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>> [Daqq tal-mużika]

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DAVID Malan: Hello, kulħadd.

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Dan huwa supersection CS50 s.

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Taqsimiet assenjati mhux se
jibdew għall ieħor ġimgħa.

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U hekk illum, jien hawn with--

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>> MARIA: Maria.

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DAVID Malan: --to attwalment
tagħti ħarsa lejn problema

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sett wieħed, il-kors tal
ewwel ġimgħat ta 'materjal,

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nikseb inti orjentati ma IDE CS50, daqsxejn
ta 'Linux, is-sistema operattiva li l-

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taħdem fuq IDE, kif ukoll
ħarsa lejn uħud mill-tranżizzjoni

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minn Scratch sa C ewlieni
sa problema sett wieħed.

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>> Allura mingħajr aktar dewmien,
fi problema sett wieħed,

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int ser tkun
introdotti biex CS50 IDE, li

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hija din il-programmazzjoni fuq l-internet
ambjent li nużaw sabiex

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jiktbu programmi.

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Huwa kien mfassla biex tħares ħafna
reminixxenti ta 'kompjuter tipiku

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sistema jmexxu operattiva
sistema, imsejħa Linux.

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Imma hija fil-sħaba hekk imsejħa,
li jfisser kulħadd fil-klassi

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jista 'attwalment ikollhom tiegħu jew tagħha
kont proprju u l-użu, kif ukoll.

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>> Allura ħafna minnkom probabbilment qatt ma użaw
ambjent Linux qabel jew forsi

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anki f'ambjent kmand tal-linja.

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U linja ta 'kmand
ambjent hija differenti.

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Dan kollu testwali.

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Huwa l-ordnijiet kollha keyboard.

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U huwa no mousing, l-ebda ikoni,
ebda twieqi djalogu, l-ebda menus.

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Huwa purament test.

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Allura fl-ewwel, it-tip
ta iħoss bħal pass

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lura fejn jidħol sofistikazzjoni.

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Iżda dan jispiċċa jkun ħafna
aktar qawwija, ċertament,

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għal xjenzat kompjuter, finalment.

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>> Mela ejja tagħti ħarsa.

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Here I am fil CS50.io, permezz li
inti tista 'log fis IDE CS50.

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U ħafna bħal fil Scratch, hemm
tliet oqsma primarji għal dan l-iskrin.

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Allura fuq in-naħa tax-xellug, għandna
x'se jkun il-fajl browser.

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U hemm this folder fuq
top, li huwa dritt issa vojta

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peress I ħassar kollha tiegħi
fajls qabel supersection.

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U li fejn aħna ser
ħlief fajls Ċ li aħna jiktbu.

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Fil-kantuniera, għandna post fejn
kollha tal-kodiċi tagħna għaddej biex tikseb bil-miktub.

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U fil-fatt, jekk I ikklikkja din plus, dan
se let me jagħżlu File Ġdid.

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U hawn I tista 'tibda tikteb kodiċi C jew,
tassew, kwalunkwe numru ta 'lingwi oħra.

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>> U mbagħad fil-qiegħ fejn
jgħid jharvard @ ide50-- u tiegħek se

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ngħid xi ħaġa ftit
different-- dak li kien dan jissejjaħ?

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Tieqa Terminal.

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Yeah.

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Allura l-tieqa terminal huwa
l-hekk imsejħa linja tal-kmand

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interface permezz tiegħu tista 'jinteraġixxu
mas-sistema operattiva sottostanti.

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U għal issa, aħna qed tmur biex
jagħmlu ftit li xejn użu ta 'this--

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biss biex jikkompilaw, li tħares lejn
messaġġi ta 'żball li naraw,

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u biex imexxu programmi tagħna.

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Iżda fl-aħħar, aħna qed tmur
li tagħmel dan ħafna aktar, kif ukoll.

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00:02:04,680 --> 00:02:07,490
U inti tista 'anki jinstallaw softwer
u jamministra workspace tiegħek

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fi ħdan CS50 IDE, kif ukoll.

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Iżda aktar fuq li xi żmien ieħor.

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>> Mela ejja imorru quddiem u jiktbu
programm sempliċi ħafna biss

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li jmorru permezz ta 'warm-up tal
hello.c, li hija forsi

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il-programm sempliċi nistgħu jiktbu.

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Stajt diġà fetħet tab ġdid.

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Jien ser jimxi 'l quddiem u
jgħidu jinkludu io.h. standard

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Imbagħad int prinċipali (vojt).

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U mbagħad printf ("hello, dinja"
backslash n, kwotazzjoni qrib,

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parentesi qrib, u virgola.

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>> Kull dritt.

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Allura issa avviż tieqa tiegħi huwa untitled.

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Hekk jien malajr ħafna li jmorru
li jitla 'sa File, Save.

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U huwa importanti li
I call dan ma "bonjour."

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Allura żball komuni ħafna,
speċjalment fl problema sett wieħed,

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huwa li aċċidentalment biss sejħa tiegħek
programm "ilma" jew "greedy" jew "Mario"

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jew "kreditu" jew simili.

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Imma inti fil-fatt tixtieq li tagħmel
ċert li jkollok l-estensjoni fajl

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għax dan huwa l-uniku mod li
l kompilatur u wkoll l-editur kodiċi

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jaf li int
fatt bil-miktub kodiċi C.

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So let me go quddiem u kklikkja Save.

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>> U issa, wisq, dak CS50 IDE
għamel għalina huwa huwa wkoll

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sintassi enfasizzat kollox.

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Allura huwa magħmul kollox ikkulurita ħafna.

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U l-għan sħiħ ta '
li mhix funzjonali.

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Huwa biss tiġbed għajnejn tiegħi għall-
biċċiet minn perspettiva kunċettwali differenti

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ta 'dan il-programm.

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Mela ejja imorru quddiem u jiġbor dan it.

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U nista 'jiġbor dan
fi ftit ta 'modi.

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U fil-ġimgħa, il-
mod qodma l-iskola għamilna

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kien litteralment fil-
kmand line-- "hello.c clang."

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U mbagħad I hit Ikteb.

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U xejn jidher li jiġri
fit-tieqa terminal.

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Imma dak li għamlet bidla fil-IDE?

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Fejn, għal darb'oħra, IDE ifisser biss
Ambjent Iżvilupp Integrat.

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Huwa mod fancy ta 'tgħid
dan l-iżvilupp integrat

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ambjent għall-iżvilupp tas-software.

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Allura dak li għamlet bidla fil-UI?

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What did tinnota
li l differenti, Maria?

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>> MARIA: I ndunat xi ħaġa
taħt il-IDE50 folder up here.

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>> DAVID Malan: Yeah.

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Allura up here, mhux biss
do għandna "hello.c."

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Għandna wkoll "a.out," li huwa
tip ta 'isem mutu għal programm.

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Iżda fil-fatt, huwa l-isem default għal
programm meta inti biss jikkompilaw kodiċi tiegħek

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u ma jgħidux il-kumpilatur
dak fajl lill output.

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Mela jekk jien tixtieq li run dan, I
trid tghid l compiler--

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jew pjuttost, I bżonn
tgħid il-workspace li I

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tixtieq li tmexxi l-programm imsejjaħ "a.out."

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Ikteb.

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U hemm "i hello,
dinja. "issa l-" ./ ".

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huwa attwalment importanti.

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Anki jekk normalment aħna biss
jiktbu l-ismijiet ta kmandi,

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meta huwa program inti stajt
miktub, inti tixtieq li jgħidu "./"

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minħabba li espliċitament tg Linux
li inti tixtieq li tmexxi programm imsejjaħ

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"a.out" li fil dan, fejn dot
ifisser dan id-direttorju li jien bħalissa

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in, li jiġri li jkun
imsejħa workspace, "a.out.

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Għaliex jekk I biss qal "a.out," Daħħal,
Jien ser tikseb "a.out kmand ma

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misjuba "għaliex l-computer--
minħabba I ivvintat "a.out;"

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din ma kinitx taqa mal-computer--
ma taf fejn tfittex għal dan,

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anki jekk huwa dritt
taħt imnieħer tiegħi, biex ngħidu hekk.

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KOLLOX SEW.

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Allura nistgħu tbiddel dan li
jkun "clang -o bonjour hello.c."

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U jekk I hit Ikteb, dak il-programm
huwa dan se output għalija?

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X'inhu l-isem tal-fajl?

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Yeah, fid-dahar.

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Dak id-dritt. "Bongu."

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Allura "bonjour" se tkun
l-isem tal-programm

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għaliex aħna ħadthom użati hekk imsejħa
argument linja tal-kmand, li huwa biss

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mod ta 'tibdil tal-imġiba ta
l kompilatur li attwalment output

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isem speċifiku fajl.

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U fil-fatt, jekk I zoom
out u jfittxu up hawn,

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issa għandi mhux biss "a.out" u
"hello.c" iżda wkoll "hello," kif ukoll.

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Allura issa I tista 'tagħmel "./hello," Ikteb.

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U hemm "hello, dinja."

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Iżda lastly-- u dan
issa se jkun il-konvenzjoni

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nużaw matul il-
semestru, typically--

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huwa inti tista 'wkoll biss jgħidu "jagħmlu bonjour."

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U fil-fatt, huwa qal huwa sa
sal-lum minħabba li diġà teżisti.

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Let me imorru quddiem u neħħi, ma
il-kmand rm, kemm "a.out" -

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u jgħidu "tneħħi a.out fajl regolari?"

135
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Li sempliċiment ifisser, huma inti
żgur inti tixtieq li iħassarha?

136
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Jien se ngħid iva.

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U allura jien ser ineħħi
"Hello" iżda mhux "hello.c."

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Jien se ngħid "iva" espliċitament,
imma "y" hija biżżejjed, kif ukoll.

139
00:05:49,920 --> 00:05:52,140
>> U issa avviż jekk I
tip ls-- li, irtirar,

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00:05:52,140 --> 00:05:55,540
ifisser list-- it listi kollha
tal-fajls folder tiegħi.

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U fil-fatt, jekk I zoom
out u ħarsa lejn quċċata xellug,

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jikkonferma li x'hemm
fil this folder, anke

143
00:05:59,730 --> 00:06:04,990
għalkemm huwa ttikkettjat bħala IDE50 up here
u mhux workspace, huwa biss "hello.c."

144
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Allura issa l hawn, jekk I
do "jagħmlu hello," Daħħal,

145
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issa nara kmand ħafna itwal iżda
kmand aktar sofistikata li għaddej

146
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li tkun utli fil-ġimgħat li ġejjin.

147
00:06:13,940 --> 00:06:16,720
U issa I tista 'tgħid "./hello."

148
00:06:16,720 --> 00:06:19,257
>> Mela ejja tagħti tour quick
xi Linux oħra jikkmanda.

149
00:06:19,257 --> 00:06:21,840
Allura għaliex ma nieħdu pass
lura u fil-fatt tħares lejn Ċ aktar

150
00:06:21,840 --> 00:06:25,020
ġeneralment, it-transizzjoni minn Scratch
sa C, u mbagħad jikkonkludi ma 'ħarsa

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fl-ewwel problema
stabbiliti fil C. Kull dritt.

152
00:06:27,305 --> 00:06:30,430
Hekk jien ser jimxi 'l quddiem u biss nadif
up workspace tiegħi ma Control L eżatt

153
00:06:30,430 --> 00:06:31,429
biex iżommu l-iskrin pulita.

154
00:06:31,429 --> 00:06:33,520
Iżda dan ma jkollux funzjonali
impatt mod ieħor.

155
00:06:33,520 --> 00:06:35,820
>> Recall li aħna stajt tidher
kmandi ftit issa.

156
00:06:35,820 --> 00:06:39,900
Allura aħna stajt tidher clang, li ġeneralment inti
mhux se jkollhom biex tesegwixxi manwalment aktar.

157
00:06:39,900 --> 00:06:41,650
Aħna ser minflok jużaw make.

158
00:06:41,650 --> 00:06:45,290
Iżda aħna wkoll raw ls, li juri
elenkar tal-fajls fil-direttorju tiegħi.

159
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U issa għaliex huwa there-- theres żewġ
fajls issa, "Hello" u "hello.c."

160
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Għaliex hemm stilla jew
asterisk wara "Hello"?

161
00:06:52,240 --> 00:06:54,900
What did li turi, ibbażata
fuq dak li raw fil-Ġimgħa waħda?

162
00:06:54,900 --> 00:06:58,852

163
00:06:58,852 --> 00:07:00,400
X'tahseb?

164
00:07:00,400 --> 00:07:02,742
X'tagħmel l-istilla turi?

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00:07:02,742 --> 00:07:04,614
>> MARIA: For---programm "Hello"?

166
00:07:04,614 --> 00:07:05,530
DAVID Malan: "Hello *".

167
00:07:05,530 --> 00:07:06,330
Yeah.

168
00:07:06,330 --> 00:07:07,760
Oh, yeah?

169
00:07:07,760 --> 00:07:08,639
Oh, eżekutibbli.

170
00:07:08,639 --> 00:07:09,180
Dak id-dritt.

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00:07:09,180 --> 00:07:10,890
Allura dan ifisser li
"Hello" hija eżegwibbli.

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00:07:10,890 --> 00:07:13,430
Allura fil-fatt, hu għalhekk
I tista 'tagħmel "./hello."

173
00:07:13,430 --> 00:07:13,930
Kull dritt.

174
00:07:13,930 --> 00:07:15,179
Allura dak li inkella 'nagħmel hawn?

175
00:07:15,179 --> 00:07:17,290
Ukoll, jirriżulta nista
joħolqu wkoll direttorji.

176
00:07:17,290 --> 00:07:20,924
So let me go quddiem u joħolqu,
per eżempju, "pset1" direttorju.

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00:07:20,924 --> 00:07:23,590
U l-problema stabbilita ispeċifikazzjoni
se jkollhom inti tagħmel eżattament dan,

178
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sabiex inti ma għandekx tiftakar llum.

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00:07:25,260 --> 00:07:27,340
Imma "pset1 mkdir" jidher
li jkollhom l-ebda impatt.

180
00:07:27,340 --> 00:07:30,540
Iżda għal darb'oħra, l-ebda messaġġ ta 'żball
huwa ġeneralment ħaġa tajba.

181
00:07:30,540 --> 00:07:34,060
Mela jekk jien tip "ls" now-- ah, issa
I jkollhom fajl eżekutibbli imsejħa

182
00:07:34,060 --> 00:07:36,570
"hello," fajl C imsejjaħ "hello.c."

183
00:07:36,570 --> 00:07:40,860
U allura l-mmejla batuta, hekk li
jitkellmu, ifisser li dan huwa direttorju.

184
00:07:40,860 --> 00:07:42,510
>> Allura fil-fatt, issa nixtieq li tiftħu.

185
00:07:42,510 --> 00:07:45,730
U jien ma ikklikkja darbtejn fuq dan simili
fil-GUI, ambjent grafika.

186
00:07:45,730 --> 00:07:48,550
I minflok ngħid "pset1 cd."

187
00:07:48,550 --> 00:07:49,640
Ikteb.

188
00:07:49,640 --> 00:07:53,100
Xejn interessanti jidher li
ġara ħlief ftit fil-pront tiegħi

189
00:07:53,100 --> 00:07:57,300
here-- dan huwa mod Linux tal fakkruha
me fejn I am, iva, liema folder huwa miftuħ.

190
00:07:57,300 --> 00:08:00,080
Huwa biss javżak me espliċitament
għall-kuntrarju grafikament.

191
00:08:00,080 --> 00:08:05,100
U jekk jien tip "ls," għaliex nara ieħor
pront immedjatament, taħseb,

192
00:08:05,100 --> 00:08:07,269
meta I telenka l-kontenut ta 'pset1?

193
00:08:07,269 --> 00:08:09,310
MARIA: You probabbilment ma
jkollhom xejn fil hemmhekk.

194
00:08:09,310 --> 00:08:09,630
DAVID Malan: Yeah.

195
00:08:09,630 --> 00:08:11,510
Hekk allura aħna ma ovvjament
maħluqa xejn fil hemm

196
00:08:11,510 --> 00:08:13,150
minħabba I biss ħolqu l-direttorju.

197
00:08:13,150 --> 00:08:17,690
Issa, jekk I riedu joħolqu file-- għall
eżempju, I tista 'toħloq fajl ġdid.

198
00:08:17,690 --> 00:08:20,190
U mbagħad I tista 'tmur għall
Issalva u ħlief bħala,

199
00:08:20,190 --> 00:08:23,090
bħal, "mario.c" jekk int tagħmel
l-edizzjoni standard ta pset wieħed.

200
00:08:23,090 --> 00:08:27,610
U mbagħad, bħal kull Mac jew PC, just
jagħżlu l-folder "pset1, Save.

201
00:08:27,610 --> 00:08:28,740
U issa l-fajl ikun vojt.

202
00:08:28,740 --> 00:08:31,160
Imma ejja zoom fl-ġdid għat-tieni.

203
00:08:31,160 --> 00:08:32,470
Ejja nagħmlu ls hawn.

204
00:08:32,470 --> 00:08:34,470
Issa naraw "mario.c".

205
00:08:34,470 --> 00:08:37,850
>> Allura hemm xi kmandi oħra ftit li
jiswew jżomm f'moħħu matul time--

206
00:08:37,850 --> 00:08:41,200
ċara, jew Control L huwa dak stajt
Kien laqtu; mkdir Rajna;

207
00:08:41,200 --> 00:08:45,240
rm Rajna, kif ukoll, li hija
għat-tneħħija jew tħassar fajl.

208
00:08:45,240 --> 00:08:49,310
Beware inti tista also-- u jekk inti tħares
fil tutorials online, inti ser rm -rf

209
00:08:49,310 --> 00:08:52,630
huwa mod komuni ħafna ta 'tgħid
tħassar folder li għandha Jittieħed fiha.

210
00:08:52,630 --> 00:08:54,280
Just tkun super, bir-reqqa super.

211
00:08:54,280 --> 00:08:58,780
-rf ifisser recursively
iħassarha kwalunkwe huwa

212
00:08:58,780 --> 00:09:01,150
int tipprova li jitħassar
u sfurzat iħassarha.

213
00:09:01,150 --> 00:09:04,630
Mela mezzi rikursivi jekk huwa folder ma '
folder bi folder bil folder,

214
00:09:04,630 --> 00:09:05,690
titħassar kull wieħed minnhom.

215
00:09:05,690 --> 00:09:08,680
U sfurzat ifisser lanqas biss
jistaqsu lili iva jew le, jien ċert?

216
00:09:08,680 --> 00:09:11,960
Allura huwa mod super perikolużi ta '
tħassir lottijiet ta 'għalf malajr.

217
00:09:11,960 --> 00:09:17,210
Iżda beware-- ħafna drabi ma 'l Intrepid
student aċċidentalment iħassru, ngħidu aħna, pset

218
00:09:17,210 --> 00:09:18,000
wieħed, per eżempju.

219
00:09:18,000 --> 00:09:19,833
>> MARIA: U jekk huma biss
do -R, dawn qed tmur

220
00:09:19,833 --> 00:09:21,870
biex jistaqsihom dwar kull fajl waħdieni.

221
00:09:21,870 --> 00:09:22,790
>> DAVID Malan: Liema huwa
moderatament annoying.

222
00:09:22,790 --> 00:09:23,480
>> MARIA: Yeah.

223
00:09:23,480 --> 00:09:25,813
>> DAVID Malan: Allura hu għalhekk
tant minna, awto inklużi,

224
00:09:25,813 --> 00:09:27,070
am fil-drawwa li jużaw -rf.

225
00:09:27,070 --> 00:09:27,861
Imma hija perikoluża.

226
00:09:27,861 --> 00:09:29,010
Allura xerrej beware.

227
00:09:29,010 --> 00:09:31,050
U allura mv huwa tip ta
interessanti jismu.

228
00:09:31,050 --> 00:09:33,600
Allura dan huwa l-kmand moviment,
li tħoss ftit stramb

229
00:09:33,600 --> 00:09:37,260
għaliex inti tista 'tabilħaqq użu minnha biex
jiċċaqalqu fajls minn post għall-ieħor.

230
00:09:37,260 --> 00:09:39,970
Per eżempju, ejja ngħidu li jien messed up.

231
00:09:39,970 --> 00:09:43,660
Ejja ngħidu li I maħluqa
fajl ġdid għall-pset.

232
00:09:43,660 --> 00:09:46,320
U jien salvat bħala "greedy.c."

233
00:09:46,320 --> 00:09:49,970
Imma suppose I aċċidentalment isalvawh
fil IDE50-- hekk fil workspace tiegħi innifsu

234
00:09:49,970 --> 00:09:51,580
u mhux fil pset1.

235
00:09:51,580 --> 00:09:53,960
>> Tista 'tara kemm fil-quċċata xellug.

236
00:09:53,960 --> 00:09:55,284
Hemm "greedy.c."

237
00:09:55,284 --> 00:09:56,450
U hemm ftit soluzzjonijiet.

238
00:09:56,450 --> 00:09:58,324
Allura wieħed, nista 'nuża l-
super faċli għall-utent mod

239
00:09:58,324 --> 00:09:59,740
ta 'ftit jittrattienu u twaqqa.

240
00:09:59,740 --> 00:10:01,910
U li kieku attwalment
tiffissa din il-problema.

241
00:10:01,910 --> 00:10:04,967
Imma llum, aħna qed jippruvaw biex tħares lejn
l-modi aktar arcane iżda qawwija

242
00:10:04,967 --> 00:10:05,550
biex dan isir.

243
00:10:05,550 --> 00:10:07,880
So let me jieħdu "ls" fil pset1.

244
00:10:07,880 --> 00:10:09,690
UI biss ara "mario.c."

245
00:10:09,690 --> 00:10:13,450
Let me imorru quddiem u jagħmlu "cd ..".

246
00:10:13,450 --> 00:10:15,320
Allura CD darb'oħra huwa direttorju bidla.

247
00:10:15,320 --> 00:10:18,130
".." Tfisser dak, għalkemm?

248
00:10:18,130 --> 00:10:21,100
Last time I said "cd
pset1 "li jmorru fis pset1.

249
00:10:21,100 --> 00:10:24,360
Allura meta I say "cd ..", dak am I tagħmel?

250
00:10:24,360 --> 00:10:24,910
Lura.

251
00:10:24,910 --> 00:10:25,150
Yeah.

252
00:10:25,150 --> 00:10:26,750
>> Allura li għaddej lill-ġenitur hekk imsejħa.

253
00:10:26,750 --> 00:10:29,730
Mur livell wieħed up, bħal
joħorġu minn folder.

254
00:10:29,730 --> 00:10:30,500
Allura Ikteb.

255
00:10:30,500 --> 00:10:31,900
U fil-fatt, tfittex dak li għamlet.

256
00:10:31,900 --> 00:10:37,070
Hija mċaqalqa me biss fis workspace minflok
tal fis pset1, li hija fil workspace.

257
00:10:37,070 --> 00:10:39,710
U issa jekk jien tip "ls",
hemm mazz sħiħ ta 'għalf.

258
00:10:39,710 --> 00:10:41,650
Fil hemm "greedy.c".

259
00:10:41,650 --> 00:10:48,720
Allura issa let me użu mv li litteralment
jimxu "greedy.c" fis pset1.

260
00:10:48,720 --> 00:10:51,120
U għalhekk ħafna ta 'Linux jikkmanda
xogħol eżattament bħal dan.

261
00:10:51,120 --> 00:10:54,470
Huma jieħdu ebda argumenti jew li jieħdu waħda
argument jew li jieħdu żewġ linja ta 'kmand

262
00:10:54,470 --> 00:10:55,449
argumenti u ibqa 'sejjer hekk.

263
00:10:55,449 --> 00:10:57,240
U f'dan il-każ, huwa
litteralment tagħmel dak

264
00:10:57,240 --> 00:11:01,670
jgħid, għalkemm succinctly--
jimxu greedy.c fis pset1.

265
00:11:01,670 --> 00:11:02,310
Ikteb.

266
00:11:02,310 --> 00:11:03,310
Xejn ma jidher li jiġri.

267
00:11:03,310 --> 00:11:06,180
Imma jekk jien do a ls darb'oħra, greedy hija marret.

268
00:11:06,180 --> 00:11:12,437
U jekk I do "pset1 cd", Daħħal, u mbagħad
ls-ġdid, issa huwa fil-post it-tajjeb.

269
00:11:12,437 --> 00:11:14,270
Bħala twarrib, jekk għal
xi reason-- speċjalment

270
00:11:14,270 --> 00:11:16,194
jekk għandek intermittenti
konnettività tan-netwerk

271
00:11:16,194 --> 00:11:18,360
jew int mixi madwar
kampus bl-għatu laptop tiegħek

272
00:11:18,360 --> 00:11:20,180
magħluqa u mbagħad iftaħ it up
darb'oħra u workspace tiegħek

273
00:11:20,180 --> 00:11:21,730
jidher kemmxejn minn sync, no big deal.

274
00:11:21,730 --> 00:11:23,646
Just rikarigu browser tiegħek
tieqa, u dan għandu

275
00:11:23,646 --> 00:11:26,339
resync sabiex il--xellug
fajl browser jidher eżattament

276
00:11:26,339 --> 00:11:27,380
bħall-tieqa terminal.

277
00:11:27,380 --> 00:11:27,921
Ma tinkwetax.

278
00:11:27,921 --> 00:11:31,460
Meta fid-dubju, rikarigu-paġna, hekk
Sakemm inti ħadthom salvati l-fajls diġà.

279
00:11:31,460 --> 00:11:31,960
KOLLOX SEW.

280
00:11:31,960 --> 00:11:34,710
Allura mv jista 'jintuża wkoll biex tibdel isem fajls.

281
00:11:34,710 --> 00:11:36,760
U ejja tagħti ħarsa lejn
dan il-kmand finali hawnhekk.

282
00:11:36,760 --> 00:11:39,950
Allura suppose-- u dan huwa
super komuni, wisq, sa minn kmieni.

283
00:11:39,950 --> 00:11:46,400
Xi studenti kultant toħloq fajl
imsejħa, ejja say-- x'hemm xulxin?

284
00:11:46,400 --> 00:11:47,730
Bħal "WATER.C."

285
00:11:47,730 --> 00:11:51,080
So I ser biss Yell, għal
ebda raġuni, fil-limiti kollha.

286
00:11:51,080 --> 00:11:53,190
Iżda dan mhuwiex il-
isem korrett għall-fajl

287
00:11:53,190 --> 00:11:56,660
jekk xejn minħabba problema tagħna stabbilit
ispeċifikazzjoni ma jgħidlek

288
00:11:56,660 --> 00:11:59,430
biex isalva l-fajl bħala kollha caps "WATER.C."

289
00:11:59,430 --> 00:12:01,320
Minflok, aħna nistennew
"water.c" fl zghar.

290
00:12:01,320 --> 00:12:03,140
U, fil-fatt, dan huwa
problematika minħabba check50,

291
00:12:03,140 --> 00:12:04,370
programm int ser
jissodisfaw problema

292
00:12:04,370 --> 00:12:07,350
sett wieħed li awtomatikament testijiet
il-korrettezza tal-kodiċi tiegħek

293
00:12:07,350 --> 00:12:11,615
se Yell fi inti jekk ma jistax
isibu "water.c" fl-zghar.

294
00:12:11,615 --> 00:12:12,712
>> So I bżonn biex jiffissaw dan.

295
00:12:12,712 --> 00:12:14,920
Allura ħafna modi differenti
tagħmel dan, l-ewwel waħda

296
00:12:14,920 --> 00:12:18,330
ikun Control-click jew dritt ikklikkja
l-isem fajl u biss bidla Semmi.

297
00:12:18,330 --> 00:12:19,740
Totally multa li tagħmel dan.

298
00:12:19,740 --> 00:12:21,820
Iżda għal darb'oħra, illum, ejja
tagħmel dan ftit fancier.

299
00:12:21,820 --> 00:12:26,680
Ejja jużaw mv għall-bidla
"WATER.C" għal "water.c."

300
00:12:26,680 --> 00:12:30,690
Allura inti tista 'wkoll tuża l-ewwel argument
li semmi mill-ġdid għat-tieni argument

301
00:12:30,690 --> 00:12:34,455
jekk it-tieni argument mhuwiex, fil
fatt, folder jew isem id-direttorju.

302
00:12:34,455 --> 00:12:35,120
>> Kull dritt.

303
00:12:35,120 --> 00:12:39,560
U fl-aħħarnett, trick-- ftit hekk jien fil
direttorju workspace tiegħi fil-mument.

304
00:12:39,560 --> 00:12:43,660
Jekk I rridu nġibu fis pset wieħed,
I jista 'ċertament tip "pset1 cd."

305
00:12:43,660 --> 00:12:47,260
Iżda huwa hekk tedious li tip "pset1" jew
itwal fajl ismijiet jew l-ismijiet tad-direttorju

306
00:12:47,260 --> 00:12:47,980
xorta.

307
00:12:47,980 --> 00:12:51,960
Allura ħafna drabi fil Linux, liema
inti tista 'tagħmel huwa tibda ittajpjar "PSE"

308
00:12:51,960 --> 00:12:56,100
u biss niddejjaq, hit Tab, u ħalli
il-figura kompjuter out għalik.

309
00:12:56,100 --> 00:12:58,190
Super utli li jsibu rwieħhom li vizzju.

310
00:12:58,190 --> 00:13:01,079
Il-qabda biss huwa jekk għandek
fajls multipli jew folders jibdew

311
00:13:01,079 --> 00:13:02,870
bl-ittra "p" jew
"ps," inti jista 'jkollok

312
00:13:02,870 --> 00:13:05,525
tip ftit aktar qabel il-
kompjuter jaf x'għandek tagħmel.

313
00:13:05,525 --> 00:13:06,820
>> MARIA: Aħna bħal shortcuts.

314
00:13:06,820 --> 00:13:08,695
>> DAVID Malan: Dan se
jiffrankaw il-ħin tant.

315
00:13:08,695 --> 00:13:11,930
U wkoll, kif għidna fil lecture, inti
jistgħu iscroll up fl-istorja, u 'l isfel,

316
00:13:11,930 --> 00:13:15,461
biex isibu esegwiti reċentement
jikkmanda, kif ukoll.

317
00:13:15,461 --> 00:13:15,960
Kull dritt.

318
00:13:15,960 --> 00:13:20,904
Allura issa, ejja tagħti attenzjoni tagħna lura
għal programm sempliċi, bonjour dinja.

319
00:13:20,904 --> 00:13:22,195
Allura konna kkumpilata din il eżattament.

320
00:13:22,195 --> 00:13:24,050
U issa għaliex ma nieħdu
ħarsa lejn it-tipi ta 'data

321
00:13:24,050 --> 00:13:26,776
u mbagħad tranżizzjoni minn xi
blokki Scratch jikkorrispondi għal C.

322
00:13:26,776 --> 00:13:27,400
MARIA: biża.

323
00:13:27,400 --> 00:13:30,031
Allura issa li inti stajt beda
miktub programmi C,

324
00:13:30,031 --> 00:13:32,530
aħna qed tmur biex tibda titkellem
dwar tipi ta 'data u fatturi varjabbli.

325
00:13:32,530 --> 00:13:37,570
Allura xi tipi ta 'data li inti
trid tkun taf tibda issa

326
00:13:37,570 --> 00:13:39,400
huma dawk li huma
enfasizzati fil-blu.

327
00:13:39,400 --> 00:13:42,420
Allura aħna għandna int l-ewwel,
li stands għall-eqreb numru sħiħ.

328
00:13:42,420 --> 00:13:46,075
U li jkollha interi, kif inti
jista 'jkollhom guessed-- hekk 1, 2, 3,

329
00:13:46,075 --> 00:13:47,950
u kull interi oħra
li inti tista 'taħseb.

330
00:13:47,950 --> 00:13:48,730
>> DAVID Malan: U wkoll negattiva.

331
00:13:48,730 --> 00:13:50,220
>> MARIA: U wkoll dawk negattivi, Yep.

332
00:13:50,220 --> 00:13:51,450
U 0.

333
00:13:51,450 --> 00:13:54,250
Imbagħad għandna sufruni, li
huma f'wiċċ l-ilma punt numri.

334
00:13:54,250 --> 00:13:58,360
Allura dak l-numri reali
li għandhom punti deċimali.

335
00:13:58,360 --> 00:14:03,960
Allura 5.0, 5.2, u saħansitra aktar
ċifri wara l-punt deċimali,

336
00:14:03,960 --> 00:14:05,620
kif ukoll, u wkoll dawk negattivi.

337
00:14:05,620 --> 00:14:07,530
Imbagħad għandna char li huwa karattru.

338
00:14:07,530 --> 00:14:10,240
So I think we tkellem dwar
dan lecture llum.

339
00:14:10,240 --> 00:14:15,682
Imma aħna għandna ittri, għal example-- A,
B, C-- li jistgħu jkunu maħżuna bħala char.

340
00:14:15,682 --> 00:14:18,390
Imma allura għandna ħafna aktar simboli
li jistgħu jkunu maħżuna bħala char.

341
00:14:18,390 --> 00:14:22,380
U dawk huma maħżuna bħala ASCII.

342
00:14:22,380 --> 00:14:25,280
>> U allura għandna BOOL,
li huma Booleans.

343
00:14:25,280 --> 00:14:29,067
U dawk tevalwa lil Veru jew
Falza jew 1 u 0, rispettivament.

344
00:14:29,067 --> 00:14:31,650
DAVID Malan: U recall li
BOOL ġej mill-bibljoteka CS50.

345
00:14:31,650 --> 00:14:33,300
Allura mhuwiex mibnija fis
C, imma hija super utli

346
00:14:33,300 --> 00:14:34,850
li jkollhom l-kunċett ta 'vera u falza.

347
00:14:34,850 --> 00:14:36,990
U anki jekk inti
jista think-- fatt gost.

348
00:14:36,990 --> 00:14:43,700
A BOOL teknikament jeħtieġ kemm bits,
tassew, li jirrappreżentaw Veru Falz versus?

349
00:14:43,700 --> 00:14:47,910
Kemm bits taħseb
għandek bżonn, maximally?

350
00:14:47,910 --> 00:14:48,790
Yeah, wieħed biss.

351
00:14:48,790 --> 00:14:52,077
Għalhekk jirriżulta li C
ma jista 'jtik biss waħda bit.

352
00:14:52,077 --> 00:14:54,160
L-iżgħar unità tal-kejl
inti tista 'tikseb huwa tmienja.

353
00:14:54,160 --> 00:14:57,090
Allura huwa ħela ftit huma int
użu ta 'byte kollu, jew tmien bits,

354
00:14:57,090 --> 00:14:58,340
li jirrappreżenta vera jew falza.

355
00:14:58,340 --> 00:15:01,807
Imma dak li biss il-mod huwa
implimentata C mill-librerija CS50.

356
00:15:01,807 --> 00:15:04,890
MARIA: U mbagħad dawk li aħna qed
mhux ser jitkellmu dwar kif estensiv

357
00:15:04,890 --> 00:15:08,060
dritt now-- doppja,
li għall sufruni akbar.

358
00:15:08,060 --> 00:15:09,811
Twil twil u qasir
huma wkoll għall-interi.

359
00:15:09,811 --> 00:15:10,643
DAVID Malan: Tabilħaqq.

360
00:15:10,643 --> 00:15:13,190
Fil Hacker edizzjoni ta 'pset waħda,
aħna attwalment jużaw twil twil.

361
00:15:13,190 --> 00:15:15,801
Iżda għall-edizzjoni standard,
m'għandux ikun meħtieġ.

362
00:15:15,801 --> 00:15:16,300
MARIA: Kessaħ.

363
00:15:16,300 --> 00:15:17,361
KOLLOX SEW.

364
00:15:17,361 --> 00:15:20,110
Allura operators-- inti għandek tkun
probabbilment familjari ma 'ħafna minn dawn.

365
00:15:20,110 --> 00:15:22,620
Barra minn hekk, +; tnaqqis, -.

366
00:15:22,620 --> 00:15:24,070
Għal multiplikazzjoni, aħna għandna l-*.

367
00:15:24,070 --> 00:15:25,900
Allura ma l-X li aħna normalment jużaw.

368
00:15:25,900 --> 00:15:27,840
Diviżjoni, aħna għandna l-backslash.

369
00:15:27,840 --> 00:15:31,380
U modulo hija operatur aħħar tagħna li
aħna ser jitkellmu dwar id-dritt issa.

370
00:15:31,380 --> 00:15:35,610
Huwa ta 'operatur li jippermetti li
jieħdu l-bqija ta 'diviżjoni.

371
00:15:35,610 --> 00:15:40,630
Mela jekk ikollna 4% 2, 4 diviża
bi 2 huwa 2 bil-bqija ta '0.

372
00:15:40,630 --> 00:15:41,740
Allura 4% 2 huwa 0.

373
00:15:41,740 --> 00:15:42,950
4% 3 huwa 1.

374
00:15:42,950 --> 00:15:44,870
4% 5 huwa ta '4, kif jista' jkollok guessed.

375
00:15:44,870 --> 00:15:48,860
U ftakar meta jużaw dawn kollha
operaturi jużaw ir-regoli PEMDAS.

376
00:15:48,860 --> 00:15:54,060
>> DAVID Malan: Allura biex tkun ċara, jekk inti
do 4% 2, għaliex huwa li 0, eżattament?

377
00:15:54,060 --> 00:15:57,480
>> MARIA: Minħabba 4 diviż bil
2 huwa 2 bil-bqija ta '0.

378
00:15:57,480 --> 00:16:00,752
Allura modulo jagħtina l-kumplament bħala
kuntrarju għar-riżultat tad-diviżjoni.

379
00:16:00,752 --> 00:16:02,960
DAVID Malan: U fil-fatt,
dak li aħna ser issib dan utli

380
00:16:02,960 --> 00:16:05,640
għal huwa li f'xi problemi
li mhux neċessarjament waħda,

381
00:16:05,640 --> 00:16:08,040
jekk inti tixtieq li jkollok l-
effett li jirrestrinġu l yourself

382
00:16:08,040 --> 00:16:10,720
għal firxa ta 'numri
bħal 0 permezz xi ħaġa,

383
00:16:10,720 --> 00:16:13,904
inti tista 'tuża modulo biex nagħlaq madwar
qabel bħall-2 biljuni

384
00:16:13,904 --> 00:16:16,320
jew il-valur 4 biljun li
konna tkellem dwar fl lecture.

385
00:16:16,320 --> 00:16:16,870
>> MARIA: Yeah.

386
00:16:16,870 --> 00:16:19,429
U anki fil- "greedy" nistgħu.

387
00:16:19,429 --> 00:16:21,345
DAVID Malan: Iva, fil
problema sett wieħed, kif ukoll.

388
00:16:21,345 --> 00:16:22,520
MARIA: Yeah, sbieħ.

389
00:16:22,520 --> 00:16:24,340
DAVID Malan: ħjiel Tajba.

390
00:16:24,340 --> 00:16:25,750
MARIA: Jiddispjacini.

391
00:16:25,750 --> 00:16:28,590
Boolean expressions-- hekk
għall-operaturi Boolean,

392
00:16:28,590 --> 00:16:31,770
se nkunu qed nitkellmu dwar l
minn dawn li tara hawn.

393
00:16:31,770 --> 00:16:35,310
Allura issa dritt, għandna żewġ
sinjali indaqs elenkati għal ugwali.

394
00:16:35,310 --> 00:16:38,650
Għalhekk dawn huma għall-paragun.

395
00:16:38,650 --> 00:16:40,830
S'issa, konna biss tidher waħda ugwali sinjal.

396
00:16:40,830 --> 00:16:44,870
Li meta aħna tassenja
valur għal varjabbli.

397
00:16:44,870 --> 00:16:50,160
Allura jekk aħna stajt tidher int n = 5, imbagħad
konna assenjat 5 għall-n varjabbli.

398
00:16:50,160 --> 00:16:55,600
Iżda jekk irridu li jużaw == għall
paragun, nistgħu tivverifika jekk == 5 n.

399
00:16:55,600 --> 00:16:58,310
U jekk n == 5, allura dan huwa veru.

400
00:16:58,310 --> 00:17:01,950
>> Operaturi hekk Boolean
inessu, bażikament,

401
00:17:01,950 --> 00:17:04,670
biex tevalwa Boolean
espressjonijiet għal Veru jew Falz.

402
00:17:04,670 --> 00:17:07,819
Allura mhux equals-- aħna għandna l-
marka exclamation u ugwali.

403
00:17:07,819 --> 00:17:14,240
Allura nistgħu wkoll jiċċekkjaw jekk n
mhux daqs 5-- hekk n! = 5.

404
00:17:14,240 --> 00:17:17,640
Inqas minn, inqas minn jew ugwali għal,
akbar minn, akbar minn jew ugwali għal,

405
00:17:17,640 --> 00:17:20,720
u allura għandna l loġiku
U u l-loġika OR.

406
00:17:20,720 --> 00:17:24,060
U dawk inessu biex tevalwa
espressjonijiet Boolean multipli flimkien

407
00:17:24,060 --> 00:17:27,930
li bażikament ġejjin flimkien bħala
wieħed espressjoni Boolean kollu.

408
00:17:27,930 --> 00:17:34,970
Mela jekk irridu li ssib numru, jiġifieri,
li huwa ikbar minn 5 imma anqas minn 15

409
00:17:34,970 --> 00:17:39,810
fl-istess ħin, aħna se jużaw il-
loġiku U operatur biex tara jekk n hija

410
00:17:39,810 --> 00:17:42,937
akbar minn 5 && n anqas minn 15.

411
00:17:42,937 --> 00:17:44,770
DAVID Malan: U hawn,
wisq, huwa verament faċli

412
00:17:44,770 --> 00:17:47,290
kmieni biex aċċidentalment
jużaw biss ampersand wieħed

413
00:17:47,290 --> 00:17:48,572
jew bar vertikali waħda.

414
00:17:48,572 --> 00:17:51,280
U nisperaw li l-kumpilatur se
Yell fi inti għaliex fil-fatt

415
00:17:51,280 --> 00:17:52,530
għandhom tifsira differenti ħafna.

416
00:17:52,530 --> 00:17:55,660
Għal dawk kurjuż, dawn qed
użati għal operazzjonijiet bitwise,

417
00:17:55,660 --> 00:17:57,197
joperaw fuq bits individwali.

418
00:17:57,197 --> 00:17:58,780
Imma inti trid li l-par ta 'hawnhekk.

419
00:17:58,780 --> 00:18:01,560
U super importanti huwa li
ewwel waħda, is-sinjal ugwali,

420
00:18:01,560 --> 00:18:05,270
li hija l-operatur ugwaljanza
kuntrarju tal-operatur assenjazzjoni.

421
00:18:05,270 --> 00:18:08,552
>> MARIA: U l-bar vertikali hija
tinsab bejn il Ħassar u Ritorn.

422
00:18:08,552 --> 00:18:09,260
DAVID Malan: Iva.

423
00:18:09,260 --> 00:18:11,420
Fuq tastiera tipiku Istati Uniti.

424
00:18:11,420 --> 00:18:13,190
>> MARIA: Yep.

425
00:18:13,190 --> 00:18:15,890
Mela ejja jaqbżu dritt fil
dikjarazzjonijiet kondizzjonali.

426
00:18:15,890 --> 00:18:18,300
Fil Scratch, inti stajt
diġà rajna, probabbilment,

427
00:18:18,300 --> 00:18:22,730
jekk id-dikjarazzjonijiet li jippermettu li inti
jiċċekkjaw jekk xi ħaġa hija vera, allura

428
00:18:22,730 --> 00:18:23,660
tagħmel xi ħaġa oħra.

429
00:18:23,660 --> 00:18:28,410
Allura inti jista 'jkollok riedu
biex jiċċekkjaw jekk Sprite tiegħek hija

430
00:18:28,410 --> 00:18:31,410
jmissu xi Sprite oħra
jew il-fruntiera tal-iskrin tiegħek.

431
00:18:31,410 --> 00:18:35,520
U allura inti jista 'jkollok riedu
tmiem il-logħba jew tagħmel xi ħaġa oħra.

432
00:18:35,520 --> 00:18:40,000
Allura l-sintassi għal dak
huwa "jekk (kundizzjoni)."

433
00:18:40,000 --> 00:18:46,820
Mela jekk Sprite tiegħek qed imiss xi ħaġa,
allura ma hu ġewwa l-braces kaboċċi.

434
00:18:46,820 --> 00:18:48,980
>> Imbagħad għandna jekk-ieħor dikjarazzjonijiet.

435
00:18:48,980 --> 00:18:54,080
Else jippermetti li nagħmlu xi ħaġa
jekk il-kundizzjoni li aħna

436
00:18:54,080 --> 00:18:55,870
check fil-bidu mhux veru.

437
00:18:55,870 --> 00:19:01,530
Allura jekk il-Sprite qed imiss il-
transkonfinali tagħmel dan, inkella tagħmel xi ħaġa oħra.

438
00:19:01,530 --> 00:19:04,030
Allura inkella tagħmel xi ħaġa oħra.

439
00:19:04,030 --> 00:19:07,530
Imbagħad għandna eżempju qasir għal dan.

440
00:19:07,530 --> 00:19:11,551
Mela jekk (military_time <12), aħna
tixtieq li printf "filgħodu Tajba!"

441
00:19:11,551 --> 00:19:13,300
Else aħna qed tmur biex
printf "Good filgħaxija!"

442
00:19:13,300 --> 00:19:14,860
Eżempju bażiku.

443
00:19:14,860 --> 00:19:15,680
>> DAVID Malan: Tajba.

444
00:19:15,680 --> 00:19:16,760
>> MARIA: Kessaħ.

445
00:19:16,760 --> 00:19:18,560
Allura issa għandna dikjarazzjonijiet swiċċ.

446
00:19:18,560 --> 00:19:21,960
Jaqilbu dikjarazzjonijiet b'mod ġenerali tista
inessu li jagħmlu ħafna ta 'l-istess ħaġa

447
00:19:21,960 --> 00:19:25,070
li aħna biss tkellimna
dwar jekk jitwettqu dikjarazzjonijiet.

448
00:19:25,070 --> 00:19:29,440
Per eżempju, id-dritt issa għandna l-
forma ġenerali tad-dikjarazzjoni swiċċ

449
00:19:29,440 --> 00:19:33,870
li jippermettilna nieħdu
varjabbli imsejjaħ n

450
00:19:33,870 --> 00:19:37,670
u jqabbilha lil ħafna
valuri differenti, li here we

451
00:19:37,670 --> 00:19:40,010
sejħu constant1, constant2.

452
00:19:40,010 --> 00:19:41,150
Aħna jista 'jkollhom ħafna aktar.

453
00:19:41,150 --> 00:19:42,930
U dawk huma msejħa każijiet.

454
00:19:42,930 --> 00:19:46,280
>> Mela jekk ikollna swiċċ
statement-- u taħdem din

455
00:19:46,280 --> 00:19:50,580
biss għal integers-- għandna
varjabbli f'dan il-każ li l-n.

456
00:19:50,580 --> 00:19:53,840
Jekk il-varjabbli huwa n
daqs constant1, aħna

457
00:19:53,840 --> 00:19:59,720
se tesegwixxi xi snippet ta 'kodiċi
jew xi ħaġa li rridu nagħmlu.

458
00:19:59,720 --> 00:20:01,280
U allura aħna se break.

459
00:20:01,280 --> 00:20:04,820
Allura l-waqfa ifisser li
id-dikjarazzjoni swiċċ

460
00:20:04,820 --> 00:20:08,120
se tieqaf esekuzzjoni jekk
n huwa daqs constant1,

461
00:20:08,120 --> 00:20:09,752
u imbagħad ipprogramma tiegħek se jkompli.

462
00:20:09,752 --> 00:20:11,835
Se ħruġ mill-
switch dikjarazzjoni u inneħħu

463
00:20:11,835 --> 00:20:13,520
tkompli tagħmel xi ħaġa oħra.

464
00:20:13,520 --> 00:20:17,204
>> Jekk, madankollu, n mhuwiex ugwali għal
constant1, allura każ għall constant2

465
00:20:17,204 --> 00:20:17,870
se jiġu kkontrollati.

466
00:20:17,870 --> 00:20:21,750
Mela jekk n ugwali constant2, li l-oħra
snippet ta 'kodiċi se jiġu esegwiti.

467
00:20:21,750 --> 00:20:23,850
U allura dan ser break
jekk dan huwa ugwali għal dan.

468
00:20:23,850 --> 00:20:27,580
U allura jista 'jkollna also-- ma
neċessarjament, though-- każ kontumaċja,

469
00:20:27,580 --> 00:20:32,290
li se jiġri jekk n mhuwiex ugwali għal
kwalunkwe mill-każijiet li għandek elenkati.

470
00:20:32,290 --> 00:20:35,400
U fil-każ normali, aħna wkoll
m'għandhomx jeħtieġu waqfa neċessarjament

471
00:20:35,400 --> 00:20:39,271
minħabba li l-istqarrija bidla se tkun taf
li jeħtieġ li jispiċċa wara l-inadempjenza

472
00:20:39,271 --> 00:20:40,270
każ jekk dan huwa l-każ.

473
00:20:40,270 --> 00:20:42,140
>> DAVID Malan: Iżda stylistically,
aħna dejjem poġġih fil hemmhekk.

474
00:20:42,140 --> 00:20:42,540
>> MARIA: Yeah.

475
00:20:42,540 --> 00:20:42,710
>> DAVID Malan: Yeah.

476
00:20:42,710 --> 00:20:44,750
Allura speċjalment meta bdew,
speċjalment jekk fost dawk inqas

477
00:20:44,750 --> 00:20:47,458
komdu, nixtieq personalment
biss jirrakkomandaw twaħħal mal-IFs

478
00:20:47,458 --> 00:20:51,564
u IFs-elses u ieħor 'jekk' elses jekk-
u oħrajn jekk biss

479
00:20:51,564 --> 00:20:53,480
għaliex qed ftit
aktar sempliċi.

480
00:20:53,480 --> 00:20:56,142
Din hija ottimizzazzjoni sbieħ, jew
xi kultant anke estetikament dan

481
00:20:56,142 --> 00:20:57,350
jagħmel il-kodiċi jinqara aħjar.

482
00:20:57,350 --> 00:20:59,599
U fil-fatt, probabbilment
nofs l-semestru Ser naraw problema

483
00:20:59,599 --> 00:21:02,504
sett fejn hija biss jistenna aħjar
u aktar faċli biex jinqara għall-bnedmin

484
00:21:02,504 --> 00:21:03,670
bl-użu stqarrija swiċċ.

485
00:21:03,670 --> 00:21:05,460
Imma ma joqogħdu jinkwetaw dwar
jaqbdu ma 'dan kmieni wisq.

486
00:21:05,460 --> 00:21:05,680
>> MARIA: Yeah.

487
00:21:05,680 --> 00:21:08,840
Jekk ikollok ħafna ta 'jekk id-dikjarazzjonijiet,
jista 'biss ma ikunu jistgħu jinqraw ħafna.

488
00:21:08,840 --> 00:21:10,965
Jista 'ma jkunx malajr ħafna
għalik biex jgħaddu minnha.

489
00:21:10,965 --> 00:21:13,230
Allura jaqilbu dikjarazzjonijiet jistgħu
jkun utli ħafna, kif ukoll.

490
00:21:13,230 --> 00:21:17,900
U wkoll, ma remember-- ma
ninsewx li tpoġġi l-pawżi fil hemmhekk.

491
00:21:17,900 --> 00:21:20,330
>> DAVID Malan: M'għandekx tiftakar dan.

492
00:21:20,330 --> 00:21:24,890
>> MARIA: Għaliex imbagħad inti tista 'taqa
permezz minn każ għall-ieħor.

493
00:21:24,890 --> 00:21:27,930
Mela ejja ngħidu li każ constant1
ma jkollha dikjarazzjoni waqfa fiha.

494
00:21:27,930 --> 00:21:31,920
Imbagħad nistgħu jaqgħu permezz
constant2 każ ġewwa.

495
00:21:31,920 --> 00:21:35,070
U ma rridux li tagħmel dan jekk
konna diġà laħqu każ constant1

496
00:21:35,070 --> 00:21:37,830
u huwa ugwali għal n.

497
00:21:37,830 --> 00:21:45,100
>> Għalhekk, per eżempju, jekk ikollna varjabbli
n li fih għadd klassi,

498
00:21:45,100 --> 00:21:48,990
u irridu naraw dak li
klassi is-- jekk n ugwali 50,

499
00:21:48,990 --> 00:21:51,957
aħna qed tmur għall-istampar "CS50 hija
Introduzzjoni għall Computer Science I. "

500
00:21:51,957 --> 00:21:53,040
Allura aħna qed tmur biex jinkiser.

501
00:21:53,040 --> 00:21:53,920
U li hu.

502
00:21:53,920 --> 00:21:55,950
Jekk, madankollu, n ikun ugwali
sa 51, aħna qed tmur

503
00:21:55,950 --> 00:21:58,494
għall-istampar "CS51 hija Introduzzjoni
li Computer Science II. "

504
00:21:58,494 --> 00:21:59,910
Imbagħad, għal darb'oħra, aħna qed tmur biex jinkiser.

505
00:21:59,910 --> 00:22:05,080
Madankollu, jekk allura npoġġux 124, 61, kull
numru ieħor li inti tista 'taħseb,

506
00:22:05,080 --> 00:22:06,890
jew programm mhux se
li jirrikonoxxu dan.

507
00:22:06,890 --> 00:22:09,010
Allura li għaddej biex jgħidu, "Jiddispjacini, jien
ma jkunux familjari mal-klassi. "

508
00:22:09,010 --> 00:22:10,009
U li għaddej biex jinkiser.

509
00:22:10,009 --> 00:22:12,847
DAVID Malan: Allura inti tista 'verament tara
l-jekk, inkella jekk, idea inkella hawn.

510
00:22:12,847 --> 00:22:15,430
Huwa sintassi biss differenti għall
jesprimi l-istess idea preċiża.

511
00:22:15,430 --> 00:22:17,690
>> MARIA: Eżattament.

512
00:22:17,690 --> 00:22:19,480
Issa għandna l-operaturi tenarji tagħna.

513
00:22:19,480 --> 00:22:24,900
Operaturi hekk ternarji jkollhom
tliet parts-- kundizzjoni,

514
00:22:24,900 --> 00:22:27,220
xi ħaġa li tagħmel jekk
din il-kundizzjoni huwa minnu,

515
00:22:27,220 --> 00:22:29,730
u mbagħad xi ħaġa li tagħmel
jekk din il-kundizzjoni hija falza.

516
00:22:29,730 --> 00:22:33,400
Allura inti tara, bażikament,
l sintassi ta 'dak hawn.

517
00:22:33,400 --> 00:22:37,792
Għandna l-kwistjoni mark, u
allura the-- dak li nsejħu dan?

518
00:22:37,792 --> 00:22:38,750
DAVID Malan: Il-kolon.

519
00:22:38,750 --> 00:22:39,100
MARIA: Kolon.

520
00:22:39,100 --> 00:22:39,599
Grazzi.

521
00:22:39,599 --> 00:22:41,880
Jiddispjacini.

522
00:22:41,880 --> 00:22:45,800
Mela ejja nħarsu lejn eżempju tagħna biex
ara jekk nistgħu jagħmlu sens ta 'this--

523
00:22:45,800 --> 00:22:47,840
== class_num 50.

524
00:22:47,840 --> 00:22:52,580
Allura hawn naraw operatur Boolean tagħna ==
li tqabbel il-class_num varjabbli

525
00:22:52,580 --> 00:22:53,100
50.

526
00:22:53,100 --> 00:22:55,150
Stores hekk class_num integer.

527
00:22:55,150 --> 00:22:58,180
U jekk dan integer
ugwali 50, allura aħna qed

528
00:22:58,180 --> 00:23:02,810
ser taħżen "David Malan"
ġewwa l-professur sekwenza.

529
00:23:02,810 --> 00:23:05,912
Jekk in-numru tal-klassi ma
daqs 50, "mhux David Malan"

530
00:23:05,912 --> 00:23:07,120
se tkun il-professur.

531
00:23:07,120 --> 00:23:08,630
>> DAVID Malan: Grazzi.

532
00:23:08,630 --> 00:23:12,110
U hekk dan jidher ekwivalenti għal
dak, tgħid, fl-ewwel daqqa t'għajn?

533
00:23:12,110 --> 00:23:17,930

534
00:23:17,930 --> 00:23:19,960
>> MARIA: Lili jidher
bħal dikjarazzjonijiet-ieħor jekk.

535
00:23:19,960 --> 00:23:20,709
>> DAVID Malan: Yeah.

536
00:23:20,709 --> 00:23:24,020
U fil-fatt, dan huwa tip
ta 'pretty inforra waħda,

537
00:23:24,020 --> 00:23:27,520
biex ngħidu hekk, għall-implimentazzjoni
eżattament il-loġika ta 'jekk' ħaddieħor

538
00:23:27,520 --> 00:23:29,010
iżda tagħmel dak kollu fi stadju wieħed.

539
00:23:29,010 --> 00:23:29,860
>> MARIA: Eżattament.

540
00:23:29,860 --> 00:23:30,360
Yeah.

541
00:23:30,360 --> 00:23:33,520
Dikjarazzjonijiet hekk jekk-ieħor jista
jieħdu ħafna ta 'spazju.

542
00:23:33,520 --> 00:23:36,283
Huma jistgħu jkunu twal wisq għall
xi ħaġa sempliċi kemm dan.

543
00:23:36,283 --> 00:23:38,350
Allura dan jista 'jkun ħafna
konċiż u sbieħ ħafna.

544
00:23:38,350 --> 00:23:40,880

545
00:23:40,880 --> 00:23:46,820
Allura issa aħna qed tmur fis tħares lejn
eżekuzzjoni xi ħaġa għal darb'oħra u għal darb'oħra,

546
00:23:46,820 --> 00:23:50,060
hekk iċċekkjar għal
kundizzjoni minn darba

547
00:23:50,060 --> 00:23:53,510
u mbagħad jkomplu jagħmlu xi ħaġa
filwaqt li din il-kundizzjoni huwa veru.

548
00:23:53,510 --> 00:23:56,740
Allura dan iwassalna
nicely fis loops waqt.

549
00:23:56,740 --> 00:23:59,270
>> Biex ix-xellug, għandna
ewwel loop filwaqt tagħna.

550
00:23:59,270 --> 00:24:03,840
Għalhekk, filwaqt li xi ħaġa hija vera,
tagħmel xi ħaġa mill-ġdid u għal darb'oħra.

551
00:24:03,840 --> 00:24:08,850
Sabiex tagħmel ċert li l-avviż li tagħna
kundizzjoni hawn huwa vvalidat fil-quċċata.

552
00:24:08,850 --> 00:24:14,150
Billi bil tieni loop-- tagħna aħna sejħa
li do-waqt loop-- nagħmlu xi ħaġa,

553
00:24:14,150 --> 00:24:15,890
allura aħna jikkontrolla għal kundizzjoni.

554
00:24:15,890 --> 00:24:17,980
U jekk din il-kundizzjoni
tkompli tkun vera,

555
00:24:17,980 --> 00:24:20,150
immorru lura u jagħmlu l-ħaġa mill-ġdid.

556
00:24:20,150 --> 00:24:23,360
Allura l-differenza prinċipali hija fejn
il-kundizzjoni tkun ikkontrollata għal.

557
00:24:23,360 --> 00:24:29,260
U l-kodiċi qatt ma jista 'jkun
esegwiti jekk il-kundizzjoni mhijiex

558
00:24:29,260 --> 00:24:30,430
veru mal-linja waqt.

559
00:24:30,430 --> 00:24:33,050
Billi bil-do-waqt
loop, aħna għandna l-kodiċi

560
00:24:33,050 --> 00:24:35,380
li huwa dejjem jitwettaq mill-inqas darba.

561
00:24:35,380 --> 00:24:37,470
U allura filwaqt li l-kundizzjoni
tkompli tkun vera,

562
00:24:37,470 --> 00:24:39,960
nistgħu mmorru lura u jtenni mill-ġdid ġewwa.

563
00:24:39,960 --> 00:24:43,625
Allura għaliex taħseb aħna se jużaw
a do-waqt li loop fuq loop filwaqt?

564
00:24:43,625 --> 00:24:48,221

565
00:24:48,221 --> 00:24:48,720
Dritt.

566
00:24:48,720 --> 00:24:52,600
Mela jekk irridu li tkun inkoraġġuta l
utent għal xi tip ta 'input,

567
00:24:52,600 --> 00:24:55,400
jekk irridu li jistaqsihom
li jidħol isem tagħhom,

568
00:24:55,400 --> 00:24:57,342
irridu tal-anqas jistaqsihom darba.

569
00:24:57,342 --> 00:24:59,050
U jekk dawn jidħlu
dak l-isem, aħna mhux qed

570
00:24:59,050 --> 00:25:00,740
ser titlob jerġgħu
għaliex aħna diġà jafu.

571
00:25:00,740 --> 00:25:02,656
Iżda jekk dawn ma jidħlux
isem tagħhom, jew jekk

572
00:25:02,656 --> 00:25:05,787
jidħol xi ħaġa li
ovvjament mhux l-isem,

573
00:25:05,787 --> 00:25:08,120
aħna xorta jridu jkomplu
talbithom fuq għal isem tagħhom.

574
00:25:08,120 --> 00:25:10,710
>> DAVID Malan: U fl lecture kellna wieħed
bħal dan mal-nikseb int pożittiv

575
00:25:10,710 --> 00:25:13,550
eżempju, fejn hemm xejn li
check fl-ewwel għaliex inti lanqas biss

576
00:25:13,550 --> 00:25:14,190
gotten int.

577
00:25:14,190 --> 00:25:16,680
Allura rridu nagħmlu this--
tikseb int mill-user--

578
00:25:16,680 --> 00:25:18,860
imbagħad check, forsi,
ġdid u għal darb'oħra u għal darb'oħra.

579
00:25:18,860 --> 00:25:21,030
>> MARIA: Eżattament.

580
00:25:21,030 --> 00:25:22,060
Għal OK loops--.

581
00:25:22,060 --> 00:25:25,842
Għal loops jistgħu jippermettu magħna biex tagħmel kważi
l-istess ħaġa eżatt, kif ukoll.

582
00:25:25,842 --> 00:25:27,300
Huwa fil-fatt l-istess ħaġa eżatt.

583
00:25:27,300 --> 00:25:30,190
Hekk hemm xejn li
inti tista 'tagħmel ma' għal linji

584
00:25:30,190 --> 00:25:32,840
li inti ma tkunx tista
x'jaqsmu ma 'loops waqt.

585
00:25:32,840 --> 00:25:36,900
Iżda għal linji jista 'jidher ftit
ftit aktar ikkumplikata sintattikament

586
00:25:36,900 --> 00:25:39,730
minħabba li jkunu
tliet partijiet ġewwa dak

587
00:25:39,730 --> 00:25:42,990
kien qabel biss il-
kundizzjoni ma loops waqt.

588
00:25:42,990 --> 00:25:48,260
Allura l-ewwel parti li inti baħar, il-
xellug kbira, aħna għandna "int dwarves = 0."

589
00:25:48,260 --> 00:25:51,490
Allura dan huwa fejn aħna
initialize varjabbli tagħna.

590
00:25:51,490 --> 00:25:55,210
>> Imbagħad għandna punto virgola
u "dwarves <7."

591
00:25:55,210 --> 00:25:57,100
Allura dan huwa fejn l
kundizzjoni fil-fatt hu.

592
00:25:57,100 --> 00:26:00,170
Allura dan huwa dak li rridu naraw
jitqiegħdu biss fis-waqt loop--

593
00:26:00,170 --> 00:26:01,880
"filwaqt dwarves <7."

594
00:26:01,880 --> 00:26:05,380
Hawnhekk, li tmur fil-
nofs ta 'tagħna għal loop.

595
00:26:05,380 --> 00:26:07,190
Allura "dwaves <7."

596
00:26:07,190 --> 00:26:11,350
U mbagħad aħħar parti tagħna huwa "dwarves ++,"
li huwa fejn aħna aġġornament varjabbli tagħna.

597
00:26:11,350 --> 00:26:15,470
Allura l-ħaġa importanti
li tirrealizza hija li din

598
00:26:15,470 --> 00:26:22,010
se jmorru permezz ta 'dan għall loop
seba 'darbiet u tesegwixxi seba' darbiet.

599
00:26:22,010 --> 00:26:24,020
Allura aħna għandna seba
dwarves, u dawn qed kollha

600
00:26:24,020 --> 00:26:26,020
se ngħid, "jien hawn
biex jgħinuk, Snow White "

601
00:26:26,020 --> 00:26:28,860
minħabba li huma lesti
biex jgħinu Snow White.

602
00:26:28,860 --> 00:26:33,600
>> Bil filwaqt loops, aħna kien jagħmel
l inizjalizzazzjoni u l-aġġornament

603
00:26:33,600 --> 00:26:37,490
mhux ġewwa l-kundizzjoni, għal darb'oħra, iżda
jew qabel jew ġewwa l-linja waqt

604
00:26:37,490 --> 00:26:40,210
biex tiżgura li we-- minħabba
aħna dejjem bżonn dawk il-partijiet.

605
00:26:40,210 --> 00:26:42,835
Allura biex tagħmel ċert li għandna
minnhom, aħna ħadthom xorta miżjud magħhom

606
00:26:42,835 --> 00:26:44,580
fuq, mhux biss ġewwa l-parentesi.

607
00:26:44,580 --> 00:26:47,288
>> DAVID Malan: U hekk jidher like--
fil-lecture, per eżempju,

608
00:26:47,288 --> 00:26:50,250
I kważi dejjem jużaw, bħal, iu
nu varjabbli pretty boring.

609
00:26:50,250 --> 00:26:53,050
Jidher qisu inti tista 'tuża aktar
cleverly varjabbli msemmija, wisq.

610
00:26:53,050 --> 00:26:56,300
>> MARIA: Yeah, huwa attwalment sbieħ ħafna
l-użu varjabbli daqsxejn aktar deskrittivi

611
00:26:56,300 --> 00:26:59,400
għaliex speċjalment jekk xi ħadd ieħor huwa
qari code-- tiegħek forsi int grader

612
00:26:59,400 --> 00:27:00,940
jew jekk int jikkollaboraw
ma somebody--

613
00:27:00,940 --> 00:27:03,481
inti tixtieq li tagħmel ċert li huma
jifhmu dak li qed isir.

614
00:27:03,481 --> 00:27:05,750

615
00:27:05,750 --> 00:27:06,400
>> KOLLOX SEW.

616
00:27:06,400 --> 00:27:11,435
Allura din hija xi ħaġa funky-- ħafna
għal loop ġewwa għall loop.

617
00:27:11,435 --> 00:27:13,060
I do not know jekk aħna stajt tidher dan qabel.

618
00:27:13,060 --> 00:27:13,830
Probabbilment le.

619
00:27:13,830 --> 00:27:17,750
Iżda nistgħu attwalment ikollhom this--
hekk ċirkwiti minflok loops.

620
00:27:17,750 --> 00:27:25,130
Allura ħadd ma tridx li forsi jimxu
lili permezz x'inhu għaddej hawn?

621
00:27:25,130 --> 00:27:28,240

622
00:27:28,240 --> 00:27:29,490
DAVID Malan: I ser tieħu stab.

623
00:27:29,490 --> 00:27:29,970
MARIA: Kessaħ.

624
00:27:29,970 --> 00:27:30,636
DAVID Malan: OK.

625
00:27:30,636 --> 00:27:34,690
Allura, spoiler-- aħna tixtieq li jistampaw l-għalf
li fil-kantuniera tal-lemin t'isfel

626
00:27:34,690 --> 00:27:35,190
hemmhekk.

627
00:27:35,190 --> 00:27:35,450
>> MARIA: Dritt.

628
00:27:35,450 --> 00:27:35,710
Ijja ijja.

629
00:27:35,710 --> 00:27:38,043
>> DAVID Malan: Allura aħna ħadthom biss
iqiegħed dak output kampjun hemmhekk.

630
00:27:38,043 --> 00:27:42,590
So I jistgħu jiddeduċu mill-
loop topmost li int

631
00:27:42,590 --> 00:27:45,680
mtennija fuq ringieli il
loop aktar imbiegħed, biex ngħidu hekk.

632
00:27:45,680 --> 00:27:48,107
U int mtennija fuq
kolonni bl-linja ġewwanett.

633
00:27:48,107 --> 00:27:50,190
U intuwittivament, dan
għandhom nisperaw jagħmel sens

634
00:27:50,190 --> 00:27:52,070
minħabba fin-natura ta '
kull programm Rajna

635
00:27:52,070 --> 00:27:55,570
qabel, printf, li hija l-
funzjoni aħna qed jużaw, finalment,

636
00:27:55,570 --> 00:27:58,190
għandu l-kapaċità li jistampaw Jittieħed
out essenzjalment linja b'linja.

637
00:27:58,190 --> 00:27:59,960
Bħal, ladarba inti ħadthom outputted
linja ġdida, hemm

638
00:27:59,960 --> 00:28:02,876
ebda irduppjar lura u l-istampar xi ħaġa
ogħla fil-iskrin, mill-inqas

639
00:28:02,876 --> 00:28:04,530
ma jużawx printf bħal dan.

640
00:28:04,530 --> 00:28:07,750
>> U hekk F'dan ir-rigward, jagħmel
sens li l-linja ta 'barra nett

641
00:28:07,750 --> 00:28:10,930
għandhom ikunu jirreferu għall-ringieli
minħabba li għal kull mogħti ringiela,

642
00:28:10,930 --> 00:28:13,650
int tmur jridu
jistampa XXXXX, u mbagħad

643
00:28:13,650 --> 00:28:15,520
jimxu fuq il-filliera li jmiss, XXXXX.

644
00:28:15,520 --> 00:28:17,317
Allura ringieli jasal l-ewwel.

645
00:28:17,317 --> 00:28:19,150
U allura f'kull
ringiela, tistampa kolonni.

646
00:28:19,150 --> 00:28:21,160
Jekk inti ippruvaw jagħmlu dan l-
oppost, ikun probabbilment mhux

647
00:28:21,160 --> 00:28:21,690
toħroġ bħala ħsiebek.

648
00:28:21,690 --> 00:28:22,190
>> MARIA: Yeah.

649
00:28:22,190 --> 00:28:24,950
Aħna biss ma setgħux imorru lura għall
il-filliera ta 'qabel ma printf.

650
00:28:24,950 --> 00:28:27,658
>> DAVID Malan: U x'hemm interessanti
kull chat lum dwar ambitu,

651
00:28:27,658 --> 00:28:31,600
fil-fatt, hija li ringiela hija int
li l-ddikjarat fil-linja topmost.

652
00:28:31,600 --> 00:28:34,030
Iżda avviż li għadu
ġewwa ta ', biex ngħidu hekk,

653
00:28:34,030 --> 00:28:35,982
l-braces kaboċċi li
minnufih issegwi,

654
00:28:35,982 --> 00:28:38,440
anki jekk mhuwiex teknikament
fi ħdan dawk braces kaboċċi.

655
00:28:38,440 --> 00:28:41,750
Allura ringiela hija fl-iskop għall-
intier tal-snippet ta 'kodiċi,

656
00:28:41,750 --> 00:28:44,690
kemm ġewwa tal-extratmosferiku għall loop
u ġewwa tal-ġewwa għall loop.

657
00:28:44,690 --> 00:28:48,050
Iżda b'kuntrast, fejn
huwa kolonna fl-ambitu?

658
00:28:48,050 --> 00:28:49,810
Il-kolonna varjabbli?

659
00:28:49,810 --> 00:28:51,310
Yeah, biss fil-linja ġewwa.

660
00:28:51,310 --> 00:28:54,280
U li OK għaliex aħna ma aċċess
dan barra tal ċingi kaboċċi tagħha.

661
00:28:54,280 --> 00:28:57,280
Kollha għandna nagħmlu huwa print out ġdid
linja fl-aħħar nett hemmhekk.

662
00:28:57,280 --> 00:28:58,670
Allura li fil-fatt huwa OK.

663
00:28:58,670 --> 00:29:03,740
>> Għalhekk dan għandu l-effett, jidher qisu,
li jagħmlu tliet ringieli u kolonni erba.

664
00:29:03,740 --> 00:29:04,370
>> MARIA: Dritt.

665
00:29:04,370 --> 00:29:06,270
Allura l-ewwel aħna jgħaddu l-ewwel ringiela tagħna.

666
00:29:06,270 --> 00:29:10,520
U biss fl-ewwel ringiela tagħna, nagħmlu l-
erba 'kolonni ġewwa l-ewwel ringiela.

667
00:29:10,520 --> 00:29:11,980
Allura aħna jistampa erba X tal.

668
00:29:11,980 --> 00:29:15,800
U allura nistgħu joħorġu mis-għal loop, peress
konna diġà stampati erba X tal.

669
00:29:15,800 --> 00:29:17,100
U aħna jistampaw linja ġdida.

670
00:29:17,100 --> 00:29:19,920
U allura aħna jgħaddu l-
istess proċess għal żewġ ringieli aktar

671
00:29:19,920 --> 00:29:21,170
li jagħmlu total ta 'tlieta.

672
00:29:21,170 --> 00:29:23,530
>> DAVID Malan: U huwa ta 'min jinnota li huwa
biss artifact tal-font, il-fatt

673
00:29:23,530 --> 00:29:25,680
li l-output kampjun
jidhru tant taller,

674
00:29:25,680 --> 00:29:27,520
bħallikieku hemm aktar
ringieli minn kolonni.

675
00:29:27,520 --> 00:29:29,824
Iżda huwa biss minħabba l-X
huwa taller milli huwa wiesa '.

676
00:29:29,824 --> 00:29:32,740
Li kollox li jiġri hemmhekk,
flimkien mal-ispazju abjad bejn il-linji.

677
00:29:32,740 --> 00:29:33,281
>> MARIA: Dritt.

678
00:29:33,281 --> 00:29:34,792
Kessaħ.

679
00:29:34,792 --> 00:29:35,750
DAVID Malan: Kull dritt.

680
00:29:35,750 --> 00:29:39,830
Allura ħarsa lejn problema sett wieħed,
jieħdu xi mistoqsijiet, u mbagħad taġġorna?

681
00:29:39,830 --> 00:29:40,330
Kull dritt.

682
00:29:40,330 --> 00:29:43,164
Għalhekk fl problema sett wieħed, hemm tliet
isfidi primarji, finalment.

683
00:29:43,164 --> 00:29:44,955
Iżda l-ewwel, inti ser issib
li l-problema stabbilita

684
00:29:44,955 --> 00:29:47,900
ispeċifikazzjoni, kif ma 'ħafna l-
psets dan it-tnaqqis, se jimxu miegħek

685
00:29:47,900 --> 00:29:50,691
permezz ftit eżerċizzji warm-up,
punt inti out ftit riżorsi

686
00:29:50,691 --> 00:29:52,440
li inti tista 'jew
ma kienu diġà raw.

687
00:29:52,440 --> 00:29:54,440
Per eżempju, CS50
għandha suite ta xorts,

688
00:29:54,440 --> 00:29:56,481
li huma vidjos qosra,
ma b'differenza dan, iżda li

689
00:29:56,481 --> 00:29:58,460
huma specific-- suġġett ħafna
forsi ħames minuti,

690
00:29:58,460 --> 00:30:02,360
10 minuti fit-tul fuq loops jew
dwar il-kondizzjonijiet jew fuq algoritmi

691
00:30:02,360 --> 00:30:04,125
jew aktar tard aktar
suġġetti avvanzati, kif ukoll.

692
00:30:04,125 --> 00:30:06,000
U aħna ġeneralment ssodata
dawk il-problema

693
00:30:06,000 --> 00:30:07,950
settijiet sabiex l-istudenti
jkollhom riżorsi li magħhom

694
00:30:07,950 --> 00:30:10,840
biex tirrevedi materjal li jista 'jkollhom
diġà joħorġu fis lecture jew taqsima.

695
00:30:10,840 --> 00:30:13,220
Iżda dan il-mod huwa aktar iffokat
u aktar fuq ponot tagħhom.

696
00:30:13,220 --> 00:30:15,928
>> Aħna wkoll tendenza li ssodata fl problema
tistabbilixxi affarijiet imsejħa walkthroughs.

697
00:30:15,928 --> 00:30:20,790
Allura kważi kollha tal-eżempji I do
fil lecture, fuq il-palk hawnhekk, aħna wkoll

698
00:30:20,790 --> 00:30:24,565
shot fuq camera fil
javvanzaw aktar bil-mod,

699
00:30:24,565 --> 00:30:28,760
walkthrough aktar intimi minni fuq
laptop tiegħi ta 'dan il-kodiċi, linja b'linja

700
00:30:28,760 --> 00:30:31,427
sabiex fil-klassi, aħna ser spiss
skim permezz xi ħaġa jew xi ħadd

701
00:30:31,427 --> 00:30:33,260
se interject ma '
twieġeb għal mistoqsija.

702
00:30:33,260 --> 00:30:35,820
Iżda dan ma jfissirx neċessarjament sink
fil għal kulħadd fl-udjenza.

703
00:30:35,820 --> 00:30:38,230
Allura inti ser issib kodiċi walkthroughs
għal ħafna mill-eżempji

704
00:30:38,230 --> 00:30:40,950
li aħna nagħmlu hawnhekk fil lecture sabiex inti
tista 'timxi permezz ta' dan fil-pass tiegħek

705
00:30:40,950 --> 00:30:43,580
u Rewind jew fast quddiem jew
skip għal kollox, jekk inti tixtieq.

706
00:30:43,580 --> 00:30:45,356
>> Hemm ħafna drabi ftit
mistoqsijiet warm-up li

707
00:30:45,356 --> 00:30:47,105
nitolbok biex issolvi ta
isaħħu dan il-materjal

708
00:30:47,105 --> 00:30:50,250
u kun żgur li int comfy qabel
ma tipproċedi bil-bqija tal-pset.

709
00:30:50,250 --> 00:30:51,700
U allura, ovvjament,
hemm il-pset innifsu.

710
00:30:51,700 --> 00:30:53,450
U waħda mill-affarijiet
aħna deliberatament ħafna

711
00:30:53,450 --> 00:30:57,202
jagħmlu fil CS50 huwa kważi kull uninteresting
jew intellettwalment uninteresting

712
00:30:57,202 --> 00:30:58,910
pass mekkanika li
inti tista 'tagħmel

713
00:30:58,910 --> 00:31:00,519
huwa dokumentat kważi dejjem tajjeb ħafna.

714
00:31:00,519 --> 00:31:03,560
Matul il-kors tat-terminu, aħna ser
jibdew jistaqsu mistoqsijiet aktar rhetorical

715
00:31:03,560 --> 00:31:06,187
bħal ftakar kif tagħmel dan jew dak?

716
00:31:06,187 --> 00:31:08,520
Iżda ġeneralment, inti ser issib
li l-settijiet problema inti tikseb

717
00:31:08,520 --> 00:31:10,269
permezz tal-mechanics
ta 'xi ħaġa hekk li

718
00:31:10,269 --> 00:31:14,160
l-interessanti, l-isfidi intelletwali
huma finalment xellug biex inti l-istudent.

719
00:31:14,160 --> 00:31:17,390
>> Ma 'dak imsemmi, Zamyla, li min aħna
jinżammu jirreferi illum fil lecture,

720
00:31:17,390 --> 00:31:20,190
huwa wieħed mill-istaff żmien twil tagħna
membru li jkollu wkoll walkthroughs

721
00:31:20,190 --> 00:31:24,520
dwar problemi speċifiċi pset bħall mario
u greedy, għalkemm mhux ilma din is-sena.

722
00:31:24,520 --> 00:31:26,540
U huwa f'dawk
walkthroughs li hi spiss

723
00:31:26,540 --> 00:31:29,450
joffri xi tips u tricks għall
kif tipproċedi, qatt tghidlek

724
00:31:29,450 --> 00:31:31,810
eżattament x'għandhom jagħmlu, iżda
rather-- bħal kundizzjoni,

725
00:31:31,810 --> 00:31:35,200
jekk inti will-- giving you inqas
ftit ideat b'tali mod li huwa sa inti,

726
00:31:35,200 --> 00:31:37,830
finalment, li jiddeċiedi
kif approċċ lilhom.

727
00:31:37,830 --> 00:31:41,200
>> MARIA: tip simili ta 'livell għoli
fehim tal-loġika ta 'dak

728
00:31:41,200 --> 00:31:42,220
aħna inti titlob sabiex tagħmel.

729
00:31:42,220 --> 00:31:42,485
>> DAVID Malan: Eżattament.

730
00:31:42,485 --> 00:31:44,190
U, fil-fatt, Zamyla ta
walkthroughs huma maħsuba

731
00:31:44,190 --> 00:31:46,190
tingħata risposta għad-frekwentement
mistoqsija ta 'fejn

732
00:31:46,190 --> 00:31:48,610
do I bdiet, speċjalment meta
dawn l-ispeċifikazzjonijiet twil huma

733
00:31:48,610 --> 00:31:51,960
ftit kbar partikolari it-test kollu
u xbihat li jkollhom fihom.

734
00:31:51,960 --> 00:31:54,890
>> Allura water.c, inti ser issib
wara li tkun ħadthom kompletati dan,

735
00:31:54,890 --> 00:31:56,920
huwa attwalment relattivament sempliċi.

736
00:31:56,920 --> 00:31:58,882
Assolutament huma mazz
minnkom se bang

737
00:31:58,882 --> 00:32:01,840
kapijiet tiegħek kontra l-ħajt jippruvaw
biex insemmu għaliex mhuwiex kumpilazzjoni

738
00:32:01,840 --> 00:32:03,450
jew għaliex huwa ma tkunx qed taħdem b'mod korrett.

739
00:32:03,450 --> 00:32:05,040
Imma ladarba inti qed isir
magħha u ladarba inti ħadthom

740
00:32:05,040 --> 00:32:07,620
qattgħu xi żmien lotta ma 'kwalunkwe
mill-bugs li jista 'jkollok,

741
00:32:07,620 --> 00:32:09,490
inti ser issib li huwa
programm qasir ħafna.

742
00:32:09,490 --> 00:32:11,770
Dan jista 'jsir biss fi ftit
linji ta 'kodiċi, li ħafna minnhom

743
00:32:11,770 --> 00:32:15,030
Rajna hawn fil lecture diġà, jekk
inti tiġbor l-blokki tal-bini dritt.

744
00:32:15,030 --> 00:32:16,810
>> U kif aħna nissuġġerixxu
hawn, li għaddej biex jistaqsu

745
00:32:16,810 --> 00:32:22,250
inti tispeċifika kemm il minuta
xi ħadd qed tieħu doċċa fuq il-kampus.

746
00:32:22,250 --> 00:32:24,779
Aħna jispeċifikaw fil-problema
iffissar tar-rata ta 'fluss ta' ilma

747
00:32:24,779 --> 00:32:27,320
fil, bħal, a-fluss baxx doċċa
ras, ħafna bħall-clip Seinfeld

748
00:32:27,320 --> 00:32:29,180
rajna bieraħ jew
l-oppost tagħha.

749
00:32:29,180 --> 00:32:30,971
U allura inti biss għandek
li jagħmlu daqsxejn ta 'matematika,

750
00:32:30,971 --> 00:32:34,710
really-- aritmetika jużaw C li tgħid
us kif ħafna, madwar, fliexken ta 'ilma

751
00:32:34,710 --> 00:32:37,720
huwa li ekwivalenti għal jekk aħna qed
jieħdu n-minuta doċċa.

752
00:32:37,720 --> 00:32:41,389
>> Issa, fil mario.c, dan se
li jkun programm kemmxejn itwal.

753
00:32:41,389 --> 00:32:42,930
Huwa għadu mhux se jkun dan twil.

754
00:32:42,930 --> 00:32:45,130
Just ftit linji itwal minn water.c.

755
00:32:45,130 --> 00:32:48,230
Iżda li għaddej biex tkun opportunità
jirrikreaw l-iskola antika Mario

756
00:32:48,230 --> 00:32:50,670
piramida mill Super Mario
Brothers jew xi ta 'segwitu.

757
00:32:50,670 --> 00:32:53,510
Mhuwiex ser tfittex bħala prettier
jew bħala colorful bħala li waħda hemm.

758
00:32:53,510 --> 00:32:56,468
Aħna biss ser tuża hashtags ftit
bħal għandna hawnhekk fuq l-iskrin

759
00:32:56,468 --> 00:32:58,120
jużaw it-test ASCII.

760
00:32:58,120 --> 00:33:00,362
Iżda se tqarreb l-istess idea.

761
00:33:00,362 --> 00:33:02,570
U li għaddej biex tkun
jeżerċita dik ewwel daqqa t'għajn

762
00:33:02,570 --> 00:33:04,720
Jidher pjuttost simple-- biss
stampar ta 'piramida sempliċi.

763
00:33:04,720 --> 00:33:07,345
Iżda hemm xi karatteristiċi koppja
hawnhekk li huma interessanti.

764
00:33:07,345 --> 00:33:12,400
Avviż li t-tarf lemini tal
il-piramida fil-fatt għandu wisa tnejn.

765
00:33:12,400 --> 00:33:14,570
Allura hemm żewġ ugwali
kolonni għoli, li

766
00:33:14,570 --> 00:33:16,804
jagħmilha jeħtieġu ftit
daqsxejn ta 'ħsieb li jagħmlu

767
00:33:16,804 --> 00:33:19,720
ruħek li tikseb dak eżattament id-dritt, kif
kuntrarju biss perfettament angolata

768
00:33:19,720 --> 00:33:20,220
linja.

769
00:33:20,220 --> 00:33:23,340
Allura dak daqsxejn ta 'każ kantuniera
imma jaqbel mal-logħba attwali.

770
00:33:23,340 --> 00:33:27,610
>> U huwa wkoll mhux ovvju fl-ewwel
t'għajn kif jistampaw l-ispazju abjad.

771
00:33:27,610 --> 00:33:29,430
Allura meta I tħares lejn l-
kampjun output here--

772
00:33:29,430 --> 00:33:32,440
u huwa wkoll fil-spec-- dan
tip ta qisu rettangolu,

773
00:33:32,440 --> 00:33:35,120
iżda djagonali tal-
rettangolu ġie mqatta off,

774
00:33:35,120 --> 00:33:37,320
u huwa biss spazji bojod, biex ngħidu hekk.

775
00:33:37,320 --> 00:33:40,100
U għalhekk spiss staqsa
kwistjoni hawnhekk hija dejjem, ukoll,

776
00:33:40,100 --> 00:33:43,302
kif nista jiċċaqalqu l-hashtags
fuq il-lemin?

777
00:33:43,302 --> 00:33:44,760
Jew kif nista jistampaw l-ispazji vojta?

778
00:33:44,760 --> 00:33:46,860
U huwa attwalment aktar faċli
milli ħafna studenti jaħsbu.

779
00:33:46,860 --> 00:33:47,360
Dritt?

780
00:33:47,360 --> 00:33:51,620
Tista approssimati viżwalment bi ftit
laqtu l-ispazju bar darba jew darbtejn

781
00:33:51,620 --> 00:33:52,700
jew tliet darbiet.

782
00:33:52,700 --> 00:33:56,260
>> U hekk anke jekk ma printf aħna kważi
dejjem jistampa string jew int

783
00:33:56,260 --> 00:33:59,950
jew kelma bħal "hello,
dinja "jew serje ta 'kliem,

784
00:33:59,950 --> 00:34:03,560
inti tista 'ukoll biss print
kwotazzjoni, l-ispazju, unquote.

785
00:34:03,560 --> 00:34:06,320
U li fil-fatt se tagħti
inti spazju abjad hemmhekk.

786
00:34:06,320 --> 00:34:08,330
Sabiex iżommu dan f'moħħhom u
ma overthink dan.

787
00:34:08,330 --> 00:34:10,570
Int verament għandhom
tiddeċiedi ringiela mill ringiela mill ringiela,

788
00:34:10,570 --> 00:34:14,280
b'differenza ma Eżempju tiegħek
mument ilu, kemm ta 'dawk

789
00:34:14,280 --> 00:34:18,420
kolonni għandhom ikunu spazji bojod u
kemm minnhom għandu jkun hashtags.

790
00:34:18,420 --> 00:34:21,560
Huwa se jieħu ftit ta 'żmien, iżda huwa
finalment puzzle loġika ta 'tip.

791
00:34:21,560 --> 00:34:22,060
>> MARIA: Yeah.

792
00:34:22,060 --> 00:34:25,060
Iżda l-loġika ta 'ringiela għaddej minn ringiela
se tkun utli ħafna hawn.

793
00:34:25,060 --> 00:34:25,810
DAVID Malan: Yeah.

794
00:34:25,810 --> 00:34:28,976
Naħseb li l-kodiċi kampjun inti gave-- anki
għalkemm ma kienx programm komplet.

795
00:34:28,976 --> 00:34:34,247
Inti xorta jkollok bżonn int u prinċipali
u stdio.h null u #include,

796
00:34:34,247 --> 00:34:35,580
ħafna ta 'l-għalf minn lecture.

797
00:34:35,580 --> 00:34:37,629
Iżda l-blokki tal-bini
jidhru li huma hemmhekk.

798
00:34:37,629 --> 00:34:39,920
U allura finalment hija xi ħaġa
ftit aktar algorithmic.

799
00:34:39,920 --> 00:34:43,210
Għalhekk jirriżulta li kull darba li inti
jmorru fil CVS jew kwalunkwe store konvenjenza

800
00:34:43,210 --> 00:34:47,810
u xi ħadd idejn inti fil-
bills kaxxier jew muniti bħala bidla,

801
00:34:47,810 --> 00:34:50,620
jirriżulta li dawn, il-bnedmin,
kemm jekk taf jew le,

802
00:34:50,620 --> 00:34:53,300
probabilment tuża x'hemm
imsejħa algoritmu greedy,

803
00:34:53,300 --> 00:34:58,170
li biha jekk int dovuti, jiġifieri, $ 21
fil-bidla għaliex għal xi raġuni

804
00:34:58,170 --> 00:35:01,580
inti xtrajt xi ħaġa ħafna rħas
bil-kont kbir ħafna fil CVS,

805
00:35:01,580 --> 00:35:05,910
ikun verament annoying jekk il
kaxxier ħadt 21 singles jew, agħar

806
00:35:05,910 --> 00:35:07,629
għadhom, lott kollu ta 'muniti.

807
00:35:07,629 --> 00:35:10,670
Pjuttost, dak li persuna raġjonevoli hija
probabbilment ser tagħmel hu li dawn qed tmur

808
00:35:10,670 --> 00:35:14,224
li grab $ 20 u mbagħad $ 1-kont, u
banda inti biss żewġ kontijiet f'dik il-kawża.

809
00:35:14,224 --> 00:35:17,390
MARIA: Allura dawn qed ifittxu li jimminimizzaw
il-bidla li jagħtu lura lilek.

810
00:35:17,390 --> 00:35:17,850
DAVID Malan: Eżattament.

811
00:35:17,850 --> 00:35:19,540
U istess jittrattaw muniti, kif ukoll.

812
00:35:19,540 --> 00:35:23,040
Jekk inti qed dovut, jiġifieri, $ 0.50,
nisperaw li int ma tridx 50 pennies.

813
00:35:23,040 --> 00:35:25,500
Inti minflok tixtieq żewġ
kwarti, per eżempju.

814
00:35:25,500 --> 00:35:27,540
Issa, dan ma jassumu
li l-kaxxier għandha

815
00:35:27,540 --> 00:35:29,940
biżżejjed ta 'kull denominazzjoni li
hu jew hi jista 'jkun irid jtik.

816
00:35:29,940 --> 00:35:32,148
Iżda aħna ma jippermettu li inti tassumi
kemm fil-problema.

817
00:35:32,148 --> 00:35:35,590
U l-għan, finalment, huwa li
jimplimentaw kodiċi C algoritmu greedy.

818
00:35:35,590 --> 00:35:37,344
Allura l-utent huma permessi
it-tip fil kemm

819
00:35:37,344 --> 00:35:40,510
bidla hu jew hi huwa dovut ma 'dollari
u ċenteżmi, xi tip ta 'floating point

820
00:35:40,510 --> 00:35:41,590
valur probabbilment.

821
00:35:41,590 --> 00:35:45,530
U allura inti għandek tagħmel l-matematika u
figura algorithmically, ukoll,

822
00:35:45,530 --> 00:35:49,020
kif muniti ħafna tista 'tagħti I
inti minimament biex jagħtuk

823
00:35:49,020 --> 00:35:50,270
eżattament dak l-ammont ta 'bidla.

824
00:35:50,270 --> 00:35:53,470
Iżda hemm għaddej li jkun
partijiet delikata ftit hawn, id-dritt?

825
00:35:53,470 --> 00:35:56,236
Simili hemm l-sħiħ
kwistjoni impreċiżjoni.

826
00:35:56,236 --> 00:35:56,860
MARIA: Eżattament.

827
00:35:56,860 --> 00:35:59,114
Punt hekk floating
Valuri jkollhom impreċiżjoni.

828
00:35:59,114 --> 00:36:00,780
Did nitkellmu dwar dan fil lecture llum?

829
00:36:00,780 --> 00:36:02,340
>> DAVID Malan: Aħna ma l-
aħħar darba fl-lecture.

830
00:36:02,340 --> 00:36:03,506
Aħna tkellimna dwar impreċiżjoni.

831
00:36:03,506 --> 00:36:08,840
U inti ma tridx li iqarrqu-utent
ta 'kemm it-tibdil hu jew hi huwa dovut.

832
00:36:08,840 --> 00:36:11,290
U għalhekk l-walkthrough, fil
il-problema sett ispeċifikazzjoni,

833
00:36:11,290 --> 00:36:15,990
jaħsbu ftit, finalment, li
kif tista 'jittaffew dawk impreċiżjoni

834
00:36:15,990 --> 00:36:17,280
żbalji, potenzjalment.

835
00:36:17,280 --> 00:36:21,050
Huwa evitabbli, ċertament, għall
l-inputs aħna qed jitkellem dwar.

836
00:36:21,050 --> 00:36:23,590
U, fil-fatt, pennies--
forsi aħna ser tiddifferixxi għall Zamyla,

837
00:36:23,590 --> 00:36:25,136
I think, għall-tricks hemmhekk.

838
00:36:25,136 --> 00:36:27,760
Allura finalment, inti ser issib
progressjoni ta 'problemi din il-ġimgħa,

839
00:36:27,760 --> 00:36:30,700
l-ewwel waħda minnhom hija pjuttost żgħira,
imbagħad medju, allura ftit akbar.

840
00:36:30,700 --> 00:36:33,200
Iżda kollha kemm huma jużaw l-bini
blokki mill din il-ġimgħa passat,

841
00:36:33,200 --> 00:36:35,280
minn dan supersection,
problema stabbiliti ispeċifikazzjoni

842
00:36:35,280 --> 00:36:36,710
tpoġġik riżorsi innumerabbli.

843
00:36:36,710 --> 00:36:41,000
Iżda xorta, jekk xejn jitħabtu,
speċjalment fost dawk inqas komdi

844
00:36:41,000 --> 00:36:42,917
bl-ebda sfond minn qabel,
jaslu għal ħinijiet tal-uffiċċju

845
00:36:42,917 --> 00:36:44,958
nhar it-Tnejn u t-Tlieta u
L-Erbgħa u l-Ħamis.

846
00:36:44,958 --> 00:36:46,950
Mur fil CS50 Iddiskuti permezz
websajt tal-kors, l

847
00:36:46,950 --> 00:36:49,080
li permezz tagħhom inti tista 'chat
b'impjegati u klassi.

848
00:36:49,080 --> 00:36:51,670
>> Iżda fl-aħħar, naħseb li l-
aħjar parir huwa biss jibdew kmieni.

849
00:36:51,670 --> 00:36:54,711
Mhuwiex-tip ta 'klassi li inti
għandhom ikunu qed jibdew psets nhar l-Erbgħa

850
00:36:54,711 --> 00:36:56,640
lejl, jew tal-lejl il-Ħamis agħar.

851
00:36:56,640 --> 00:36:59,067
>> MARIA: aħjar parir tiegħi huwa
li bdew mill Tnejn.

852
00:36:59,067 --> 00:36:59,900
DAVID Malan: it-tnejn.

853
00:36:59,900 --> 00:37:02,490
Mela jekk int ma bdew already-- ebda.

854
00:37:02,490 --> 00:37:04,732
Iżda anke jekk mhux it-tnejn, imbagħad it-Tlieta.

855
00:37:04,732 --> 00:37:05,690
L-ewwel l-aħjar.

856
00:37:05,690 --> 00:37:08,605
U dak l-raġuni l-
kors tant ġranet tardivi

857
00:37:08,605 --> 00:37:10,535
biex jagħtuk daqsxejn ta '
pressjoni psikoloġika

858
00:37:10,535 --> 00:37:13,684
biex jibdew aktar kmieni iżda xorta jħallu
affarijiet slip meta l-affarijiet jieħu aktar

859
00:37:13,684 --> 00:37:14,350
milli għandek tistenna.

860
00:37:14,350 --> 00:37:17,950
>> MARIA: U inti tixtieq li tagħmel użu ta '
ħinijiet tal-uffiċċju kif kemm tista ', wisq.

861
00:37:17,950 --> 00:37:20,291
>> DAVID Malan: Kwalunkwe mistoqsijiet?

862
00:37:20,291 --> 00:37:20,790
Kull dritt.

863
00:37:20,790 --> 00:37:22,930
Well, għaliex ma we taġġorna hawn?

864
00:37:22,930 --> 00:37:23,487