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00:00:10,550 --> 00:00:14,050
>> DAVID J. Malan: Dan huwa CS50 u
dan huwa l-bidu ta 'erba' ġimgħat.

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00:00:14,050 --> 00:00:18,630
U, boy, huwa Volkswagen fil
trouble kollha minħabba software.

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00:00:18,630 --> 00:00:20,264
Let us tagħti ħarsa.

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00:00:20,264 --> 00:00:20,930
[Daqq video]

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00:00:20,930 --> 00:00:25,560
-Cars, Il-karattri smartest
fil-films Fast u Furious.

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00:00:25,560 --> 00:00:29,100
Din il-ġimgħa automaker Ġermaniż
Volkswagen sabet ruħha

8
00:00:29,100 --> 00:00:32,490
fin-nofs ta 'skandlu ta
proporzjonijiet potenzjalment kriminali.

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00:00:32,490 --> 00:00:36,060
>> -Volkswagen Huwa bracing għal biljuni
fil-multi, ħlasijiet kriminali possibbli

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00:00:36,060 --> 00:00:38,560
għall-uffiċjali eżekuttivi tagħha, kif
il-kumpanija apologizes

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għall armar 11 miljun karozza li
jgħinuha taħbit testijiet ta 'emissjoni.

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>> Mudelli tad-diżil -Certain kienu
mfassla ma 'softwer sofistikati

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dik l-informazzjoni użata inkluż il-
pożizzjoni tal-istering u l-vettura

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veloċità li jiddetermina l-karozza kienet
għaddejjin minn ittestjar tal-emissjonijiet.

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Taħt din iċ-ċirkustanza, il-magna
inaqqas l-emissjonijiet tossiċi.

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Iżda l-karozza kienet armati li bypass
li meta kien qed tiġi misjuqa.

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Emissjonijiet żdiedu 10 sa 40
ħinijiet ogħla mil-livelli EPA aċċettabbli.

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>> [END Daqq]

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>> DAVID J. Malan: Mela ejja
tagħti ħarsa lejn din

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u jara eżattament kif dan
jista 'jiġi implimentat

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u kif dan jista 'jaffettwa
karozzi tant bħal dan.

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Allura fl-idejn tiegħi hawn huma l-istampa
rilaxx li nħarġet mill-EPA--

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l Ambjentali
Aġenzija għall-Protezzjoni li

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huwa l-aġenzija regolatorja Istati Uniti li
mankijiet tħassib ambjentali,

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u mbagħad l-attwali
Avviż Legali li kien

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jibagħtu lill Volkswagen ftit jiem ilu.

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>> Allura l-EPA jikteb, u tiżvela issa
pubblikament, softwer sofistikati

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algoritmu fuq ċerti
Vetturi Volkswagen jiskopri

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00:01:29,390 --> 00:01:32,630
meta l-karozza għaddejja
ittestjar tal-emissjonijiet uffiċjali

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u dawriet emissjonijiet sħiħa
kontrolli fuq biss waqt it-test.

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L-effettività ta '
dawn it-tniġġis vetturi

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mezzi ta 'kontroll emissjonijiet huwa ferm
mnaqqas matul kull sewqan normali

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sitwazzjonijiet.

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Dan jirriżulta fil-karozzi li jilħqu l-
istandards fil-laboratorju jew l-ittestjar

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istazzjon, iżda matul l-operazzjoni normali
jarmu oxides-- nitroġenu jew NOx--

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fuq sa 40 darba l-istandard.

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Is-software prodott mill Volkswagen
huwa mezz unquote kwotazzjoni, telfa,

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kif definit mill-Nadif
Air Act fl-Istati Uniti.

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>> Jitilgħu jgħid li
l-EPA u l-aġenzija oħra

40
00:02:03,410 --> 00:02:07,020
mikxufa l-mekkaniżmu ta 'telf
softwer wara analiżi indipendenti

41
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mir-riċerkaturi fl West
Virginia Università.

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Tniġġis NOx tikkontribwixxi għall
dijossidu tan-nitroġenu, l-ożonu troposferiku,

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u partiċelli fini.

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Espożizzjoni għal dawn
pollutanti ġiet marbuta

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ma 'firxa wiesgħa ta'
effetti serji ta 'saħħa,

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fosthom aktar ażżma
attakki u respiratorju ieħor

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00:02:23,637 --> 00:02:26,470
mard li jistgħu jkunu serji biżżejjed
li tibgħat lin-nies l-isptar.

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Espożizzjoni għall-ożonu u
materja partikulata għandha wkoll

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kien assoċjat ma 'prematur
mewt minħabba respiratorja relatati

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00:02:31,960 --> 00:02:35,690
jew kardjovaskulari effetti relatati.

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It-tfal, l-anzjani, persuni
mard respiratorju preexisting

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huma partikolarment f'riskju għall
effetti tas-saħħa ta 'dawn l-inkwinanti.

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>> Huwa biżżejjed li jingħad, huwa pjuttost serji.

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U ejja jmorru biex taqra
wieħed biss silta aktar

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u mbagħad aħna ser tagħti ħarsa lejn
l-implikazzjonijiet sottostanti

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ta 'dan fil-kuntest ta' karozza.

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Speċifikament, Volkswagen
immanifatturata u installata

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softwer fl-hekk imsejħa
kontroll elettroniku

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module-- jew ECM-- ta
dawn il-vetturi li nħassu

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meta l-vettura kienet qed tiġi ttestjata għall
konformità ma 'standards ta' emissjoni EPA.

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Ibbażat fuq inputs varji inkluż il-
pożizzjoni tal-isteering wheel, tal-vettura

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veloċità, it-tul tal-magna tal
operazzjoni, u l-pressjoni barometrika,

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dawn l-inputs preċiżament
tracked-parametri

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tal-proċedura tat-test federali użata għall
ittestjar ta 'emissjoni għal ċertifikazzjoni EPA

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skopijiet.

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>> Matul l-ittestjar ta 'emissjoni EPA,
is-softwer vetturi ECM

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dam software li pproduċiet
riżultati emissjonijiet konformi.

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F'kull żmien ieħor, l
softwer ECM vettura

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dam triq separata
kalibrazzjoni li naqqset

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l-effettività tal-
sistema ġenerali ta 'kontroll ta' emissjoni,

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speċifikament l katalitiku selettiv
tnaqqis tal-NOx Lean trap--

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li aħna ser tara dwar fil-mument.

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Bħala riżultat, l-emissjonijiet ta 'NOx
miżjuda b'fattur ta '10 sa 40 darba

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fuq mil-livelli konformi EPA
skond it-tip ta 'ċiklu drive.

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>> Allura dak li dan verament ifisser, u l
kodiċi tas-sors għall-software running

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DWAR L-Volkswagen ma jkunx
ġewx żvelati b'mod pubbliku,

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hija li, effettivament, dan
ekwivalenti hemm x'imkien ġewwa

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tal-kodiċi Volkswagen.

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Jekk inti qed jiġu ttestjati, u jekk il-karozza
jiskopri ċerti fatturi ambjentali

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bħall-isteering wheel
pożizzjoni jew il-moviment

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jew in-nuqqas tiegħu tal-karozza jew
kwalunkwe numru ta 'fatturi oħra

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li bħalissa qed hypothesized
li jkun parti minn din il-formula,

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huma sempliċiment dawwar fuq
tikkontrolla l-emissjonijiet sħiħa.

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Fi kliem ieħor, dawn jibdew
li jarmu inqas tal-pollutanti.

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>> Else, f'kull sitwazzjoni oħra
meta huwa ma jinstabux bħala

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fil-laboratorju, huma biss ma.

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U għalhekk inti tista 'tissimplifika dan in aktar
pseudocode konkreta ma 'xi ħaġa

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bħal dan.

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Jekk ir-roti qed iduru iżda l-
isteering wheel hija le, suġġestivi

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li l-karozza hija fuq xi
tip ta 'ċilindru li jdur

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iżda f'xi tip ta '
maħżen qed jiġi ttestjat,

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imbagħad jaġixxu bħala l-
EPA tixtieq inti.

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Inkella ma.

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Mela ejja tagħti ħarsa
fi video qasir li

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jagħti ħarsa lejn dak li l-implikazzjonijiet
huma ta 'dan fil-fatt mekkaniku.

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>> [Daqq video]

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>> -Last Ġimgħa l-EPA ħabbret li xi
Karozzi Volkswagen Audi magħmula bejn l-2009

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u din is-sena kienu qed jużaw
hekk imsejħa strumenti ta 'riduzzjoni

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li tikseb madwar liġijiet emissjonijiet
maħsuba biex iżommu l-arja nadifa.

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Imma xi jfisser eżattament?

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>> Ukoll, karozzi moderni għexieren
ta 'kompjuters ġo fihom.

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U xi wħud minn dawn il-kompjuters
jgħin jikkoordina l-funzjonijiet

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tal-magna għal aħjar
prestazzjoni filwaqt li niżguraw

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li ma jkunx hemm wisq żibel
ġejjin mill-pajp.

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Huma ħadthom attwalment qegħdin jaħdmu
B'dan il-mod għal diversi għexieren ta 'snin issa.

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Bażikament, kull parti
ta 'magna ta' karozza moderna

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għandha sensor jew kontrollur
fuqha, u dawn il-kompjuters

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qari fid-dejta eluf ta
darba kull sekonda aġġustamenti teħid

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bħall-proporzjon ta 'fjuwil fl-arja
li għaddej fis-ċilindri.

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>> Dawn Volkswagen qerq
u mudelli Audi huma Bijodiżils,

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u Bijodiżils jkollhom waħda aktar
kompjuter verament importanti

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parametri kkontrollati, li huwa
l-ammont ta 'fjuwil mhux maħruq għaddej

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fil-exhaust.

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Issa li l-ħsejjes ħażina.

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Ma ħoss bħal inti tixtieq
fjuwil mhux maħruq jmorru fil-exhaust.

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00:05:39,642 --> 00:05:41,600
Iżda fil-każ ta '
diesel, għandek xi ħaġa

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imsejħa nassa NOx li huwa mezz li
jassorbi u nases għall-ossidi tan-nitroġenu

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li huma pollutanti li kieku
inkella jmorru fl-atmosfera.

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U l-effett ta 'dik nassa NOx
hija msaħħa bil-karburant mhux maħruq.

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Allura apparat manipulattiv huwa programm speċjali
ġewwa dawn il-kompjuters li jista 'jagħmilha

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jidhru bħall-karozza jissodisfa emissjoni
standards anki meta ma.

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Volkswagen kellhom problema fuq idejh.

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Magni diesel tagħha kienu magħrufa
biex jinkiseb ekonomija tal-karburant kbir,

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iżda l-nassa NOx biss jaħdem tajjeb
meta jkun qed jintuża aktar fjuwil.

125
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Allura l-karozza jagħrfux,
jużaw dan il-mezz telfa,

126
00:06:10,460 --> 00:06:13,870
meta kien jkollna emissjonijiet
test, għandha tuża aktar fjuwil,

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jagħmel ix-xogħol nassa NOx sew,
emissjonijiet tkun multa.

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Imma mbagħad ikollok fuq it-triq, l-apparat
tintefa, int ħruq inqas fjuwil

129
00:06:21,130 --> 00:06:24,256
imma int tqegħid kemm 40 darba
aktar inkwinanti fl-atmosfera.

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Imma kif l-Heck ma
il-karozza jafu li kien

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qed jiġi ttestjat għall-konformità emissjonijiet?

132
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L-EPA jgħid li kien sofistikat
sistema li iċċekkjata affarijiet

133
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bħal pożizzjoni isteering wheel,
veloċità, kemm żmien il-magna kienet fuq,

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u anki l-pressjoni atmosferika.

135
00:06:35,507 --> 00:06:37,673
Fi kliem ieħor, kien hemm
ebda mod dan kien aċċidentali

136
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minħabba li l-software kien
mfassla b'attenzjoni kbira biex jikxfu

137
00:06:40,260 --> 00:06:41,630
test emissjonijiet uffiċjali.

138
00:06:41,630 --> 00:06:43,588
Li xi pretty serji
qerq u li

139
00:06:43,588 --> 00:06:45,420
għaliex Volkswagen hija
bħal problemi serji.

140
00:06:45,420 --> 00:06:48,600
Fil-fatt, CEO tagħhom, Martin
Winterkorn, biss irriżenja.

141
00:06:48,600 --> 00:06:49,820
>> Allura x'jiġri li jmiss?

142
00:06:49,820 --> 00:06:53,900
Ukoll, jekk int wieħed mill-nofs miljun
jettas diesel, Beatles, golfs, Passats,

143
00:06:53,900 --> 00:06:56,220
jew Audi A3s effettwata,
l-aħbar tajba hija hija

144
00:06:56,220 --> 00:06:57,886
li l-karozza tiegħek għadu sikur biex issuq.

145
00:06:57,886 --> 00:07:00,510
Inti ma għandekx li tqiegħed lilha bogħod
sakemm Volkswagen joħroġ recall.

146
00:07:00,510 --> 00:07:02,509
Iżda f'xi punt dawn qed
probabbilment se jkollhom

147
00:07:02,509 --> 00:07:04,230
li taġġorna s-software ġewwa karozza tiegħek.

148
00:07:04,230 --> 00:07:06,927
Meta dan iseħħ inti tista
jiksbu inqas mil fis tank.

149
00:07:06,927 --> 00:07:09,260
L-avukati huma diġà gearing
up għall kawżi ta 'azzjoni klassi

150
00:07:09,260 --> 00:07:12,500
hekk sidien tista 'tikseb kkumpensati
f'xi punt fil-futur.

151
00:07:12,500 --> 00:07:15,832
Iżda dan mhux se
jiġri kwalunkwe ħin hekk.

152
00:07:15,832 --> 00:07:16,711
>> [END Daqq]

153
00:07:16,711 --> 00:07:19,960
DAVID J. Malan: Allura dan fil-fatt iqajjem
interessanti akbar mistoqsija istampa

154
00:07:19,960 --> 00:07:20,660
kif l-fiduċja.

155
00:07:20,660 --> 00:07:21,160
Dritt?

156
00:07:21,160 --> 00:07:24,300
Lkoll iPhones jew Androids jew
xi ħaġa fil-bwiet tagħna aktar probabbli

157
00:07:24,300 --> 00:07:26,500
f'dawn il-jiem, jew laptops
fuq dawriet tagħna li huma

158
00:07:26,500 --> 00:07:28,510
softwer li jaħdem magħmula
minn Apple u Microsoft

159
00:07:28,510 --> 00:07:30,710
u għenieqed ta 'kumpanniji oħra.

160
00:07:30,710 --> 00:07:34,240
Imma kif nafu li dak li
dawn il-prodotti ta 'softwer qed jagħmlu

161
00:07:34,240 --> 00:07:37,680
huwa attwalment liema dawn
kumpaniji jgħidu li qed jagħmlu?

162
00:07:37,680 --> 00:07:39,610
>> Per eżempju, li li
jgħidu li kull darba li inti

163
00:07:39,610 --> 00:07:42,200
jagħmlu telefonata fuq iPhone tiegħek
jew telefon Android jew bħalhom,

164
00:07:42,200 --> 00:07:45,650
li dak in-numru tat-telefon huwa wkoll mhux
qed tittella server xi kumpanija

165
00:07:45,650 --> 00:07:48,399
minħabba xi program inti stajt
bil-miktub, jekk huwa l-operattiva

166
00:07:48,399 --> 00:07:51,070
sistema nnifisha bħal IOS jew Android,
jew għaliex inti ħadthom jitniżżel

167
00:07:51,070 --> 00:07:53,880
xi app parti terza
li b'xi mod huwa smigħ

168
00:07:53,880 --> 00:07:57,120
li kollox int ittajpjar fi jew
kollox int tgħid attwalment.

169
00:07:57,120 --> 00:07:59,500
Kif tkun taf li, meta
inti guys qed jitħaddmu Clang

170
00:07:59,500 --> 00:08:02,590
jew Agħmel biex jikkompilaw tiegħek
software stess fl CS50, kif

171
00:08:02,590 --> 00:08:06,080
do inti persunal li CS50 stess,
permezz tal-librerija CS50,

172
00:08:06,080 --> 00:08:08,690
ma kienx qtugħ kull
string inti stajt qatt gotten

173
00:08:08,690 --> 00:08:10,276
jew kull pulzier inti stajt qatt gotten?

174
00:08:10,276 --> 00:08:12,900
Well, inti tista 'ċertament tfittex
fil-kodiċi tas-sors għal xi ħaġa

175
00:08:12,900 --> 00:08:15,233
bħall-librerija CS50, inti
tista 'tħares lejn il-kodiċi tas-sors

176
00:08:15,233 --> 00:08:18,170
għas-sistema operattiva Linux
taħdem fuq IDE CS50.

177
00:08:18,170 --> 00:08:23,090
Iżda preżentazzjoni aqwa
ingħata lura fl-1984

178
00:08:23,090 --> 00:08:26,730
jirċievi l-Premju Turing minn
xjentist kompjuter famużi ħafna magħruf

179
00:08:26,730 --> 00:08:29,750
as-- jismu Ken Thompson li
irċieva l-Premju Turing li

180
00:08:29,750 --> 00:08:33,500
huwa tip ta 'xjenza tal-kompjuter
Premju Nobel, jekk inti se,

181
00:08:33,500 --> 00:08:35,309
għall-ħidma tiegħu fuq
sistema operattiva imsejħa

182
00:08:35,309 --> 00:08:39,039
Unix, li hija simili ħafna fl
ispirtu li dak li nużaw li huwa Linux.

183
00:08:39,039 --> 00:08:41,960
U l-kwistjoni huwa talab fil tiegħu
diskors aċċettazzjoni, essenzjalment

184
00:08:41,960 --> 00:08:44,910
li jippreskrivi l-qafas għall
snin u snin ta 'diskussjoni

185
00:08:44,910 --> 00:08:46,970
dwar il-fiduċja u s-sigurtà, kien dan.

186
00:08:46,970 --> 00:08:50,410
Safejn għandha fiduċja waħda minn
dikjarazzjoni li program-- biċċa

187
00:08:50,410 --> 00:08:53,010
tal software-- huwa mingħajr Trojan horses?

188
00:08:53,010 --> 00:08:56,500
Forsi huwa aktar importanti li l-fiduċja
il-persuni li kiteb l-software.

189
00:08:56,500 --> 00:08:58,650
>> U fil-fatt, konna marbuta
għall-talk li hu

190
00:08:58,650 --> 00:09:02,400
taw meta jaċċettaw dan il-premju
fis-snin 80 fuq il-websajt CS50 s

191
00:09:02,400 --> 00:09:04,030
taħt il-paġna Lectures għal-lum.

192
00:09:04,030 --> 00:09:06,071
Minħabba dak li int ser tara
hu li fil-fatt jagħti

193
00:09:06,071 --> 00:09:09,430
eżempju pjuttost sempliċi ta 'kif anke
kompilatur bħal Clang jew kwalunkwe

194
00:09:09,430 --> 00:09:13,950
kompilaturi oħrajn użati fil-passat,
X'jiġri jekk inkorporati fil-kompilatur aħna

195
00:09:13,950 --> 00:09:18,190
lilna nfusna qed tuża huwa xi ftit jekk
kundizzjoni li essenzjalment jgħid,

196
00:09:18,190 --> 00:09:22,360
jekk tinnota li dan il-kodiċi qed tuża
il-funzjoni GetString jew l GetInt

197
00:09:22,360 --> 00:09:26,600
, il-funzjoni imorru quddiem u daħħal
a bieb ta 'wara jew Trojan horse

198
00:09:26,600 --> 00:09:29,340
b'tali mod li dak il-programm
issa għandha xi żerijiet

199
00:09:29,340 --> 00:09:30,930
u dawk li jagħmlu xi ħaġa malizzjużi.

200
00:09:30,930 --> 00:09:33,080
Qtugħ kollha ta 'tiegħek
keystrokes, uploading li d-data

201
00:09:33,080 --> 00:09:35,100
għal xi server, jew verament xi ħaġa.

202
00:09:35,100 --> 00:09:37,290
>> U dak Ken Thompson
tmur fuq li jagħmlu fil talk tiegħu

203
00:09:37,290 --> 00:09:40,580
huwa li turi li anke jekk
ikollok aċċess għall-sors

204
00:09:40,580 --> 00:09:43,794
kodiċi ta kompilatur li
malizzjuż jista 'jkun tagħmel dan,

205
00:09:43,794 --> 00:09:46,210
ma jimpurtax għax
hemm dan tiġieġ u l-bajd

206
00:09:46,210 --> 00:09:49,500
realtà mill-ħafna passat
snin li biha kompilaturi

207
00:09:49,500 --> 00:09:51,960
huma użati biex jikkompilaw infushom.

208
00:09:51,960 --> 00:09:55,440
Fi kliem ieħor, mod lura meta xi ħadd
kellhom kitbu l-ewwel kompilatur.

209
00:09:55,440 --> 00:09:59,060
U wara, kull darba li ħadthom aġġornati
kompilatur billi jbiddlu kodiċi sors tagħha,

210
00:09:59,060 --> 00:10:02,020
jżid karatteristiċi u recompiling dan
għall-persuni bħalna għall-użu, ukoll,

211
00:10:02,020 --> 00:10:04,270
li qed jużaw l-qodma
Verżjoni tal-kompilatur

212
00:10:04,270 --> 00:10:06,370
biex jikkompilaw l-ġdida
Verżjoni tal-kompilatur.

213
00:10:06,370 --> 00:10:08,370
U jekk inti tagħti ħarsa
fil-taħdita li taw,

214
00:10:08,370 --> 00:10:10,970
tkun taf tara li minħabba
ta 'dak ċirkolarità,

215
00:10:10,970 --> 00:10:14,330
inti tista 'attwalment jkollhom bugs jew
Trojan horses inkorporati fis-software

216
00:10:14,330 --> 00:10:14,990
aħna qed jużaw.

217
00:10:14,990 --> 00:10:18,010
U anki jekk inti tħares lejn l-
kodiċi tas-sors għall dawk il-programmi,

218
00:10:18,010 --> 00:10:21,550
ma jista 'anke jkun evidenti
minħabba li l-trickery huwa attwalment

219
00:10:21,550 --> 00:10:24,710
f'xi verżjoni anzjani ta '
kompilatur li peress li qatt kien

220
00:10:24,710 --> 00:10:27,340
tinjetta t-theddida fis-softwer tagħna.

221
00:10:27,340 --> 00:10:29,740
>> Liema hija biss jgħidu, aħna
verament ma tistax u m'għandhiex

222
00:10:29,740 --> 00:10:32,939
software fiduċja li jaħdem fuq laptops tagħna
jew tat-telefons jew kwalunkwe numru ta 'postijiet.

223
00:10:32,939 --> 00:10:36,230
U fil-fatt, aktar tard f'dan semestru meta
nibdew nitkellmu dwar l-ipprogrammar tal-web

224
00:10:36,230 --> 00:10:38,521
u fil-fatt jibda jinbena
applikazzjonijiet web nfusna,

225
00:10:38,521 --> 00:10:40,285
aħna ser nitkellmu dwar dawn
theddid u oħrajn.

226
00:10:40,285 --> 00:10:43,410
Issa, inti jista 'jkollok staqsiet u ndunat
li kien hemm ftit Darth żgħira

227
00:10:43,410 --> 00:10:45,842
Vader fil-clips li
Il-ponta kien juri hemmhekk

228
00:10:45,842 --> 00:10:47,550
dwar Volkswagen. Jekk
inti stajt qatt rat, I

229
00:10:47,550 --> 00:10:49,190
ħsibt aħna għandu jħaffef
l-burdata għaliex dan huwa kollu

230
00:10:49,190 --> 00:10:50,780
ħafna deprimenti u biża.

231
00:10:50,780 --> 00:10:52,910
Jien ser inħarsu lura
fil Super Bowl 2011

232
00:10:52,910 --> 00:10:55,300
meta kummerċjali mill
Volkswagen-- u dan

233
00:10:55,300 --> 00:10:59,620
kważi jagħmilhom likable again--
imxandra għall-ewwel darba fuq it-TV.

234
00:10:59,620 --> 00:11:04,039
Hu l-tieni clip 60
li naħseb li inti ser igawdu.

235
00:11:04,039 --> 00:11:04,705
[Daqq video]

236
00:11:04,705 --> 00:11:08,198
[MUSIC - TEMA minn "Star Wars"]

237
00:11:08,198 --> 00:11:35,643

238
00:11:35,643 --> 00:11:38,138
[Barks kelb]

239
00:11:38,138 --> 00:11:50,114

240
00:11:50,114 --> 00:11:53,607
[CAR Tibda]

241
00:11:53,607 --> 00:12:04,086

242
00:12:04,086 --> 00:12:05,955
[END Daqq]

243
00:12:05,955 --> 00:12:06,830
DAVID J. Malan: Yeah.

244
00:12:06,830 --> 00:12:07,663
I kien biss verifika.

245
00:12:07,663 --> 00:12:11,360
Dik il-karozza hija fuq il-lista ta 'vjolazzjonijiet.

246
00:12:11,360 --> 00:12:12,000
Kull dritt.

247
00:12:12,000 --> 00:12:14,040
Allura aħna nħarsu lejn uħud
pseudocode mument ilu.

248
00:12:14,040 --> 00:12:15,380
U hawnhekk akbar
snippet ta 'kodiċi pseudocode

249
00:12:15,380 --> 00:12:16,921
li Rajna xi ftit drabi s'issa.

250
00:12:16,921 --> 00:12:19,970
U ejja jużaw din hija opportunità
issa li tintroduċi pprogrammar ġdid

251
00:12:19,970 --> 00:12:23,776
teknika li għamilna
tara algorithmically

252
00:12:23,776 --> 00:12:25,400
ġimgħa li għaddiet meta ħarisna lejn sort jingħaqdu.

253
00:12:25,400 --> 00:12:28,270
Imma ejja jifformalizzaw u tara kif
nistgħu jużawha fil-kodiċi attwali,

254
00:12:28,270 --> 00:12:30,350
u allura aħna qed tmur biex jużaw dan
teknika fl-triq l-aktar

255
00:12:30,350 --> 00:12:32,000
probabbli li jiġu solvuti ċerti problemi oħra.

256
00:12:32,000 --> 00:12:35,790
>> Allura dan kien wieħed mill-ewwel programmi we
qatt kiteb, għalkemm kodiċi pseudocode.

257
00:12:35,790 --> 00:12:37,790
U dak dan il-programm
ħallietna nsiru biex jagħmlu kors

258
00:12:37,790 --> 00:12:41,510
kienet li jsibu Mike Smith fil-ktieb tat-telefon.

259
00:12:41,510 --> 00:12:46,216
U avviż f'xi linji ta 'tmien
u 11 li kellhom din l-istqarrija Go To.

260
00:12:46,216 --> 00:12:48,090
U fil-fatt, ċerti
lingwi, C fosthom,

261
00:12:48,090 --> 00:12:50,006
fil-fatt do jkollhom
dikjarazzjoni li hu litteralment

262
00:12:50,006 --> 00:12:52,710
mur li jippermettilek li
tiżdied għal linja speċifika.

263
00:12:52,710 --> 00:12:55,470
Huwa ġeneralment frowned fuq għaliex
jista 'jiġi faċilment abbużati

264
00:12:55,470 --> 00:12:58,490
u inti tista 'tibda jaqbeż tiegħek
programm kollu fuq il-post għall-kuntrarju

265
00:12:58,490 --> 00:13:00,690
għall-użu it-tip ta '
loġika u l-fluss kontroll

266
00:13:00,690 --> 00:13:04,000
li konna użati s'issa ma biss
loops u kondizzjonijiet u simili.

267
00:13:04,000 --> 00:13:08,660
>> Iżda nistgħu jissimplifika dan algoritmu
fil-kodiċi pseudocode kif ġej.

268
00:13:08,660 --> 00:13:11,250
Minflok dan iterattiv
jew looping approċċ

269
00:13:11,250 --> 00:13:14,160
fejn inżommu tmur lura u
lura u lura għal-linja tlieta,

270
00:13:14,160 --> 00:13:18,300
għaliex ma we biss tip ta 'Punt u aktar
ġeneralment jgħidu konformi seba u 10,

271
00:13:18,300 --> 00:13:20,570
biss jissostitwixxu dawn iż-żewġ
pari ta 'linji,

272
00:13:20,570 --> 00:13:22,810
inkella jekk Smith tiġi qabel
fil-ktieb aħna ser

273
00:13:22,810 --> 00:13:25,110
tfittxija għall Mike fil-
nofs tax-xellug tal-ktieb.

274
00:13:25,110 --> 00:13:28,560
Else jekk Smith tkun iktar tard fil-
ktieb, tfittxija għal Mike fid-dritt

275
00:13:28,560 --> 00:13:29,540
nofs il-ktieb.

276
00:13:29,540 --> 00:13:31,180
U avviż diġà l-ċirkolarità.

277
00:13:31,180 --> 00:13:31,680
Dritt?

278
00:13:31,680 --> 00:13:34,250
Jien tiftix għal Mike fil
il-ktieb tat-telefon u mbagħad

279
00:13:34,250 --> 00:13:37,090
I eventwalment hit forsi
line seba 'jew forsi linja 10

280
00:13:37,090 --> 00:13:41,089
u l-istruzzjoni tiegħi li myself huwa tfittxija
għall Mike fil nofs il-ktieb tat-telefon.

281
00:13:41,089 --> 00:13:42,380
Ukoll, kif nista tfittxija għal Mike?

282
00:13:42,380 --> 00:13:44,213
Jien fin-nofs ta
tiftix għal Mike, għaliex

283
00:13:44,213 --> 00:13:45,860
huma inti tip ta 'jibghatni f'ċirku?

284
00:13:45,860 --> 00:13:49,590
Imma dak li OK għaliex dak li hu
jiġri għad-daqs tal-problema,

285
00:13:49,590 --> 00:13:52,630
kif miktun fid linja 7 u 10?

286
00:13:52,630 --> 00:13:54,989
Aħna mhux biss qal tfittxija
għall Mike, tfittxija għal Mike.

287
00:13:54,989 --> 00:13:56,280
Aħna qed tgħid speċifikament liema?

288
00:13:56,280 --> 00:13:58,694

289
00:13:58,694 --> 00:14:01,610
Fittex għalih fl-ewwel nofs tax-xellug tal
in-nofs dritt li huwa effettivament

290
00:14:01,610 --> 00:14:03,440
nofs id-daqs tal-problema.

291
00:14:03,440 --> 00:14:07,170
Allura huwa OK li aħna qed tip ta '
involviment f'dan ċirkolarità,

292
00:14:07,170 --> 00:14:09,180
dan l-argument ċirkolari,
għaliex mill-inqas aħna qed

293
00:14:09,180 --> 00:14:11,090
jagħmlu l-problema iżgħar.

294
00:14:11,090 --> 00:14:14,220
U eventwalment aħna qed tmur biex jilħqu
li l-hekk imsejħa każ bażi fejn

295
00:14:14,220 --> 00:14:16,780
għadna kemm paġna waħda left--
kif voluntier tagħna aħħar ġimgħa

296
00:14:16,780 --> 00:14:18,684
did-- kellna paġna waħda
xellug u mbagħad aħna ma

297
00:14:18,684 --> 00:14:21,600
għandhom iżommu tiftix għal Mike Smith
għaliex huwa jew fuq dik il-paġna

298
00:14:21,600 --> 00:14:23,080
jew huwa ma jkunx.

299
00:14:23,080 --> 00:14:27,480
>> Allura kif nistgħu nimplimentaw din l-idea, dan
tip ta 'ċirkolarità fil-kodiċi attwali?

300
00:14:27,480 --> 00:14:31,030
Well, nistgħu lieva teknika
thats ġeneralment magħrufa bħala recursion.

301
00:14:31,030 --> 00:14:33,960
U Rajna dan fil-
pseudocode għall tip jingħaqdu ġimgħa li għaddiet.

302
00:14:33,960 --> 00:14:37,190
Ifakkar li dan kien il-
pseudocode għall tip jingħaqdu.

303
00:14:37,190 --> 00:14:40,560
Huwa probabbli ħafna aktar sempliċi milli
bużżieqa jew għażla jew inserzjoni tip

304
00:14:40,560 --> 00:14:43,310
biss f'termini tal-sempliċità
li magħhom inti tista 'tesprimi lilha.

305
00:14:43,310 --> 00:14:46,750
>> Iżda dan għaliex
aħna qed tip ta 'circularly

306
00:14:46,750 --> 00:14:51,350
qal, tfittex xi ħaġa
minn tiftix għal darb'oħra.

307
00:14:51,350 --> 00:14:53,960
Iżda aħna qed tfittex jew fuq
in-nofs tax-xellug jew il-nofs tal-lemin

308
00:14:53,960 --> 00:14:56,070
u mbagħad eventwalment aħna qed
jingħaqdu f'dan il-każ.

309
00:14:56,070 --> 00:14:58,520
Iżda hawnhekk, wisq, ma
dawn iż-żewġ linji sort,

310
00:14:58,520 --> 00:15:01,320
aħna ma jerġa 'jkollhom dan
idea ta 'recursion.

311
00:15:01,320 --> 00:15:05,350
U konkret dak li dan ifisser,
fil-kuntest ta 'algoritmu,

312
00:15:05,350 --> 00:15:10,880
hija li algoriżmu huwa rikursivi
jekk hija tuża jew sejħiet innifsu.

313
00:15:10,880 --> 00:15:14,330
>> Jew f'termini ta C, funzjoni hija
recursive-- funzjoni msejħa

314
00:15:14,330 --> 00:15:18,510
foo huwa rikursivi jekk foo,
x'imkien fil-kodiċi sors tagħha,

315
00:15:18,510 --> 00:15:21,250
jitlob l-foo funzjoni hija stess.

316
00:15:21,250 --> 00:15:25,790
U li ħażina jekk kollox foo qatt ma
huwa sejħa nnifisha mill-ġdid u għal darb'oħra.

317
00:15:25,790 --> 00:15:30,600
Huwa OK jekk foo eventwalment waqfiet, bħal ma
jingħaqdu sort, billi qal, stenna minuta,

318
00:15:30,600 --> 00:15:32,980
jekk din il-problema huwa super
żgħar, per eżempju,

319
00:15:32,980 --> 00:15:35,840
jew I sabuh min jien
tfittex, biss jirritorna.

320
00:15:35,840 --> 00:15:41,000
Ma recursively, ma
ċiklikament sejħa myself darb'oħra.

321
00:15:41,000 --> 00:15:44,200
>> U hekk ejja tagħti ħarsa lejn
kif dan jista 'attwalment jaħdmu.

322
00:15:44,200 --> 00:15:48,430
Hekk jien ser jimxi 'l quddiem u miftuħa
żewġ eżempji source code hawn.

323
00:15:48,430 --> 00:15:50,321
Li waħda minnhom huwa msejjaħ sigma 0.

324
00:15:50,321 --> 00:15:52,320
U dan mhuwiex f'kull
rikursivi, imma ejja tieħu

325
00:15:52,320 --> 00:15:53,694
ħarsa lejn dak il-programm ma.

326
00:15:53,694 --> 00:15:55,737
Stajt imqaxxar barra kollha
kummenti minnha iżda kollha

327
00:15:55,737 --> 00:15:58,070
tas-source code fuq l CS50
websajt kummenti jekk inti

328
00:15:58,070 --> 00:15:59,570
trid taqra permezz ta 'dan again later.

329
00:15:59,570 --> 00:16:02,010
U ejja jagħmlu koppja
tal sanità kontrolli hawn.

330
00:16:02,010 --> 00:16:06,640
>> Allura fil-quċċata ta 'dan il-kodiċi,
għandna jinkludu CS50.h.

331
00:16:06,640 --> 00:16:07,650
Xi jfisser dan do?

332
00:16:07,650 --> 00:16:08,990
Għaliex huwa hawnhekk?

333
00:16:08,990 --> 00:16:11,740
F'termini layman raġonevoli tal.

334
00:16:11,740 --> 00:16:12,424
X'tikkontrolla do?

335
00:16:12,424 --> 00:16:12,858
Yeah.

336
00:16:12,858 --> 00:16:14,160
>> UDJENZA: Allura dik il-funzjoni GetInt jaħdem.

337
00:16:14,160 --> 00:16:16,243
>> DAVID J. Malan: Allura li
il-funzjoni GetInt xogħlijiet.

338
00:16:16,243 --> 00:16:18,115
Minħabba ġewwa ta 'dan
fajl, CS50.h, li

339
00:16:18,115 --> 00:16:20,950
Ser naraw qabel twil fil
termini tal-kodiċi sors tagħha,

340
00:16:20,950 --> 00:16:23,270
għandha mazz ta 'funzjonijiet
declared-- GetInt, GetString,

341
00:16:23,270 --> 00:16:26,950
u mazz ta 'others-- u sakemm
għandna attwalment ikollhom li Inkludi linja,

342
00:16:26,950 --> 00:16:29,320
l Clang kompilatur mhuwiex
ser tkun taf li jeżisti.

343
00:16:29,320 --> 00:16:32,400
U istess jgħodd għal-linja
tnejn fejn int huwa definit

344
00:16:32,400 --> 00:16:35,101
printf, li huwa funzjoni
inżommu użu pjuttost ftit.

345
00:16:35,101 --> 00:16:37,850
Issa, linja erbgħa jidher funky ftit
għaliex huwa biss inforra wieħed.

346
00:16:37,850 --> 00:16:41,570
Huwa ltqajna punto virgola, l-ebda kaboċċi
ċingi, l-ebda kodiċi ġewwa ta 'dan.

347
00:16:41,570 --> 00:16:44,640
Imma dak li għamilt li nsejħu
dan ħaġa fil-ġimgħat passat?

348
00:16:44,640 --> 00:16:45,140
Yeah.

349
00:16:45,140 --> 00:16:46,060
Allura prototip.

350
00:16:46,060 --> 00:16:48,390
U għaliex għandna
prototip li jidher

351
00:16:48,390 --> 00:16:51,050
li jkun żejjed ftit
tipikament għaliex aħna normalment

352
00:16:51,050 --> 00:16:53,474
tara l-funzjoni mill-ġdid
aktar tard fil-fajl, id-dritt?

353
00:16:53,474 --> 00:16:56,390
Allura għaliex għandna have-- int biss
grif ras tiegħek imma jien ser teħodha.

354
00:16:56,390 --> 00:16:57,302
Yeah.

355
00:16:57,302 --> 00:17:00,000
>> UDJENZA: [inaudible]
funzjoni wara l-prinċipali.

356
00:17:00,000 --> 00:17:01,000
DAVID J. Malan: Eżattament.

357
00:17:01,000 --> 00:17:04,089
Sabiex il-kompilatur jaf int
eventwalment se tiddefinixxi jew timplimenta

358
00:17:04,089 --> 00:17:06,579
dik il-funzjoni wara ewlenija, preżumibbilment.

359
00:17:06,579 --> 00:17:08,462
Allura Clang u aktar
kompilaturi huma tip ta 'dumb

360
00:17:08,462 --> 00:17:10,510
u dawn ser jafu biss
dak li jgħidulhom.

361
00:17:10,510 --> 00:17:12,569
U jekk inti tixtieq li tuża
funzjoni msejħa sigma,

362
00:17:12,569 --> 00:17:15,710
inti aħjar jgħallmu l-kumpilatur
li jeżisti minn qabel.

363
00:17:15,710 --> 00:17:17,970
>> Issa, hija stess prinċipali, anki
għalkemm huwa mazz ta 'linji,

364
00:17:17,970 --> 00:17:19,839
huwa pjuttost familjari nisperaw minn issa.

365
00:17:19,839 --> 00:17:21,942
Huwa ltqajna do filwaqt loop
iskop li fil-ħajja

366
00:17:21,942 --> 00:17:24,400
hawn apparentement huwa li tikseb
numru sħiħ pożittiv mill-utent.

367
00:17:24,400 --> 00:17:27,349
U biss iżommu pestering lilu
jew tagħha sakemm jikkooperaw.

368
00:17:27,349 --> 00:17:30,670
Imbagħad konformi 16 I jkollhom
sejħa interessanti.

369
00:17:30,670 --> 00:17:31,570
IntAnswer.

370
00:17:31,570 --> 00:17:33,710
Li min-naħa tax-xellug
naħa tagħti me Int

371
00:17:33,710 --> 00:17:36,650
li jistgħu store-- imsejħa Answer--
li se taħżen, apparentement,

372
00:17:36,650 --> 00:17:39,090
il-valur ritorn ta 'sigma.

373
00:17:39,090 --> 00:17:41,840
Allura sigma huwa biss
isem arbitrarja iżda sinifikanti

374
00:17:41,840 --> 00:17:44,500
li stajt mogħtija għal funzjoni
iskop li fil-ħajja

375
00:17:44,500 --> 00:17:47,680
huwa li jieħdu argument-- wieħed
aħna ser sejħa hija N f'din case--

376
00:17:47,680 --> 00:17:52,280
u biss biex jieħdu s-somma ta 'dak in-numru
plus kull numru pożittiv li l-

377
00:17:52,280 --> 00:17:53,200
iżgħar minn dan.

378
00:17:53,200 --> 00:17:58,140
>> Mela jekk jien jgħaddu fin-numru 2 li
sigma, I tixtieq iżżid 2 flimkien ma '1

379
00:17:58,140 --> 00:18:00,240
plus 0-- mhux 0-- sabiex tagħti me 3.

380
00:18:00,240 --> 00:18:05,320
Jekk I jgħaddu fi 3 sa sigma, nixtieq li
jkollhom 3 flimkien ma '2 flimkien ma' 1, li tagħti me 6.

381
00:18:05,320 --> 00:18:05,900
U oħrajn.

382
00:18:05,900 --> 00:18:09,750
Allura hija biss iżid up kollha l-
numri inqas minn jew ugwali għal dan.

383
00:18:09,750 --> 00:18:12,040
>> Issa, stabbiliti hawn jien biss se
li jistampa l-risposta.

384
00:18:12,040 --> 00:18:17,330
Allura bħala kontroll sanità malajr, ejja
jagħmlu sigma 0-- sigma dot slash 0--

385
00:18:17,330 --> 00:18:18,690
u let me tip fil 2.

386
00:18:18,690 --> 00:18:19,960
U jien tassew nikseb 3.

387
00:18:19,960 --> 00:18:21,240
Let me tip fi 3.

388
00:18:21,240 --> 00:18:22,860
I tabilħaqq nikseb 6.

389
00:18:22,860 --> 00:18:27,636
U jekk kulħadd jista 'jagħmel l-matematika malajr,
jekk nagħmel 50 dak li jien ser nikseb?

390
00:18:27,636 --> 00:18:29,839
>> UDJENZA: [inaudible].

391
00:18:29,839 --> 00:18:30,880
DAVID J. Malan: Well, no.

392
00:18:30,880 --> 00:18:33,340
Iżda 1,275 li huwa pjuttost qrib.

393
00:18:33,340 --> 00:18:38,850
Allura dan huwa r-riżultat ta 'kif isir 50
plus 49 plus 48 plus 47 plus 46

394
00:18:38,850 --> 00:18:40,349
it-triq kollha sa 1.

395
00:18:40,349 --> 00:18:41,390
Allura li kollox sigma ma.

396
00:18:41,390 --> 00:18:43,350
Imma ejja naraw kif konna
implimentat dan issa.

397
00:18:43,350 --> 00:18:45,790
Allura stabbiliti hawn hija l-funzjoni nnifisha.

398
00:18:45,790 --> 00:18:49,000
U dan ma jidhirx li
xejn x'jaqsmu ma 'recursion s'issa.

399
00:18:49,000 --> 00:18:51,070
Fil-fatt, aħna qed jużaw
teknika iskola antika.

400
00:18:51,070 --> 00:18:56,680
Jien initializing varjabbli imsejjaħ somma
għal żero, imbagħad I jkollhom foreloop hawn,

401
00:18:56,680 --> 00:19:00,790
u jien ddikjarata Int imsejħa
I, dan ikun iffissat ugwali għal 1--

402
00:19:00,790 --> 00:19:04,080
għalkemm I jistgħu jistabbilixxu li egwali għal
żero, imma peress li jien qed nagħmel minn hekk,

403
00:19:04,080 --> 00:19:05,340
quién jekk huwa żero jew wieħed.

404
00:19:05,340 --> 00:19:06,660
Huwa ser ikollha effett.

405
00:19:06,660 --> 00:19:10,110
>> Hekk jien mtennija sakemm I huwa
inqas minn jew ugwali għal m, li

406
00:19:10,110 --> 00:19:11,671
huwa l-argument li kienet għaddiet.

407
00:19:11,671 --> 00:19:13,670
U mbagħad I biss iżommu
inkrementazzjoni I. U ħarsa

408
00:19:13,670 --> 00:19:20,010
tal-linja kollha li qed nagħmel qed tagħmel somma
plus ugwali I. U li intenzjonat.

409
00:19:20,010 --> 00:19:22,326
Ma rridx li tagħmel, f'dan
każ, bħal somma plus plus.

410
00:19:22,326 --> 00:19:24,790
Irrid li attwalment iżidu
il-valur kurrenti ta 'I

411
00:19:24,790 --> 00:19:28,190
li jżomm dejjem akbar u akbar
u akbar għall-jaqblu running.

412
00:19:28,190 --> 00:19:30,210
>> U mbagħad I jirritornaw somma.

413
00:19:30,210 --> 00:19:33,850
U għalhekk tweġiba gets-somma valur.

414
00:19:33,850 --> 00:19:35,282
U mbagħad I ipprintjaha.

415
00:19:35,282 --> 00:19:37,740
Allura hemm opportunità hawn,
għalkemm, li tip ta 'jissimplifikaw

416
00:19:37,740 --> 00:19:41,260
dan il-kodiċi kunċettwalment
u t-tip ta 'blow wieħed huwa

417
00:19:41,260 --> 00:19:43,250
mind f'termini tal-
sempliċità anki jekk

418
00:19:43,250 --> 00:19:45,700
tieħu filwaqt li sort
ta japprezzaw għaliex dan

419
00:19:45,700 --> 00:19:47,330
hija qawwija f'dawn l-eżempji żgħar.

420
00:19:47,330 --> 00:19:50,380
Hawnhekk huwa sigma one-- hekk il-
tieni verżjoni ta 'din il-kodiċi.

421
00:19:50,380 --> 00:19:55,290
Kollox top up huwa identiku hekk
l-istess storja tapplika qabel.

422
00:19:55,290 --> 00:19:59,220
Imma issa ejja nħarsu lejn il-
implimentazzjoni ta 'sigma li

423
00:19:59,220 --> 00:20:05,040
Stajt fadal biss dawn
lines-- erba 'linji ta' kodiċi, verament,

424
00:20:05,040 --> 00:20:06,980
flimkien ma 'xi braces kaboċċi u l-ispazju abjad.

425
00:20:06,980 --> 00:20:07,930
>> Imma dak am I tagħmel?

426
00:20:07,930 --> 00:20:11,050
Jekk m hija inqas minn jew ugwali għal
żero, I-ħtieġa li tip ta 'jimmaniġġjaw

427
00:20:11,050 --> 00:20:12,490
F'dak il-każ super sempliċi.

428
00:20:12,490 --> 00:20:15,450
U jekk inti idejn lili żero jew xejn
negattiva li huwa biss stramb,

429
00:20:15,450 --> 00:20:17,909
Jien biss ser arbitrarjament
imma dejjem jirritorna żero.

430
00:20:17,909 --> 00:20:20,200
Ma rridx dan ħaġa li
jsibu rwieħhom xi infinita stramb

431
00:20:20,200 --> 00:20:21,810
loop minħabba valur negattiv.

432
00:20:21,810 --> 00:20:25,070
Hekk jien biss qal, jekk inti tagħti me
żero jew inqas, jien jirritornaw żero.

433
00:20:25,070 --> 00:20:28,220
>> Imma dak li tajba għaliex dan huwa
dik il-paġna waħda tal-ktieb tat-telefon

434
00:20:28,220 --> 00:20:28,790
li ħalla.

435
00:20:28,790 --> 00:20:32,660
Jien gdim off problema speċifika ħafna
u mhux ssejjaħ xi ħaġa recursively.

436
00:20:32,660 --> 00:20:36,580
Iżda fil-linja 31, dak
do I jidhru li tkun qiegħda tagħmel?

437
00:20:36,580 --> 00:20:39,780
Il-parentesi huma biss iż-żamma
affarijiet, wieħed jittama, ftit aktar ċara.

438
00:20:39,780 --> 00:20:42,110
Imma kollha li qed nagħmel huwa jien
jirritornaw m-- x'ikun

439
00:20:42,110 --> 00:20:45,790
inti naħa me-- flimkien mal-
valur tal sorry m--,

440
00:20:45,790 --> 00:20:49,052
flimkien mal-valur tal sigma tal m minus 1.

441
00:20:49,052 --> 00:20:50,010
Allura dak li jfisser dan?

442
00:20:50,010 --> 00:20:53,965
Jekk inti tagħti me-numru 3 bħala input,
ir-risposta I rridu nġibu finalment

443
00:20:53,965 --> 00:20:57,307
hija ta '6 għaliex 3 u 2 flimkien ma' 1 tagħti me 6.

444
00:20:57,307 --> 00:20:59,390
Imma kif nista jaħsbu dwar
kif din il-kodiċi tkun qed taħdem?

445
00:20:59,390 --> 00:21:03,070
L-ewwel darba I call sigma
u I jgħaddu fil-valur 3,

446
00:21:03,070 --> 00:21:07,960
dan huwa simili qal fuq biċċa
tal-karta, hawn l-valur 3

447
00:21:07,960 --> 00:21:09,920
u stajt ġiet mgħoddija dan bħala sigma.

448
00:21:09,920 --> 00:21:13,090
3 hija ovvjament mhux inqas minn 0 hekk
il-kundizzjoni IF ma japplikax.

449
00:21:13,090 --> 00:21:14,020
Il ieħor ma.

450
00:21:14,020 --> 00:21:14,990
Mela xi do I do?

451
00:21:14,990 --> 00:21:19,902
I jridu jirritornaw m, li huwa
3, flimkien ma sigma ta m minus 1.

452
00:21:19,902 --> 00:21:21,110
So let me jżommu rekord ta 'dan.

453
00:21:21,110 --> 00:21:22,710
Jien ser tpoġġi din
biċċa karta isfel.

454
00:21:22,710 --> 00:21:24,668
U liema valur, li tkun
ċara, am I se jgħaddu

455
00:21:24,668 --> 00:21:26,540
fis sigma f'dan il-punt fl-istorja?

456
00:21:26,540 --> 00:21:28,080
Liema numru?

457
00:21:28,080 --> 00:21:28,610
2, id-dritt?

458
00:21:28,610 --> 00:21:29,670
3 minus 1 hija ta '2.

459
00:21:29,670 --> 00:21:32,000
So I biss bżonn ftit
Ruttam ta 'karti hawn.

460
00:21:32,000 --> 00:21:33,931
Allura issa sigma huwa jkollna msejjaħ mill-ġdid.

461
00:21:33,931 --> 00:21:35,930
U stajt deliberatament tqiegħed
din stabbiliti għaliex dan huwa

462
00:21:35,930 --> 00:21:38,070
tip simili espressjonijiet fit
dik il-verżjoni tal-istorja

463
00:21:38,070 --> 00:21:40,720
għaliex issa jien iffukat
fuq sinjal ta 'm minus 1.

464
00:21:40,720 --> 00:21:42,660
Allura m kien 3, m minus 1 hija ta '2.

465
00:21:42,660 --> 00:21:45,110
Allura hawnhekk huwa 2 li stajt ġiet mgħoddija.

466
00:21:45,110 --> 00:21:48,510
2 hija ovvjament mhux inqas minn
0 hekk il-każ ma japplikax.

467
00:21:48,510 --> 00:21:53,445
Inkella I ritorn m, li huwa dan
ħaġa, flimkien ma sigma ta 'dak il-valur?

468
00:21:53,445 --> 00:21:56,160

469
00:21:56,160 --> 00:21:59,650
Mela jekk sigma tal 1-- minħabba m hija
dritt issa 2 hekk 2 minus 1 huwa 1.

470
00:21:59,650 --> 00:22:01,950
Allura issa I jkollhom biss il-valur 1.

471
00:22:01,950 --> 00:22:04,810
Jien tgħaddi biss in-numru
1 għall-sigma-- funzjoni

472
00:22:04,810 --> 00:22:09,120
jew myself here-- hekk 1 hija ovvjament mhux
inqas minn żero, xorta ma japplikax.

473
00:22:09,120 --> 00:22:12,970
>> Ritorn Else 1 plus sigma ta 'dak?

474
00:22:12,970 --> 00:22:13,470
0.

475
00:22:13,470 --> 00:22:14,678
So let me biss ftakar li.

476
00:22:14,678 --> 00:22:15,920
I ser terġa 'lura li aktar tard.

477
00:22:15,920 --> 00:22:18,060
Issa jien ser jimxi 'l quddiem u LOGHOME
l-għadd 0 minħabba li l

478
00:22:18,060 --> 00:22:19,470
argument tiegħi jew parametru.

479
00:22:19,470 --> 00:22:22,400
Jien għadda n-numru 0
u finalment dan il-proċess

480
00:22:22,400 --> 00:22:25,760
ta 'ftit tirrepeti myself ad
nauseum ma jieqfu għaliex dak

481
00:22:25,760 --> 00:22:28,820
do I immedjatament tagħmel darba nara dan 0?

482
00:22:28,820 --> 00:22:29,790
I-ritorn żero.

483
00:22:29,790 --> 00:22:31,790
Allura issa inti għandek kontrina l-istorja.

484
00:22:31,790 --> 00:22:34,430
>> Jekk I issa jmorru lura fil-ħin,
dak li kien il-ħaġa aktar riċenti

485
00:22:34,430 --> 00:22:36,670
Jien għamilt jekk inti kienu litteralment
rewinding video?

486
00:22:36,670 --> 00:22:41,630
Jien ser jittellgħu l-aktar reċenti
1 u li tagħti me 1 plus 0 hija l-1.

487
00:22:41,630 --> 00:22:44,100
Jekk I iżommu rewinding l
istorja, li għaddej biex jagħti me

488
00:22:44,100 --> 00:22:46,880
2 flimkien ma 'dan il-valur running, li hija l-1.

489
00:22:46,880 --> 00:22:47,789
Allura li għamilhom 3.

490
00:22:47,789 --> 00:22:49,330
U allura jien ser iżommu rewinding.

491
00:22:49,330 --> 00:22:54,220
Meta I-ewwel darba l-għadd
3-- hekk 3 miżjuda bi 3 tagħti me 6.

492
00:22:54,220 --> 00:22:57,272
>> U issa, jekk inti ħadthom rewound
l-video sa dan il-punt,

493
00:22:57,272 --> 00:22:58,980
dan kien il-ħafna
ewwel domanda staqsejt.

494
00:22:58,980 --> 00:23:01,450
Meta għadda 3, dak li huwa sigma tat-3?

495
00:23:01,450 --> 00:23:04,204
Huwa tabilħaqq 6, is-somma ta '
dawn il-biċċiet kollha ta 'karti.

496
00:23:04,204 --> 00:23:07,120
Hekk jekk li tieħu ftit filwaqt li
wrap moħħok madwar, li l-multa.

497
00:23:07,120 --> 00:23:10,700
Iżda jikkunsidraw kien little-- it
kien intenzjonat ħafna li I f'munzelli

498
00:23:10,700 --> 00:23:12,990
dawn in-numri fuq quċċata ta 'xulxin.

499
00:23:12,990 --> 00:23:17,440
Huwa tip ta 'prodotti simili li jkollhom
memory-- rekord fil-ħin,

500
00:23:17,440 --> 00:23:19,940
bħal scrubber fil-video,
li I tista 'tabilħaqq kontrina fil.

501
00:23:19,940 --> 00:23:24,350
U aħna qed tmur biex terga 'lura għal
li metafora fi ftit ftit.

502
00:23:24,350 --> 00:23:28,240
>> Iżda l-ewwel, jirriżulta li hemm
ħafna geeks u nies umoristiċi,

503
00:23:28,240 --> 00:23:29,614
I raden, fuq Google.

504
00:23:29,614 --> 00:23:31,530
Would xi ħadd li ħafna
tajba fil Googling mind

505
00:23:31,530 --> 00:23:34,270
ġejjin għal ftit mument u
għinni tfittex xi ħaġa?

506
00:23:34,270 --> 00:23:35,650
Ħafna, ta 'ċavetta baxx ħafna.

507
00:23:35,650 --> 00:23:37,870
Xi ħadd li qatt
toħroġ qabel, forsi.

508
00:23:37,870 --> 00:23:38,370
KOLLOX SEW.

509
00:23:38,370 --> 00:23:39,030
Yeah?

510
00:23:39,030 --> 00:23:39,530
Come fuq.

511
00:23:39,530 --> 00:23:41,410
Come fuq l isfel.

512
00:23:41,410 --> 00:23:42,183
X'hemm isem tiegħek?

513
00:23:42,183 --> 00:23:42,870
>> SAM: Sam.

514
00:23:42,870 --> 00:23:44,290
>> DAVID J. Malan: Sam, jaqgħu fuq l isfel.

515
00:23:44,290 --> 00:23:45,320
Dan huwa Istess.

516
00:23:45,320 --> 00:23:46,280
Għandi pjaċir.

517
00:23:46,280 --> 00:23:46,780
Ħej.

518
00:23:46,780 --> 00:23:47,580
Come fuq matul.

519
00:23:47,580 --> 00:23:51,290
So I kollha bżonn li inti tagħmel, jekk
inti tista ', Sam, hawn Google.

520
00:23:51,290 --> 00:23:53,240
Inti tista 'tfittex għall-recursion tul?

521
00:23:53,240 --> 00:23:55,770

522
00:23:55,770 --> 00:23:56,270
Ma jħassru.

523
00:23:56,270 --> 00:23:59,940

524
00:23:59,940 --> 00:24:00,970
>> U issa let's-- yeah.

525
00:24:00,970 --> 00:24:03,380
OK Ikklikkja dik.

526
00:24:03,380 --> 00:24:04,315
Aħjar ikklikkja dan.

527
00:24:04,315 --> 00:24:07,020

528
00:24:07,020 --> 00:24:08,020
Ahh, ġġibu.

529
00:24:08,020 --> 00:24:08,520
Nru?

530
00:24:08,520 --> 00:24:09,050
KOLLOX SEW.

531
00:24:09,050 --> 00:24:10,430
Mela ejja do a oħrajn koppja.

532
00:24:10,430 --> 00:24:12,830
Mhux tant relatati
akkademikament hawn, iżda jkunu inti

533
00:24:12,830 --> 00:24:14,520
qatt mfittxija Google għall anagram?

534
00:24:14,520 --> 00:24:15,280
>> SAM: Le

535
00:24:15,280 --> 00:24:15,520
>> DAVID J. Malan: OK.

536
00:24:15,520 --> 00:24:17,186
Tiftix għal anagram minflok recursion.

537
00:24:17,186 --> 00:24:22,540

538
00:24:22,540 --> 00:24:23,790
Kif dwar askew.

539
00:24:23,790 --> 00:24:25,515
Inti qatt mfittxija għall askew?

540
00:24:25,515 --> 00:24:29,260

541
00:24:29,260 --> 00:24:32,692
Issa, dan wieħed huwa ftit diffiċli biex
tara iżda nisperaw everything's-- OK.

542
00:24:32,692 --> 00:24:34,150
Huwa biss int u jien jgawdu dan.

543
00:24:34,150 --> 00:24:34,690
KOLLOX SEW.

544
00:24:34,690 --> 00:24:38,950
>> Allura finalment, dan one's--
huwa askew ftit.

545
00:24:38,950 --> 00:24:40,810
Issa do a roll barmil.

546
00:24:40,810 --> 00:24:44,460

547
00:24:44,460 --> 00:24:45,310
Wonderful.

548
00:24:45,310 --> 00:24:45,910
Kull dritt.

549
00:24:45,910 --> 00:24:47,110
Big nirringrazzjak għall Sam.

550
00:24:47,110 --> 00:24:49,416
Hawnhekk inti tmur.

551
00:24:49,416 --> 00:24:50,400
Grazzi.

552
00:24:50,400 --> 00:24:52,807
>> Allura x'inhu għaddej fl-
ta 'dawn l-eżempji iblah?

553
00:24:52,807 --> 00:24:55,640
Allura verament, taħt il-barnuża ta
Miljuni Google ta 'linji ta' kodiċi

554
00:24:55,640 --> 00:24:58,860
apparentement huwa iblah ftit IF
kondizzjonijiet li huma essenzjalment

555
00:24:58,860 --> 00:25:01,160
verifika jekk l-utent ikollu
ittajpjat fil din il-frażi,

556
00:25:01,160 --> 00:25:03,760
tagħmel xi ħaġa li probabbilment ħa
ammont nontrivial ta 'żmien

557
00:25:03,760 --> 00:25:06,080
biex jimplimentaw biss biex
tkun divertenti b'dan il-mod.

558
00:25:06,080 --> 00:25:08,430
Imma li kollox tagħli
u ddur ma 'hood.

559
00:25:08,430 --> 00:25:11,570
Imma, naturalment, recursion
huwa aktar ta 'l-geekier

560
00:25:11,570 --> 00:25:13,880
Eżempju fost dawk tricks speċjali.

561
00:25:13,880 --> 00:25:16,880
U żgur hemm oħrajn hemmhekk
kif ukoll li aħna forsi lanqas biss

562
00:25:16,880 --> 00:25:18,230
skoperti għadha biss.

563
00:25:18,230 --> 00:25:22,830
>> Allura tagħti ħarsa, jew jikkunsidra
issa l-programm li ġej,

564
00:25:22,830 --> 00:25:24,830
u ċertament grab xi
minn dawn fuq tiegħek mod out.

565
00:25:24,830 --> 00:25:28,820
Jien ser jimxi 'l quddiem u
jiftħu programm li s

566
00:25:28,820 --> 00:25:30,920
ser jippruvaw li tpartit żewġ valuri.

567
00:25:30,920 --> 00:25:33,210
Iżda qabel immorru hemm, ejja tagħmel dan.

568
00:25:33,210 --> 00:25:38,500
Nistgħu tikseb wieħed aktar
voluntier, I think?

569
00:25:38,500 --> 00:25:40,480
Tixtieq li voluntier?

570
00:25:40,480 --> 00:25:40,980
Nru?

571
00:25:40,980 --> 00:25:41,890
Come fuq up.

572
00:25:41,890 --> 00:25:42,390
Come fuq up.

573
00:25:42,390 --> 00:25:42,890
Kull dritt.

574
00:25:42,890 --> 00:25:44,136
Allura isem tiegħek huwa dak?

575
00:25:44,136 --> 00:25:44,810
>> Lauren: Lauren.

576
00:25:44,810 --> 00:25:45,768
>> DAVID J. Malan: Lauren.

577
00:25:45,768 --> 00:25:46,890
Come on up, Lauren.

578
00:25:46,890 --> 00:25:50,140
Allura Lauren qed
kkontestat hawnhekk kif ġej.

579
00:25:50,140 --> 00:25:52,310
Għandi pjaċir.

580
00:25:52,310 --> 00:25:55,730
Allura Lauren hawn kellha għad
ta 'żewġ tazzi vojta tagħha.

581
00:25:55,730 --> 00:25:57,570
U aħna għandna xi oranġjo
meraq u xi ħalib

582
00:25:57,570 --> 00:26:00,301
u aħna qed tmur biex tmur
quddiem u tagħmel dan li ġej.

583
00:26:00,301 --> 00:26:01,550
Aħna biss ser timla din.

584
00:26:01,550 --> 00:26:07,840
Ftit uqija ta 'ħalib minn hawn u ejja
timla meraq tal-larinġ ftit hawn.

585
00:26:07,840 --> 00:26:11,475
>> U quddiem kollha
dawn membri tal-udjenza,

586
00:26:11,475 --> 00:26:13,550
tpartit iż-żewġ valuri ta 'dawn tazzi.

587
00:26:13,550 --> 00:26:16,970
Poġġi l-meraq tal-larinġ fil-tazza ħalib
u l-ħalib fit-tazza meraq tal-larinġ.

588
00:26:16,970 --> 00:26:22,380

589
00:26:22,380 --> 00:26:26,150
Kif inti tagħmel dan jekk inti kienu fil
dar u kellhom aċċess għal provvisti oħra?

590
00:26:26,150 --> 00:26:27,400
Lauren: Poġġi dan fil-tazza ieħor.

591
00:26:27,400 --> 00:26:28,191
DAVID J. Malan: OK.

592
00:26:28,191 --> 00:26:31,940
Mela ejja jkollhom temporanju
varjabbli, jekk aħna se.

593
00:26:31,940 --> 00:26:35,871
U jimxi 'l quddiem issa u jimplimentaw
l-istess proċedura iskambji.

594
00:26:35,871 --> 00:26:36,370
Allura, tajba.

595
00:26:36,370 --> 00:26:41,490
Imxejna tpoġġi ĠU fil-temporanju
varjabbli, ħalib fil-ĠU varjabbli,

596
00:26:41,490 --> 00:26:44,481
u issa l-varjabbli temporanju
fil-varjabbli ħalib.

597
00:26:44,481 --> 00:26:44,980
KOLLOX SEW.

598
00:26:44,980 --> 00:26:48,740
Hekk ukoll ħafna sar s'issa.

599
00:26:48,740 --> 00:26:50,990
Għalhekk jirriżulta out-- tiddeċiedi li
maħsub għal ftit mument.

600
00:26:50,990 --> 00:26:54,479
Hawnhekk, għal ftit geek it up a bit, dan
ikun l-kodiċi C li jikkorrispondi

601
00:26:54,479 --> 00:26:55,520
li aħna biss implimentati.

602
00:26:55,520 --> 00:26:58,650
Kellna żewġ inputs, au b, it-tnejn
li aħna ser ngħidu biss għall-sempliċità huma

603
00:26:58,650 --> 00:26:59,260
s int.

604
00:26:59,260 --> 00:27:02,780
U avviż hawn, jekk irrid li tpartit
il-valuri ta 'żewġ varjabbli, A u B,

605
00:27:02,780 --> 00:27:06,890
aħna tabilħaqq bżonn middleman, a
varjabbli temporanju, tazza temporanju,

606
00:27:06,890 --> 00:27:10,830
li fih l-pour wieħed mill-valuri
hekk li għandna placeholder għal dan.

607
00:27:10,830 --> 00:27:13,480
Imma mbagħad il-kodiċi huwa eżattament
kif Lauren hawn implimentati.

608
00:27:13,480 --> 00:27:15,500
>> Issa, biss li tikseb
ftit crazier, jirriżulta

609
00:27:15,500 --> 00:27:20,930
li inti tista 'tagħmel dan mingħajr
varjabbli temporanju.

610
00:27:20,930 --> 00:27:24,870
Biex tagħmel dan b'mod xieraq, għalkemm, aħna qed tmur
li jkollhom iqarrqu ma 'xi kimika.

611
00:27:24,870 --> 00:27:26,380
Għandna xi tazzi żejda hawn.

612
00:27:26,380 --> 00:27:29,600
Allura l-eqreb ħaġa li jistenna
bħall-ħalib u l-ilma perhaps--

613
00:27:29,600 --> 00:27:34,090
jew ħalib u OJ-- hija li għandna xi
ilma, hekk aħna ser jimlew dan wieħed up

614
00:27:34,090 --> 00:27:36,486
bi ftit uqija ta 'ilma ċar.

615
00:27:36,486 --> 00:27:38,332
Li probabbilment wisq.

616
00:27:38,332 --> 00:27:38,832
Yeah.

617
00:27:38,832 --> 00:27:39,934
Li definittivament wisq.

618
00:27:39,934 --> 00:27:40,600
Żomm fuq waħda taqs.

619
00:27:40,600 --> 00:27:43,520

620
00:27:43,520 --> 00:27:48,420
>> U issa għandna żejt, li, kif niftakar
minn nofs klassi kimika iskola,

621
00:27:48,420 --> 00:27:49,990
nisperaw li ma jitħallatx mas-ilma.

622
00:27:49,990 --> 00:27:53,650
Iżda huwa tip ta 'tip ta'
Dehra ħalib u ĠU.

623
00:27:53,650 --> 00:27:55,760
Allura issa, mingħajr l-użu
varjabbli temporanju,

624
00:27:55,760 --> 00:27:59,260
inti tista 'tpartit dawn iż-żewġ valuri?

625
00:27:59,260 --> 00:28:03,884
Allura żjut tmur fil-tazza ilma,
ilma tmur fil-tazza żejt.

626
00:28:03,884 --> 00:28:04,800
Lauren: L-ebda tazzi oħra?

627
00:28:04,800 --> 00:28:05,940
DAVID J. Malan: L-ebda tazzi oħra.

628
00:28:05,940 --> 00:28:07,860
U stajt ma attwalment
ttestjati dan qabel din is-sena

629
00:28:07,860 --> 00:28:10,110
so I do not know jekk dan se
attwalment jaħdmu kimikament.

630
00:28:10,110 --> 00:28:16,130

631
00:28:16,130 --> 00:28:18,650
Li ma kienx suppost li jiġri.

632
00:28:18,650 --> 00:28:19,761
Huwa jaħdem?

633
00:28:19,761 --> 00:28:20,260
Kull dritt.

634
00:28:20,260 --> 00:28:20,990
So separazzjoni?

635
00:28:20,990 --> 00:28:21,490
Tajba.

636
00:28:21,490 --> 00:28:24,714
Issa aħna ltqajna biex jiksbu l-
ilma fil-tazza oħra.

637
00:28:24,714 --> 00:28:27,630
Konċentraturi kimika Smarter tista
probabbilment jagħmlu dan aħjar minn lili.

638
00:28:27,630 --> 00:28:28,510
>> Lauren: L-ilma huwa fuq il-qiegħ.

639
00:28:28,510 --> 00:28:31,910
>> DAVID J. Malan: Il-water-- li kienet
x'hemm ewlenin l-aħħar darba għamilna dan.

640
00:28:31,910 --> 00:28:33,950
Inti għandek tagħmel dan fl-ordni dritt.

641
00:28:33,950 --> 00:28:34,450
Yeah.

642
00:28:34,450 --> 00:28:35,270
OK That's--.

643
00:28:35,270 --> 00:28:37,290
Allura issa għandna żewġ tazzi ta 'żejt.

644
00:28:37,290 --> 00:28:37,790
KOLLOX SEW.

645
00:28:37,790 --> 00:28:38,510
Li OK.

646
00:28:38,510 --> 00:28:40,110
Imma kimikament jekk dan maħduma milli I--

647
00:28:40,110 --> 00:28:41,200
>> Lauren: Dan huwa l-ilma.

648
00:28:41,200 --> 00:28:41,930
>> DAVID J. Malan: Li l-aktar ilma.

649
00:28:41,930 --> 00:28:42,430
Kull dritt.

650
00:28:42,430 --> 00:28:44,210
Imma dak li għadu l-istess tazza bħal qabel.

651
00:28:44,210 --> 00:28:47,570
Allura pour it-- jippruvaw dan hemmhekk.

652
00:28:47,570 --> 00:28:49,300
KOLLOX SEW.

653
00:28:49,300 --> 00:28:51,010
Dan huwa użu tajjeb ta 'żmien tal-klassi llum.

654
00:28:51,010 --> 00:28:51,510
KOLLOX SEW.

655
00:28:51,510 --> 00:28:53,890
Allura issa we-- sbieħ.

656
00:28:53,890 --> 00:28:55,460
Tip ta '.

657
00:28:55,460 --> 00:28:55,960
Kull dritt.

658
00:28:55,960 --> 00:28:56,690
Hekk tajjeb ħafna.

659
00:28:56,690 --> 00:29:00,006
Grazzi għall Lauren.

660
00:29:00,006 --> 00:29:01,950
Isir ħafna tajjeb.

661
00:29:01,950 --> 00:29:04,570
>> Hekk biss blow imħuħ tiegħek,
u din hija forsi xi ħaġa

662
00:29:04,570 --> 00:29:08,660
jilagħbu ma jekk inti tixtieq fil CS50 ID,
inti tista ', fil-fatt, tpartit żewġ varjabbli

663
00:29:08,660 --> 00:29:11,470
mingħajr l-użu ta 'numru sħiħ temporanju.

664
00:29:11,470 --> 00:29:13,060
U dan huwa l-kodiċi C korrispondenti.

665
00:29:13,060 --> 00:29:16,110
U jekk inti recall mill-aħħar
L-Erbgħa, aħna introdotti, jekk fil-qosor,

666
00:29:16,110 --> 00:29:19,720
xi operaturi ġodda fis C. U ma
xi ħadd jiftakar dak il-karrotta ftit

667
00:29:19,720 --> 00:29:23,660
simbolu hija, li trijangolari ftit
simbolu mill-keyboard jirrappreżenta?

668
00:29:23,660 --> 00:29:26,003
Liema bitwise operatur?

669
00:29:26,003 --> 00:29:26,770
>> UDJENZA: Exor.

670
00:29:26,770 --> 00:29:27,645
>> DAVID J. Malan: Exor.

671
00:29:27,645 --> 00:29:28,560
Esklussiva Or.

672
00:29:28,560 --> 00:29:32,920
Mela jekk inti tixtieq, biss għall-gost fil
dar, li tagħti u b 'żewġ arbitrarja

673
00:29:32,920 --> 00:29:36,072
Valuri bħal kull eight-- u I
se jagħżlu valur ta 'tmien bit.

674
00:29:36,072 --> 00:29:38,530
Jekk inti tagħmel dan ma '32 bit,
inti ser malajr ħafna niddejjaq.

675
00:29:38,530 --> 00:29:42,150
Iżda biss jagħtu l tmien bits
valur li l-x'ikun, wieħed jew tnejn,

676
00:29:42,150 --> 00:29:43,790
u jagħtu b valur simili.

677
00:29:43,790 --> 00:29:46,810
U mbagħad tuża d-definizzjoni
tal XOR minn l-Erbgħa li għadda,

678
00:29:46,810 --> 00:29:52,560
tapplika din ftit ftit, kull wieħed
dawk it-tmien bits f'kull wieħed mill au b,

679
00:29:52,560 --> 00:29:54,980
u mbagħad jagħmluh eżattament per dan il-kodiċi.

680
00:29:54,980 --> 00:29:58,170
U m'humiex korretti dak
tara hawn fuq l-iskrin.

681
00:29:58,170 --> 00:30:02,100
Hija tabilħaqq jeħodna
tliet operazzjonijiet XOR

682
00:30:02,100 --> 00:30:05,910
u b'xi mod magically au
b ser jiskambjaw pożizzjonijiet

683
00:30:05,910 --> 00:30:08,010
mingħajr ma jitilfu ebda informazzjoni.

684
00:30:08,010 --> 00:30:11,580
>> Allura l-żejt u l-ilma trick huwa l-
eqreb Inkarnazzjoni dinja reali

685
00:30:11,580 --> 00:30:12,980
I jista 'jaħseb biex jimitaw dak.

686
00:30:12,980 --> 00:30:15,950
Iżda huwa żgur aktar faċli li
użu ta 'varjabbli temporanju,

687
00:30:15,950 --> 00:30:16,920
bħal f'dan il-każ hawnhekk.

688
00:30:16,920 --> 00:30:21,190
U din ukoll opportunità jgħidu,
wisq, dan it-tip ta 'ottimizzazzjoni mikro,

689
00:30:21,190 --> 00:30:23,590
bħala xjenzat kompjuter
ngħid, filwaqt tip ta 'gost

690
00:30:23,590 --> 00:30:27,060
li brag dwar kif għamilt dan mingħajr
bħal iskambji ma 'varjabbli żejda,

691
00:30:27,060 --> 00:30:28,640
huwa mhux kollha li konvinċenti.

692
00:30:28,640 --> 00:30:31,619
Minħabba li jiffranka 32 bits, kif
fil-każ ta 'int attwali,

693
00:30:31,619 --> 00:30:33,410
mhux kollha li konvinċenti
fuq sistema fejn

694
00:30:33,410 --> 00:30:36,722
inti tista 'tuża għexieren ta' megabytes
jew saħansitra aktar memorja bħal dawn il-jiem.

695
00:30:36,722 --> 00:30:38,680
U fil-fatt, meta nikbru
għal sett problema aktar tard

696
00:30:38,680 --> 00:30:41,010
u inti jimplimentaw jespliċitaw
kontrollur u tkun taf

697
00:30:41,010 --> 00:30:43,550
jiġu kkontestati li jagħmlu dan mal
dan RAM inqas u inqas

698
00:30:43,550 --> 00:30:46,820
żmien possibbli fuq il-
computer-- inti xorta

699
00:30:46,820 --> 00:30:50,160
jkollhom ġimgħa biex jimplimentaw
it-- inti ser have-- inti ser tkun

700
00:30:50,160 --> 00:30:51,799
isfida li jimminimizzaw dawn ir-riżorsi.

701
00:30:51,799 --> 00:30:53,840
U li tassew l-uniku
okkażjoni dan is-semestru

702
00:30:53,840 --> 00:30:57,940
fejn inti ser ikunu mħeġġa biex tqaxxar
off anki l-prestazzjoni ifjen

703
00:30:57,940 --> 00:30:59,340
ispejjeż mod ieħor.

704
00:30:59,340 --> 00:31:02,200
>> Allura what-- kif nistgħu
tara dan fil-kodiċi attwali?

705
00:31:02,200 --> 00:31:04,530
Let me imorru quddiem issa
u jiftħu eżempju

706
00:31:04,530 --> 00:31:07,700
li deliberatament tissejjaħ
Nru Swap minħabba li ma

707
00:31:07,700 --> 00:31:10,670
fil-fatt tpartit-varjabbli
kif int attwalment tista 'tistenna.

708
00:31:10,670 --> 00:31:12,260
Mela ejja tagħti ħarsa.

709
00:31:12,260 --> 00:31:17,050
Hawn programm li m'għandha l-ebda CS50
librerija għaddejjin, I biss standard / O.

710
00:31:17,050 --> 00:31:19,560
Issa għandna prototip
għall swap up top li ftit

711
00:31:19,560 --> 00:31:21,540
ifisser huwa ltqajna biex jiġu ddefiniti aktar tard.

712
00:31:21,540 --> 00:31:22,550
U hawnhekk prinċipali.

713
00:31:22,550 --> 00:31:26,000
>> I arbitrarju assenjat xuy,
rispettivament, il-wieħed valuri u tnejn

714
00:31:26,000 --> 00:31:28,590
sempliċiment minħabba li qed żgħar
u faċli li wieħed jaħseb dwar.

715
00:31:28,590 --> 00:31:32,280
U mbagħad I biss mazz ta printfs
fejn I jkollhom kontroll sanità. x hija l-1

716
00:31:32,280 --> 00:31:35,110
u y hija 2 huwa preżumibbilment
x'inhuma dawn printfs se ngħid.

717
00:31:35,110 --> 00:31:36,530
Allura l-ebda magic s'issa.

718
00:31:36,530 --> 00:31:40,100
>> Imbagħad jien ser titlob bil
jistampa def, jagħmlu skambju dot dot dot.

719
00:31:40,100 --> 00:31:43,730
Jien ser sejħa-tpartit
funzjoni, li jgħaddi fil x uy.

720
00:31:43,730 --> 00:31:47,350
U ejja nassumu għal issa li
tpartit huwa implimentat eżattament

721
00:31:47,350 --> 00:31:49,930
kif kien mument ilu
ma 'varjabbli temporanju.

722
00:31:49,930 --> 00:31:52,670
U so I jallegaw boldly, skambjati.

723
00:31:52,670 --> 00:31:55,429
x issa huwa issa dan u y hija dik.

724
00:31:55,429 --> 00:31:57,220
Iżda l-fajl, naturalment,
huwa msejjaħ Nru Swap.

725
00:31:57,220 --> 00:31:58,678
Mela ejja attwalment tara x'jiġri.

726
00:31:58,678 --> 00:32:04,450
Jekk I jikkompilaw l-ebda swap u mbagħad
do ./noswap, x hija l-1, y hija 2.

727
00:32:04,450 --> 00:32:05,770
Iskambji biddlu.

728
00:32:05,770 --> 00:32:07,200
x hija l-1, y hija 2.

729
00:32:07,200 --> 00:32:11,980
Allura fil-fatt jidher li jkun żbaljat anke
għalkemm swap-- ejja iscroll down now--

730
00:32:11,980 --> 00:32:16,542
hija implimentata eżattament kull l-
kodiċi I propost mument ilu.

731
00:32:16,542 --> 00:32:19,000
Allura aħna ma tkunx qed tmur biex tikseb fancy
mal-għalf XOR għal issa.

732
00:32:19,000 --> 00:32:21,890
Dan, ukoll, għandhom jaħdmu biss
bħal ma l-ħalib u l ĠU

733
00:32:21,890 --> 00:32:25,820
iżda ma jidhirx li tkun qed taħdem.

734
00:32:25,820 --> 00:32:27,180
>> Mela ejja tagħmel dan mill-ġdid.

735
00:32:27,180 --> 00:32:29,310
Forsi I biss ma kien għaddej dan id-dritt.

736
00:32:29,310 --> 00:32:32,010
Mela ejja jimxu Nru Swap mill-ġdid.

737
00:32:32,010 --> 00:32:32,900
Forsi I-- ebda.

738
00:32:32,900 --> 00:32:34,400
Allura huwa biss mhux qed jaħdem.

739
00:32:34,400 --> 00:32:36,060
Mela ejja tagħmel verifika sanità ftit.

740
00:32:36,060 --> 00:32:39,690
Let me imorru quddiem hawn fil Swap
u biss żid, stenna minuta,

741
00:32:39,690 --> 00:32:43,856
a huwa% i / nu ejja
plug-in-valur ta '.

742
00:32:43,856 --> 00:32:45,730
Minħabba I verament irridu
biex tara x'inhu għaddej.

743
00:32:45,730 --> 00:32:47,570
U fil-fatt, dan huwa
teknika debugging

744
00:32:47,570 --> 00:32:50,028
li tista 'tkun tuża fil
ħinijiet tal-uffiċċju jew fid-dar diġà,

745
00:32:50,028 --> 00:32:53,560
simili għall-ewwel nofs ta 'Dan
Video Armendáriz fil PSET3

746
00:32:53,560 --> 00:32:56,870
fejn aħna introdotti print def bħala
a teknika rakkomandata, mill-inqas

747
00:32:56,870 --> 00:32:58,080
għall-każijiet sempliċi.

748
00:32:58,080 --> 00:33:01,720
Let me imorru quddiem u run jagħmlu
ebda tpartit darb'oħra, ./noswap.

749
00:33:01,720 --> 00:33:04,370

750
00:33:04,370 --> 00:33:05,840
>> Interessanti.

751
00:33:05,840 --> 00:33:11,670
Allura avviż dak li jidher li jkun veru. x
huwa 1, y hija 2, iżda huwa 2 meta b hija l-1.

752
00:33:11,670 --> 00:33:16,790
Allura dawn iż-żewġ b'xi ltqajna biddlu
iżda xuy mhux qed skambjati.

753
00:33:16,790 --> 00:33:21,090
Allura biex tkun ċara, dak li qed jiġri
huwa, up here I jkollhom xuy

754
00:33:21,090 --> 00:33:25,380
u dawk huma varjabbli lokali fil-
ambitu ta 'prinċipali, jien tgħaddi fil xuy

755
00:33:25,380 --> 00:33:26,170
li tpartit.

756
00:33:26,170 --> 00:33:29,080
Issa, tpartit, bħala funzjoni separata,
huwa liberu li call argumenti tagħha

757
00:33:29,080 --> 00:33:30,590
jew parametri xejn tagħha trid.

758
00:33:30,590 --> 00:33:33,280
Foo jew bar jew x jew y jew jew b.

759
00:33:33,280 --> 00:33:36,870
Just biex tagħmilha ċara li dawn qed
mhux identiku għal xuy per se,

760
00:33:36,870 --> 00:33:38,020
Stajt qal aub.

761
00:33:38,020 --> 00:33:40,040
Iżda nistgħu jsejħulhom xejn li rridu.

762
00:33:40,040 --> 00:33:43,960
>> U hekk jidher qisu
tpartit qed jiġi mgħoddi

763
00:33:43,960 --> 00:33:48,980
x-- AKA a-- u huwa
li jiġu mgħoddija y-- AKA b.

764
00:33:48,980 --> 00:33:51,900
B'xi dawn it-tliet linji huma
iskambji dawk il-valuri eżattament

765
00:33:51,900 --> 00:33:53,510
kif Lauren għamlet mal-ħalib u ĠU.

766
00:33:53,510 --> 00:33:56,010
Iżda meta aħna jistampa
il-valuri, au b

767
00:33:56,010 --> 00:34:01,340
huma tabilħaqq tpartit iżda x u
y jkollhom l-ebda bidla lilhom.

768
00:34:01,340 --> 00:34:03,150
Ifakkar li x uy huma up here.

769
00:34:03,150 --> 00:34:05,320
>> Allura nistgħu naraw dan permezz
teknika oħra kif ukoll.

770
00:34:05,320 --> 00:34:08,110
U dan ukoll hija teknika
inkorporati fl problema stabbiliti tlieta.

771
00:34:08,110 --> 00:34:10,780
Ejja imorru quddiem u tagħmel dan fi
CS50 ID jekk inti ma jkunux diġà.

772
00:34:10,780 --> 00:34:13,730
Fuq in-naħa tal-lemin aħna
jkollhom din tab Debugger.

773
00:34:13,730 --> 00:34:16,159
U jekk inti tiftaħ dan up,
hemm xi informazzjoni arcane

774
00:34:16,159 --> 00:34:17,530
li l-jintefgħu fil int inizjalment.

775
00:34:17,530 --> 00:34:19,310
Imma ejja tease dan apparti reali fast.

776
00:34:19,310 --> 00:34:21,620
>> Allura wieħed, tara varjabbli lokali.

777
00:34:21,620 --> 00:34:26,230
Jirriżulta li jibnu fis IDE CS50, u
ħafna ta 'ambjenti ta' programmazzjoni aktar

778
00:34:26,230 --> 00:34:28,060
ġeneralment, huwa debugger.

779
00:34:28,060 --> 00:34:31,340
A għodda li tippermetti li inti tara viżwalment
x'inhu għaddej ġewwa tal-programm tiegħek

780
00:34:31,340 --> 00:34:34,380
mingħajr ma jkollhom jirrikorru għal żieda
printfs u kompilazzjoni u t-tmexxija

781
00:34:34,380 --> 00:34:37,588
u żżid l printf u l-kumpilazzjoni u
tmexxija, li diġà, fil-ħinijiet uffiċċju

782
00:34:37,588 --> 00:34:40,070
jew dar, huwa probabbilment
jkollna pretty tedious.

783
00:34:40,070 --> 00:34:43,090
>> Allura hawnhekk, fi ftit mument, aħna qed
ser tara fil-ħin reali

784
00:34:43,090 --> 00:34:44,760
il-valuri ta 'varjabbli lokali tagħna.

785
00:34:44,760 --> 00:34:47,880
Aħna wkoll qed tmur biex ikunu jistgħu jistabbilixxu
liema huma msejħa breakpoints li

786
00:34:47,880 --> 00:34:52,570
opportunitajiet fil-programm tiegħi biex nieqaf
eżekuzzjoni fi linja speċifika tal-kodiċi

787
00:34:52,570 --> 00:34:53,710
li jien kurjużi dwar.

788
00:34:53,710 --> 00:34:54,210
Dritt?

789
00:34:54,210 --> 00:34:55,969
Dawn il-programmi mmexxija fit-tieni qasma.

790
00:34:55,969 --> 00:35:00,450
Huwa tip ta 'sbieħ għalina l-bnedmin kajman
li tkun tista 'nieqaf, tieħu mument, ara

791
00:35:00,450 --> 00:35:02,380
x'inhu għaddej madwar
linja partikolari ta 'kodiċi

792
00:35:02,380 --> 00:35:05,050
mingħajr il-ħrit programm
permezz ta 'dan u l-irfinar kompletament.

793
00:35:05,050 --> 00:35:08,510
Allura breakpoints se jippermettilna naslu biex
tinkiser u nieqaf f'ċertu punt.

794
00:35:08,510 --> 00:35:12,990
>> Sejħa munzell huwa mod fancy ta
qal liema funzjonijiet huma bħalissa

795
00:35:12,990 --> 00:35:14,140
qed jissejjaħ fil-mument.

796
00:35:14,140 --> 00:35:15,370
Main huwa dejjem jissejjaħ ewwel.

797
00:35:15,370 --> 00:35:17,230
Imma jekk Main sejħiet
funzjoni msejħa Swap,

798
00:35:17,230 --> 00:35:20,470
aħna qed attwalment għaddejjin biex tara dan
torri ta 'funzjonijiet li jkunu ġew

799
00:35:20,470 --> 00:35:22,400
jissejħu f'ordni kronoloġika reverse.

800
00:35:22,400 --> 00:35:23,310
Mela ejja ara dak.

801
00:35:23,310 --> 00:35:24,327
>> Jien ser zoom out.

802
00:35:24,327 --> 00:35:25,660
Jien se jmorru lura għall-kodiċi tiegħi.

803
00:35:25,660 --> 00:35:27,540
U biss għaliex nixtieq
li jkun pedantic hawn,

804
00:35:27,540 --> 00:35:31,100
Jien ser jimxi 'l quddiem u kklikkja
biss għall-xellug tal-linja ħamsa.

805
00:35:31,100 --> 00:35:32,830
U li toħloq tikka ħamra.

806
00:35:32,830 --> 00:35:36,200
U avviż fuq il-lemin
li l-debugger jaf, ħej,

807
00:35:36,200 --> 00:35:41,020
I biss qal breakpoint fil
linja noswap.c ħames, speċifikament

808
00:35:41,020 --> 00:35:42,480
fil din il-linja tal-kodiċi.

809
00:35:42,480 --> 00:35:45,090
Allura l-debugger jaf li I
talbu li l-ħin li jmiss

810
00:35:45,090 --> 00:35:48,530
I run tiegħi program pause
eżekuzzjoni hemm aktar milli biss

811
00:35:48,530 --> 00:35:50,390
jmexxu l-ħaġa sħiħa super fast.

812
00:35:50,390 --> 00:35:53,889
>> Allura issa jien ser ikklikkja l-debug
buttuna fil-quċċata nett tal-IDE

813
00:35:53,889 --> 00:35:55,430
u li għaddej biex jagħmlu dan li ġej.

814
00:35:55,430 --> 00:36:00,680
Huwa ser tiftaħ inizjalment kemmxejn
scary tieni terminal tfittex window--

815
00:36:00,680 --> 00:36:02,679
debugging bogħod mill
ospitanti tali u such--

816
00:36:02,679 --> 00:36:04,970
u aħna ser terga 'lura għal dak
dak kollu li jfisser qabel twil.

817
00:36:04,970 --> 00:36:09,020
Imma x'inhu importanti għal issa
huwa li dan dot aħmar ntlaqtet,

818
00:36:09,020 --> 00:36:11,735
l debugger ikun deliberatament
waqfa qasira execution--

819
00:36:11,735 --> 00:36:15,560
mhux fuq dik il-linja per se imma fuq l-ewwel
linja ta 'kodiċi attwali f'dik il-funzjoni.

820
00:36:15,560 --> 00:36:18,040
U hu għalhekk line seba hija
issa enfasizzati bl-isfar.

821
00:36:18,040 --> 00:36:20,550
>> U issa ejja tagħti ħarsa
fuq in-naħa tal-lemin.

822
00:36:20,550 --> 00:36:27,300
Jidher qisu, awtomatikament,
nicely biżżejjed, x ikollu liema valur?

823
00:36:27,300 --> 00:36:27,860
0.

824
00:36:27,860 --> 00:36:29,750
U y għandu liema valur?

825
00:36:29,750 --> 00:36:30,410
Zero.

826
00:36:30,410 --> 00:36:35,540
U li jkun mistenni fis-sens
li x u y-- li line-- isfar għandu

827
00:36:35,540 --> 00:36:36,770
mhux esegwiti s'issa.

828
00:36:36,770 --> 00:36:38,510
Allura x m'għandhomx ikollhom l-valur 1.

829
00:36:38,510 --> 00:36:41,470
Jista 'jkollhom kwalunkwe valur ieħor,
valur żibel hekk imsejħa.

830
00:36:41,470 --> 00:36:44,320
U aħna ltqajna xxurtjati f'dak li huwa
żero f'dan il-punt, essenzjalment.

831
00:36:44,320 --> 00:36:46,400
>> Allura issa hemm biss ftit
buttuni għandna bżonn kura

832
00:36:46,400 --> 00:36:48,100
dwar meta debugging b'dan il-mod.

833
00:36:48,100 --> 00:36:49,970
Avviż hawnhekk, għandna buttuna Play.

834
00:36:49,970 --> 00:36:51,877
U jekk aħna play jew jolqtu
jerġa, li jinsab biss

835
00:36:51,877 --> 00:36:53,710
ser tgħaddi minn ġos
il-bqija tal-programm

836
00:36:53,710 --> 00:36:55,300
jew sakemm hits breakpoint ieħor.

837
00:36:55,300 --> 00:36:56,910
Imma stajt ma jistabbilixxi l-ebda oħra
breakpoints dan huwa biss

838
00:36:56,910 --> 00:36:58,118
ser jgħaddi mill-aħħar.

839
00:36:58,118 --> 00:37:00,280
Dak it-tip ta 'telfiet l
iskop ta 'poking madwar.

840
00:37:00,280 --> 00:37:03,290
>> Allura minflok, I care about
dawn ikoni fuq il-lemin.

841
00:37:03,290 --> 00:37:05,360
U jekk I imbagħad jerġgħu jsiru fuq
minnhom, kif inti għandek wisq,

842
00:37:05,360 --> 00:37:07,450
tkun taf tara ftit tips għodda tips--.

843
00:37:07,450 --> 00:37:09,020
Dan huwa wieħed pass fuq.

844
00:37:09,020 --> 00:37:11,290
Issa dan ma jfissirx skip
il-linja tal-kodiċi ta 'wara.

845
00:37:11,290 --> 00:37:14,840
Li sempliċiment ifisser esegwit u
jimxu għall-ieħor, jimxu għall-ieħor,

846
00:37:14,840 --> 00:37:15,580
jimxu għall-ieħor.

847
00:37:15,580 --> 00:37:17,610
Fi kliem ieħor, permezz
li buttuna, jista I walk

848
00:37:17,610 --> 00:37:20,390
permezz my pass kodiċi wieħed kull darba.

849
00:37:20,390 --> 00:37:21,914
Linja b'linja, litteralment.

850
00:37:21,914 --> 00:37:23,830
Issa, id-dritt ta
li, hemm ieħor

851
00:37:23,830 --> 00:37:25,163
li aħna ser tara fi ftit mument.

852
00:37:25,163 --> 00:37:27,820
Dan huwa l-hekk imsejħa
Pass Into ikona li l-

853
00:37:27,820 --> 00:37:30,300
ser ippermettuli adsa
fil-funzjoni ieħor.

854
00:37:30,300 --> 00:37:31,800
Imma ejja naraw dan fi ftit mument.

855
00:37:31,800 --> 00:37:33,280
Hekk jien ser ikklikkja pass fuq.

856
00:37:33,280 --> 00:37:35,820
U issa avviż, kif I ikklikkja
din il-buttuna fil kantuniera,

857
00:37:35,820 --> 00:37:41,260
żżomm għajnejk bejn wieħed u ieħor taħt Lokali
Varjabbli u tara x'jiġri lill x.

858
00:37:41,260 --> 00:37:44,115
x issa huwa 1 minħabba l-
linja isfar issa esegwita

859
00:37:44,115 --> 00:37:45,840
u konna ċċaqalqu sal-linja 8.

860
00:37:45,840 --> 00:37:49,840
U fi ftit mument y
għandhom nisperaw isiru 2.

861
00:37:49,840 --> 00:37:52,330
>> Issa, xejn li interessanti
jiġri għal bit.

862
00:37:52,330 --> 00:37:53,390
Dan kollu huwa huwa printf.

863
00:37:53,390 --> 00:37:58,010
U avviż, fl terminal sekondarja tiegħi
tieqa, nara l-output ta 'def print.

864
00:37:58,010 --> 00:38:01,080
U issa I għandhom jagħmlu
deċiżjoni dwar l-programmer.

865
00:38:01,080 --> 00:38:04,360
I tista 'pass fuq din il-linja ta'
kodiċi, eżekuzzjoni iżda mhux

866
00:38:04,360 --> 00:38:06,220
jkollna kurjużi dwar x'hemm ġewwa.

867
00:38:06,220 --> 00:38:11,130
Jew I jistgħu attwalment pass lejn it
u jmorru ġewwa ta 'Swap innifsu.

868
00:38:11,130 --> 00:38:12,340
Mela ejja jagħmlu l-aħħar.

869
00:38:12,340 --> 00:38:15,550
>> Let me imorru quddiem u kklikkja
mhux Pass Over iżda Pass Into.

870
00:38:15,550 --> 00:38:17,300
Avviż, kollha f'daqqa
il-bidliet tieqa

871
00:38:17,300 --> 00:38:19,330
li tenfasizza l-ewwel
linja tal-kodiċi fil-Swap.

872
00:38:19,330 --> 00:38:20,710
C'est linja 21.

873
00:38:20,710 --> 00:38:25,220
U issa, liema tip ta 'funky hija li,
jekk inti tħares fuq hawn, kif mistenni,

874
00:38:25,220 --> 00:38:29,720
comma b hija l-1 u 2, rispettivament.

875
00:38:29,720 --> 00:38:33,840
Għaliex hija temperatura 32767?

876
00:38:33,840 --> 00:38:36,560
Waqt li jfakkar li temperatura, simili ħafna
l-tazza vojta mument ilu,

877
00:38:36,560 --> 00:38:38,980
hija dikjarata hawn fuq il-linja 21.

878
00:38:38,980 --> 00:38:43,390
Għaliex 32,000- I mean, għaliex hija
hija biss xi valur stramb?

879
00:38:43,390 --> 00:38:43,890
Yeah?

880
00:38:43,890 --> 00:38:45,190
>> UDJENZA: Mhuwiex initialized.

881
00:38:45,190 --> 00:38:46,940
>> DAVID J. Malan: Huwa
ma ġewx initialized.

882
00:38:46,940 --> 00:38:49,370
Allura kompjuter tagħna dejjem
memorja fiżika.

883
00:38:49,370 --> 00:38:50,544
Hija dejjem għandha RAM fiżiku.

884
00:38:50,544 --> 00:38:52,710
U dejjem hemm żero ta
u wieħed fil hemm, id-dritt?

885
00:38:52,710 --> 00:38:54,626
Għaliex aħna qed tuża tagħna
kompjuter il-ġurnata kollha,

886
00:38:54,626 --> 00:38:57,210
inti qed tuża l-IDE CS50
jew l-servers kollha jum twil.

887
00:38:57,210 --> 00:39:01,159
Allura li RAM jew għandha xi żerijiet jew
xi s membru jew iktar żerijiet u dawk.

888
00:39:01,159 --> 00:39:02,950
Ma jimpurtax jekk jew
Ma inti qed jużawhom.

889
00:39:02,950 --> 00:39:05,270
Inti ma tistax sempliċiment għandek vojt
spazji fejn inti tixtieq bits.

890
00:39:05,270 --> 00:39:06,850
Huma qed kemm żerijiet u dawk.

891
00:39:06,850 --> 00:39:09,610
>> Għalhekk jirriżulta li temperatura, minħabba
konna ma initialized encore,

892
00:39:09,610 --> 00:39:14,580
għandna dawk 32 bits iżda li ħadthom mhux
ġew initialized għal kwalunkwe valuri magħrufa.

893
00:39:14,580 --> 00:39:18,110
Allura kull ma kienu l-aktar
użat reċentement for-- dawk 32 bits--

894
00:39:18,110 --> 00:39:23,000
aħna qed biss tara l-artifacts ta 'xi
użu preċedenti ta 'dawk partikolari 32

895
00:39:23,000 --> 00:39:23,500
bits.

896
00:39:23,500 --> 00:39:27,780
Hekk kif I ikklikkja pass fuq għalkemm,
Phew, temperatura hija se tikseb l-valur 1.

897
00:39:27,780 --> 00:39:31,600
U jekk jien tagħmel dan mill-ġdid, a huwa
se tkun minħabba l-valur 2

898
00:39:31,600 --> 00:39:33,830
u mbagħad b se
jingħataw il-valur 1.

899
00:39:33,830 --> 00:39:36,390
>> U hekk x'hemm sbieħ issa fil
dan il-punt fl-istorja

900
00:39:36,390 --> 00:39:39,750
huwa li l-debugger hija
juru lili, super bil-mod

901
00:39:39,750 --> 00:39:42,640
fil-pass tiegħi stess, liema
l-istat ta 'Swap huwa.

902
00:39:42,640 --> 00:39:47,490
Iżda avviż fil-quċċata hawn, avviż
li l-munzell sejħa attwalment

903
00:39:47,490 --> 00:39:49,180
għandha żewġ saffi lilha.

904
00:39:49,180 --> 00:39:53,240
Issa l-wieħed li enfasizzati bħala
Swap, jekk I ikklikkja fuq Main minflok,

905
00:39:53,240 --> 00:39:57,100
avviż kif il-varjabbli lokali bidla
minħabba li l-iżviluppatur jista ħops biss

906
00:39:57,100 --> 00:39:59,740
madwar u jmorru fi kwalunkwe ambitu differenti.

907
00:39:59,740 --> 00:40:04,070
Allura anke jekk aħna qed tagħmel dan kollu
xogħol u iskambji korrett u b,

908
00:40:04,070 --> 00:40:09,080
jekk immur quddiem u lura bejn Swap
fejn a hija 2 u b hija l-1 u Main,

909
00:40:09,080 --> 00:40:11,851
tkun Main ġie affettwat xejn?

910
00:40:11,851 --> 00:40:12,350
No

911
00:40:12,350 --> 00:40:13,930
Allura x'inhu l-takeaway hawn?

912
00:40:13,930 --> 00:40:18,200
Ukoll, jirriżulta li kull ħin
inti sejħa funzjoni bħal Swap,

913
00:40:18,200 --> 00:40:21,600
u inti tgħaddi l-argumenti it, dak
int tgħaddi għall-funzjoni Swap

914
00:40:21,600 --> 00:40:24,730
f'dan il-każ hija kopja
ta 'dawn l-argumenti.

915
00:40:24,730 --> 00:40:28,620
Mela jekk x uy huma kull rispettivament
32 bits, dak Swap huwa jkollna

916
00:40:28,620 --> 00:40:30,760
huwa lokali żewġ ġdida
varjabbli, jew argumenti,

917
00:40:30,760 --> 00:40:34,380
jissejjaħ u b-- iżda dawk huma arbitrarji
names-- iżda l-mudell ta 'żerijiet

918
00:40:34,380 --> 00:40:39,520
u dawk ġewwa ta aub huma
ħejjew biex tkun identika għall xuy

919
00:40:39,520 --> 00:40:42,610
iżda mhumiex l-
istess ħaġa bħat xuy.

920
00:40:42,610 --> 00:40:46,880
>> Huwa bħallikieku Main għandha fuq biċċa tagħha ta
karta in-numru 1 u 2 għall xuy,

921
00:40:46,880 --> 00:40:49,260
u mbagħad meta idejn li
biċċa karta li tpartit,

922
00:40:49,260 --> 00:40:51,970
Swap malajr ħafna gets
pinna tiegħu stess, jikteb isfel

923
00:40:51,970 --> 00:40:56,240
1 u 2 fuq folja tal-karta tagħha stess,
idejn lura l xy oriġinali Main

924
00:40:56,240 --> 00:40:58,790
u mbagħad ma tagħha stess
ħaġa ma aub.

925
00:40:58,790 --> 00:41:01,940
U issa dan huwa super importanti għaliex
dan għandu implikazzjonijiet nontrivial

926
00:41:01,940 --> 00:41:06,260
għall-fatt kitba kodiċi korrett
għaliex jidher ma nistgħux tpartit

927
00:41:06,260 --> 00:41:07,500
żewġ varjabbli.

928
00:41:07,500 --> 00:41:09,150
>> Ktibtu funzjoni Swap korretta.

929
00:41:09,150 --> 00:41:12,770
Imxejna implimentati bl Lauren bħala
funzjoni tpartit korretta fir-realtà,

930
00:41:12,770 --> 00:41:16,700
imma apparentement ebda wieħed li
kwistjonijiet jekk inti ma tistax attwalment

931
00:41:16,700 --> 00:41:19,530
tpartit żewġ valuri permanenti.

932
00:41:19,530 --> 00:41:21,970
Allura għandna bżonn mod ieħor
li fil-fatt tikseb fuq dan,

933
00:41:21,970 --> 00:41:24,472
u għandna bżonn biex ikunu jistgħu
attwalment issolvi din il-problema.

934
00:41:24,472 --> 00:41:27,180
U jirriżulta out-- u aħna ser jiġu
lura għall din l-istampa partikolari

935
00:41:27,180 --> 00:41:30,500
qabel long-- dan huwa mod wieħed li
inti tista 'tiġbed memorja tal-kompjuter tiegħek.

936
00:41:30,500 --> 00:41:31,460
Huwa biss rettangolu.

937
00:41:31,460 --> 00:41:32,960
Inti tista 'tiġbed xi
numru ta 'modi iżda huwa

938
00:41:32,960 --> 00:41:35,740
konvenjenti biex tiġbed bħala
rettangolu għar-raġuni li ġejja.

939
00:41:35,740 --> 00:41:40,040
>> Aħna qed tmur biex tibda llum u lil hinn
jitkellem dwar l-hekk imsejħa munzell.

940
00:41:40,040 --> 00:41:43,870
U l-munzell huwa biss blokki
ta RAM-- blokki ta 'memory--

941
00:41:43,870 --> 00:41:47,100
li l-funzjonijiet jkollhom aċċess
li meta jkunu qed jissejjaħ.

942
00:41:47,100 --> 00:41:49,800
U għalhekk jirriżulta li fl
-qiegħ nett ta 'dan munzell

943
00:41:49,800 --> 00:41:53,590
huwa fejn kollha ta 'varjabbli lokali ewlenin tal
u org C u V org u dak kollu li Jittieħed

944
00:41:53,590 --> 00:41:56,950
se jmorru awtomatikament. U jekk Main
jitlob xi funzjoni oħra bħal Swap,

945
00:41:56,950 --> 00:42:00,330
ukoll, Swap hija se tikseb ieħor
saff ta 'memorja up hawn fuq.

946
00:42:00,330 --> 00:42:04,490
>> U hekk biss biex jagħtuk sommarju ta 'malajr
stampa ta 'dan, jekk immur fuq here--

947
00:42:04,490 --> 00:42:09,450
u let me mera dan fuq il-
overhead kif well-- dak li verament jien,

948
00:42:09,450 --> 00:42:12,100
jekk aħna kura biss dwar il-
qiegħ ta 'din l-istampa għal issa,

949
00:42:12,100 --> 00:42:15,070
hija li meta I run program
u Main gets imsejħa,

950
00:42:15,070 --> 00:42:18,330
Main jingħata blokki ta '
RAM fil-kompjuter tiegħi li hija

951
00:42:18,330 --> 00:42:20,060
fil-qiegħ ta 'din l-hekk imsejħa munzell.

952
00:42:20,060 --> 00:42:22,143
U jien ser tiġbed
deliberatament bħala kwadru.

953
00:42:22,143 --> 00:42:24,540
Allura huwa simili 32 bits jew erba bytes.

954
00:42:24,540 --> 00:42:28,790
U jekk din il-funzjoni prinċipali għandha
varjabbli imsejħa x b'valur ta 1

955
00:42:28,790 --> 00:42:32,626
u għandu varjabbli imsejjaħ
y mal-valur ta '2, li l-

956
00:42:32,626 --> 00:42:35,750
bħal li jieħdu din sliver ta 'memorja li
Main tkun ingħatat mill-makkinarju tal-

957
00:42:35,750 --> 00:42:38,850
sistema u jaqsmuh, b'tali mod li
l-ewwel varjabbli lokali tmur hawn,

958
00:42:38,850 --> 00:42:40,930
it-tieni wieħed imur hawn, u li hu.

959
00:42:40,930 --> 00:42:45,590
>> Meta Main jitlob Swap, Swap
gets porzjon tagħha stess ta 'memorja

960
00:42:45,590 --> 00:42:48,280
li aħna ser jiġbed bħal dan
mis-sistema operattiva,

961
00:42:48,280 --> 00:42:50,820
u li għaddej biex ikollhom tiegħu
varjabbli lokali stess ibbażati

962
00:42:50,820 --> 00:42:53,825
dwar l-implimentazzjoni tagħna aktar kmieni
bil varjabbli lokali ta '

963
00:42:53,825 --> 00:42:58,010
u b li inizjalment
jiksbu l-valuri 1 u 2.

964
00:42:58,010 --> 00:43:00,450
Iżda mbagħad, hekk kif
il-kodiċi Swap tesegwixxi,

965
00:43:00,450 --> 00:43:03,760
u Lauren attwalment swaps l
ĠU u ħalib, dak li qed jiġri?

966
00:43:03,760 --> 00:43:09,030
Ukoll, dan 2 qed isir 1, dan
1 qed issir 2, u, mill-mod,

967
00:43:09,030 --> 00:43:13,360
hemm varjabbli temperatura li l-jiġu
użati dak iż-żmien kollu li eventwalment

968
00:43:13,360 --> 00:43:14,470
tmur bogħod.

969
00:43:14,470 --> 00:43:16,720
Iżda dan ma jimpurtax
kemm ix-xogħol li tagħmel

970
00:43:16,720 --> 00:43:22,160
f'dan il-linja of-- f'dan l-ispazju memorja,
x uy huma kompletament mhux mittiefsa.

971
00:43:22,160 --> 00:43:26,320
>> Allura għandna bżonn xi mod kif tingħata
Swap u funzjonijiet bhalu

972
00:43:26,320 --> 00:43:32,640
aċċess sigriet, jekk inti se, biex
funzjonijiet like-- memorja bħal xuy.

973
00:43:32,640 --> 00:43:35,110
Mela ejja tagħti ħarsa lejn
eżempju li jgħin

974
00:43:35,110 --> 00:43:38,220
naraw eżattament dak kien
għaddej dan iż-żmien kollu.

975
00:43:38,220 --> 00:43:40,284
Jien ser jimxi 'l quddiem
u jiftħu Qabbel Zero.

976
00:43:40,284 --> 00:43:42,200
U jien ser tagħlaq
debugger tagħna, jien ser

977
00:43:42,200 --> 00:43:44,360
li tagħlaq dan scary tfittex messaġġ
l-ftit jgħid, stenna minuta,

978
00:43:44,360 --> 00:43:45,800
int fil-debugging nofs.

979
00:43:45,800 --> 00:43:48,383
Jien ser jaħbu dan tab hawn
biss li jmorru lura għall-sempliċità.

980
00:43:48,383 --> 00:43:50,160
Għalhekk tinkwetax jekk GDB jinqatel.

981
00:43:50,160 --> 00:43:53,910
Li biss ifisser li l-programm
ġew nieqaf, deliberatament f'dan il-każ,

982
00:43:53,910 --> 00:43:54,820
minni.

983
00:43:54,820 --> 00:43:57,700
>> U issa Qabbel Zero ma dan.

984
00:43:57,700 --> 00:44:00,110
Jien bl-użu CS50
librerija fl-I standard / O.

985
00:44:00,110 --> 00:44:04,319
Stajt ltqajna funzjoni ewlenija li l-ewwel
jgħid, jgħidu xi ħaġa, u gets string.

986
00:44:04,319 --> 00:44:06,110
Imbagħad jgħid mill-ġdid u
gets string ieħor.

987
00:44:06,110 --> 00:44:09,910
U Avviż li dawn iż-żewġ kordi
huma msejħa iu t, rispettivament.

988
00:44:09,910 --> 00:44:12,910
U issa dan il-programm, Qabbel
Żero, l-iskop tagħha fil-ħajja,

989
00:44:12,910 --> 00:44:15,470
huwa suppost li tell me,
ma I tip l-istess ħaġa?

990
00:44:15,470 --> 00:44:16,910
U hekk jien ser lura għal ġimgħa.

991
00:44:16,910 --> 00:44:19,950
Jien jużaw operatur ugwali tiegħi ugwali
li hija l-operatur kwalità.

992
00:44:19,950 --> 00:44:22,220
Mhux l-operatur assenjazzjoni,
l-operatur ugwaljanza.

993
00:44:22,220 --> 00:44:23,890
Jien biss jqabbel iu t.

994
00:44:23,890 --> 00:44:27,470
>> Mela ejja fil-fatt imorru quddiem u tagħmel dan.

995
00:44:27,470 --> 00:44:32,680
U jien ser jimxi 'l quddiem
u jagħmlu Qabbel Zero.

996
00:44:32,680 --> 00:44:35,110
Jien ser tagħmel ./comparezero.

997
00:44:35,110 --> 00:44:37,150
U jien se jmorru
quddiem u ngħid xi ħaġa

998
00:44:37,150 --> 00:44:43,450
simili, ejja jagħmlu mom fil lowercase
u kif madwar mom fil uppercase.

999
00:44:43,450 --> 00:44:45,034
U ovvjament I tip affarijiet differenti.

1000
00:44:45,034 --> 00:44:45,533
Kull dritt.

1001
00:44:45,533 --> 00:44:46,570
Dak li jkun mistenni.

1002
00:44:46,570 --> 00:44:47,640
>> Ejja run mill-ġdid.

1003
00:44:47,640 --> 00:44:49,740
Iż-żewġ ħinijiet do zghar, zghar.

1004
00:44:49,740 --> 00:44:51,490
Li tidher super identiċi lili.

1005
00:44:51,490 --> 00:44:52,930
Ikteb.

1006
00:44:52,930 --> 00:44:53,430
KOLLOX SEW.

1007
00:44:53,430 --> 00:44:55,804
Forsi huwa biss stramb għaliex
mhuwiex Predisposizzjoni grammatika tiegħi.

1008
00:44:55,804 --> 00:44:59,930
Mela ejja do a MOM kapital,
kapital MOM, identiċi.

1009
00:44:59,930 --> 00:45:01,490
Affarijiet differenti.

1010
00:45:01,490 --> 00:45:03,907
>> Allura għaliex huwa li?

1011
00:45:03,907 --> 00:45:06,240
Ukoll, dak li attwalment għaddejjin
fuq minn taħt il-barnuża hawn?

1012
00:45:06,240 --> 00:45:08,180
Mela ejja jmorru lura fuq
hawn għal ftit mument

1013
00:45:08,180 --> 00:45:10,910
u jikkunsidraw liema GetString
huwa fil-fatt jagħmlu.

1014
00:45:10,910 --> 00:45:13,385
Meta inti sejħa GetString,
li l-funzjoni aħna

1015
00:45:13,385 --> 00:45:16,510
nfusna kiteb u qualche gets
sekwenza ta 'karattri mill-utent.

1016
00:45:16,510 --> 00:45:20,280
U ejja nassumu li l-ewwel
darba I call GetString, li tagħti me

1017
00:45:20,280 --> 00:45:21,930
blokki ta 'memorja li tidher bħal dan.

1018
00:45:21,930 --> 00:45:26,990
U jekk I ittajpjat fil kollha lowercase
m-o-m-- u dak li jmur wara dan?

1019
00:45:26,990 --> 00:45:28,840
Just verifika sanità malajr.

1020
00:45:28,840 --> 00:45:29,780
>> Żero backslash.

1021
00:45:29,780 --> 00:45:30,510
Aħna nafu li.

1022
00:45:30,510 --> 00:45:32,784
U tfakkar li aħna lagħbu
madwar bl-isem Zamila tal

1023
00:45:32,784 --> 00:45:34,950
u mazz ta 'ismijiet oħra
meta Rob hawn kien qed ifittex

1024
00:45:34,950 --> 00:45:36,280
lejn dak li jiġri ġewwa tal-memorja.

1025
00:45:36,280 --> 00:45:37,780
Allura li l-istorja eżattament l-istess.

1026
00:45:37,780 --> 00:45:40,160
Dan huwa dak GetString
huwa jirritorna lili.

1027
00:45:40,160 --> 00:45:44,780
Issa, il-kodiċi tiegħi mument ilu maħżun
il-valur ritorn ta GetString

1028
00:45:44,780 --> 00:45:47,510
fil-varjabbli imsejħa s.

1029
00:45:47,510 --> 00:45:51,390
U mbagħad it-tieni darba I sejħitilha,
dan maħżuna dan fil-varjabbli imsejjaħ t.

1030
00:45:51,390 --> 00:45:55,070
>> Mela jekk jien jmorru fuq hawn, I bżonn
tiġbed dan variable-- lokali

1031
00:45:55,070 --> 00:45:59,610
u jien ġeneralment ser
jiġbed string kif just-- aħna ser

1032
00:45:59,610 --> 00:46:02,360
sejħa hija s-- bħala kwadru ftit hawn.

1033
00:46:02,360 --> 00:46:09,760
U issa, somehow-- kif ma mom
mur ġewwa ta 'dan il-varjabbli i?

1034
00:46:09,760 --> 00:46:12,010
Well, għandna bżonn immorru lura
li ewwel prinċipji hawn.

1035
00:46:12,010 --> 00:46:15,660
X'inhu GetString attwalment jirritornaw?

1036
00:46:15,660 --> 00:46:19,030
>> Għalhekk jirriżulta li M-O-M
backslash żero, u kull numru

1037
00:46:19,030 --> 00:46:22,364
ta 'spag oħra fil-memorja bħall
Zamila u Rob jew Andy jew xi oħrajn,

1038
00:46:22,364 --> 00:46:24,280
huma ta 'kors fil tagħna
RAM kompjuter jew memorja.

1039
00:46:24,280 --> 00:46:27,760
U RAM tiegħek għandu like-- għandek
GIG ta 'RAM, żewġ gigs ta' RAM,

1040
00:46:27,760 --> 00:46:30,860
jew biljun jew tnejn biljun bytes,
jew forsi saħansitra aktar dawn il-jiem.

1041
00:46:30,860 --> 00:46:34,070
Mela ejja nassumu, għal skopijiet tal-lum,
li ma jimpurtax kif aħna numru

1042
00:46:34,070 --> 00:46:36,640
minnhom, iżda nistgħu tagħti numru lil kull
ta 'dawk biljun jew tnejn biljun

1043
00:46:36,640 --> 00:46:37,880
jew erba 'biljun bytes.

1044
00:46:37,880 --> 00:46:42,240
>> U ejja biss jgħidu li b'mod arbitrarju
dan huwa l-ewwel gidma, it-tieni gidma,

1045
00:46:42,240 --> 00:46:43,380
tielet, ir-raba.

1046
00:46:43,380 --> 00:46:46,570
Jien deliberatament ma jużawx żero għall
lum, iżda aħna ser terga 'lura għal dan.

1047
00:46:46,570 --> 00:46:49,570
Allura fi kliem ieħor, jekk dan huwa l-
ewwel darba jien jużaw il-programm,

1048
00:46:49,570 --> 00:46:52,715
Jien biss jkollna xortik tajba u l-ewwel
gidma huwa fil waħda lokazzjoni imbagħad tnejn

1049
00:46:52,715 --> 00:46:53,590
imbagħad tlieta minn erba '.

1050
00:46:53,590 --> 00:46:57,430
U jekk I tinżamm tpinġija, numru Kaxxa
żewġ biljun ikun mod minn hawn.

1051
00:46:57,430 --> 00:47:02,200
>> Allura dak li taħseb, imbagħad,
GetString attwalment prospetti?

1052
00:47:02,200 --> 00:47:06,010
Mhuwiex jirritornaw backslash M-O-M
żero nnifisha għaliex li b'mod ċar

1053
00:47:06,010 --> 00:47:08,180
mhux se jaqbel fil-kaxxa li stajt mfassla.

1054
00:47:08,180 --> 00:47:11,210
Allura dak li inkella jista GetString attwalment
jirritorna kollha dawn il-ġimgħat?

1055
00:47:11,210 --> 00:47:14,410

1056
00:47:14,410 --> 00:47:16,820
It-tweġiba hija fuq il-
board hawn x'imkien.

1057
00:47:16,820 --> 00:47:20,390
Inti ma jistgħux jitwaħħlu backslash M-O-M żero,
hekk dak li jista 'jagħmel sens minflok?

1058
00:47:20,390 --> 00:47:23,424
Jekk kellek li tkun super għaqlija, it-tqegħid
fuq l-hekk imsejħa hat inġinerija,

1059
00:47:23,424 --> 00:47:24,340
dak li jista inti tirritorna?

1060
00:47:24,340 --> 00:47:27,340
X'inhu l-inqas ammont ta 'informazzjoni
inti tista 'ritorn li xorta

1061
00:47:27,340 --> 00:47:30,610
let issib M-O-M fil-memorja?

1062
00:47:30,610 --> 00:47:31,270
Yeah?

1063
00:47:31,270 --> 00:47:31,950
>> UDJENZA: One.

1064
00:47:31,950 --> 00:47:32,200
>> DAVID J. Malan: One.

1065
00:47:32,200 --> 00:47:33,021
U għaliex wieħed?

1066
00:47:33,021 --> 00:47:35,520
UDJENZA: Minħabba li se tell
inti fejn imorru [inaudible].

1067
00:47:35,520 --> 00:47:38,391

1068
00:47:38,391 --> 00:47:39,390
DAVID J. Malan: Eżattament.

1069
00:47:39,390 --> 00:47:44,300
I am biss ser jirritorna l-indirizz
tas-sekwenza li jien gotten.

1070
00:47:44,300 --> 00:47:46,570
L-indirizz f'dan
każ huwa post wieħed.

1071
00:47:46,570 --> 00:47:51,280
Allura dak li verament qed jiġi maħżun fil s--
u kull varjabbli string b'hekk far--

1072
00:47:51,280 --> 00:47:53,430
għadu kif ġie l-
indirizz ta 'dak string.

1073
00:47:53,430 --> 00:47:57,840
>> Sadanittant, jekk I call
GetString tieni darba u I

1074
00:47:57,840 --> 00:48:03,300
tip fil litteralment l-istess thing--
M-O-M ma lowercase-- M-O-M

1075
00:48:03,300 --> 00:48:06,200
u backslash ieħor żero,
u issa forsi l-programm tiegħi

1076
00:48:06,200 --> 00:48:09,820
ilu għaddej għal xi żmien hekk forsi din
huwa 10, dan huwa post 11, dan huwa 12,

1077
00:48:09,820 --> 00:48:10,700
dan huwa 13.

1078
00:48:10,700 --> 00:48:13,590
Il-kompjuters li jużaw xi oħra
memorja għal kwalunkwe raġuni.

1079
00:48:13,590 --> 00:48:18,172
Dak li issa tmur fit-tieni tiegħi
varjabbli f't programm tiegħi?

1080
00:48:18,172 --> 00:48:19,390
10.

1081
00:48:19,390 --> 00:48:20,050
Eżattament.

1082
00:48:20,050 --> 00:48:23,910
>> U hekk meta nħarsu lejn l-
kodiċi tas-sors ta 'dan il-programm

1083
00:48:23,910 --> 00:48:26,550
fejn jien sempliċiment jippruvaw
li jitqabblu ż-żewġ valuri,

1084
00:48:26,550 --> 00:48:32,180
huwa s ugwali daqs ta 't, x'hemm
ir-risposta tal-bniedem ovvja?

1085
00:48:32,180 --> 00:48:34,890
Biss l-ebda għax 1 mhuwiex ugwali għal 10.

1086
00:48:34,890 --> 00:48:36,861
U hekk hawnhekk tinsab l
opportunità għalina verament

1087
00:48:36,861 --> 00:48:39,610
li jmorru biss lura għall-, għal darb'oħra, l-ewwel
prinċipji u jaħsbu dwar, sew,

1088
00:48:39,610 --> 00:48:41,110
x'inhu għaddej taħt il-barnuża?

1089
00:48:41,110 --> 00:48:43,240
Imxejna ġiet jitkellem dwar
bits u bytes u l-memorja,

1090
00:48:43,240 --> 00:48:46,820
iżda huwa attwalment utli li wieħed jifhem
għaliex meta inti sejħa GetString,

1091
00:48:46,820 --> 00:48:50,280
anke jekk aħna jaħsbu li huwa
jirritornaw M-O-M jew string mom

1092
00:48:50,280 --> 00:48:53,120
jew Andy jew Zamila jew
bħalhom, teknikament

1093
00:48:53,120 --> 00:48:55,510
huwa biss jirritorna l-indirizz
ta 'dak blokki ta' memorja.

1094
00:48:55,510 --> 00:48:56,910
>> Imma dak li OK.

1095
00:48:56,910 --> 00:49:00,570
Minħabba kif inkun naf
fejn il-sekwenza jispiċċa?

1096
00:49:00,570 --> 00:49:03,840
Jekk jien biss minħabba l-bidu?

1097
00:49:03,840 --> 00:49:05,380
Ukoll, il-backslash żero, id-dritt?

1098
00:49:05,380 --> 00:49:08,800
Just fil-ħin lineari nista '
jistampa mal def print M-O-M.

1099
00:49:08,800 --> 00:49:11,820
U hekk kif nara backslash
żero, I do not care fejn bdejt,

1100
00:49:11,820 --> 00:49:14,950
I diġà jafu impliċitament
I fejn jeħtieġ biex tintemm.

1101
00:49:14,950 --> 00:49:18,700
>> U hekk illum jimmarka l-beginning-- u
let me tagħmel dan b'mod drammatiku għaliex aħna

1102
00:49:18,700 --> 00:49:21,800
għaddiet minn ħafna problemi li
tikseb dawn taħriġ wheels-- hawn

1103
00:49:21,800 --> 00:49:29,840
hekk illum ir-roti ta 'taħriġ jibdew
li ġejjin off u aħna jiżvelaw fi least--

1104
00:49:29,840 --> 00:49:31,373
>> [Applause]

1105
00:49:31,373 --> 00:49:33,220

1106
00:49:33,220 --> 00:49:36,160
>> Dan kien ukoll jiswa l-vjaġġ
ma 'Target dalgħodu, iva?

1107
00:49:36,160 --> 00:49:39,600
Allura now-- hemm, jirriżulta
out, l-ebda ħaġa bħal string.

1108
00:49:39,600 --> 00:49:41,140
String ma teżistix.

1109
00:49:41,140 --> 00:49:43,760
Huwa sinonimu li aħna kellna
ġewwa tal-librerija CS50.

1110
00:49:43,760 --> 00:49:48,660
Minn issa, aħna qed tmur biex tibda sejħa
iu t mhux kordi iżda istilel char.

1111
00:49:48,660 --> 00:49:51,180
U l-istilla char Aħna ser
tease apparti qabel fit-tul.

1112
00:49:51,180 --> 00:49:53,510
Iżda dan fi kliem ieħor,
li anke jekk aħna nkomplu

1113
00:49:53,510 --> 00:49:56,180
użu GetString għal issa,
teknikament I għandu

1114
00:49:56,180 --> 00:49:59,010
tkun tgħid star char u stilla char.

1115
00:49:59,010 --> 00:50:01,720
>> U jirriżulta liema dik star
se juri hija xi ħaġa

1116
00:50:01,720 --> 00:50:04,340
imsejħa pointer jew indirizz.

1117
00:50:04,340 --> 00:50:06,110
U fil-fatt, teaser
għall dak li jinsab quddiem

1118
00:50:06,110 --> 00:50:09,760
hija din 20 sekonda clip minn tagħna
ħabib Nick Parlante fil Stanford

1119
00:50:09,760 --> 00:50:12,927
li, pjuttost xi żmien ilu, iqattgħu
redikoli ammont ta 'żmien,

1120
00:50:12,927 --> 00:50:15,010
bħala l-aħjar I tista 'tgħid fil tiegħu
kċina jew kantina tiegħu,

1121
00:50:15,010 --> 00:50:17,140
jagħmlu claymation
introduzzjoni għad-dinja

1122
00:50:17,140 --> 00:50:20,010
karattru jismu
Binky li magħhom aħna se

1123
00:50:20,010 --> 00:50:22,010
jiġu introdotti ħin li jmiss biex pointers.

1124
00:50:22,010 --> 00:50:24,588
Allura hawnhekk hija preview tal dak li ġejjin.

1125
00:50:24,588 --> 00:50:26,370
>> [Daqq video]

1126
00:50:26,370 --> 00:50:27,510
>> -Hey, Binky.

1127
00:50:27,510 --> 00:50:28,260
Wake up.

1128
00:50:28,260 --> 00:50:30,672
Wasal iż-żmien għall-gost pointer.

1129
00:50:30,672 --> 00:50:31,616
>> -Dak X'inhu?

1130
00:50:31,616 --> 00:50:33,032
Tgħallem dwar pointers?

1131
00:50:33,032 --> 00:50:34,450
Oh, Goody.

1132
00:50:34,450 --> 00:50:35,431
>> [END Daqq]

1133
00:50:35,431 --> 00:50:38,055
DAVID J. Malan: U fuq din in-nota,
aħna se tara int nhar l-Erbgħa.

1134
00:50:38,055 --> 00:50:47,590

1135
00:50:47,590 --> 00:50:48,090
Kull dritt.

1136
00:50:48,090 --> 00:50:48,740
Min hu żfin?

1137
00:50:48,740 --> 00:50:49,240
Come fuq.

1138
00:50:49,240 --> 00:50:50,330
Min hu żfin?

1139
00:50:50,330 --> 00:50:51,820
Inti trid lili biex tikseb dan beda?

1140
00:50:51,820 --> 00:50:53,770
I ser tingħata dan beda.

1141
00:50:53,770 --> 00:50:54,270
Woooo!

1142
00:50:54,270 --> 00:51:04,070

1143
00:51:04,070 --> 00:51:07,580
>> Lauren: fancy Sweet Mosè.