,500
Well ejja ara jekk aħna ma tistax tagħmel dan a
ftit differenti dwar x'hemm

341
00:14:46,500 --> 00:14:47,180
jiġri hawn fuq.

342
00:14:47,180 --> 00:14:51,250
L-ewwel, let me zoom fl fuq tagħna
tpinġija iskrin hawn.

343
00:14:51,250 --> 00:14:54,160
U let me tipproponi għal mument - u
kulmeta I tfassal hawnhekk se jkunu riflessi

344
00:14:54,160 --> 00:14:58,660
up issa hemm - let me jipproponi li
hawn mazz sħiħ ta 'memorja, jew

345
00:14:58,660 --> 00:15:00,540
RAM, ġewwa tal-kompjuter tiegħi.

346
00:15:00,540 --> 00:15:04,140
>> U dan ikun in-numru gidma,
ejja ngħidu, 1.

347
00:15:04,140 --> 00:15:05,720
Dan se jkun bytes numru 2.

348
00:15:05,720 --> 00:15:08,220
U jien ser tagħmel mazz sħiħ aktar, u
allura mazz ta 'dot dot tikek li

349
00:15:08,220 --> 00:15:10,880
jindikaw li hemm 2 biljun fis-
ta 'dawn l-affarijiet.

350
00:15:10,880 --> 00:15:13,520
4, 5, u oħrajn.

351
00:15:13,520 --> 00:15:17,055
>> Allura hemm l-ewwel ħames bytes
ta 'memorja tal-kompjuter tiegħi.

352
00:15:17,055 --> 00:15:17,560
Kull dritt?

353
00:15:17,560 --> 00:15:19,060
Ftit minn 2 biljuni.

354
00:15:19,060 --> 00:15:21,120
Imma issa jien ser tipproponi
dan li ġej.

355
00:15:21,120 --> 00:15:27,490
Jien ser nipproponi li x ser
jaħżnu in-numru 1, uy va

356
00:15:27,490 --> 00:15:29,690
li jaħżen in-numru 2.

357
00:15:29,690 --> 00:15:35,000
U let me imorru quddiem issa u jirrappreżenta
dawn il-valuri kif ġej.

358
00:15:35,000 --> 00:15:41,510
>> Ejja nagħmlu dan kif ġej.

359
00:15:41,510 --> 00:15:42,870
Agħti me wieħed biss sekonda.

360
00:15:42,870 --> 00:15:44,150
Tieni waħda.

361
00:15:44,150 --> 00:15:45,680
OK.

362
00:15:45,680 --> 00:15:47,560
Irrid nagħmel dan ftit -

363
00:15:47,560 --> 00:15:50,440
ejja tagħmel dan mill-ġdid.

364
00:15:50,440 --> 00:15:53,250
Inkella jien ser u bl-użu
istess numri, mhux intenzjonalment,

365
00:15:53,250 --> 00:15:54,230
minn darba.

366
00:15:54,230 --> 00:15:57,320
>> Hekk biss hekk aħna numri differenti
biex jitkellmu dwar, ejja sejħa dan byte

367
00:15:57,320 --> 00:16:03,391
numru 123, 124, 125, 126,
u dot dot dot.

368
00:16:03,391 --> 00:16:08,400
U let me jsostnu issa li jien ser
tpoġġi l-valur 1 hawn, u l-valur 2

369
00:16:08,400 --> 00:16:11,990
hawn, magħrufa wkoll bħala xuy.

370
00:16:11,990 --> 00:16:15,300
Allura hija biss hekk jiġri li
dan huwa x, dan huwa y.

371
00:16:15,300 --> 00:16:18,180
>> U biss minn xi ċans każwali, l-
kompjuter, is-sistema operattiva,

372
00:16:18,180 --> 00:16:21,890
ġara li tpoġġi x fil-lokalità
numru 123.

373
00:16:21,890 --> 00:16:25,590
U y spiċċaw fil-lokalità 124 -

374
00:16:25,590 --> 00:16:26,330
kkritikat dan.

375
00:16:26,330 --> 00:16:28,700
I kellha tiffissa dan.

376
00:16:28,700 --> 00:16:34,040
Oh bniedem, għandi verament jixtiequ jagħmlu dan?

377
00:16:34,040 --> 00:16:37,340
Iva, nixtieq li jiffissaw dan u
b xierqa dwar dan illum.

378
00:16:37,340 --> 00:16:39,950
Jiddispjacini, ġodda fuq dan.

379
00:16:39,950 --> 00:16:45,020
>> 127, 131, u jien ma riedx li jkun dan
kumplessi, iżda għaliex ma I jibdlu l-

380
00:16:45,020 --> 00:16:46,340
numri hemmhekk?

381
00:16:46,340 --> 00:16:48,360
Għaliex nixtieq l ints li
fil-fatt tkun erba bytes.

382
00:16:48,360 --> 00:16:49,810
Mela ejja tkun anali super dwar dan.

383
00:16:49,810 --> 00:16:53,800
B'tali mod li jekk jiġri li 1 jiġu indirizzati
123, l-2 se tkun fl-indirizz

384
00:16:53,800 --> 00:16:55,730
127 għaliex dan huwa biss 4 byes bogħod.

385
00:16:55,730 --> 00:16:56,210
Li kollox.

386
00:16:56,210 --> 00:16:58,640
U aħna ser tinsa dwar kollha ta 'l-
indirizzi l-oħra fid-dinja.

387
00:16:58,640 --> 00:17:03,320
>> Allura x hija fil lokazzjoni 123,
y hija fil post 127.

388
00:17:03,320 --> 00:17:05,770
U issa, liema do I attwalment
trid tagħmel?

389
00:17:05,770 --> 00:17:10,099
Meta I call swap issa, x'hemm
attwalment għaddejjin?

390
00:17:10,099 --> 00:17:14,920
Well, meta I sejħa swap, jien tgħaddi fis
l-indirizz tal xu l-indirizz ta 'y.

391
00:17:14,920 --> 00:17:18,540
Għalhekk per eżempju, jekk dawn iż-żewġ biċċiet
tal-karta issa jirrappreżentaw it-tnejn

392
00:17:18,540 --> 00:17:23,510
argumenti au b li tpartit, dak am I
ser jikteb fuq l-ewwel ta 'dawn,

393
00:17:23,510 --> 00:17:27,720
li jien ser sejħa jirreferu għalih bħala?

394
00:17:27,720 --> 00:17:30,610
>> Eżattament, 123.

395
00:17:30,610 --> 00:17:31,905
Allura dan nitlob huwa.

396
00:17:31,905 --> 00:17:32,955
Dan huwa l-parametru a.

397
00:17:32,955 --> 00:17:35,856
Jien tqegħid-indirizz ta 'x fil hemmhekk.

398
00:17:35,856 --> 00:17:38,152
>> X'hemm li?

399
00:17:38,152 --> 00:17:40,890
>> X'hemm li?

400
00:17:40,890 --> 00:17:41,190
>> No, no.

401
00:17:41,190 --> 00:17:41,720
Li OK.

402
00:17:41,720 --> 00:17:42,570
Still tajba, għadu tajjeb.

403
00:17:42,570 --> 00:17:43,530
Allura dan huwa.

404
00:17:43,530 --> 00:17:46,240
U issa fit-tieni biċċa karta,
din se tkun b, u dak am I

405
00:17:46,240 --> 00:17:49,010
se jkun miktub fuq
din il-biċċa ta 'karta?

406
00:17:49,010 --> 00:17:50,080
127.

407
00:17:50,080 --> 00:17:53,720
>> Allura l-unika ħaġa li biddel peress
javżak preċedenti tagħna ta 'din l-istorja hija,

408
00:17:53,720 --> 00:17:58,590
minflok litteralment 1 u 2, jien
ser jgħaddu 123 u 127.

409
00:17:58,590 --> 00:18:02,130
U jien issa se timplimenta dawn ġewwa
ta 'din il-kaxxa, id-dritt?

410
00:18:02,130 --> 00:18:04,640
Allura li kaxxa s-sewda issa jirrappreżenta
il-funzjoni tpartit.

411
00:18:04,640 --> 00:18:07,230
>> Sadanittant, ejja issa jkollhom xi ħadd
jimplimentaw il-funzjoni tpartit.

412
00:18:07,230 --> 00:18:09,090
Would xi ħadd up here
tixtieq voluntier?

413
00:18:09,090 --> 00:18:09,560
Come fuq up.

414
00:18:09,560 --> 00:18:11,080
X'hemm isem tiegħek?

415
00:18:11,080 --> 00:18:11,460
Charlie.

416
00:18:11,460 --> 00:18:12,080
Kull dritt, Charlie.

417
00:18:12,080 --> 00:18:14,810
Come fuq up.

418
00:18:14,810 --> 00:18:17,310
>> Allura Charlie huwa se jkollu
ir-rwol ta 'kaxxa s-sewda tagħna.

419
00:18:17,310 --> 00:18:21,460
U Charlie, dak I tixtieq li tagħmel
issa qed timplimenta tpartit b'tali mod

420
00:18:21,460 --> 00:18:25,320
li, minħabba dawn iż-żewġ indirizzi,
inti kienu attwalment għaddejjin

421
00:18:25,320 --> 00:18:26,330
li jibdlu l-valuri.

422
00:18:26,330 --> 00:18:28,290
U jien ser whisper fil-widnejn tiegħek
kif jitmexxa l-TV hawn.

423
00:18:28,290 --> 00:18:29,930
>> Allura aqbad, u int l-kaxxa s-sewda.

424
00:18:29,930 --> 00:18:30,920
Reach fil hemmhekk.

425
00:18:30,920 --> 00:18:34,054
What valuri tara għal, u
dak valuri tara għal b?

426
00:18:34,054 --> 00:18:36,740
>> CHARLIE: a huwa 123 u b huwa 127.

427
00:18:36,740 --> 00:18:37,530
>> DAVID Malan: OK, eżattament.

428
00:18:37,530 --> 00:18:38,940
Issa nieqaf hemm għal ftit mument.

429
00:18:38,940 --> 00:18:41,680
L-ewwel ħaġa int ser tagħmel issa,
skont il-kodiċi - li

430
00:18:41,680 --> 00:18:43,220
I issa ser pull up fuq l-iskrin -

431
00:18:43,220 --> 00:18:46,750
se tkun li talloka ftit
daqsxejn ta 'memorja imsejħa temperatura.

432
00:18:46,750 --> 00:18:48,850
Hekk jien ser jimxi 'l quddiem u
jtik li memorja.

433
00:18:48,850 --> 00:18:52,210
>> Allura dan se tkun terz varjabbli
li inti għandek aċċessibbli għal

434
00:18:52,210 --> 00:18:54,080
ċempilt temperatura.

435
00:18:54,080 --> 00:18:57,120
U liema huma inti ser jikteb
fuq il-biċċa temperatura tal-karta?

436
00:18:57,120 --> 00:19:02,524

437
00:19:02,524 --> 00:19:03,470
>> CHARLIE: Pointers, right?

438
00:19:03,470 --> 00:19:04,790
>> DAVID Malan: OK, ukoll mhux
neċessarjament pointers.

439
00:19:04,790 --> 00:19:07,230
Allura l-linja tal-kodiċi li stajt
enfasizzata fuq il-lemin,

440
00:19:07,230 --> 00:19:07,900
ejja tibda hemmhekk.

441
00:19:07,900 --> 00:19:08,890
Hija tgħid star a.

442
00:19:08,890 --> 00:19:11,670
Allura bħalissa ħażna
in-numru 123.

443
00:19:11,670 --> 00:19:16,660
U biss intuwittivament, liema
ma star 123 jfisser?

444
00:19:16,660 --> 00:19:21,630
>> Iżda speċifikament, jekk ikun
123, star mezz liema?

445
00:19:21,630 --> 00:19:22,560
Il-valur ta '.

446
00:19:22,560 --> 00:19:24,580
Jew aktar każwali, jmorru hemm.

447
00:19:24,580 --> 00:19:28,620
So let me jipproponi li, li jkollu l-kontribut in
naħa tiegħek, aqbad u jittrattaw dak

448
00:19:28,620 --> 00:19:29,430
bħallikieku huwa mappa.

449
00:19:29,430 --> 00:19:32,940
U jimxu lilek innifsek fuq il-kompjuter tal-
memorja, u ssib us dak li huwa

450
00:19:32,940 --> 00:19:36,520
fil-post 123.

451
00:19:36,520 --> 00:19:37,720
Eżattament.

452
00:19:37,720 --> 00:19:41,100
>> Allura naraw fil-lokalità 123
huwa dak, ovvjament?

453
00:19:41,100 --> 00:19:44,240
OK, iva, liema valur issa huma inti
ser jitqiegħdu fis temperatura?

454
00:19:44,240 --> 00:19:44,750
Eżattament.

455
00:19:44,750 --> 00:19:45,600
Allura aqbad u tagħmel dan.

456
00:19:45,600 --> 00:19:51,280
U jiktbu n-numru 1 fuq il-biċċa ta '
karta thats bħalissa titolat temp.

457
00:19:51,280 --> 00:19:53,540
>> U issa l-pass li jmiss li
int ser jimplimentaw

458
00:19:53,540 --> 00:19:54,310
se tkun dak.

459
00:19:54,310 --> 00:19:57,820
Ukoll, fuq il-lemin tal-
linja li jmiss tal-kodiċi hija stilla b. b, tal

460
00:19:57,820 --> 00:19:59,260
Naturalment, ħwienet indirizz.

461
00:19:59,260 --> 00:20:02,270
Li tindirizza 127.

462
00:20:02,270 --> 00:20:06,620
Star b ifisser dak, każwali jitkellem?

463
00:20:06,620 --> 00:20:08,700
>> Mur f'dak il-post.

464
00:20:08,700 --> 00:20:14,988
Allura aqbad u ssib us x'hemm
fil-post 127.

465
00:20:14,988 --> 00:20:15,480
OK.

466
00:20:15,480 --> 00:20:19,170
Of course, fil-post 127,
għadu l-valur 2.

467
00:20:19,170 --> 00:20:24,060
Allura dak li huma inti tmur issa store fi
x'ikun l fil-post fil-?

468
00:20:24,060 --> 00:20:26,860
Allura star mezz tmur għall-post ta '.

469
00:20:26,860 --> 00:20:29,770
X'inhu l-post ta '?

470
00:20:29,770 --> 00:20:30,430
>> Eżattament.

471
00:20:30,430 --> 00:20:34,190
Allura issa, jekk inti tixtieq li tibdel
x'hemm f'dak il-post -

472
00:20:34,190 --> 00:20:36,470
I ser imorru quddiem u run
l-eraser huma hawnhekk.

473
00:20:36,470 --> 00:20:37,760
U issa poġġih lura fuq il-brush.

474
00:20:37,760 --> 00:20:42,190
Dak in-numru huma inti ser jikteb
f'dik il-kaxxa vojta issa?

475
00:20:42,190 --> 00:20:42,850
>> Eżattament.

476
00:20:42,850 --> 00:20:46,470
Allura din il-linja tal-kodiċi, li jkun ċar - let
me nieqaf dak Charlie qed jagħmel u

477
00:20:46,470 --> 00:20:51,730
jfakkru, dak hu biss isir huwa
jikteb fil-kaxxa fil-lokalità 123

478
00:20:51,730 --> 00:20:55,150
il-valur li kien preċedentement fil b.

479
00:20:55,150 --> 00:20:59,140
U hekk aħna issa stajt implimentati tabilħaqq
din it-tieni linja tal-kodiċi.

480
00:20:59,140 --> 00:21:01,920
>> Issa sfortunatament, hemm
xorta linja waħda fadal.

481
00:21:01,920 --> 00:21:04,900
Issa dak li huwa fil temperatura, litteralment?

482
00:21:04,900 --> 00:21:06,200
Huwa ovvjament in-numru wieħed.

483
00:21:06,200 --> 00:21:07,020
Li mhux l-indirizz.

484
00:21:07,020 --> 00:21:09,380
Huwa biss numru, tip ta '
varjabbli minn ġimgħa.

485
00:21:09,380 --> 00:21:13,520
>> U issa meta inti tgħidli star b, dan ifisser
mur l-indirizz b, li huwa ta '

486
00:21:13,520 --> 00:21:15,090
kors hawn.

487
00:21:15,090 --> 00:21:16,020
Allura ladarba inti naslu s'hemm -

488
00:21:16,020 --> 00:21:18,320
I ser imorru quddiem u tħassar x'hemm attwalment
hemm - u liema huma inti

489
00:21:18,320 --> 00:21:20,820
ser jikteb issa fil 127 post?

490
00:21:20,820 --> 00:21:22,010
>> CHARLIE: Temp, li hija waħda.

491
00:21:22,010 --> 00:21:23,430
>> DAVID Malan: Temp, li hija waħda.

492
00:21:23,430 --> 00:21:25,670
U dak li jiġri għall temperatura fl-aħħar?

493
00:21:25,670 --> 00:21:26,600
Well, aħna ma verament jafu.

494
00:21:26,600 --> 00:21:27,420
Aħna ma verament kura.

495
00:21:27,420 --> 00:21:31,090
Kwalunkwe ħin konna implimentati funzjoni
s'issa, kwalunkwe varjabbli lokali għandek

496
00:21:31,090 --> 00:21:31,890
huma tabilħaqq lokali.

497
00:21:31,890 --> 00:21:33,060
U huma biss jisparixxu.

498
00:21:33,060 --> 00:21:35,040
Huma qed reklamata mill-operattiva
sistema eventwalment.

499
00:21:35,040 --> 00:21:39,800
>> Allura l-fatt li Temperatura għad għandha l-
valur 1 huwa tip ta fundamentalment

500
00:21:39,800 --> 00:21:41,150
uninteresting lilna.

501
00:21:41,150 --> 00:21:43,100
Kull dritt, hekk rawnd ta 'applause
jekk nistgħu għal Charlie.

502
00:21:43,100 --> 00:21:46,400
Ħafna isir ukoll.

503
00:21:46,400 --> 00:21:51,520
>> Kull dritt, iva, liema aktar ma
Dan ifisser li nistgħu nagħmlu?

504
00:21:51,520 --> 00:21:54,400
Għalhekk jirriżulta li aħna kont qed
javżak tinsab abjad ftit

505
00:21:54,400 --> 00:21:55,540
għal żmien pjuttost twil.

506
00:21:55,540 --> 00:21:59,990
Tabilħaqq, jirriżulta li string,
kollha ta 'dan iż-żmien huwa, mhuwiex verament

507
00:21:59,990 --> 00:22:02,190
sekwenza ta 'karattri per se.

508
00:22:02,190 --> 00:22:03,980
Huwa tip ta 'hija li intuwittivament.

509
00:22:03,980 --> 00:22:08,270
>> Iżda teknikament speaking, string hija
tip ta 'data li aħna iddikjarat ġewwa tal

510
00:22:08,270 --> 00:22:12,170
il-librerija CS50 biex jissimplifikaw id-dinja
għall-ewwel ftit ġimgħat ta 'klassi.

511
00:22:12,170 --> 00:22:20,130
What a string huwa verament huwa l-indirizz
ta 'karattru x'imkien RAM.

512
00:22:20,130 --> 00:22:25,530
A string huwa verament numru, bħal 123
jew 127, li jiġri jiddemarkaw

513
00:22:25,530 --> 00:22:28,420
fejn string jibda
memorja tal-kompjuter tiegħek.

514
00:22:28,420 --> 00:22:31,870
>> Iżda dan ma jirrappreżentax il-
spag, per se, hija stess.

515
00:22:31,870 --> 00:22:33,460
U nistgħu naraw dan kif ġej.

516
00:22:33,460 --> 00:22:35,980
Let me imorru quddiem u tiftaħ
xi kodiċi thats fost

517
00:22:35,980 --> 00:22:38,340
Eżempji source code tal-lum.

518
00:22:38,340 --> 00:22:42,225
U jien ser imorru quddiem u tiftaħ
up, ejja ngħidu, iqabblu 0.c.

519
00:22:42,225 --> 00:22:44,830

520
00:22:44,830 --> 00:22:48,790
Dan huwa programm Buggy li ser
li għandhom jiġu implimentati kif ġej.

521
00:22:48,790 --> 00:22:49,040
>> Ewwel.

522
00:22:49,040 --> 00:22:50,420
Jien se ngħid xi ħaġa.

523
00:22:50,420 --> 00:22:52,660
Imbagħad jien ser jimxi 'l quddiem u
tikseb string mill-utent

524
00:22:52,660 --> 00:22:53,750
f'dik il-linja li jmiss.

525
00:22:53,750 --> 00:22:55,370
Imbagħad jien se ngħid mill-ġdid.

526
00:22:55,370 --> 00:22:57,540
Imbagħad jien ser tikseb ieħor
string mill-utent.

527
00:22:57,540 --> 00:23:00,390
>> U avviż, jien li juri waħda mill-
irbit varjabbli msejħa s, u

528
00:23:00,390 --> 00:23:03,040
ieħor ta 'dawn kordi
fil-varjabbli imsejjaħ t.

529
00:23:03,040 --> 00:23:07,480
U issa jien ser jitolbu, ħafna
raġonevolment, li jekk s ugwali ugwali t,

530
00:23:07,480 --> 00:23:08,940
il-kordi huma l-istess.

531
00:23:08,940 --> 00:23:09,970
Inti tip l-istess ħaġa.

532
00:23:09,970 --> 00:23:11,830
Else, il-kordi huma
mhux l-istess ħaġa.

533
00:23:11,830 --> 00:23:15,440
>> Wara kollox, jekk aħna input żewġ ints, żewġ
Chars, żewġ sufruni, żewġ jirdoppja, kwalunkwe ta '

534
00:23:15,440 --> 00:23:18,400
tip ta 'data konna tkellem dwar
s'issa biex iqabblu lilhom -

535
00:23:18,400 --> 00:23:22,070
recall għamilna ċara ħafna filwaqt li ilu
li inti ma tagħmel dan, għaliex

536
00:23:22,070 --> 00:23:25,840
sinjal ugwali uniku huwa ta 'kors
l-operatur assenjazzjoni.

537
00:23:25,840 --> 00:23:26,820
Allura li tkun bug.

538
00:23:26,820 --> 00:23:29,260
>> Aħna nużaw is-sinjal ugwali ugwali,
li tabilħaqq tqabbel

539
00:23:29,260 --> 00:23:31,050
affarijiet għall-ugwaljanza vera.

540
00:23:31,050 --> 00:23:32,275
Imma I titlob dan huwa Buggy.

541
00:23:32,275 --> 00:23:37,400
Jekk I jimxi 'l quddiem u jagħmlu jqabblu żero,
u allura ma dot mmejla jqabblu żero.

542
00:23:37,400 --> 00:23:39,700
U jien tip, ejja ngħidu, bonjour.

543
00:23:39,700 --> 00:23:41,590
U mbagħad ejja jgħidu bonjour mill-ġdid.

544
00:23:41,590 --> 00:23:46,040
Litteralment l-istess ħaġa, il-kompjuter
pretensjonijiet I ittajpjat affarijiet differenti.

545
00:23:46,040 --> 00:23:47,640
>> Issa forsi I biss mistyped xi ħaġa.

546
00:23:47,640 --> 00:23:49,910
I ser tip isem tiegħi dan iż-żmien.

547
00:23:49,910 --> 00:23:52,580
I mean, bonjour.

548
00:23:52,580 --> 00:23:54,770
Hello.

549
00:23:54,770 --> 00:23:57,360
Huwa differenti kull wieħed ħin.

550
00:23:57,360 --> 00:23:58,430
>> Well, għaliex huwa li?

551
00:23:58,430 --> 00:24:00,140
X'qed verament għaddejjin
taħt il-barnuża?

552
00:24:00,140 --> 00:24:03,270
Ukoll, dak li verament għaddejjin taħt
il-barnuża huwa l-sekwenza imbagħad

553
00:24:03,270 --> 00:24:07,410
I ittajpjat f'dan l-ewwel darba, pereżempju
hija l-kelma hello, tal-kors.

554
00:24:07,410 --> 00:24:11,660
Imma jekk aħna nirrappreżentaw dan taħt
il-barnuża, ifakkar li

555
00:24:11,660 --> 00:24:13,470
sekwenza huwa fil-firxa.

556
00:24:13,470 --> 00:24:15,040
U konna qal kemm fil-passat.

557
00:24:15,040 --> 00:24:20,200
>> Hekk jekk I tfassal dak firxa bħal dan, jien
ser jirrappreżentaw xi ħaġa pjuttost

558
00:24:20,200 --> 00:24:23,030
simili għal dak li għamilna mument ilu.

559
00:24:23,030 --> 00:24:25,390
U hemm attwalment xi ħaġa
partikolari hawn, wisq.

560
00:24:25,390 --> 00:24:28,090
What did aħna jiddeterminaw kienet fi
l-aħħar ta 'kull string?

561
00:24:28,090 --> 00:24:30,760
Yeah, dan żero backslash, li hija
biss il-mod li jirrappreżentaw,

562
00:24:30,760 --> 00:24:33,610
litteralment, 00000000.

563
00:24:33,610 --> 00:24:35,680
Tmien 0 bits fil-filliera.

564
00:24:35,680 --> 00:24:37,610
>> I do not know, franchement,
x'hemm wara dan.

565
00:24:37,610 --> 00:24:40,090
Li jinsab biss mazz aktar RAM
ġewwa tal-kompjuter tiegħi.

566
00:24:40,090 --> 00:24:40,970
Iżda dan huwa firxa.

567
00:24:40,970 --> 00:24:42,260
Tkellimna dwar arrays qabel.

568
00:24:42,260 --> 00:24:45,010
U aħna tipikament nitkellmu dwar arrays
bħala post żero,

569
00:24:45,010 --> 00:24:46,580
allura wieħed, imbagħad tnejn.

570
00:24:46,580 --> 00:24:47,950
Iżda li biss għall-konvenjenza.

571
00:24:47,950 --> 00:24:49,380
U li kollox relattiv.

572
00:24:49,380 --> 00:24:53,010
>> Meta int attwalment jkollna memorja minn
il-kompjuter, huwa naturalment kwalunkwe

573
00:24:53,010 --> 00:24:55,450
2000000000 bytes xi fard, potenzjalment.

574
00:24:55,450 --> 00:24:59,100
Allura verament taħt il-barnuża,
dan il-ħin, iva.

575
00:24:59,100 --> 00:25:01,670
Dan jista 'jkun tajjeb ħafna bracket żero.

576
00:25:01,670 --> 00:25:04,780
Imma jekk inti ħaffer aktar fil-fond taħt
il-barnuża, li tassew

577
00:25:04,780 --> 00:25:07,000
jindirizzaw numru 123.

578
00:25:07,000 --> 00:25:09,150
Dan huwa l-indirizz 124.

579
00:25:09,150 --> 00:25:11,040
Dan huwa l-indirizz 125.

580
00:25:11,040 --> 00:25:12,540
>> U jien ma screw up dan iż-żmien.

581
00:25:12,540 --> 00:25:15,840
Dawn issa huma wieħed bytes
apparti għal liema raġuni?

582
00:25:15,840 --> 00:25:17,930
Kif big huwa char?

583
00:25:17,930 --> 00:25:19,170
A char huwa biss wieħed byte.

584
00:25:19,170 --> 00:25:20,570
An int huwa tipikament erba bytes.

585
00:25:20,570 --> 00:25:24,850
Allura hu għalhekk li I magħmula 123,
127, 131 u oħrajn.

586
00:25:24,850 --> 00:25:27,560
Now I tista 'żżomm l-matematika sempliċi
u biss tagħmel plus 1.

587
00:25:27,560 --> 00:25:30,510
U issa din x'inhu verament għaddej huwa
fuq taħt il-barnuża.

588
00:25:30,510 --> 00:25:37,760
>> Allura meta inti tiddikjara xi ħaġa bħal din,
string s, dan huwa attwalment -

589
00:25:37,760 --> 00:25:39,170
jirriżulta -

590
00:25:39,170 --> 00:25:41,190
star char.

591
00:25:41,190 --> 00:25:44,640
Star, naturalment, ifisser
indirizz, pointer aka.

592
00:25:44,640 --> 00:25:46,200
Allura huwa l-indirizz ta 'xi ħaġa.

593
00:25:46,200 --> 00:25:47,510
X'inhu l-indirizz ta '?

594
00:25:47,510 --> 00:25:47,760
>> Well -

595
00:25:47,760 --> 00:25:51,680
Jien l-unika waħda li tista 'tara l-ħafna
Punt importanti jien jagħmlu, jew taħseb

596
00:25:51,680 --> 00:25:52,560
Jien jagħmlu.

597
00:25:52,560 --> 00:25:55,270
Allura string -

598
00:25:55,270 --> 00:25:57,180
il-ħaġa diqa hija I jkollhom monitor
hemm dritt fejn I

599
00:25:57,180 --> 00:25:58,100
seta 'jara li.

600
00:25:58,100 --> 00:26:00,990
>> Kull dritt, hekk string s huwa dak
I kienet iddikjarat qabel.

601
00:26:00,990 --> 00:26:04,600
Iżda jirriżulta, grazzi għal ftit
magic fil-librerija CS50, dan kollu

602
00:26:04,600 --> 00:26:08,780
string ħin għandha litteralment
Kien star char.

603
00:26:08,780 --> 00:26:11,310
L-istilla darb'oħra ifisser
pointer jew l-indirizz.

604
00:26:11,310 --> 00:26:14,180
Il-fatt li huwa akkumpanjament il-
kelma char ifisser li huwa l-

605
00:26:14,180 --> 00:26:15,970
indirizz ta 'karattru.

606
00:26:15,970 --> 00:26:23,100
>> Mela jekk tikseb string huwa msejjaħ, u tip I
fl H-E-L-L-O, tipproponi issa dak li tikseb

607
00:26:23,100 --> 00:26:27,330
string litteralment ġew jirritornaw kollha ta '
dan iż-żmien, anke jekk aħna ħadthom pjuttost

608
00:26:27,330 --> 00:26:29,980
eżaġerat id-dinja?

609
00:26:29,980 --> 00:26:33,310
Xi jfisser nikseb string attwalment
ritorn bħala valur tar-ritorn tagħha?

610
00:26:33,310 --> 00:26:35,830

611
00:26:35,830 --> 00:26:38,720
>> 123 F'dan il-każ, per eżempju.

612
00:26:38,720 --> 00:26:42,630
Imxejna diġà qal li tikseb string
sempliċiment jirritorna string, sekwenza ta '

613
00:26:42,630 --> 00:26:43,300
karattri.

614
00:26:43,300 --> 00:26:44,790
Iżda li l-daqsxejn ta 'gidba abjad.

615
00:26:44,790 --> 00:26:48,010
Il-mod tikseb string tassew jaħdem
taħt il-barnuża huwa jiġrilha

616
00:26:48,010 --> 00:26:48,930
string mill-utent.

617
00:26:48,930 --> 00:26:51,530
Hija plops-karattri li
hu jew hi tipi fil-memorja.

618
00:26:51,530 --> 00:26:54,680
Huwa jpoġġi żero backslash fl-aħħar
ta 'dawk sekwenza ta' karattri.

619
00:26:54,680 --> 00:26:57,310
>> Iżda mbagħad dak ma nikseb string
litteralment ritorn?

620
00:26:57,310 --> 00:27:02,710
Huwa letteralment jirritorna l-indirizz tal-
ħafna ewwel bytes fil-RAM li

621
00:27:02,710 --> 00:27:04,130
hija użat għal dik il-qawwa.

622
00:27:04,130 --> 00:27:07,500
U jirriżulta li biss billi jirritorna
indirizz wieħed ta 'l-

623
00:27:07,500 --> 00:27:12,120
ewwel karattru fis-sekwenza, jiġifieri
suffiċjenti għall-konstatazzjoni tal intier ta '

624
00:27:12,120 --> 00:27:12,630
l-sekwenza.

625
00:27:12,630 --> 00:27:16,930
>> Fi kliem ieħor, jiksbu string ma jkollux
li jirritornaw 123 u 124 u 125.

626
00:27:16,930 --> 00:27:19,950
Huwa ma jkollu li tagħti me twil
lista ta 'kollha tal-bytes li

627
00:27:19,950 --> 00:27:20,740
string tiegħi qed tuża.

628
00:27:20,740 --> 00:27:22,670
Għaliex wieħed, dawn qed kollha lura lura.

629
00:27:22,670 --> 00:27:28,160
U tnejn, ibbażata fuq l-ewwel indirizz, I
tista figura fejn il-sekwenza jispiċċa.

630
00:27:28,160 --> 00:27:29,910
Kif?

631
00:27:29,910 --> 00:27:33,490
>> Il-karattru null speċjali, il-
backslash żero fl-aħħar.

632
00:27:33,490 --> 00:27:35,430
Allura fi kliem ieħor, jekk
inti tgħaddi madwar -

633
00:27:35,430 --> 00:27:36,530
ġewwa ta 'varjabbli -

634
00:27:36,530 --> 00:27:41,300
l-indirizz ta 'char, u għandek tassumi
li fl-aħħar ta 'kull spag, kwalunkwe

635
00:27:41,300 --> 00:27:45,040
sekwenza ta 'karattri kif aħna bnedmin
think ta 'spag, jekk għandek tassumi li

636
00:27:45,040 --> 00:27:48,600
fl-aħħar ta 'kull sekwenza bħal hemm
żero backslash, int tad-deheb.

637
00:27:48,600 --> 00:27:52,430
Għaliex inti tista 'dejjem issib
l-aħħar ta 'sekwenza.

638
00:27:52,430 --> 00:27:54,870
>> Issa x'inhu verament għaddej mbagħad
fuq f'dan il-programm?

639
00:27:54,870 --> 00:27:59,990
Għaliex dan il-programm,
iqabblu 0.c, Buggy?

640
00:27:59,990 --> 00:28:01,690
Dak li huwa attwalment qed jiġu mqabbla?

641
00:28:01,690 --> 00:28:02,420
Yeah?

642
00:28:02,420 --> 00:28:05,000
>> STUDENT: [inaudible].

643
00:28:05,000 --> 00:28:05,730
>> DAVID Malan: Eżattament.

644
00:28:05,730 --> 00:28:08,350
Huwa jitqabblu l-postijiet
tal-kordi.

645
00:28:08,350 --> 00:28:12,420
Mela jekk l-utent ikun ittajpjat fil bonjour darba,
kif għamilt, il-memorja tista 'tispiċċa

646
00:28:12,420 --> 00:28:13,430
tfittex bħal dan.

647
00:28:13,430 --> 00:28:18,210
Jekk l-utent imbagħad tipi fil bonjour mill-ġdid,
iżda billi ċċempel tikseb string darb'oħra, c huwa

648
00:28:18,210 --> 00:28:21,800
mhux partikolarment għaqlija sakemm inti jgħallmu
li tkun għaqlija minn kodiċi miktub.

649
00:28:21,800 --> 00:28:22,430
>> C -

650
00:28:22,430 --> 00:28:23,860
u kompjuters aktar ġenerali -

651
00:28:23,860 --> 00:28:27,370
jekk inti tip fil-kelma Hello għal darb'oħra,
inti taf dak li int ser tikseb.

652
00:28:27,370 --> 00:28:31,480
Int biss ser tikseb tieni firxa
ta 'memorja li, iva, jiġri jkun

653
00:28:31,480 --> 00:28:35,510
ħażna H-E-L-L-O u oħrajn.

654
00:28:35,510 --> 00:28:38,240
>> Huwa ser tħares l-istess għall-
us bnedmin, iżda dan l-indirizz

655
00:28:38,240 --> 00:28:39,460
jista 'ma jkunx 123.

656
00:28:39,460 --> 00:28:42,470
Jista 'hekk jiġri biss li l-
sistema operattiva għandha xi disponibbli

657
00:28:42,470 --> 00:28:45,430
ispazju per eżempju fil-post -

658
00:28:45,430 --> 00:28:49,820
ejja ngħidu xi ħaġa arbitrarja,
bħal dan huwa post 200.

659
00:28:49,820 --> 00:28:51,620
U dan huwa post 201.

660
00:28:51,620 --> 00:28:53,060
U dan huwa post 202.

661
00:28:53,060 --> 00:28:55,730
Għandna l-ebda idea fejn dan huwa
ser ikunu fil-memorja.

662
00:28:55,730 --> 00:28:59,110
>> Imma dak li dan ifisser huwa li dak li huwa
ser jiġi maħżun finalment i?

663
00:28:59,110 --> 00:29:00,750
In-numru 123.

664
00:29:00,750 --> 00:29:04,860
X'hemm ser jiġi maħżun fil-t,
f'dan l-eżempju arbitrarja?

665
00:29:04,860 --> 00:29:06,300
In-numru 200.

666
00:29:06,300 --> 00:29:11,410
U dak kollu li jfisser allura hija ovvjament,
123 ma tkunx daqs 200.

667
00:29:11,410 --> 00:29:14,940
U hekk dan jekk il-kundizzjoni qatt
jevalwa l veru.

668
00:29:14,940 --> 00:29:18,430
Minħabba string get qed tuża differenti
biċċiet ta 'memorja kull darba.

669
00:29:18,430 --> 00:29:20,360
>> Issa nistgħu naraw dan jerġa
fl-eżempju ieħor.

670
00:29:20,360 --> 00:29:23,764
Let me imorru quddiem u tiftaħ kopja 0.c.

671
00:29:23,764 --> 00:29:28,770
I jsostnu li dan l-eżempju se
ipprova - iżda jonqsu - li tikkopja żewġ kordi

672
00:29:28,770 --> 00:29:29,910
kif ġej.

673
00:29:29,910 --> 00:29:31,730
>> Jien se ngħid xi ħaġa
għall-utent.

674
00:29:31,730 --> 00:29:34,490
Jien imbagħad ser tikseb
spag u sejħa hija s.

675
00:29:34,490 --> 00:29:36,400
U issa, jien tagħmel dan il-kontroll hawnhekk.

676
00:29:36,400 --> 00:29:37,990
Aħna msemmija f'dan filwaqt li lura.

677
00:29:37,990 --> 00:29:42,490
Imma meta tista 'tikseb null ritorn string,
karattru ieħor speċjali, jew speċjali

678
00:29:42,490 --> 00:29:45,050
simbolu Ejja ngħidu.

679
00:29:45,050 --> 00:29:45,900
Jekk huwa tal-memorja.

680
00:29:45,900 --> 00:29:48,970
>> Per eżempju, jekk l-utent huwa verament
diffiċli, u t-tipi ta 'atroċi

681
00:29:48,970 --> 00:29:51,220
numru ta 'karattri fil-
tastiera u hits Ikteb.

682
00:29:51,220 --> 00:29:54,580
Jekk dak in-numru ta 'karattri biss ma tistax
tiffittja RAM għal kwalunkwe crazy

683
00:29:54,580 --> 00:29:57,820
raġuni, ukoll nikseb string jista
tajjeb ħafna ritorn null.

684
00:29:57,820 --> 00:30:01,080
>> Jew jekk program tiegħek stess qed tagħmel ħafna
ta 'affarijiet oħra u hemm biss

685
00:30:01,080 --> 00:30:03,790
mhux memorja biżżejjed għall string get
biex jirnexxu, Huwa jista 'jispiċċa

686
00:30:03,790 --> 00:30:05,240
up jirritornaw null.

687
00:30:05,240 --> 00:30:07,160
Imma ejja tkun aktar preċiża
dwar liema dan huwa.

688
00:30:07,160 --> 00:30:10,280
X'inhu tip ta 'data i tal tassew?

689
00:30:10,280 --> 00:30:11,610
Star Char.

690
00:30:11,610 --> 00:30:14,560
>> Għalhekk jirriżulta li issa nistgħu qoxra
lura l-saff ta 'nulla.

691
00:30:14,560 --> 00:30:17,500
Jirriżulta, null hija - iva, ovvjament
simbolu speċjali.

692
00:30:17,500 --> 00:30:19,190
Imma dak huwa tassew?

693
00:30:19,190 --> 00:30:25,220
Really, null hija biss simbolu li aħna
bnedmin tuża biex jirrappreżentaw żero ukoll.

694
00:30:25,220 --> 00:30:29,010
>> Allura l-awturi ta 'C, u kompjuters
b'mod aktar ġenerali, iddeċieda snin ilu

695
00:30:29,010 --> 00:30:30,010
dan, inti taf liema.

696
00:30:30,010 --> 00:30:34,850
Għaliex ma we jiżguraw li l-ebda utent
data hija qatt, qatt, qatt

697
00:30:34,850 --> 00:30:36,730
maħżuna fil bye żero?

698
00:30:36,730 --> 00:30:39,610
Fil-fatt, anki fl-eżempju arbitrarja tiegħi
qabel, I ma tibda numerazzjoni l-

699
00:30:39,610 --> 00:30:40,390
bytes f'żero.

700
00:30:40,390 --> 00:30:41,540
I bdiet fil waħda.

701
00:30:41,540 --> 00:30:44,950
Għaliex kont naf li n-nies fid-dinja
jiddeċiedi li jirriżerva l-żero

702
00:30:44,950 --> 00:30:47,970
byte fl RAM ħadd bħala
xi ħaġa speċjali.

703
00:30:47,970 --> 00:30:52,020
>> Ir-raġuni li, ghaċ tixtieq
sinjal li xi ħaġa marret ħażin

704
00:30:52,020 --> 00:30:55,960
fir-rigward indirizzi, inti lura
null - inkella magħruf bħala zero -

705
00:30:55,960 --> 00:30:59,410
u għaliex inti taf li hemm l-ebda
leġittimu data fl-indirizz żero, b'mod ċar

706
00:30:59,410 --> 00:31:00,400
dan ifisser żball.

707
00:31:00,400 --> 00:31:04,080
U huwa għalhekk li għandna, b'konvenzjoni, check
għall null u r-ritorn xi ħaġa

708
00:31:04,080 --> 00:31:06,260
bħal wieħed f'dawk il-każijiet.

709
00:31:06,260 --> 00:31:09,300
>> Allura jekk aħna iscroll issa, dan huwa biss
mbagħad ftit verifika żball, biss fil-każ

710
00:31:09,300 --> 00:31:10,610
xi ħaġa li marret ħażin ma [? bail?]

711
00:31:10,610 --> 00:31:13,470
kollox u nieqaf-programm
billi jirritorna kmieni.

712
00:31:13,470 --> 00:31:19,030
Din il-linja issa jistgħu jiġu miktuba mill-ġdid
kif dan, li jfisser liema?

713
00:31:19,030 --> 00:31:23,155
Min-naħa tax-xellug, tagħti me ieħor
pointer għal karattru, u sejħa hija t.

714
00:31:23,155 --> 00:31:26,935
What am I ħażna ġewwa ta 't, ibbażata
fuq din il-linja waħda tal-kodiċi?

715
00:31:26,935 --> 00:31:30,950

716
00:31:30,950 --> 00:31:32,170
>> Jien jaħżen post.

717
00:31:32,170 --> 00:31:34,742
Speċifikament il-post
li kien i.

718
00:31:34,742 --> 00:31:39,000
Mela jekk l-utent ikun ittajpjat fil hello, u
li l-ewwel bonjour jiġri li jispiċċaw

719
00:31:39,000 --> 00:31:42,567
hawn, allura l-123 numru huwa
ser jiġu lura minn tikseb

720
00:31:42,567 --> 00:31:43,810
string u jiġu maħżuna -

721
00:31:43,810 --> 00:31:44,780
kif għidna qabel -

722
00:31:44,780 --> 00:31:45,440
fl-i.

723
00:31:45,440 --> 00:31:50,560
>> Meta I issa niddikjara pointer ieħor biex
a t char u sejħa hija, dak in-numru huwa

724
00:31:50,560 --> 00:31:53,940
litteralment ser jispiċċaw fl
f't skont l-istorja?

725
00:31:53,940 --> 00:31:55,420
Allura 123.

726
00:31:55,420 --> 00:32:00,310
>> Allura teknikament issa kemm iu
t huma tipponta lejn il-eżatt

727
00:32:00,310 --> 00:32:02,410
istess biċċiet ta 'memorja.

728
00:32:02,410 --> 00:32:06,140
Allura avviż dak li jien ser tagħmel issa li
jipprova li dan il-programm huwa Buggy.

729
00:32:06,140 --> 00:32:08,820
>> Ewwel Jien ser jitolbu, ma
print f, kapitalizzazzjoni

730
00:32:08,820 --> 00:32:10,080
il-kopja tas-sekwenza.

731
00:32:10,080 --> 00:32:11,660
Imbagħad jien ser tagħmel ftit
Kontroll Żball.

732
00:32:11,660 --> 00:32:12,160
Jien ser tagħmel ċert.

733
00:32:12,160 --> 00:32:16,710
Ejja kun żgur li l-sekwenza t huwa fil
inqas ogħla minn żero fit-tul,

734
00:32:16,710 --> 00:32:19,190
hekk hemm xi karattru hemm
li attwalment kapitalizzazzjoni.

735
00:32:19,190 --> 00:32:22,840
>> U allura inti tista 'recall dan
minn eżempji preċedenti.

736
00:32:22,840 --> 00:32:25,630
2 ta 'fuq - li huwa
il-fajl ctype.h.

737
00:32:25,630 --> 00:32:30,800
T bracket żero me tagħti l-zero
karattru tal-t sekwenza.

738
00:32:30,800 --> 00:32:34,360
U 2 ta 'fuq tal-istess valur, ta'
Naturalment, tikkonverti li uppercase.

739
00:32:34,360 --> 00:32:38,230
>> Allura intuwittivament, din il-linja enfasizzat
ta 'kodiċi hija kapitalizzazzjoni-ewwel

740
00:32:38,230 --> 00:32:40,250
ittra f't.

741
00:32:40,250 --> 00:32:44,485
Iżda mhuwiex kapitalizzazzjoni, intuwittivament,
l-ewwel ittra fl-i.

742
00:32:44,485 --> 00:32:48,130
Imma jekk int taħseb quddiem, dak am I
waslu biex tara meta I run dan il-programm

743
00:32:48,130 --> 00:32:54,220
u jistampa kemm l-oriġinali,
i, u l-kopja hekk imsejħa, t?

744
00:32:54,220 --> 00:32:55,350
>> Huma qed fil-fatt se tkun l-istess.

745
00:32:55,350 --> 00:32:56,600
U għaliex dawn huma ser ikunu l-istess?

746
00:32:56,600 --> 00:32:58,970

747
00:32:58,970 --> 00:33:01,020
Huma qed kemm tipponta lejn
eżattament l-istess ħaġa.

748
00:33:01,020 --> 00:33:01,610
Mela ejja jagħmlu dan.

749
00:33:01,610 --> 00:33:03,160
>> Jagħmlu kopja żero.

750
00:33:03,160 --> 00:33:04,070
Tiġbor OK.

751
00:33:04,070 --> 00:33:06,500
Let me run kopja żero.

752
00:33:06,500 --> 00:33:10,110
Let me tip xi ħaġa bħal bonjour
kollha lowercase mbagħad hit Ikteb.

753
00:33:10,110 --> 00:33:16,520
U hija ssostni li kemm il-s oriġinali
u l-kopja huma tabilħaqq identiċi.

754
00:33:16,520 --> 00:33:17,920
>> Allura dak li verament ġara hawn?

755
00:33:17,920 --> 00:33:20,100
Let me tiġbed din l-istampa biss
li tgħid l-istorja fil-

756
00:33:20,100 --> 00:33:21,340
b'mod kemmxejn differenti.

757
00:33:21,340 --> 00:33:26,060
X'qed verament għaddejjin minn taħt il-
hood meta Niddikjara xi ħaġa simili

758
00:33:26,060 --> 00:33:30,410
char s bidu, jew spag s,
I am jkollna pointer -

759
00:33:30,410 --> 00:33:33,090
li jiġri li jkun ta 'erba bytes
fil-appliance CS50

760
00:33:33,090 --> 00:33:34,410
u fil-lott ta 'kompjuters.

761
00:33:34,410 --> 00:33:36,008
U jien ser sejħa dan i.

762
00:33:36,008 --> 00:33:39,810
U dan bħalissa għandha
xi valur mhux magħruf.

763
00:33:39,810 --> 00:33:43,900
>> Meta inti tiddikjara varjabbli, sakemm inti
yourself nagħtu valur hemmhekk, li

764
00:33:43,900 --> 00:33:44,570
jaf x'hemm hemmhekk.

765
00:33:44,570 --> 00:33:48,110
Jista 'jkun hemm xi sekwenza każwali ta'
bits mill-eżekuzzjoni ta 'qabel.

766
00:33:48,110 --> 00:33:52,490
Allura meta I, f'konformità tiegħi tal-kodiċi ma jiksbu
spag, u mbagħad aħżen-ritorn

767
00:33:52,490 --> 00:33:54,800
valur s nikseb string b'xi mod -

768
00:33:54,800 --> 00:33:58,520
u aħna ser eventwalment qoxra lura kif tikseb
xogħlijiet spag, b'xi jalloka

769
00:33:58,520 --> 00:34:00,480
array li probabbilment jistenna
qisu dan.

770
00:34:00,480 --> 00:34:05,390
H-E-L-L-O, backslash żero.

771
00:34:05,390 --> 00:34:09,510
>> Ejja nassumu li din hija indirizz
123 biss l-ewwel konsistenza.

772
00:34:09,510 --> 00:34:13,000
Sabiex tikseb prospetti spag, fil-
linja enfasizzat hemmhekk, dan jirritorna l-

773
00:34:13,000 --> 00:34:15,000
numru għidna, 123.

774
00:34:15,000 --> 00:34:17,420
Allura dak li verament tmur ġewwa ta 'i hawn?

775
00:34:17,420 --> 00:34:26,590
>> Ukoll, dak li verament tmur
ġewwa ta 's huwa 123.

776
00:34:26,590 --> 00:34:29,250
Iżda franchement, jien jkollna ftit
konfużi minn kulħadd ta 'dawn l-indirizzi,

777
00:34:29,250 --> 00:34:30,320
kollha ta 'dawn in-numri arbitrarji.

778
00:34:30,320 --> 00:34:32,290
123, 124, 127.

779
00:34:32,290 --> 00:34:34,570
Mela ejja attwalment jissimplifikaw
id-dinja ftit.

780
00:34:34,570 --> 00:34:38,800
>> Meta nitkellmu dwar pointers, franchement, li
us bnedmin, li l-Heck cares fejn

781
00:34:38,800 --> 00:34:39,870
affarijiet huma fil-memorja?

782
00:34:39,870 --> 00:34:41,080
C'est kompletament arbitrarja.

783
00:34:41,080 --> 00:34:43,370
Huwa ser jiddependi fuq kif
RAM ħafna l-utent għandu.

784
00:34:43,370 --> 00:34:46,590
Huwa ser jiddependu fuq meta fil-ġurnata
inti tmexxi l-programm, forsi, u

785
00:34:46,590 --> 00:34:48,250
dak input-utent jagħtik.

786
00:34:48,250 --> 00:34:50,060
Aħna abitazzjoni fuq id-dettalji mhux importanti.

787
00:34:50,060 --> 00:34:54,230
>> Mela ejja astratt bogħod u jgħidu li,
meta inti tmexxi linja tal-kodiċi bħal dan,

788
00:34:54,230 --> 00:34:57,320
char star s gets-ritorn
valur ta 'spag get.

789
00:34:57,320 --> 00:35:02,720
Għaliex ma we minflok biss jiġbed dak li aħna
iżommu ssejjaħ pointer bħallikieku huwa

790
00:35:02,720 --> 00:35:04,140
tipponta lejn xi ħaġa?

791
00:35:04,140 --> 00:35:07,000
So I jsostnu issa li s up
hemm pointer -

792
00:35:07,000 --> 00:35:08,480
taħt il-barnuża huwa ta 'indirizz.

793
00:35:08,480 --> 00:35:11,330
Iżda huwa biss li tipponta lejn
l-ewwel byte fil-

794
00:35:11,330 --> 00:35:12,780
string li kien lura.

795
00:35:12,780 --> 00:35:16,710
>> Jekk I issa lura għall-kodiċi hawn,
x'inhu għaddej fil din il-linja?

796
00:35:16,710 --> 00:35:20,020
Ukoll, f'dan il-linja enfasizzat issa,
Jien tiddikjara apparentement ieħor

797
00:35:20,020 --> 00:35:21,070
varjabbli imsejħa t.

798
00:35:21,070 --> 00:35:25,700
Imma hija wkoll pointer, hekk jien ser
biex tiġbed bħala, fit-teorija, il-eżatt

799
00:35:25,700 --> 00:35:26,710
kaxxa istess daqs.

800
00:35:26,710 --> 00:35:28,160
U jien ser sejħa hija t.

801
00:35:28,160 --> 00:35:33,500
>> U issa jekk immorru lura għall-kodiċi mill-ġdid,
meta I jaħżnu s ġewwa ta 't,

802
00:35:33,500 --> 00:35:36,920
dak am I teknikament
tqegħid ġewwa ta 't?

803
00:35:36,920 --> 00:35:39,350
Well teknikament, dan
kien il-123 numru.

804
00:35:39,350 --> 00:35:42,270
Sabiex verament I għandu jkun miktub
l-123 numru hemmhekk.

805
00:35:42,270 --> 00:35:43,900
Imma ejja teħodha livell ogħla.

806
00:35:43,900 --> 00:35:48,090
t, jekk din hija biss pointer,
intuwittivament, huwa biss li.

807
00:35:48,090 --> 00:35:49,800
Li kollox thats qed
maħżuna hemmhekk.

808
00:35:49,800 --> 00:35:54,970
>> Allura issa fl-aħħar linji interessanti
tal-kodiċi, meta I attwalment tmur dwar

809
00:35:54,970 --> 00:36:00,680
jikkapitalizza-karattru żero
f't, dak li qed jiġri?

810
00:36:00,680 --> 00:36:06,310
Ukoll, t bracket żero issa tipponta
għal dak karattru, preżumibbilment?

811
00:36:06,310 --> 00:36:07,460
>> Huwa tipponta lejn h.

812
00:36:07,460 --> 00:36:08,870
Minħabba t bracket zero -

813
00:36:08,870 --> 00:36:12,490
recall, dan huwa sintassi qodma. t bracket
zero ifisser biss jekk t hija sekwenza, t

814
00:36:12,490 --> 00:36:15,590
bracket żero ifisser li jkollna l-zero
karattru li l-qawwa.

815
00:36:15,590 --> 00:36:18,650
Allura dak li verament ifisser
hu li tmur għal dan array -

816
00:36:18,650 --> 00:36:21,520
u iva, dan jista 'jkun 123,
dan jista 'jkun 124.

817
00:36:21,520 --> 00:36:22,790
Imma dan kollu relattiva, ftakar.

818
00:36:22,790 --> 00:36:25,640
Kull meta jitkellem dwar firxa, għandna
l-vantaġġ ta 'jitkellem dwar

819
00:36:25,640 --> 00:36:27,000
indiċijiet relattivi.

820
00:36:27,000 --> 00:36:31,120
>> U hekk issa nistgħu biss wieħed jassumi
li t bracket żero huwa h.

821
00:36:31,120 --> 00:36:35,090
Mela jekk jien sejħa 2 massimu fuq dan, dak li l-
verament tagħmel huwa kapitalizzazzjoni

822
00:36:35,090 --> 00:36:38,290
il-h zghar li uppercase H.
Iżda naturalment, dak li huwa s?

823
00:36:38,290 --> 00:36:41,010
Huwa tipponta lejn l-istess sekwenza darn.

824
00:36:41,010 --> 00:36:44,200
>> Allura dan huwa dak kollu li kien qed jiġri
f'dan kodiċi s'issa.

825
00:36:44,200 --> 00:36:45,960
Allura x'inhu l allura l-implikazzjoni?

826
00:36:45,960 --> 00:36:48,300
Kif nistgħu jiffissaw dawn iż-żewġ problemi?

827
00:36:48,300 --> 00:36:50,870
Kif nistgħu iqabblu kordi attwali?

828
00:36:50,870 --> 00:36:53,720
>> Ukoll intuwittivament, kif kieku
inti tmur dwar tqabbel żewġ

829
00:36:53,720 --> 00:36:55,090
kordi għall-ugwaljanza vera?

830
00:36:55,090 --> 00:36:58,920

831
00:36:58,920 --> 00:37:00,750
>> Xi jfisser jekk tnejn
kordi huma ugwali?

832
00:37:00,750 --> 00:37:04,330
Ovvjament mhux li indirizzi huma
ugwali fil-memorja, għaliex thats baxxa

833
00:37:04,330 --> 00:37:06,590
livell dettall implimentazzjoni.

834
00:37:06,590 --> 00:37:08,360
L-karattri huma l-istess.

835
00:37:08,360 --> 00:37:12,810
So let me tipproponi, u let me jintroduċu
fil-verżjoni waħda ta compare.c

836
00:37:12,810 --> 00:37:14,970
hawn, hekk iqabblu 1.c.

837
00:37:14,970 --> 00:37:19,590
>> Let me tipproponi li aħna xorta jiksbu
pointer imsejħa s, u maħżen fiha l-

838
00:37:19,590 --> 00:37:20,610
ritorn valur ta 'spag get.

839
00:37:20,610 --> 00:37:21,750
Ejja nagħmlu l-istess ħaġa ma 't.

840
00:37:21,750 --> 00:37:23,230
Allura l-ebda kodiċi hija differenti.

841
00:37:23,230 --> 00:37:25,420
Jien ser żid ftit
aktar iċċekkjar għall-iżbalji issa.

842
00:37:25,420 --> 00:37:29,390
Allura issa li aħna qed tip ta 'tqaxxir lura
dan saffi fil CS50 ta 'dak string

843
00:37:29,390 --> 00:37:33,520
fil-fatt hu, għandna bżonn li jkunu aktar anali
dwar l-iżgurar aħna ma jabbużawx

844
00:37:33,520 --> 00:37:35,330
Valuri invalidi bħal null.

845
00:37:35,330 --> 00:37:36,440
>> Hekk jien biss jmorru biex jiċċekkjaw.

846
00:37:36,440 --> 00:37:41,490
Jekk i ma null ugwali u t ma
null ugwali, li jfisser aħna qed OK.

847
00:37:41,490 --> 00:37:44,460
Get string ma screw up jkollna
waħda minn dawk il-kordi.

848
00:37:44,460 --> 00:37:51,270
U inti tista 'forsi raden issa, dak li
ma STR CMP preżumibbilment do?

849
00:37:51,270 --> 00:37:52,000
String jqabblu.

850
00:37:52,000 --> 00:37:55,470
>> Mela jekk inti stajt programm java qabel,
dan huwa bħall-metodu ugwali fil-

851
00:37:55,470 --> 00:37:56,490
klassi string.

852
00:37:56,490 --> 00:37:57,890
Iżda għal dawk fostkom li għadhom ma
programmati qabel,

853
00:37:57,890 --> 00:37:59,320
din hija biss funzjoni c.

854
00:37:59,320 --> 00:38:02,180
Dan jiġri li jaqgħu fil-
inkartament imsejjaħ string.h.

855
00:38:02,180 --> 00:38:03,830
Li fejn huwa ddikjarat.

856
00:38:03,830 --> 00:38:05,110
>> U string tqabbel -

857
00:38:05,110 --> 00:38:07,530
I attwalment tinsa l-użu tagħha,
iżda qatt f'moħħhom dik.

858
00:38:07,530 --> 00:38:10,470
Ifakkar li nistgħu nagħmlu
bniedem, ħawwad jqabblu.

859
00:38:10,470 --> 00:38:12,590
U dan se iġibu l-
Programmaturi Linux manwali.

860
00:38:12,590 --> 00:38:14,060
U huwa, franchement, ftit cryptic.

861
00:38:14,060 --> 00:38:15,270
Imma I jista 'jara hawnhekk li, yep.

862
00:38:15,270 --> 00:38:17,570
I għandhom jinkludu string.h.

863
00:38:17,570 --> 00:38:20,590
>> U jgħid hawn taħt deskrizzjoni, "il-
Qabbel funzjoni string jikkompara

864
00:38:20,590 --> 00:38:24,560
iż-żewġ kordi S1 ​​u S2. "U S1
u S2 huma apparentament it-tnejn

865
00:38:24,560 --> 00:38:26,120
argumenti għadda pulzieri

866
00:38:26,120 --> 00:38:28,650
I ma verament tiftakar dak
const hija, iżda issa avviż -

867
00:38:28,650 --> 00:38:31,480
u inti tista raw dan diġà meta
inti stajt tuża l-paġni bniedem jekk inti

868
00:38:31,480 --> 00:38:32,390
jkollhom dan kollu -

869
00:38:32,390 --> 00:38:36,220
li star char huwa biss sinonimu
ma string.

870
00:38:36,220 --> 00:38:40,440
>> Allura jikkompara iż-żewġ kordi, S1 u
S2, u dan jirritorna integer inqas

871
00:38:40,440 --> 00:38:44,930
minn jew ugwali għal jew akbar minn żero
jekk S1 jinstab, rispettivament, li jkun

872
00:38:44,930 --> 00:38:47,450
inqas minn, jew jaqblux, jew
ikun akbar minn S2.

873
00:38:47,450 --> 00:38:51,220
Li jinsab biss mod kumpless ħafna ta 'tgħid
li string jqabblu prospetti

874
00:38:51,220 --> 00:38:55,760
żero jekk żewġ kordi huma intuwittivament
identiċi, karattru għal

875
00:38:55,760 --> 00:38:57,120
karattru għall-karattru.

876
00:38:57,120 --> 00:38:59,970
>> Dan jirritorna numru negattiv jekk
i, alfabetikament, suppost

877
00:38:59,970 --> 00:39:01,010
biex jiġi qabel t.

878
00:39:01,010 --> 00:39:05,300
Jew prospetti numru pożittiv jekk
i suppost li jiġu wara t

879
00:39:05,300 --> 00:39:06,170
alfabetikament.

880
00:39:06,170 --> 00:39:08,360
Allura ma din il-funzjoni sempliċi, jista
inti, per eżempju, sort a

881
00:39:08,360 --> 00:39:09,770
mazz sħiħ ta 'kliem?

882
00:39:09,770 --> 00:39:13,984
>> Allura f'dan il-verżjoni l-ġdida, jien ser
jimxi 'l quddiem u jagħmlu compare1.

883
00:39:13,984 --> 00:39:15,750
Dot slash jqabblu wieħed.

884
00:39:15,750 --> 00:39:18,030
I ser tip bonjour kollha żgħira.

885
00:39:18,030 --> 00:39:20,300
Jien ser tip fil bonjour
fil kollha zghar mill-ġdid.

886
00:39:20,300 --> 00:39:23,340
U Thankfully issa jirrealizza
I ttajpjati l-istess ħaġa.

887
00:39:23,340 --> 00:39:27,520
>> Sadanittant, jekk I tip bonjour t'isfel
każ u HELLO fil-każ ta 'fuq u

888
00:39:27,520 --> 00:39:29,710
jqabbluhom, I ittajpjat
affarijiet differenti.

889
00:39:29,710 --> 00:39:32,530
Minħabba li mhux biss huma l-indirizzi
differenti, iżda aħna qed jitqabblu

890
00:39:32,530 --> 00:39:35,350
karattri differenti u għal darb'oħra.

891
00:39:35,350 --> 00:39:37,320
>> Well ejja go u tiffissa wieħed
problema l-oħra issa.

892
00:39:37,320 --> 00:39:41,590
Let me jiftħu verżjoni waħda ta '
kopja, li issa jindirizza

893
00:39:41,590 --> 00:39:42,900
din il-kwistjoni kif ġej.

894
00:39:42,900 --> 00:39:45,650
U dan wieħed għaddej biex tfittex
ftit aktar kumplessa.

895
00:39:45,650 --> 00:39:49,320
Imma jekk inti taħseb dwar liema problema aħna
bżonn biex issolvi, wieħed jittama li dan se jkun

896
00:39:49,320 --> 00:39:51,870
ċar fil-ftit mument issa.

897
00:39:51,870 --> 00:39:57,280
>> Allura dan l-ewwel linja, char-bidu t, fil
F'termini layman tista 'tipproponi xi ħadd

898
00:39:57,280 --> 00:39:59,450
dak il-linja hawnhekk tfisser?

899
00:39:59,450 --> 00:40:01,050
Star t Char, dak hu li tagħmel?

900
00:40:01,050 --> 00:40:06,660

901
00:40:06,660 --> 00:40:07,210
>> Tajba.

902
00:40:07,210 --> 00:40:09,500
Oħloq pointer għal xi
post fil-memorja.

903
00:40:09,500 --> 00:40:10,930
U let me tirfina ftit.

904
00:40:10,930 --> 00:40:17,180
Tiddikjara varjabbli li ser taħżen l-
indirizz ta 'xi char fil-memorja, biss

905
00:40:17,180 --> 00:40:18,480
li jkun ftit aktar xierqa.

906
00:40:18,480 --> 00:40:21,210
>> OK, hekk issa fuq il-lemin, stajt
qatt ma tidher waħda minn dawn il-funzjonijiet

907
00:40:21,210 --> 00:40:22,660
qabel, malloc.

908
00:40:22,660 --> 00:40:26,980
Imma dak li jista 'jfisser?

909
00:40:26,980 --> 00:40:28,050
Allokazzjoni ta 'memorja.

910
00:40:28,050 --> 00:40:29,410
Allokazzjoni memorja.

911
00:40:29,410 --> 00:40:33,050
>> Għalhekk jirriżulta li, sa issa, aħna
ma verament kellu mod qawwi ta '

912
00:40:33,050 --> 00:40:36,210
titlob lill-sistema operattiva,
tagħti me xi memorja.

913
00:40:36,210 --> 00:40:39,980
Pjuttost, issa għandna funzjoni msejħa
malloc li ma eżattament dan.

914
00:40:39,980 --> 00:40:42,960
Anke jekk dan huwa daqsxejn ta '
distrazzjoni dritt issa, avviż li

915
00:40:42,960 --> 00:40:46,200
bejn iż-żewġ parentesi hemm
biss se jkun hemm numru.

916
00:40:46,200 --> 00:40:48,510
Fejn stajt ittajpjat fil-kwistjoni
marki tista 'tkun numru.

917
00:40:48,510 --> 00:40:51,020
>> U dak in-numru jfisser,
tagħti me 10 bytes.

918
00:40:51,020 --> 00:40:52,320
Agħti me 20 bytes.

919
00:40:52,320 --> 00:40:53,820
Agħti me 100 bytes.

920
00:40:53,820 --> 00:40:56,500
U malloc se tagħmel ħilitha biex
titlob lill-sistema operattiva -

921
00:40:56,500 --> 00:40:57,630
Linux, f'dan il-każ -

922
00:40:57,630 --> 00:40:59,630
ħej, huma 100 bytes tagħhom
ta 'RAM disponibbli?

923
00:40:59,630 --> 00:41:04,320
Jekk iva, jirritorna dawk bytes lili minn
jirritorna l-indirizz ta 'liema ta'

924
00:41:04,320 --> 00:41:06,610
dawk bytes, forsi?

925
00:41:06,610 --> 00:41:07,610
L-ewwel waħda ħafna.

926
00:41:07,610 --> 00:41:10,460
>> Allura hawnhekk wisq - u dan huwa predominanti
fis-C, kwalunkwe ħin int

927
00:41:10,460 --> 00:41:11,680
jittrattaw indirizzi?

928
00:41:11,680 --> 00:41:15,830
Inti kważi dejjem jittrattaw mal-
ewwel indirizz bħal dak, l-ebda kwistjoni kemm hu kbir

929
00:41:15,830 --> 00:41:19,490
blokki ta 'memorja inti qed
mogħtija lura, biex ngħidu hekk.

930
00:41:19,490 --> 00:41:20,880
>> Mela ejja adsa fil hawn.

931
00:41:20,880 --> 00:41:23,940
I am tipprova talloka kif
ħafna bytes, eżattament?

932
00:41:23,940 --> 00:41:24,080
Well.

933
00:41:24,080 --> 00:41:26,090
Tul sensiela ta 's - ejja
jagħmlu eżempju konkret.

934
00:41:26,090 --> 00:41:30,700
Jekk i huwa hello, H-E-L-L-O, x'inhu l-
tul sensiela ta 'i, ovvjament?

935
00:41:30,700 --> 00:41:32,010
Allura huwa ħamsa.

936
00:41:32,010 --> 00:41:34,590
Imma jien tagħmel plus 1 fuq li, għaliex?

937
00:41:34,590 --> 00:41:37,700
Għaliex nixtieq sitt bytes
minflok ħamsa?

938
00:41:37,700 --> 00:41:38,790
Il-karattru null.

939
00:41:38,790 --> 00:41:41,210
>> Ma rridx li jħallu off din
karattru null speċjali.

940
00:41:41,210 --> 00:41:45,160
Għaliex jekk I jagħmel kopja ta 'Hello u
biss tagħmel H-E-L-L-O, imma jien ma jitqiegħdu

941
00:41:45,160 --> 00:41:50,160
dan il-karattru speċjali, il-kompjuter
jista 'ma jkollhomx, b'kumbinazzjoni, backslash

942
00:41:50,160 --> 00:41:51,730
żero hemm għalija.

943
00:41:51,730 --> 00:41:55,570
U hekk jekk jien jippruvaw biex insemmu l-
tul tal-kopja, I jista 'jaħseb li

944
00:41:55,570 --> 00:41:59,360
huwa 20 karattri fit-tul, jew miljun
karattri twil jekk I biss qatt jiġri

945
00:41:59,360 --> 00:42:01,050
hit żero backslash.

946
00:42:01,050 --> 00:42:05,780
>> Allura għandna bżonn sitt bytes li jaħżen
H-E-L-L-O, backslash żero.

947
00:42:05,780 --> 00:42:07,870
U allura dan huwa biss
li jkun anali super.

948
00:42:07,870 --> 00:42:10,700
Ejja ngħidu li ninsa dak
id-daqs ta 'char huwa.

949
00:42:10,700 --> 00:42:12,020
Aħna nżommu qal huwa wieħed byte.

950
00:42:12,020 --> 00:42:12,860
U normalment huwa.

951
00:42:12,860 --> 00:42:15,425
Fit-teorija, jista 'jkun xi ħaġa
differenti, fuq Mac differenti jew

952
00:42:15,425 --> 00:42:16,250
PC differenti.

953
00:42:16,250 --> 00:42:19,650
>> Għalhekk jirriżulta li hemm dan l-operatur
imsejħa sizeof li jekk inti tgħaddi din l-

954
00:42:19,650 --> 00:42:22,680
isem ta 'tip ta' dejta - bħal
char, jew int, jew float -

955
00:42:22,680 --> 00:42:26,930
se jgħidlek, dinamiku, kemm
bytes a char jieħu fuq dan

956
00:42:26,930 --> 00:42:28,090
partikolari kompjuter.

957
00:42:28,090 --> 00:42:31,360
>> Allura dan huwa effettivament biss
simili qal ħinijiet 1 jew

958
00:42:31,360 --> 00:42:32,440
żminijiet xejn.

959
00:42:32,440 --> 00:42:36,340
Imma jien tagħmel dan biss sabiex ikunu anali super,
li biss fil-każ li char differenti

960
00:42:36,340 --> 00:42:40,610
fuq il-kompjuter tiegħek kontra mini, b'dan il-mod
l-matematika huwa dejjem se check out.

961
00:42:40,610 --> 00:42:43,720
>> Fl-aħħar nett, stabbiliti hawn I jiċċekkja għal null,
li huwa dejjem prattika tajba - għal darb'oħra,

962
00:42:43,720 --> 00:42:44,920
kwalunkwe ħin aħna qed jittrattaw pointers.

963
00:42:44,920 --> 00:42:47,520
Jekk malloc kienx kapaċi jagħtu
me sitt byes - li huwa

964
00:42:47,520 --> 00:42:49,210
improbabbli, iżda biss fil-każ -

965
00:42:49,210 --> 00:42:50,730
ritorn wieħed immedjatament.

966
00:42:50,730 --> 00:42:53,290
U issa, imorru quddiem u kopja
l-sekwenza kif ġej.

967
00:42:53,290 --> 00:42:57,240
U dan huwa sintassi familjari,
għalkemm fi rwol differenti.

968
00:42:57,240 --> 00:43:01,210
>> Jien ser jimxi 'l quddiem u jiksbu l-sekwenza
tul ta 'i u jaħżen fil n.

969
00:43:01,210 --> 00:43:06,620
Jien imbagħad ser jtenni mill-i huwa ugwali
żero sa u inkluż n,

970
00:43:06,620 --> 00:43:08,410
ikbar minn jew ugwali għal.

971
00:43:08,410 --> 00:43:13,540
Allura li fuq kull iterazzjoni, nressaq il-
karattru ith ta 'i fil-ith

972
00:43:13,540 --> 00:43:15,380
karattru ta 't.

973
00:43:15,380 --> 00:43:18,190
>> Allura x'inhu verament għaddej taħt
il-barnuża hawn?

974
00:43:18,190 --> 00:43:22,140
Ukoll jekk dan, per eżempju, huwa s -

975
00:43:22,140 --> 00:43:26,400
u jien ittajpjat fil-kelma H-E-L-L-O
u hemm żero backslash.

976
00:43:26,400 --> 00:43:29,020
U għal darb'oħra, dan huwa s tipponta hawn.

977
00:43:29,020 --> 00:43:30,830
U hawn huwa issa t.

978
00:43:30,830 --> 00:43:34,860
>> U dan hija li tipponta issa biex
kopja ta 'memorja, id-dritt?

979
00:43:34,860 --> 00:43:37,340
Malloc tani kollu
blokki ta 'memorja.

980
00:43:37,340 --> 00:43:41,440
I do not know inizjalment x'hemm
fi kwalunkwe ta 'dawn il-lokalitajiet.

981
00:43:41,440 --> 00:43:44,340
Hekk jien ser taħseb dawn bħala
mazz sħiħ ta 'trade marks in kwistjoni.

982
00:43:44,340 --> 00:43:50,190
>> Iżda hekk kif nibda looping minn żero
fuq up permezz-tul ta 'i, t

983
00:43:50,190 --> 00:43:52,790
bracket żero u t bracket 1 -

984
00:43:52,790 --> 00:43:55,080
u jien ser tpoġġi dan issa
fuq l-overhead -

985
00:43:55,080 --> 00:44:04,190
t bracket żero u s bracket żero jfisser
li jien ser tkun ikkupjar

986
00:44:04,190 --> 00:44:09,875
iteratively h fil hawn, E-L-L-O.
Plus, minħabba I ma l-plus

987
00:44:09,875 --> 00:44:12,370
1, backslash żero.

988
00:44:12,370 --> 00:44:19,060
>> Allura issa fil-każ ta iqabblu 1.c,
fl-aħħar, jekk I jistampa l-

989
00:44:19,060 --> 00:44:24,760
kapitalizzazzjoni ta 't, għandna
tara li s ma jinbidilx.

990
00:44:24,760 --> 00:44:26,090
Let me imorru quddiem u tagħmel dan issa.

991
00:44:26,090 --> 00:44:28,630
Sabiex tagħmel copy1.

992
00:44:28,630 --> 00:44:30,860
Dot slash copy1.

993
00:44:30,860 --> 00:44:33,670
Jien ser tip fil hello, Ikteb.

994
00:44:33,670 --> 00:44:37,430
U issa avviż, biss il-kopja
ġie kapitalizzat.

995
00:44:37,430 --> 00:44:40,890
Minħabba I verament għandhom żewġ
biċċiet ta 'memorja.

996
00:44:40,890 --> 00:44:44,390
>> Sfortunatament, inti tista 'tagħmel xi pretty
ħżiena u pretty perikolużi affarijiet hawn.

997
00:44:44,390 --> 00:44:49,290
Let me pull up eżempju hawn issa,
li jagħtina eżempju ta 'ftit

998
00:44:49,290 --> 00:44:51,540
linji differenti.

999
00:44:51,540 --> 00:44:56,040
Hekk biss intuwittivament hawn, l-ewwel linja
tal-kodiċi, x int stilla, hija tiddikjara

1000
00:44:56,040 --> 00:44:57,340
varjabbli msejħa x.

1001
00:44:57,340 --> 00:44:58,810
U x'inhu l-tip ta 'data
ta 'dak il-varjabbli?

1002
00:44:58,810 --> 00:45:01,820

1003
00:45:01,820 --> 00:45:04,290
X'hemm-tip ta 'data ta' dak il-varjabbli?

1004
00:45:04,290 --> 00:45:06,980
Dan ma kienx il cliffhanger.

1005
00:45:06,980 --> 00:45:08,350
>> It-tip tad-data hija stilla int.

1006
00:45:08,350 --> 00:45:12,600
Allura dak ma jfisser? x se
jaħżnu l-indirizz ta 'int.

1007
00:45:12,600 --> 00:45:13,520
Sempliċi bħal dik.

1008
00:45:13,520 --> 00:45:16,220
Y se jaħżnu l-
indirizz ta 'int.

1009
00:45:16,220 --> 00:45:18,390
X'inhu l-tielet linja
tal-kodiċi tagħmel hemm?

1010
00:45:18,390 --> 00:45:21,850
Huwa allokazzjoni kemm
bytes, x'aktarx?

1011
00:45:21,850 --> 00:45:22,350
Erbgħa.

1012
00:45:22,350 --> 00:45:25,460
Minħabba d-daqs ta 'int huwa
ġeneralment erba, malloc ta 'erba jagħti

1013
00:45:25,460 --> 00:45:29,950
me back-indirizz ta 'blokki ta'
memorja, l-ewwel ta 'bytes li huwa

1014
00:45:29,950 --> 00:45:32,110
maħżuna issa x.

1015
00:45:32,110 --> 00:45:34,410
>> Issa aħna qed jiċċaqilqu ftit malajr.

1016
00:45:34,410 --> 00:45:35,760
Star x ifisser liema?

1017
00:45:35,760 --> 00:45:38,480

1018
00:45:38,480 --> 00:45:42,590
Dan ifisser tmur f'dak indirizz
u mqiegħda dak in-numru hemmhekk?

1019
00:45:42,590 --> 00:45:43,870
Poġġi n-numru 42 hemmhekk.

1020
00:45:43,870 --> 00:45:47,590
Star y ifisser mur x'hemm fil y
u n-numru 13 hemmhekk.

1021
00:45:47,590 --> 00:45:48,600
>> Imma stenna minuta.

1022
00:45:48,600 --> 00:45:51,640
X'inhu y fil-mument?

1023
00:45:51,640 --> 00:45:54,950
X'inhu l-indirizz huwa y ħażna?

1024
00:45:54,950 --> 00:45:55,770
Ma nafux, right?

1025
00:45:55,770 --> 00:45:59,230
Aħna qatt darba tuża l-assenjazzjoni
operatur li jinvolvu y.

1026
00:45:59,230 --> 00:46:03,370
Allura y kif dikjarata fit-tieni linja ta '
kodiċi huwa biss ftit valur żibel, big

1027
00:46:03,370 --> 00:46:04,760
kwistjoni mark biex ngħidu hekk.

1028
00:46:04,760 --> 00:46:07,230
Jista 'jiġi tipponta bl-addoċċ
li xejn fil-memorja, li

1029
00:46:07,230 --> 00:46:08,340
huwa ġeneralment ħażin.

1030
00:46:08,340 --> 00:46:13,540
>> Allura hekk kif aħna hit dik il-linja hemm,
star y ugwali 13, xi ħaġa ħażina,

1031
00:46:13,540 --> 00:46:17,220
xi ħaġa ħażina ħafna huwa dwar
li jiġri Binky.

1032
00:46:17,220 --> 00:46:25,810
Mela ejja ara dak li għaddej biex jispiċċaw
jiġri Binky hawn f'dan il minuta

1033
00:46:25,810 --> 00:46:26,200
jew sabiex tfittex.

1034
00:46:26,200 --> 00:46:26,490
>> [Daqq video]

1035
00:46:26,490 --> 00:46:26,745
>> -Ħej, Binky.

1036
00:46:26,745 --> 00:46:27,000
Wake up.

1037
00:46:27,000 --> 00:46:29,296
Wasal iż-żmien għall-gost pointer.

1038
00:46:29,296 --> 00:46:30,680
>> -X'hemm li?

1039
00:46:30,680 --> 00:46:31,980
Tgħallem dwar pointers?

1040
00:46:31,980 --> 00:46:34,010
Oh, goodie.

1041
00:46:34,010 --> 00:46:37,220
>> Well, biex tibda, I raden aħna qed
ser jeħtieġu pointers koppja.

1042
00:46:37,220 --> 00:46:37,930
>> -OK.

1043
00:46:37,930 --> 00:46:41,650
Dan il-kodiċi jalloka żewġ pointers
li jista 'jiġbed l interi.

1044
00:46:41,650 --> 00:46:43,760
>> OK, ukoll, I tara l-żewġ pointers.

1045
00:46:43,760 --> 00:46:45,850
Iżda dawn ma jidhirx li
tipponta lejn xejn.

1046
00:46:45,850 --> 00:46:46,490
>> -Dak id-dritt.

1047
00:46:46,490 --> 00:46:48,630
Inizjalment, pointers ma
punt għal xejn.

1048
00:46:48,630 --> 00:46:51,700
L-affarijiet li jindikaw huma msejħa
pointees, u li jistabbilixxu lilhom up huwa

1049
00:46:51,700 --> 00:46:52,850
pass separat.

1050
00:46:52,850 --> 00:46:53,740
>> Oh, id-dritt, id-dritt.

1051
00:46:53,740 --> 00:46:54,500
Jien kont naf li.

1052
00:46:54,500 --> 00:46:56,270
Il pointees huma separati.

1053
00:46:56,270 --> 00:46:58,553
Allura kif taħseb li jallokaw pointee?

1054
00:46:58,553 --> 00:46:59,480
>> -OK.

1055
00:46:59,480 --> 00:47:03,707
Ukoll, dan il-kodiċi jalloka interi ġodda
pointee, u din il-parti tistabbilixxi x

1056
00:47:03,707 --> 00:47:05,520
għall-punt lilha.

1057
00:47:05,520 --> 00:47:06,760
>> -Ħej, li jistenna aħjar.

1058
00:47:06,760 --> 00:47:08,520
Sabiex tagħmel dan jagħmlu xi ħaġa.

1059
00:47:08,520 --> 00:47:09,530
>> -OK.

1060
00:47:09,530 --> 00:47:14,110
I ser dereference l pointer x biex jaħżnu
in-numru 42 fis pointee tagħha.

1061
00:47:14,110 --> 00:47:17,660
Għal dan trick, I bzonn magic tiegħi
wand ta dereferencing.

1062
00:47:17,660 --> 00:47:20,695
>> Your-bastun maġiku ta dereferencing?

1063
00:47:20,695 --> 00:47:22,632
Uh, li l-kbir.

1064
00:47:22,632 --> 00:47:24,620
>> -Dan huwa dak l-kodiċi Dehra.

1065
00:47:24,620 --> 00:47:27,526
I ser biss twaqqaf in-numru, u -

1066
00:47:27,526 --> 00:47:28,250
>> -Ħej, ħarsa.

1067
00:47:28,250 --> 00:47:29,680
Hemm tmur.

1068
00:47:29,680 --> 00:47:34,520
Allura tagħmel dereference fuq x ġej
il-vleġġa għall-aċċess pointee tagħha.

1069
00:47:34,520 --> 00:47:36,690
F'dan il-każ, li jaħżen 42 fil hemmhekk.

1070
00:47:36,690 --> 00:47:40,890
Ħej, ipprova uża dan biex jaħżnu l-għadd
13 permezz tal-pointer oħra, y.

1071
00:47:40,890 --> 00:47:42,125
>> -OK.

1072
00:47:42,125 --> 00:47:46,810
I ser biss jmorru fuq hawn biex yu
nikseb in-numru 13 jitwaqqaf.

1073
00:47:46,810 --> 00:47:50,890
U mbagħad ħu l-bastun tal-
dereferencing u biss -

1074
00:47:50,890 --> 00:47:52,430
Whoa!

1075
00:47:52,430 --> 00:47:53,030
>> Oh, ħej.

1076
00:47:53,030 --> 00:47:54,610
Li ma ħadmux.

1077
00:47:54,610 --> 00:47:58,200
Say, Binky, ma naħsibx l-
dereferencing y hija idea tajba,

1078
00:47:58,200 --> 00:48:01,370
minħabba twaqqif tal-pointee
huwa pass separat.

1079
00:48:01,370 --> 00:48:03,460
U jien ma think we qatt ma kien.

1080
00:48:03,460 --> 00:48:03,810
>> Hmm-.

1081
00:48:03,810 --> 00:48:05,160
Punt tajjeb.

1082
00:48:05,160 --> 00:48:07,410
>> Yeah-, aħna allokat il-y pointer.

1083
00:48:07,410 --> 00:48:10,045
Imma aħna qatt tistabbilixxi li
jippuntaw lejn pointee.

1084
00:48:10,045 --> 00:48:10,490
>> Hmm-.

1085
00:48:10,490 --> 00:48:12,170
Attent ħafna.

1086
00:48:12,170 --> 00:48:13,790
>> -Ħej, qed tfittex
tajba hemmhekk, Binky.

1087
00:48:13,790 --> 00:48:16,920
Inti tista 'tiffissa lilha hekk li l-punti y
għall-istess pointee bħala x?

1088
00:48:16,920 --> 00:48:17,810
>> Sure-.

1089
00:48:17,810 --> 00:48:20,300
I ser tuża bastun maġiku tiegħi ta '
assenjazzjoni pointer.

1090
00:48:20,300 --> 00:48:22,240
>> -Hija li għaddej biex tkun
problema bħal qabel?

1091
00:48:22,240 --> 00:48:22,665
>> Nru-.

1092
00:48:22,665 --> 00:48:24,300
Dan ma tmissx il-pointees.

1093
00:48:24,300 --> 00:48:27,880
Hija biss bidliet wieħed pointer għall-punt
għall-istess ħaġa bħat ieħor.

1094
00:48:27,880 --> 00:48:28,970
>> Oh, nara.

1095
00:48:28,970 --> 00:48:31,730
Issa punti y għall-istess post bħall x.

1096
00:48:31,730 --> 00:48:32,450
Allura stenna.

1097
00:48:32,450 --> 00:48:33,490
Issa y hija ffissata.

1098
00:48:33,490 --> 00:48:34,630
Hija għandha pointee.

1099
00:48:34,630 --> 00:48:36,520
Allura inti tista 'tipprova l-wand
ta dereferencing darb'oħra

1100
00:48:36,520 --> 00:48:39,200
li tibgħat il-13 fuq.

1101
00:48:39,200 --> 00:48:39,840
>> -OK.

1102
00:48:39,840 --> 00:48:41,570
Hawnhekk tmur.

1103
00:48:41,570 --> 00:48:42,870
>> -Ħej, tħares lejn dak.

1104
00:48:42,870 --> 00:48:44,320
Issa dereferencing xogħlijiet fuq y.

1105
00:48:44,320 --> 00:48:47,020
U minħabba l-pointers huma qsim
li pointee waħda, huma

1106
00:48:47,020 --> 00:48:48,585
kemm tara l-13.

1107
00:48:48,585 --> 00:48:49,040
>> Yeah-.

1108
00:48:49,040 --> 00:48:49,670
Qsim.

1109
00:48:49,670 --> 00:48:50,380
Tkun xi tkun.

1110
00:48:50,380 --> 00:48:52,290
Allura aħna se postijiet swiċċ issa?

1111
00:48:52,290 --> 00:48:52,970
>> Oh, tħares.

1112
00:48:52,970 --> 00:48:54,150
Aħna qed barra ta 'żmien.

1113
00:48:54,150 --> 00:48:55,200
>> Iżda--

1114
00:48:55,200 --> 00:48:57,060
>> Just remember-it-tliet
regoli pointer.

1115
00:48:57,060 --> 00:49:00,100
Numru wieħed, l-istruttura bażika
huwa li inti għandek pointer.

1116
00:49:00,100 --> 00:49:02,170
U hija tirreferi fuq għal pointee.

1117
00:49:02,170 --> 00:49:04,160
Iżda l-pointer u pointee
huma separati.

1118
00:49:04,160 --> 00:49:06,460
U l-iżball komuni huwa li
twaqqaf pointer, iżda li

1119
00:49:06,460 --> 00:49:08,540
ninsewx li tingħata pointee.

1120
00:49:08,540 --> 00:49:12,460
>> Numru tnejn, dereferencing pointer jibda
fil-pointer u jsegwi tagħha

1121
00:49:12,460 --> 00:49:14,570
vleġġa fuq l-aċċess pointee tagħha.

1122
00:49:14,570 --> 00:49:18,640
Kif nafu lkoll, dan jaħdem biss jekk ikun hemm
huwa pointee, li gets lura għall

1123
00:49:18,640 --> 00:49:19,790
Regola numru wieħed.

1124
00:49:19,790 --> 00:49:23,670
>> Numru tlieta, assenjazzjoni pointer jieħu
wieħed pointer u bidliet li jindikaw

1125
00:49:23,670 --> 00:49:25,850
l-istess pointee bħala pointer ieħor.

1126
00:49:25,850 --> 00:49:27,840
Hekk wara l-assenjazzjoni,
iż-żewġ pointers se

1127
00:49:27,840 --> 00:49:29,430
punt li l-istess pointee.

1128
00:49:29,430 --> 00:49:31,600
Kultant li sejjaħ qsim.

1129
00:49:31,600 --> 00:49:33,430
U li kollox hemm għaliha, verament.

1130
00:49:33,430 --> 00:49:33,840
Bye bye issa.

1131
00:49:33,840 --> 00:49:34,300
>> [Daqq video END]

1132
00:49:34,300 --> 00:49:36,940
>> DAVID Malan: Allura aktar fuq pointers,
aktar fuq ġimgħa d-dieħla Binky.

1133
00:49:36,940 --> 00:49:38,190
Aħna ser tara inti nhar it-Tnejn.

1134
00:49:38,190 --> 00:49:42,187