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>> DAVID J Malan: All
dritt, għalhekk dan huwa CS50.

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U dan huwa manifestament il-ġimgħa.

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U dan huwa l-aħħar ta 'ġimgħa.

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Allura inti tista 'tfakkar li aħna jitħalla' off,
aħħar darba, ma 'cliffhanger ta' tip.

6
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Li biha aħna jesponu dan jinsabu, li l-ebda
jimpurtax dak li inti kont qed mgħallem tikber

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up, 1 maqsum f'10 mhuwiex, fil
fatt, 0.1 jew 0.100 jew 0.10000.

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Fil-fatt, jekk aħna jiġbor dan
programm, kif għamilna bieraħ, bil,

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jagħmlu impreċiżjoni, u mbagħad
do dot, mmejla, impreċiżjoni,

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aħna tgħallimna li dan huwa dak li
1 maqsum f'10 fatt hu.

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Allura li mhux verament pjuttost il-każ.

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Iżda dan ma ħjiel f'xi
limitazzjoni fundamentali ta 'kompjuters.

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U fil-fatt, fost l-
affarijiet aħna qed tmur biex tagħmel

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llum hija tagħti ħarsa lejn għaliex dan għandu
ġara, x'implikazzjonijiet dan għandu,

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kif umanità naqset
li jaħtfu din f'xi ħafna

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situations-- serju
ir-riżultat tal-li

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kienet pjuttost traġika
u expensive-- u wkoll

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tagħti ħarsa lejn kif aħna
jistgħu attwalment tiddefendi

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kontra dawn it-tipi ta 'limitazzjonijiet.

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Allura intuwittivament, forsi,
għaliex huwa 1 maqsum f'10,

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skond il-kompjuter tiegħi
hawn, mhux biss 1/10, 0.10?

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Yeah.

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What do you think?

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>> Udjenza membru: Il radix hija differenti?

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>> DAVID J Malan: Il x'inhu?

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Oh, il radix huwa differenti?

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Allura ma pjuttost.

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Huwa attwalment aktar
fundamentali għall-hardware.

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Ħsibijiet oħra?

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Yeah.

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Udjenza membru: Huma
jirrappreżentaw numri differenti?

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DAVID J Malan: Allura they-- Dritt.

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Huma jirrappreżentaw numri differenti.

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Impreċiż, apparentement.

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Allura li is-- Well,
differenti minn dak?

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Jew minn min?

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Minna?

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Udjenza membru: Yeah.

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Ma jużawx l-deċimali
sistema biex [inaudible].

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DAVID J Malan: OK.

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Allura f'ċertu sens, dawn ma
jużaw is-sistema deċimali.

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Taht il-barnuża,
kollox huwa, tabilħaqq, binarja,

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u li kienet tirrigwarda, fil-fatt.

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Iżda huwa saħansitra aktar sempliċi
spjegazzjoni minn dak.

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Yeah.

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>> Udjenza membru: Huma
biss tant bits.

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Huma jistgħu biss jaħżen sa ċertu
punt, bħal ma l-deċimali.

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>> DAVID J Malan: Yeah.

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Dan huwa dak li verament jkollna fiha.

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Jirriżulta li l-kompjuters
tipikament, dejjem se biss

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jużaw ammont finit ta 'informazzjoni
li jirrappreżentaw xi ħaġa.

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Dritt?

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Wara kollox, aħna biss ikollhom fissa
ammont ta 'spazju hard disk.

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Aħna biss ammont fiss
RAM, jew memorja tal-kompjuter.

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U jekk inti biss għandek
ammont fiss ta 'xi ħaġa,

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żgur inti ma tistax attwalment joqgħod up
għall-infinit jew kwalunkwe numru tixtieq.

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You, tip ta ', għandek
toqgħod tagħżel liema firxa

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ta 'valuri int ser tappoġġja.

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>> U għalhekk per eżempju, ġimgħa jew tnejn
ilu, meta aħna tkellem dwar ASCII,

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u tkellimna madwar 8 bits,
jew byte, biex ngħidu hekk,

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l-akbar numru nistgħu
jirrappreżentaw bi 8 bits kien dak?

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255.

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U nistgħu jirrappreżentaw 256-valuri totali
iżda mhux jekk nonfqu wieħed minnhom

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fuq 0-- Ukoll, imma jekk irridu
jonfqu wieħed minnhom fuq 0,

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allura l-akbar numru
huwa, ovvjament, 255.

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>> Għalhekk jirriżulta li, li dan huwa
il-każ ukoll, f'dan il-kuntest.

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Bdejna nitkellmu, l-aħħar darba,
dwar b'punt numri, li

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huma differenti minn interi, fil
li dawn ikollhom punt deċimali

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u, wieħed jittama, xi numri
wara li, iżda huma wisq.

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A kompjuter huwa biss tipikament se
li uża 32 bits, forsi 64 bits

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li jirrappreżenta valur b'punt li jvarja.

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Għalhekk anki jekk konna kibret
matematika tagħlim u jafu

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li inti tista 'assolutament ma
numru infinit ta 'numri

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wara l-punt deċimali, mhux
jekk għandek memorja finite.

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You, tip ta ', jkollu jarrotonda,
jew toqgħod tagħżel liema

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numri int ser jirrappreżentaw.

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U għalhekk inti tista 'taħseb, f'ċertu sens,
dan huwa l-kompjuter eqreb

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approssimazzjoni tal-valur 1/10 li
hija tista 'tikseb, bi ftit 32 jew hekk bits.

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U m'humiex biss 1/10.

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>> Per eżempju, jekk nibdel dan
03/01, li aħna naħsbu li hija saħansitra aktar sempliċi.

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Allura 1 maqsum bi 3.

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Let me tiffranka l-fajl.

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Let me imorru quddiem u recompile dan.

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U let me terġa 'run.

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Hawnhekk ukoll, apparentement, 03/01 mhuwiex 0.3
u mbagħad numru infinit ta '3 ta

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wara.

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Inti għandek dan nuqqas ta 'preċiżjoni fl-aħħar.

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Allura aħna bnedmin huma korretti, u liema
inti tgħallimt jiġifieri, fil-fatt, korretta,

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imma aħna qed bumping up
kontra xi limitazzjonijiet.

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>> U dak li ħsibt
aħna'd tagħmel illum, huwa tibda

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billi tħares lejn, franchement, il
konsegwenzi traġiċi tat dan

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kultant, meta umanità
ma pjuttost jimplimentaw

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għal din ir-realtà u dawn il-limitazzjonijiet.

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U aħna ser tara serje ta 'vignettes
mill-Kanal Istorja li jieħu

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ħarsa lejn kif l-affarijiet marru ħażin.

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Huwa madwar 8 minuti fit-tul,
u aħna ser terga 'lura wara din

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u tagħti ħarsa lejn eżattament
x'iktar tista 'tmur ħażin.

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Jekk nistgħu dim l lights--

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>> [Daqq video]

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>> -Computers, Aħna ve kollha waslu li jaċċettaw
il-problemi spiss frustranti li

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jmorru magħhom.

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Bugs, viruses, u software
glitches huma l-prezzijiet żgħar

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li tħallas għall-konvenjenza.

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Iżda ta 'teknoloġija għolja fil u ta' veloċità għolja
applikazzjonijiet programm spazjali militari u,

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l-iżgħar problema tista
jiġi eżaltat fil diżastru.

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4 Ġunju, 1996, xjentisti ippreparata
li tniedi mingħajr ekwipaġġ Ariane 5 rokit.

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Kien jġorru xjentifika
satelliti mfassla

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biex tistabbilixxi preċiżament kif l-
Jinteraġixxi Dinja kamp manjetiku

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mal-irjieħ solari.

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Il rokit kienet mibnija għall
l-Aġenzija Spazjali Ewropea

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u tintrefa 'minn faċilità tagħha
fuq il-kosta tal-Gujana Franċiża.

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>> -u Madwar 30 sekonda fi
it-titjira, l-ewwel

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xi ħaġa ndunat kienet tmur ħażina.

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Li l-żennuni kienu swiveling
b'mod li verament m'għandhomx.

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Madwar 40 sekonda fil-titjira,
b'mod ċar il-vettura kien fl-inkwiet,

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u li meta huma jkunu għamlu
id-deċiżjoni li tiddistruġġih.

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A Uffiċjal tas-Sigurtà Medda ma
imsaren tremendi ippressat il-buttuna,

118
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nefaħ l-rokit qabel ma seta '
issir periklu għas-sigurtà pubblika.

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>> -Dan Kien il xebba
vjaġġ tal-5 Ariane,

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u l-qerda tagħha ħa
post minħabba difett

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inkorporati fis-software tal-rokit li.

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-Il-Problema fuq il-
Ariane kienet li hemm

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kien numru dak meħtieġ
64 bits li jesprimi,

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u ried li jikkonvertu
lil numru 16 bit.

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Assumew li l-għadd
qatt kienet se tkun kbira ħafna,

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li ħafna minn dawk ċifri fil
in-numru 64 bit kienu 0 tal.

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Huma kienu żbaljati.

128
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>> -Il-Inkapaċità ta 'waħda
programm tas-software li jaċċettaw

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it-tip ta 'numru iġġenerat mill
ieħor kien fil-għerq tan-nuqqas.

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Żvilupp tas-softwer kienet saret
parti jiswew ħafna ta 'teknoloġija ġdida.

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L-rokit Ariane 4 kien ferm
suċċess, tant tas-software

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maħluqa għall kien ukoll
użati fuq il Ariane 5.

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>> -Il-Problema bażika kienet li l-Ariane
5 kien aktar mgħaġġel, mgħaġġla aktar malajr.

134
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U s-software ma kinitx
ammontaw għal dan.

135
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>> -Il-Qerda tal-rokit
kien hemm diżastru finanzjarju kbir,

136
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kollha minħabba żball software minuta.

137
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Iżda dan ma kienx l-ewwel
problemi ta 'konverżjoni data fil-ħin

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kien ibati teknoloġija rokit moderna.

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>> -In 1991, bil-bidu
tal-Ewwel Gwerra tal-Golf,

140
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l-missili Patriot
esperjenzaw tip simili

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ta 'problema konverżjoni numru.

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Bħala riżultat, 28 nies,
28 suldati Amerikani

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nqatlu u madwar
100 oħrajn feruti,

144
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meta l-Patriot, li suppost kellha
għall-protezzjoni kontra scuds deħlin,

145
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naqas milli nar missili.

146
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>> -Meta Iraq invadiet Kuwajt u l-Amerika
imnedija deżert Storm fil-bidu 1991,

147
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Batteriji missili Patriot ġew skjerati
biex jipproteġu Għarabja Sawdita u l-Iżrael

148
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minn attakki bil-missili Scud Iraqini.

149
00:06:37,000 --> 00:06:40,610
Il Patriot hija Istati Uniti, firxa medja
wiċċ-to-air sistema

150
00:06:40,610 --> 00:06:43,010
manifatturat mill-kumpanija Raytheon.

151
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>> -Il-Daqs tal-interċetturi Patriot,
innifsu, huwa dwar, madwar 20 pied fit-tul.

152
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U li jiżen madwar 2000 liri.

153
00:06:51,250 --> 00:06:55,195
U twettaq warhead ta about--
Naħseb li huwa bejn wieħed u ieħor 150 £.

154
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U l-warhead, hija stess,
huwa splussiv ħafna,

155
00:06:59,500 --> 00:07:02,570
li għandha frammenti madwaru.

156
00:07:02,570 --> 00:07:06,890
Il-kaxxa tal-warhead huwa
mfassla biex jaġixxu bħall buckshot.

157
00:07:06,890 --> 00:07:09,130
>> -Il Missili huma
mwettqa, 4 għal kull kontenitur,

158
00:07:09,130 --> 00:07:12,080
u huma trasportati minn semi-karru.

159
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>> -Il Anti missili Patriot
tmur lura għall-inqas 20 snin issa.

160
00:07:19,100 --> 00:07:22,320
Din kienet oriġinarjament iddisinjata
bħala missili difiża arja

161
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li rimja fl ajruplani ghadu.

162
00:07:24,180 --> 00:07:27,860
Fil-Gwerra tal-Golf ewwel,
meta dik gwerra daħlet tul,

163
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l-Armata riedu jużawh għal
rimja fl scuds, mhux ajruplani.

164
00:07:32,745 --> 00:07:36,150
Il-Forza Iraqi ma kienx
hekk ħafna ta 'problema,

165
00:07:36,150 --> 00:07:39,110
iżda l-Armata kien inkwetat dwar scuds.

166
00:07:39,110 --> 00:07:42,340
U għalhekk huma ppruvaw
jaġġornaw il-Patriot.

167
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>> -Intercepting Ghadu
missili jivvjaġġaw mach ħamsa

168
00:07:44,760 --> 00:07:47,250
kienet se tkun sfida biżżejjed.

169
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Iżda meta l-Patriot
kien ġrew fis-servizz,

170
00:07:50,000 --> 00:07:54,030
l-Armata ma kienx konxju ta '
Modifika Iraqi li għamel

171
00:07:54,030 --> 00:07:56,840
scuds tagħhom kważi impossibbli li hit.

172
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>> Liema ġara, hija l-scuds li
kienu ġejjin fi, kienu instabbli,

173
00:08:01,020 --> 00:08:02,310
kienu wobbling.

174
00:08:02,310 --> 00:08:05,140
Ir-raġuni għal dan,
kien l-Iraqini, sabiex

175
00:08:05,140 --> 00:08:09,450
tikseb 600 kilometru mill
missili medda 300 kilometru,

176
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ħa piż mill-warhead ta 'quddiem
u għamel l-warhead eħfef.

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00:08:12,930 --> 00:08:17,710
Allura issa, l-Patriot tipprova toħroġ
fil-SCUD, u ħafna mill-ħin,

178
00:08:17,710 --> 00:08:21,700
il-maġġoranza assoluta tal-
ħin, ikun biss jtiru mill-SCUD.

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00:08:21,700 --> 00:08:25,700
>> -Ladarba L-operaturi tas-sistema Patriot
realizzati l-Patriot spiċċa barra,

180
00:08:25,700 --> 00:08:29,790
dawn jisplodu warhead tal-Patriot, il
biex jiġi evitat diżgrazzji possibbli jekk hija

181
00:08:29,790 --> 00:08:32,380
kien permess li jaqa 'l-art.

182
00:08:32,380 --> 00:08:36,340
>> -Li Kien dak li ħafna nies raw,
dawk fireballs kbar fis-sema,

183
00:08:36,340 --> 00:08:41,289
u mifhuma ħażin bħala
interċettazzjonijiet ta testati Scud.

184
00:08:41,289 --> 00:08:43,590
Għalkemm fil-lejl
smewwiet, Patriots deher

185
00:08:43,590 --> 00:08:47,020
li jkun b'suċċess
jeqirdu scuds, fil Dhahran,

186
00:08:47,020 --> 00:08:49,730
jista 'jkun hemm l-ebda żball
dwar ir-rendiment tagħha.

187
00:08:49,730 --> 00:08:53,990
Hemm, sistema radar tal-Patriot tal
mitlufa binarji ta 'Scud li jmiss,

188
00:08:53,990 --> 00:08:56,650
u qatt tnieda,
minħabba difett software.

189
00:08:56,650 --> 00:08:59,650

190
00:08:59,650 --> 00:09:04,100
Kien l-Iżraeljani li l-ewwel skoperti
li l-aktar is-sistema kien fuq,

191
00:09:04,100 --> 00:09:07,510
l-akbar il diskrepanza ħin
saret, minħabba arloġġ integrati

192
00:09:07,510 --> 00:09:09,490
fil-kompjuter tas-sistema.

193
00:09:09,490 --> 00:09:12,670
>> -About 2 ġimgħat qabel
l-traġedja fil Dhahran,

194
00:09:12,670 --> 00:09:15,010
l-Iżraeljani rrapportati lill
Dipartiment tad-Difiża,

195
00:09:15,010 --> 00:09:17,940
li s-sistema ġiet jitilfu l-ħin,
li wara madwar 8 sigħat ta 'ħidma,

196
00:09:17,940 --> 00:09:21,410
ndunat li s-sistema kienet
isiru notevolment inqas preċiż.

197
00:09:21,410 --> 00:09:25,290
Id-Dipartiment tad-Difiża wieġbet billi
javżak kollha tal-batteriji Patriot

198
00:09:25,290 --> 00:09:28,070
li ma jħallux is-sistemi
fuq għal żmien twil.

199
00:09:28,070 --> 00:09:29,960
Huma qatt ma qal dak żmien twil kien.

200
00:09:29,960 --> 00:09:30,460
8 sigħat?

201
00:09:30,460 --> 00:09:30,960
10 siegħa?

202
00:09:30,960 --> 00:09:31,870
1000 siegħa?

203
00:09:31,870 --> 00:09:33,734
Ħadd ma kien jaf.

204
00:09:33,734 --> 00:09:35,650
-Il Batterija Patriot
stazzjonati fuq il-kwartieri

205
00:09:35,650 --> 00:09:40,410
fil Dhahran, u interna mudelli tiegħu
arloġġ, kien fuq matul 100 siegħa

206
00:09:40,410 --> 00:09:43,041
fil-lejl tal 25 Frar.

207
00:09:43,041 --> 00:09:47,416
>> -Hija Tracked ħin bi preċiżjoni
ta 'madwar 1/10 ta' sekonda.

208
00:09:47,416 --> 00:09:49,290
Issa 1/10 tat-tieni huwa
numru interessanti

209
00:09:49,290 --> 00:09:52,700
għaliex ma jistax ikun
espressi binarju, eżattament.

210
00:09:52,700 --> 00:09:54,820
Li jfisser, ma jistax
jiġu espressi, eżattament,

211
00:09:54,820 --> 00:09:57,420
fi kwalunkwe kompjuter diġitali moderna.

212
00:09:57,420 --> 00:10:01,460
Huwa diffiċli li wieħed jemmen, iżda
jużaw dan bħala eżempju.

213
00:10:01,460 --> 00:10:03,520
Ejja tieħu n-numru, 03/01.

214
00:10:03,520 --> 00:10:07,110
03/01 ma tistax tiġi espressa
fl deċimali, eżattament.

215
00:10:07,110 --> 00:10:11,490
03/01 huwa 0.333 għaddej għal infinità.

216
00:10:11,490 --> 00:10:15,486
M'hemm l-ebda mod biex tagħmel dan, ma
eżattezza assoluta, fl deċimali.

217
00:10:15,486 --> 00:10:18,360
Dan huwa eżattament l-istess tip ta '
problema li ġara fil-Patriot.

218
00:10:18,360 --> 00:10:22,510
L-itwal-sistema dam, il-
agħar l-iżball ħin sar.

219
00:10:22,510 --> 00:10:28,420
>> -After 100 siegħa ta 'tħaddim, l-iżball
fi żmien kienet biss madwar 1/3 ta 'sekonda.

220
00:10:28,420 --> 00:10:31,830
Iżda f'termini ta jimmira għal
missili jivvjaġġaw mach 5,

221
00:10:31,830 --> 00:10:35,890
dan wassal għal traċċar
żball ta 'aktar minn 600 metru.

222
00:10:35,890 --> 00:10:38,970
Ikun żball fatali
għall-suldati fil Dhahran.

223
00:10:38,970 --> 00:10:45,035
>> Liema ġara, hija tnedija Scud kienet
osservata minn satelliti ta 'twissija bikrija,

224
00:10:45,035 --> 00:10:48,930
u huma ġdid li l-Scud kienet
ġejjin fil-direzzjoni ġenerali tagħhom.

225
00:10:48,930 --> 00:10:51,170
Dawn ma kinux jafu fejn kien ġejjin.

226
00:10:51,170 --> 00:10:53,990
>> -Hija Issa kien sal-radar
komponent tas-sistema Patriot,

227
00:10:53,990 --> 00:10:58,520
difiża Dhahran, li jinstabu u jżommu
kont tal-missili ghadu dieħla.

228
00:10:58,520 --> 00:10:59,690
>> -Il Radar kien intelliġenti ħafna.

229
00:10:59,690 --> 00:11:01,710
Hija fil-fatt track
il-pożizzjoni tal-Scud

230
00:11:01,710 --> 00:11:04,040
u mbagħad previżjoni fejn
probabbilment ikun,

231
00:11:04,040 --> 00:11:06,140
il-ħin li jmiss, il-
radar bagħtet polz out.

232
00:11:06,140 --> 00:11:07,660
Li kienet tissejjaħ l-gate firxa.

233
00:11:07,660 --> 00:11:11,870
>> -Then, Ladarba l-Patriot
jiddeċiedi biżżejjed żmien għandu

234
00:11:11,870 --> 00:11:16,280
għadda li jmorru lura u jivverifika l-li jmiss
post għal dan l-oġġett misjuba,

235
00:11:16,280 --> 00:11:17,280
din tmur lura.

236
00:11:17,280 --> 00:11:21,690
Allura meta marru lura lill-ħażin
post, imbagħad tara l-ebda oġġett

237
00:11:21,690 --> 00:11:25,230
u tiddeċiedi li ma kien hemm l-ebda
oġġett, kien kxif falza,

238
00:11:25,230 --> 00:11:26,650
u qtar il-binarju.

239
00:11:26,650 --> 00:11:29,690
Il Scud dieħla sparixxa
mill-iskrin tar-radar,

240
00:11:29,690 --> 00:11:32,670
u sekondi wara,
slammed fil-kwartieri.

241
00:11:32,670 --> 00:11:38,100
Il Scud maqtula 28 u kienet l-aħħar
wieħed sparati matul l-Ewwel Gwerra tal-Golf.

242
00:11:38,100 --> 00:11:43,460
Traġikament, is-software aġġornat
waslu fil Dhahran l-għada.

243
00:11:43,460 --> 00:11:46,150
L-difett softwer kellhom
Kien fiss, għeluq

244
00:11:46,150 --> 00:11:48,940
kapitolu fil-mnikkta
istorja tal-missili Patriot.

245
00:11:48,940 --> 00:11:50,220
>> [END Daqq]

246
00:11:50,220 --> 00:11:54,340
>> DAVID J Malan: Allura aħna ser tagħti ħarsa lejn
xi limitazzjonijiet simili biss daqsxejn.

247
00:11:54,340 --> 00:11:58,470
Iżda l-ewwel, ejja
tranżizzjoni għal ftit FYI l.

248
00:11:58,470 --> 00:12:01,575
Allura one-- dan il-weekend, hemm
se jkun sezzjonijiet super,

249
00:12:01,575 --> 00:12:04,200
li huma maħsuba biex jieħdu post
sezzjonijiet skedat regolarment, li

250
00:12:04,200 --> 00:12:05,460
se jibdew fil-ġimgħa għalhekk.

251
00:12:05,460 --> 00:12:08,204
Agħti ħarsa lejn websajt tal-CS50 tal
għal aktar informazzjoni fuq dawk.

252
00:12:08,204 --> 00:12:11,120
Huma se jkunu wkoll iffilmjati u streaming
ħajjin għal dawk li ma jistgħux jattendu.

253
00:12:11,120 --> 00:12:12,980
Problema stabbilixxa l-1 huwa fuq il-
website kors li diġà,

254
00:12:12,980 --> 00:12:15,105
u aħna ser tagħti ħarsa lejn
li fi ftit ftit.

255
00:12:15,105 --> 00:12:18,350
U ħinijiet tal-uffiċċju wisq, se tieħu
qiegħed dan it-tnejn permezz Ħamis.

256
00:12:18,350 --> 00:12:20,960
>> Allura dan kien l-aktar canonical
programm ħarisna lejn l-aħħar darba.

257
00:12:20,960 --> 00:12:23,590
Huwa bħall-sempliċi
programm tista 'tikteb fil C,

258
00:12:23,590 --> 00:12:25,250
u anki li daqsxejn ta 'talba bold.

259
00:12:25,250 --> 00:12:25,750
Dritt?

260
00:12:25,750 --> 00:12:28,070
Għaliex hemm ħafna ta '
seeming kumplessità għal dan.

261
00:12:28,070 --> 00:12:30,445
Mela ejja tagħti ħarsa lejn
dak li xi wħud minn dawn l-elementi

262
00:12:30,445 --> 00:12:33,080
kienu u mbagħad jippruvaw jipprovdu
mudell mentali għal kemm

263
00:12:33,080 --> 00:12:35,710
dawn sempliċi ta 'programmi
xogħol, u mbagħad aħna ser tibda

264
00:12:35,710 --> 00:12:38,050
tħares lejn l-affarijiet dejjem aktar kumplessi.

265
00:12:38,050 --> 00:12:41,280
Allura din il-linja hawnhekk, enfasizzat issa,
bl-isfar, dak li ma ngħidu, l-aħħar darba,

266
00:12:41,280 --> 00:12:43,200
li dan ma għalina?

267
00:12:43,200 --> 00:12:45,220
X'inhu l-iskop li sservi?

268
00:12:45,220 --> 00:12:46,984
Xi ħadd mill farther lura?

269
00:12:46,984 --> 00:12:47,483
Yeah.

270
00:12:47,483 --> 00:12:48,649
>> Udjenza membru: [inaudible]

271
00:12:48,649 --> 00:12:50,871

272
00:12:50,871 --> 00:12:51,704
DAVID J Malan: Tajba.

273
00:12:51,704 --> 00:12:53,537
Allura tagħtik aċċess
li jikkmanda, jew ejja

274
00:12:53,537 --> 00:12:56,750
jsejħulhom funzjonijiet, li xi ħadd
inkella kiteb, li huma ddikjarati,

275
00:12:56,750 --> 00:12:58,350
biex ngħidu hekk, f'xi fajl ieħor.

276
00:12:58,350 --> 00:13:02,370
Allura aħna ser tara eżattament dak fajl .h
huwa versus fajl .c, eventwalment.

277
00:13:02,370 --> 00:13:04,710
Iżda għal issa, biss jafu
li printf, per eżempju,

278
00:13:04,710 --> 00:13:08,370
hija fost l-funzjonijiet li ġew
iddikjarat xi fajl ieħor, x'imkien

279
00:13:08,370 --> 00:13:12,930
inkella fuq hard drive-sħaba li
jippermetti li jaċċessaw printf u jużawh

280
00:13:12,930 --> 00:13:15,240
mingħajr ma jkollhom jivvinta
dik ir-rota nfusna.

281
00:13:15,240 --> 00:13:16,930
Sadanittant, prinċipali.

282
00:13:16,930 --> 00:13:19,690
Liema kienet l-Analog ta prinċipali, ġimgħa li għaddiet?

283
00:13:19,690 --> 00:13:20,190
Yeah.

284
00:13:20,190 --> 00:13:21,460
>> Udjenza membru: flag Paper huwa għafast.

285
00:13:21,460 --> 00:13:21,740
>> DAVID J Malan: Yeah.

286
00:13:21,740 --> 00:13:23,490
Tal-bidu nett, meta bandiera aħdar għafast.

287
00:13:23,490 --> 00:13:25,560
Huwa bħall-biċċa puzzle
li kicks off affarijiet.

288
00:13:25,560 --> 00:13:28,306
U għalhekk b'mod simili, ma l-dinja
iddeċieda xi snin ilu li fl C,

289
00:13:28,306 --> 00:13:30,930
u mazz ta 'lingwi oħra,
jekk inti tixtieq li jikteb programm,

290
00:13:30,930 --> 00:13:33,410
ewwel funzjoni tiegħek
għandu jiġi msejjaħ, prinċipali.

291
00:13:33,410 --> 00:13:34,641
U għandu look like dan.

292
00:13:34,641 --> 00:13:36,640
Iżda aħna ser terga 'lura,
ħin ieħor, għal dak li, int,

293
00:13:36,640 --> 00:13:38,690
u, null, ifisser fil-kuntest.

294
00:13:38,690 --> 00:13:42,860
Għal issa, il-braces kaboċċi huma tip
ta 'prodotti simili forma biċċa puzzle Scratch ta

295
00:13:42,860 --> 00:13:45,080
li tiġbor xi numru ta 'linji.

296
00:13:45,080 --> 00:13:47,070
U fost fuq il-linji
hawn, huwa dan wieħed hawn.

297
00:13:47,070 --> 00:13:51,610
printf hija funzjoni li l-għan fil
ħajja huwa li jistampaw string formattjati.

298
00:13:51,610 --> 00:13:55,010
U mill ifformattjat, I jfissirx li inti
tista 'plug fil-valuri placeholder,

299
00:13:55,010 --> 00:13:58,360
u inti tista 'tispeċifika deċimali kemm
punti, kemm in-numri li jistampaw

300
00:13:58,360 --> 00:14:00,040
wara punt deċimali u simili.

301
00:14:00,040 --> 00:14:05,040
U printf, naturalment, tieħu waħda
jew aktar argumenti jew parametri,

302
00:14:05,040 --> 00:14:06,770
magħruf xorta oħra, aktar sempliċi, kif inputs.

303
00:14:06,770 --> 00:14:09,230
>> Allura printf, simili ħafna ta '
funzjonijiet, jieħu inputs.

304
00:14:09,230 --> 00:14:12,730
U dawk l-inputs huma ħaddnu
miż-żewġ parentesi hawn.

305
00:14:12,730 --> 00:14:15,180
U ġewwa minn dawn huwa input wieħed.

306
00:14:15,180 --> 00:14:18,600
Huwa string, kif konna imsejħa,
li huwa biss sekwenza ta 'karattri,

307
00:14:18,600 --> 00:14:22,310
bħal kelma, jew frażi, jew kollu kemm hu
essay anki, fl bejn kwotazzjonijiet doppja.

308
00:14:22,310 --> 00:14:25,712
U dan huwa dak li għaddej biex jinfluwenzaw il-
imġieba ta 'printf minħabba, naturalment,

309
00:14:25,712 --> 00:14:27,170
huwa biss funzjoni tal-istampar ġenerika.

310
00:14:27,170 --> 00:14:29,600
Huwa mhux se tkun taf dak
li jistampaw, sakemm inti tgħid dan.

311
00:14:29,600 --> 00:14:31,000
U mbagħad, xi dettalji.

312
00:14:31,000 --> 00:14:34,056
What did ngħidu dan stramb
sekwenza ta 'simboli hu?

313
00:14:34,056 --> 00:14:34,556
Yeah.

314
00:14:34,556 --> 00:14:35,410
>> Udjenza membru: Linja ġdida.

315
00:14:35,410 --> 00:14:35,990
>> DAVID J Malan: Linja ġdida.

316
00:14:35,990 --> 00:14:39,340
Għalhekk jirriżulta li, inti ma tistax biss hit,
jidħlu, meta int bil-miktub il-programm.

317
00:14:39,340 --> 00:14:42,590
Ġeneralment, il-kompilatur hija se tikseb
ftit konfuż dwar dak li jfisser.

318
00:14:42,590 --> 00:14:45,340
Pjuttost, inti għandek litteralment
jgħidu, tagħti me a line ġdid hawn.

319
00:14:45,340 --> 00:14:49,506
U għalhekk / n huwa dak li aħna ġeneralment
sejħa karattru salvataġġ.

320
00:14:49,506 --> 00:14:50,870
Allura n, għal linja ġdida.

321
00:14:50,870 --> 00:14:53,810
U l-kompilatur jaf
li meta jara / n,

322
00:14:53,810 --> 00:14:57,420
dan għandu attwalment jinduċi l-kompjuter,
finalment, jew printf, f'dan il-każ,

323
00:14:57,420 --> 00:15:00,260
biex jistampa l-ġdida attwali
linja, bħall laqtu l-jidħol,

324
00:15:00,260 --> 00:15:01,480
ewlenin fuq it-tastiera tiegħek.

325
00:15:01,480 --> 00:15:05,620
U fl-aħħar, dak li għamilt ngħidu
din il-biċċa ta 'sintassi huwa għall?

326
00:15:05,620 --> 00:15:06,591
X'tikkontrolla jirrappreżenta?

327
00:15:06,591 --> 00:15:07,090
Yeah.

328
00:15:07,090 --> 00:15:07,490
>> Udjenza membru: [inaudible]

329
00:15:07,490 --> 00:15:08,660
>> DAVID J Malan: Huwa biss
l-aħħar tal-linja.

330
00:15:08,660 --> 00:15:09,909
Hu l-aħħar ta 'l-istqarrija.

331
00:15:09,909 --> 00:15:11,890
U jirrealizzaw li aħna ma
jpoġġuhom kullimkien.

332
00:15:11,890 --> 00:15:13,900
Aħna ċertament ma jpoġġuhom
fit-truf ta 'kull linja.

333
00:15:13,900 --> 00:15:16,680
Per eżempju, hemm xejn fuq il-
ewwel linja, hemm xejn fuq il-linja

334
00:15:16,680 --> 00:15:18,680
ma ', prinċipali, hemm xejn
wara l-braces kaboċċi,

335
00:15:18,680 --> 00:15:21,740
imma inti ser tibda biex tara u jiksbu
familjari mal fejn huwa msejjaħ għall.

336
00:15:21,740 --> 00:15:26,014
U huwa kważi dejjem wara funzjoni
sejħa jew dikjarazzjoni, xi azzjoni

337
00:15:26,014 --> 00:15:27,180
li int fil-fatt tieħu.

338
00:15:27,180 --> 00:15:29,520
>> U jafu issa, speċjalment jekk
fost dawk inqas komdi,

339
00:15:29,520 --> 00:15:32,540
dawn huma t-tipi ta 'affarijiet stupid
li inti ser jispiċċaw aċċidentalment banging

340
00:15:32,540 --> 00:15:33,873
ras tiegħek kontra l-ħajt fuq.

341
00:15:33,873 --> 00:15:36,107
Għaliex inti ser tkun loġikament
kunfidenti f'xi problema

342
00:15:36,107 --> 00:15:38,440
inti ħadthom solvuta għal problema
sett, u l-ħaġa kkritikat biss

343
00:15:38,440 --> 00:15:40,187
mhux se tikkompila jew saħansitra run.

344
00:15:40,187 --> 00:15:43,270
U hekk spiss, sa minn kmieni, li għaddej biex
jkun għaliex inti qbiżt parentesi,

345
00:15:43,270 --> 00:15:44,455
jew tkun insejt tieħu punto virgola.

346
00:15:44,455 --> 00:15:46,547
U hekk biss tkun konxja
ta 'dawn it-tipi ta' affarijiet,

347
00:15:46,547 --> 00:15:49,380
u nipprova biex ma joħorġux frustrati bl
minnhom minħabba malajr ħafna ma dan

348
00:15:49,380 --> 00:15:50,640
jsiru hat qodma.

349
00:15:50,640 --> 00:15:53,910
Imma huwa faċli ħafna li tikseb
frustrati kmieni, bħala riżultat.

350
00:15:53,910 --> 00:15:57,020
>> Allura issa, ejja tagħti ħarsa lejn kif
din il-linja huwa attwalment taħdem

351
00:15:57,020 --> 00:15:59,170
u mbagħad tħares lejn ftit
wieħed aktar ikkumplikat.

352
00:15:59,170 --> 00:16:02,017
Allura għandna aktar minn hawn, il-
abbilità biex jagħmlu fuq dan l-iskrin.

353
00:16:02,017 --> 00:16:04,100
U ejja nassumu li
dan huwa iskrin tal-kompjuter tiegħi,

354
00:16:04,100 --> 00:16:08,589
imma I am miktub fil, Hello programm,
u jien ma implimentawx, printf.

355
00:16:08,589 --> 00:16:10,130
Xi ħadd ieħor implimentat, printf.

356
00:16:10,130 --> 00:16:12,420
Li jixtiequ jitolbu li
implimentaw, printf?

357
00:16:12,420 --> 00:16:12,920
Jekk nistgħu?

358
00:16:12,920 --> 00:16:13,830
Kull dritt, x'hemm isem tiegħek?

359
00:16:13,830 --> 00:16:14,155
>> STUDENT 1: [? Copal. ?]

360
00:16:14,155 --> 00:16:15,529
>> DAVID J Malan: Copal, jaqgħu fuq up.

361
00:16:15,529 --> 00:16:16,430
Come fuq up.

362
00:16:16,430 --> 00:16:17,070
Kull dritt.

363
00:16:17,070 --> 00:16:22,260
Allura aħna għandna, hawn, xi tikketti l-isem,
peress li aħna ser jagħmlu logħba ftit ta 'dan.

364
00:16:22,260 --> 00:16:26,270
U aħna se sejħa inti, printf.

365
00:16:26,270 --> 00:16:30,170
U jekk inti tixtieq li ġejjin hawn,
dak li stajt biss imfassal fuq l-iskrin,

366
00:16:30,170 --> 00:16:32,340
huwa pjuttost sempliċi, hemm me, dan.

367
00:16:32,340 --> 00:16:35,550
>> Kull dritt, hekk, Hello jien jisimni,
printf, jekk inti tixtieq li tqiegħed dak fuq.

368
00:16:35,550 --> 00:16:35,740
Kull dritt.

369
00:16:35,740 --> 00:16:37,360
U jekk inti tista 'tmur stand
mill-iskrin tal-kompjuter

370
00:16:37,360 --> 00:16:39,730
daqslikieku inti huma l-funzjoni li
daħal b'din is-sistema tal-kompjuter.

371
00:16:39,730 --> 00:16:42,063
U l-iskop tiegħek fil-ħajja huwa
li attwalment jistampaw xi ħaġa.

372
00:16:42,063 --> 00:16:44,560
Iżda ħafna bħall-programm we
biss kellhom fuq l-iskrin, hawn,

373
00:16:44,560 --> 00:16:47,060
aħna qed tmur biex ikollhom
attwalment jagħtuk xi input.

374
00:16:47,060 --> 00:16:51,810
>> U hekk, jekk id-dħul tiegħi, hawnhekk, huwa
apparentement, dak li huwa mgħoddi lill printf,

375
00:16:51,810 --> 00:16:53,730
ejja tip ta 'mock up bħal dan.

376
00:16:53,730 --> 00:16:58,720
Jien ser litteralment jikteb fuq
biċċa karta, "hello, dinja,"

377
00:16:58,720 --> 00:17:03,020
backslash N. U biex tkun ċara, dak
Stajt biss imfassal fuq din il-biċċa ta 'karta,

378
00:17:03,020 --> 00:17:04,020
tidher bħal dan.

379
00:17:04,020 --> 00:17:08,730
Allura meta I run dan il-programm, u dan
linja isfar tal-kodiċi gets esegwiti,

380
00:17:08,730 --> 00:17:12,970
huwa bħallikieku I, il-programm hello,
am għoti xi kontribut off għal funzjoni

381
00:17:12,970 --> 00:17:13,970
li xi ħadd ieħor kiteb.

382
00:17:13,970 --> 00:17:16,595
>> U jekk inti, b'subgħajk,
jista 'attwalment, b'subgħajk,

383
00:17:16,595 --> 00:17:21,520
tibbaża fuq l-iskrin ikun x'ikun
huwa ġejt mogħtija,

384
00:17:21,520 --> 00:17:27,465
l-effett, finalment, huwa li
tara eżattament dak, fuq l-iskrin.

385
00:17:27,465 --> 00:17:29,140
U każ kantuniera Little hawn.

386
00:17:29,140 --> 00:17:31,540
U tajjeb, aħna ma tara
l-, linja ġdida, f'dan il-punt.

387
00:17:31,540 --> 00:17:33,900
Ikun żbaljat għalik
tiġbed b'mod espliċitu l-newline.

388
00:17:33,900 --> 00:17:36,810
Imma jekk irridu tinżamm bil-miktub kliem fuq il-
screen, dawn jispiċċaw taħt dak.

389
00:17:36,810 --> 00:17:39,560
>> Allura nirringrazzjak ħafna, iżda stick
madwar hawn għal wieħed biss mument.

390
00:17:39,560 --> 00:17:42,860
Issa neħtieġu ieħor
voluntier, jekk nistgħu,

391
00:17:42,860 --> 00:17:46,830
li għaddej biex bżonn biex jilagħbu l-irwol
of-- Huwa biss persuni fil-orkestra

392
00:17:46,830 --> 00:17:47,355
dritt issa.

393
00:17:47,355 --> 00:17:47,980
Kif about-- OK.

394
00:17:47,980 --> 00:17:48,480
Dritt hawn.

395
00:17:48,480 --> 00:17:49,180
Come fuq up.

396
00:17:49,180 --> 00:17:49,955
X'hemm isem tiegħek?

397
00:17:49,955 --> 00:17:50,922
>> STUDENT 2: [? Ivay. ?]

398
00:17:50,922 --> 00:17:51,796
DAVID J Malan: Jiddispjacini?

399
00:17:51,796 --> 00:17:52,990
STUDENT 2: [? Ivay. ?]

400
00:17:52,990 --> 00:17:55,320
DAVID J Malan: Ethan, jaqgħu fuq up.

401
00:17:55,320 --> 00:17:55,820
Nru?

402
00:17:55,820 --> 00:17:58,390
Did I nikseb li żbaljat, anke
wara li qal li darbtejn?

403
00:17:58,390 --> 00:17:58,890
Come fuq up.

404
00:17:58,890 --> 00:18:00,030
Huwa diffiċli biex tisma up here.

405
00:18:00,030 --> 00:18:05,240

406
00:18:05,240 --> 00:18:05,740
OK.

407
00:18:05,740 --> 00:18:07,190
U jien sorry, dak l-isem tiegħek?

408
00:18:07,190 --> 00:18:07,680
>> STUDENT 2: [? Ivay. ?]

409
00:18:07,680 --> 00:18:08,790
>> [? DAVID J Malan: Ivay. ?] OK.

410
00:18:08,790 --> 00:18:10,430
Għal issa, jekk inti ma
mind, inti GetString.

411
00:18:10,430 --> 00:18:11,013
>> STUDENT 2: OK.

412
00:18:11,013 --> 00:18:11,797
Kessaħ.

413
00:18:11,797 --> 00:18:14,630
DAVID J Malan: Mela jekk inti tixtieq
toqgħod hawn għal ftit mument,

414
00:18:14,630 --> 00:18:17,100
ejja tagħti ħarsa lejn ftit
aktar programm kumpless, li

415
00:18:17,100 --> 00:18:18,670
issa għandha tliet linji ta 'kodiċi.

416
00:18:18,670 --> 00:18:24,080
Allura aħna għandna, wieħed, agħti l-isem tiegħek billi tuża
printf; tnejn, sejħa għall GetString,

417
00:18:24,080 --> 00:18:28,060
segwit minn assenjazzjoni għal
varjabbli imsejħa, spag s, jew imsejħa s;

418
00:18:28,060 --> 00:18:31,260
u mbagħad sejħa oħra għal, printf,
iżda din id-darba ma 'żewġ inputs.

419
00:18:31,260 --> 00:18:33,646
>> Istat Allura konna diġà sar
isem tiegħek, jew minflok, konna

420
00:18:33,646 --> 00:18:34,770
diġà għamlu sejħa printf.

421
00:18:34,770 --> 00:18:38,960
Hekk jien ser jikteb,-Istat ismek.

422
00:18:38,960 --> 00:18:42,089
U iva, dak li jien ser
jgħaddu, printf, fi ftit mument,

423
00:18:42,089 --> 00:18:43,005
hija pjuttost sempliċi, dan.

424
00:18:43,005 --> 00:18:47,760
Mela jekk inti tixtieq li tmur quddiem u tiġbed dan
fuq l-iskrin, li l-input tiegħek issa.

425
00:18:47,760 --> 00:18:48,260
Kull dritt.

426
00:18:48,260 --> 00:18:51,160
U tinsa string, issa għandna
linja tagħna stess ta 'kodiċi hawn.

427
00:18:51,160 --> 00:18:54,470
Allura fi, GetString, għandna bżonn
li attwalment sejħa, GetString.

428
00:18:54,470 --> 00:18:57,920
Allura l-iskop tiegħek fil-ħajja huwa biss walk
barra fil-orkestra, jekk inti tista ',

429
00:18:57,920 --> 00:18:58,980
u jiksbu l-isem ta 'xi ħadd.

430
00:18:58,980 --> 00:19:00,860
Imma ejja jagħtuk
xi ħaġa li poġġih fuq.

431
00:19:00,860 --> 00:19:02,908
Jekk inti tixtieq li, mur
quddiem u jiksbu string,

432
00:19:02,908 --> 00:19:05,241
jiksbu l-isem ta 'xi ħadd fuq li
biċċa karta, jekk inti tista '.

433
00:19:05,241 --> 00:19:12,940

434
00:19:12,940 --> 00:19:13,530
>> Kull dritt.

435
00:19:13,530 --> 00:19:15,250
U aħna ser tara, fi ftit mument,
li ismu aħna qed jkollna.

436
00:19:15,250 --> 00:19:17,630
Sadanittant, dak li jien ser
tkun lesta, hija biċċa vojt

437
00:19:17,630 --> 00:19:21,340
tal-karta, li fihom, jien ser
li jaħżen x'ikun il-valur huwa

438
00:19:21,340 --> 00:19:25,752
huwa li GetString huwa jirritorna lili,
I, bħala varjabbli string imsejjaħ, s.

439
00:19:25,752 --> 00:19:26,252
Kull dritt.

440
00:19:26,252 --> 00:19:27,293
Allura dak li għandek hawn?

441
00:19:27,293 --> 00:19:27,950
Nik.

442
00:19:27,950 --> 00:19:28,450
Kull dritt.

443
00:19:28,450 --> 00:19:30,910
Allura aħna għandna l-isem Nik hawn.

444
00:19:30,910 --> 00:19:33,750
Allura dan huwa dak litteralment
ġie ripatrijat

445
00:19:33,750 --> 00:19:35,810
lili, biex ngħidu hekk, mill GetString.

446
00:19:35,810 --> 00:19:38,720
>> I, issa, vais
tesegwixxi in-naħa tax-xellug

447
00:19:38,720 --> 00:19:43,440
ta 'dik l-espressjoni, fejn I sempliċiment
kopja isfel, għal skopijiet tal-lum, Nik.

448
00:19:43,440 --> 00:19:46,470
Allura issa, għandi varjabbli
imsejħa, i, ħażna isem Nik tal.

449
00:19:46,470 --> 00:19:49,520
Stajt diġà kellhom jaħtru lil
printf, argument preċedenti.

450
00:19:49,520 --> 00:19:52,800
Iżda fit-tielet u l-aħħar linja tagħna ta '
kodiċi, I attwalment ikollhom printf idejn

451
00:19:52,800 --> 00:19:58,500
xi ħaġa different-- ftit
"hello,% s," backslash n.

452
00:19:58,500 --> 00:20:01,510
>> U għalhekk l-aħħar linja jien ser
li send-- l-aħħar ħaġa jien

453
00:20:01,510 --> 00:20:03,060
se jikteb issa, hija din.

454
00:20:03,060 --> 00:20:06,310
Allura l-żewġ linji ta 'kodiċi, jew
pjuttost l-aħħar linja ta 'kodiċi,

455
00:20:06,310 --> 00:20:10,690
jitlob li jkun hemm żewġ inputs--
wieħed, dan, u tnejn, dan.

456
00:20:10,690 --> 00:20:13,330
Mela jekk il-funzjoni printf tagħna
issa tista 'tieħu dawn bħala input,

457
00:20:13,330 --> 00:20:16,000
let me ċar l-iskrin għalik.

458
00:20:16,000 --> 00:20:17,250
Attwalment ebda, inti tista 'tmur quddiem.

459
00:20:17,250 --> 00:20:19,333
Aħna ser tħalli f'idejn, peress
huwa fuq l-istess programm.

460
00:20:19,333 --> 00:20:21,760

461
00:20:21,760 --> 00:20:27,380
Għandna tara, hello, Nik.

462
00:20:27,380 --> 00:20:27,880
Kull dritt.

463
00:20:27,880 --> 00:20:29,670
Allura dan kien pjuttost ftit
ċrieki biex tiżdied permezz, just

464
00:20:29,670 --> 00:20:31,620
tikteb, jiddikjara tiegħek
isem, u, hello, Nik.

465
00:20:31,620 --> 00:20:37,210
Iżda din l-idea sempliċi ta 'mogħdija messaġġ,
tal tgħaddi input u output tirċievi,

466
00:20:37,210 --> 00:20:40,430
huwa eżattament l-mudell aħna qed tmur biex ikollhom
għall anki l-funzjonijiet l-aktar kumplessi.

467
00:20:40,430 --> 00:20:41,804
Allura nirringrazzjak tant li inti kemm.

468
00:20:41,804 --> 00:20:43,730
Għandna stress sabiħ
ballun hawn għalik.

469
00:20:43,730 --> 00:20:48,890
U nirringrazzjak għall GetString tagħna
u voluntiera printf simili.

470
00:20:48,890 --> 00:20:49,551
Grazzi.

471
00:20:49,551 --> 00:20:50,050
Kull dritt.

472
00:20:50,050 --> 00:20:50,966
Grazzi lilek tnejn.

473
00:20:50,966 --> 00:20:56,640

474
00:20:56,640 --> 00:21:00,430
>> Allura aħna kont qed jitkellem dwar
s'issa, l-aktar dwar kordi.

475
00:21:00,430 --> 00:21:06,550
U jirriżulta li C jistgħu attwalment
jifhmu ftit tipi differenti ta 'data.

476
00:21:06,550 --> 00:21:08,860
Fil-fatt, ejja tagħti
ħarsa lejn dawn hawn.

477
00:21:08,860 --> 00:21:12,490
Allura C, u ħafna ta 'lingwi,
jifhmu affarijiet imsejħa Chars.

478
00:21:12,490 --> 00:21:16,852
A char huwa ġeneralment
byte wieħed, jew tmien bits.

479
00:21:16,852 --> 00:21:19,810
U dan jirrappreżenta karattru wieħed,
bħall-ittra A, jew il-kapital

480
00:21:19,810 --> 00:21:21,990
ittra A, jew f'ittri żgħar
A, jew il-punt exclamation,

481
00:21:21,990 --> 00:21:25,440
jew kwalunkwe karattru li inti tista tip fuq
keyboard tiegħek, u xi kultant anke aktar.

482
00:21:25,440 --> 00:21:26,795
Aħna wkoll jiġri li tara sufruni.

483
00:21:26,795 --> 00:21:31,160
A float huwa, ġeneralment, ta '
32-bit valur, jew erba 'bytes

484
00:21:31,160 --> 00:21:33,660
għaliex darb'oħra, byte wieħed huwa tmien bits.

485
00:21:33,660 --> 00:21:36,675
>> Allura float huwa valur b'punt li jvarja,
xi ħaġa ma 'punt deċimali.

486
00:21:36,675 --> 00:21:38,550
U fil-fatt, dan huwa dak
l-film kien jitkellem

487
00:21:38,550 --> 00:21:42,240
dwar meta tkellem dwar f'wiċċ l-ilma
valuri tal-punti, xi numru fiss ta 'bits

488
00:21:42,240 --> 00:21:43,940
qed jintużaw biex jirrappreżentaw numru reali.

489
00:21:43,940 --> 00:21:45,740
Iżda hemm ukoll affarijiet imsejħa jirdoppja.

490
00:21:45,740 --> 00:21:47,860
Dawn jeżistu fl Java,
jekk inti ħadt APCs,

491
00:21:47,860 --> 00:21:51,540
u doppju, bħala l-isem Thankfully
jissuġġerixxi, huwa darbtejn akbar bħala float.

492
00:21:51,540 --> 00:21:54,540
Huwa għadu numru reali,
hija biss għandha aktar bits

493
00:21:54,540 --> 00:21:58,390
li biex tkun dejjem aktar preċiżi,
jew li jaħżnu numri saħansitra akbar.

494
00:21:58,390 --> 00:21:58,890
int huwa faċli.

495
00:21:58,890 --> 00:22:00,181
Aħna tkellimna dwar dan l-aħħar darba.

496
00:22:00,181 --> 00:22:01,160
Huwa biss numru sħiħ.

497
00:22:01,160 --> 00:22:03,980
U huwa ġeneralment 32
bits, jew erba 'bytes.

498
00:22:03,980 --> 00:22:07,850
>> U hekk, jekk għandek, ejja naraw issa,
32 bits-- u għamilna dan fil-ġimgħa 0,

499
00:22:07,850 --> 00:22:10,820
dejjem hekk briefly-- jekk ikollok
32 bits, x'inhu l-akbar

500
00:22:10,820 --> 00:22:13,580
numru li jista 'jirrappreżenta bħala numru sħiħ?

501
00:22:13,580 --> 00:22:16,080
Agħti jew jieħdu?

502
00:22:16,080 --> 00:22:18,380
Huwa simili 4 biljun,
u dak li biss jekk aħna qed

503
00:22:18,380 --> 00:22:20,690
li jirrappreżenta numri pożittivi biss.

504
00:22:20,690 --> 00:22:23,930
Jekk għandek 32 bits, u inti tixtieq li
jirrappreżentaw numri negattivi kif ukoll,

505
00:22:23,930 --> 00:22:27,100
firxa tiegħek huwa, essenzjalment, negattivi
2 biljuni għall-pożittiv 2 biljuni.

506
00:22:27,100 --> 00:22:29,250
Iżda ġeneralment, aħna ser tibda
f'0 jitla 'għal 4 biljun.

507
00:22:29,250 --> 00:22:32,400
>> Inti ma għandekx tkun taf b'mod preċiż, iżda
nistgħu naraw dan, fil-fatt, jekk I biss

508
00:22:32,400 --> 00:22:36,400
jiftħu calculator ftit, hawn.

509
00:22:36,400 --> 00:22:41,070
I tista 'tagħmel 2 l 32, u
dan huwa eżattament kemm hu kbir,

510
00:22:41,070 --> 00:22:43,190
kif il-valuri ħafna tista
jirrappreżentaw, 32 bits.

511
00:22:43,190 --> 00:22:44,442
U huwa bejn wieħed u ieħor 4 biljun.

512
00:22:44,442 --> 00:22:46,900
Allura aħna ser tibqa 'tara dak in-numru
fi ftit postijiet differenti.

513
00:22:46,900 --> 00:22:48,890
Imma jekk għandek bżonn itwal
numri minn dan,

514
00:22:48,890 --> 00:22:51,670
jirriżulta hemm
xi ħaġa imsejħa twil twil.

515
00:22:51,670 --> 00:22:54,005
U fit-tul huwa
ġeneralment 64 bits, li

516
00:22:54,005 --> 00:22:56,380
ifisser li huwa ordni ta 'kobor
saħansitra ikbar minn int.

517
00:22:56,380 --> 00:22:59,510
>> So I can not anki jippronunzja l-akbar
numru li inti tista 'tirrappreżenta,

518
00:22:59,510 --> 00:23:01,340
imma hija nettament akbar.

519
00:23:01,340 --> 00:23:05,190
Issa bħala twarrib, storikament,
jekk int tkun 32 bits,

520
00:23:05,190 --> 00:23:12,780
u fit-tul huwa 64 bits, kif
big huwa twil, u mhux twil twil?

521
00:23:12,780 --> 00:23:16,500

522
00:23:16,500 --> 00:23:20,330
Youd taħseb li għandu aktar minn int
imma forsi inqas twila minn twil twil,

523
00:23:20,330 --> 00:23:21,400
iżda fil-fatt jiddependi.

524
00:23:21,400 --> 00:23:23,400
>> U għalhekk jirriżulta waħda
tal-frustrazzjonijiet wisq,

525
00:23:23,400 --> 00:23:26,830
bil-kitba kodiċi fuq ċerti sistemi,
hija li mhux kollha ta 'dawn it-tipi ta' data

526
00:23:26,830 --> 00:23:28,440
għandhom valuri stabbiliti minn qabel.

527
00:23:28,440 --> 00:23:29,771
Xi kultant huwa dan ħafna bits.

528
00:23:29,771 --> 00:23:31,020
Xi kultant huwa li ħafna bits.

529
00:23:31,020 --> 00:23:32,750
Allura inti fil-fatt għandek tkun taf,
kultant, liema hardware

530
00:23:32,750 --> 00:23:34,083
int taħdem software tiegħek fuq.

531
00:23:34,083 --> 00:23:36,960
B'xorti tajba, ilsna oħra u
tipi ta 'data oħra li issa jeżistu,

532
00:23:36,960 --> 00:23:38,400
jippermetti li inti tkun aktar preċiża.

533
00:23:38,400 --> 00:23:41,220
Well, rajna spag,
u rajna BOOL, wisq,

534
00:23:41,220 --> 00:23:43,960
iżda jirriżulta dawk ġejjin
biss bil-librerija CS50.

535
00:23:43,960 --> 00:23:46,240
Allura dawn huma mhux mibnija
fis C. Dawk minflok,

536
00:23:46,240 --> 00:23:49,340
jaqgħu fil dan il-fajl imsejħa
CS50.h, li aħna ser eventwalment

537
00:23:49,340 --> 00:23:51,831
qoxra lura l-saffi ta '.

538
00:23:51,831 --> 00:23:53,830
Iżda għal issa, dawn qed biss
tipi ta 'data addizzjonali.

539
00:23:53,830 --> 00:23:57,060
A BOOL hija vera jew falza, u
string hija sekwenza ta 'karattri,

540
00:23:57,060 --> 00:23:57,970
bħal kelma.

541
00:23:57,970 --> 00:24:01,690
Issa printf, Rajna, għandha
placeholders,% s hija waħda.

542
00:24:01,690 --> 00:24:05,430
U inti tista 'tkun kapaċi, għal issa,
jiddeduċu minn dawn l-eżempji l-oħra, kif

543
00:24:05,430 --> 00:24:07,720
inti jista 'jkollhom placeholder
għal tipi differenti ta 'data.

544
00:24:07,720 --> 00:24:11,150
Per eżempju, tieħu raden, jekk inti
riedu jistampa char waħda bl-użu

545
00:24:11,150 --> 00:24:15,270
printf, il placeholder huwa probabbilment% c.

546
00:24:15,270 --> 00:24:19,650
U jekk inti tixtieq li jistampa l
numru sħiħ ma 'l-placeholder,% i.

547
00:24:19,650 --> 00:24:25,150
% LLD hija valur deċimali twil twil,
iżda twil twil, b'tali mod li mapep għal dan.

548
00:24:25,150 --> 00:24:28,640
U mbagħad% f għas f'wiċċ l-ilma
valur tal-punt jew għal doppja,

549
00:24:28,640 --> 00:24:31,270
hekk kultant dawn qed jintużaw mill-ġdid
f'kuntesti differenti.

550
00:24:31,270 --> 00:24:33,350
Allura aħna ser tara u l-użu
xi wħud minn dawk matul iż-żmien.

551
00:24:33,350 --> 00:24:36,420
U printf u funzjonijiet oħra wkoll
sekwenzi jaħarbu appoġġ oħrajn ",

552
00:24:36,420 --> 00:24:38,080
u xi kultant, dawn huma neċessarji.

553
00:24:38,080 --> 00:24:39,770
Allura n backslash hija linja ġdida.

554
00:24:39,770 --> 00:24:42,886
Backslash t, ħadd ma
tixtieq li tieħu stab?

555
00:24:42,886 --> 00:24:43,760
Udjenza membru: Tab.

556
00:24:43,760 --> 00:24:44,551
DAVID J Malan: Tab.

557
00:24:44,551 --> 00:24:46,810
Mela jekk inti fil-fatt tixtieq
biex jistampa tab, mhux

558
00:24:46,810 --> 00:24:49,940
numru fiss ta 'spazji iżda attwali
karattru tab, inti ma hit tiegħek,

559
00:24:49,940 --> 00:24:53,490
tab, buttuna fuq it-tastiera, ġeneralment,
inti fil-fatt tagħmel backslash t.

560
00:24:53,490 --> 00:24:57,750
Kwotazzjoni doppja backslash,
għaliex kieku I qatt trid li?

561
00:24:57,750 --> 00:24:58,250
Dritt?

562
00:24:58,250 --> 00:25:00,417
Għaliex ma tistax I biss tip ta '
kwotazzjoni doppja fuq it-tastiera tiegħi?

563
00:25:00,417 --> 00:25:02,124
Udjenza membru:
Minħabba, inkella, huwa

564
00:25:02,124 --> 00:25:04,830
se jaħsbu huwa l-aħħar
ta 'prodotti simili print tiegħek [? test. ?]

565
00:25:04,830 --> 00:25:05,420
>> DAVID J Malan: Eżattament.

566
00:25:05,420 --> 00:25:07,211
Ftakar, ma tagħna
eżempji printf, meta aħna

567
00:25:07,211 --> 00:25:10,075
kienu jgħaddu lil printf fil input,
fuq ix-xellug ta 'dik string input

568
00:25:10,075 --> 00:25:12,950
u fuq il-lemin ta 'dik input
rebbiegħa, naturalment, kien kwotazzjoni doppja.

569
00:25:12,950 --> 00:25:16,270
Jekk input tiegħek stess ikollu doppja
kwotazzjoni fin-nofs ta 'dak,

570
00:25:16,270 --> 00:25:18,920
il-kompjuter jista 'potenzjalment
nikseb konfuż, dwar,

571
00:25:18,920 --> 00:25:20,760
ma dan quote doppju
jappartjenu fin-nofs?

572
00:25:20,760 --> 00:25:22,150
Ma jappartjenu ma 'dak tax-xellug?

573
00:25:22,150 --> 00:25:23,566
Ma jappartjenu ma 'dak id-dritt?

574
00:25:23,566 --> 00:25:26,780
U hekk, jekk inti tixtieq li tagħmel dan super
ċara, inti tagħmel backslash kwotazzjoni doppja,

575
00:25:26,780 --> 00:25:30,480
b'tali mod li huwa ħarbu, biex ngħidu hekk, u
mhuwiex conflated għal xi ħaġa oħra.

576
00:25:30,480 --> 00:25:34,400
U hemm ftit oħrajn hawn,
r backslash, kwotazzjonijiet uniku, 0,

577
00:25:34,400 --> 00:25:36,510
li nistgħu naraw matul iż-żmien, kif ukoll.

578
00:25:36,510 --> 00:25:37,760
U issa, dak dwar il-funzjonijiet?

579
00:25:37,760 --> 00:25:41,630
>> Allura azzjonijiet li nistgħu nieħdu s'issa
f'din il-lingwa, C, ukoll, Rajna,

580
00:25:41,630 --> 00:25:44,320
printf, naturalment, u kollha
mill-oħrajn fuq l-iskrin,

581
00:25:44,320 --> 00:25:47,140
hawn, li aħna ser tuża għall-
kors tal-ewwel ftit ġimgħat biss,

582
00:25:47,140 --> 00:25:48,485
ġejjin meta l-librerija CS50.

583
00:25:48,485 --> 00:25:51,850
U dawn jagħmluha ħafna aktar faċli, fil
C, li fil-fatt tikseb jintuza mill-utent.

584
00:25:51,850 --> 00:25:54,200
Jirriżulta li fl C, u
franchement fi ftit lingwi,

585
00:25:54,200 --> 00:25:57,450
huwa reali uġigħ fl-għonq li tagħmel
xi ħaġa sempliċi, bħal fil-pront lill-utent

586
00:25:57,450 --> 00:26:01,310
għall keyboard, għal input tiegħu jew tagħha.

587
00:26:01,310 --> 00:26:03,240
U hekk dawn il-funzjonijiet jagħmluha aktar faċli.

588
00:26:03,240 --> 00:26:05,472
>> U għandha wkoll żball
verifika kollu,

589
00:26:05,472 --> 00:26:07,180
sabiex, meta inti
ifakkar l-Erbgħa, aħna

590
00:26:07,180 --> 00:26:09,740
raw il-, retry, twissija,
meta I ma kkooperawx,

591
00:26:09,740 --> 00:26:11,700
u I ittajpjat kelma, minflok in-numru?

592
00:26:11,700 --> 00:26:15,402
We ghamilt l-irfigħ kmieni
biex tiżgura l-utent tikkoopera.

593
00:26:15,402 --> 00:26:17,860
Iżda dawn huma biss it-taħriġ
roti li aħna se eventwalment,

594
00:26:17,860 --> 00:26:19,640
u malajr, tluq.

595
00:26:19,640 --> 00:26:22,630
>> Allura biex terġa, imbagħad,
ejja tagħti ħarsa,

596
00:26:22,630 --> 00:26:26,620
ferm simili għamilna ma Scratch, fil
xi constructs canonical fil C.

597
00:26:26,620 --> 00:26:28,580
Dan huwa maħsub biex, sort
ta ', jkun tour whirlwind,

598
00:26:28,580 --> 00:26:30,990
biss sabiex ikollok referenza
u li inti stajt tidher l-affarijiet fl-ewwel.

599
00:26:30,990 --> 00:26:34,100
Iżda mbagħad aħna ser tħares lejn kodifikazzjoni attwali
jużaw xi wħud minn dawn il-blokok tal-bini.

600
00:26:34,100 --> 00:26:36,710
Tant simili fl Scratch,
meta kellna dikjarazzjonijiet simili,

601
00:26:36,710 --> 00:26:41,570
tgħid jew, stenna, fis-C, għandna l
funzjonijiet kif ukoll, bħal printf.

602
00:26:41,570 --> 00:26:45,350
>> Jekk irridu li jesprimu kundizzjoni
fis-C, huwa simili, fl-ispirtu,

603
00:26:45,350 --> 00:26:47,840
li dik il-biċċa puzzle li
dehru qishom dan fil Scratch.

604
00:26:47,840 --> 00:26:49,850
Iżda minflok, aħna
litteralment biss jiktbu, jekk.

605
00:26:49,850 --> 00:26:51,830
U mbagħad, fil-parentesi,
npoġġux kundizzjoni,

606
00:26:51,830 --> 00:26:54,807
fejn din il-kundizzjoni huwa dak li aħna ser
sejħa, għal darb'oħra, espressjoni Boolean.

607
00:26:54,807 --> 00:26:56,390
U għal darb'oħra, dan huwa tip ta 'pseudocode.

608
00:26:56,390 --> 00:26:58,830
U, fil-fatt, il-// huwa kumment.

609
00:26:58,830 --> 00:27:00,550
Huwa biss kliem Ingliż li myself.

610
00:27:00,550 --> 00:27:03,000
Iżda dan huwa l-ġenerali
istruttura ta ', jekk, kundizzjoni.

611
00:27:03,000 --> 00:27:05,220
Iżda aħna ser tara konkreti
eżempji ftit mument.

612
00:27:05,220 --> 00:27:07,960
>> Jekk inti tixtieq li jkollok
two-way furketta fit-triq,

613
00:27:07,960 --> 00:27:11,740
ferm simili għamilna ma voluntier tagħna fuq
L-Erbgħa, inti jista 'jkollhom, inkella jekk.

614
00:27:11,740 --> 00:27:16,020
U jekk inti tixtieq li jkollok terz u
kundizzjoni finali, jew sitwazzjoni default,

615
00:27:16,020 --> 00:27:19,006
inti jista 'jkollhom biss blokk ieħor, hemm.

616
00:27:19,006 --> 00:27:21,880
U l-istess, ma espressjonijiet Boolean,
inti tista ', u, flimkien.

617
00:27:21,880 --> 00:27:24,296
U rajna nhar l-Erbgħa, li
mhuwiex ampersand wieħed,

618
00:27:24,296 --> 00:27:28,220
huwa tnejn, għal raġunijiet ta 'livell aktar baxx li
aħna ser eventwalment tara u jilagħbu bil.

619
00:27:28,220 --> 00:27:30,410
Jew Ing affarijiet flimkien
huwa ta '2 bars vertikali.

620
00:27:30,410 --> 00:27:32,240
Fuq tastiera Istati Uniti, dan
huwa ġeneralment ewlieni

621
00:27:32,240 --> 00:27:35,730
bl-buttuni Shift hawn fuq
tiegħek Enter jew Ritorn ewlenin.

622
00:27:35,730 --> 00:27:38,620
>> Imbagħad hemm dawn l-affarijiet li
aħna ser tuża forsi darba jew darbtejn.

623
00:27:38,620 --> 00:27:42,570
Huma funzjonalment ekwivalenti għal
x'tista 'tagħmel ma', jekk, inkella jekk,

624
00:27:42,570 --> 00:27:44,950
inkella jekk inkella, tibni,
iżda dawn qed jissejjaħ bidla.

625
00:27:44,950 --> 00:27:48,020
Huma jqisu differenti ħafna, imma aħna ser
tara f'xi kodiċi tad-distribuzzjoni tagħna,

626
00:27:48,020 --> 00:27:51,890
għal sett problema futur, x'aktarx,
li huwa kultant biss prettier

627
00:27:51,890 --> 00:27:54,060
mezz li jesprimu kollu kemm hu
mazz ta 'kondizzjonijiet,

628
00:27:54,060 --> 00:27:57,590
mingħajr ma jkollhom ħafna ta 'ċineg kaboċċi u
ħafna ta 'parentesi u indentazzjoni.

629
00:27:57,590 --> 00:28:01,910
Iżda dawn tagħtina aktar
qawwa mill aħna diġà.

630
00:28:01,910 --> 00:28:02,550
U issa loops.

631
00:28:02,550 --> 00:28:05,020
U dan wieħed, aħna ser tħares
fi ftit aktar bil-mod.

632
00:28:05,020 --> 00:28:08,470
Iżda mbagħad, aħna ser tibda tuża dawn,
speċjalment għal dawk li diġà familjari.

633
00:28:08,470 --> 00:28:13,830
Dan huwa l-mod canonical, jekk oerhört
mod arcane, jiktbu linja fil C.

634
00:28:13,830 --> 00:28:15,896
>> Issa loop fil Scratch kien
pjuttost sempliċi.

635
00:28:15,896 --> 00:28:17,020
Għandek, dejjem, blokk.

636
00:28:17,020 --> 00:28:19,760
Għandek, irrepeti, blokk bl
biss numru għandek tip fil.

637
00:28:19,760 --> 00:28:22,220
U mal-, għal loop, inti tista
implimentati kemm ta 'dawk l-ideat,

638
00:28:22,220 --> 00:28:23,595
imma hija ftit aktar teknika.

639
00:28:23,595 --> 00:28:25,994
Iżda franchement, huwa wkoll
relattivament sempliċi.

640
00:28:25,994 --> 00:28:28,160
Ladarba inti taf l-ordni ta '
operazzjonijiet, inti litteralment

641
00:28:28,160 --> 00:28:30,910
huma biss se plagg fil-valuri
u għid il-kompjuter x'għandu jsir.

642
00:28:30,910 --> 00:28:32,800
Allura hawnhekk eżempju.

643
00:28:32,800 --> 00:28:38,040
Din hija linja li, pjuttost
sempliċi, jgħodd minn numru wieħed up

644
00:28:38,040 --> 00:28:40,187
permezz ieħor.

645
00:28:40,187 --> 00:28:42,020
U biss mill glancing
lejn dan, anke jekk ikollok

646
00:28:42,020 --> 00:28:44,660
ebda esperjenza minn qabel ma '
din il-lingwa, liema numru

647
00:28:44,660 --> 00:28:46,920
ma probabbilment jibdew jingħaddu mill-?

648
00:28:46,920 --> 00:28:47,730
OK, 0.

649
00:28:47,730 --> 00:28:50,240
U jien guessing dan għaliex inti
tara li hemm xi int u jien,

650
00:28:50,240 --> 00:28:51,073
li hija varjabbli.

651
00:28:51,073 --> 00:28:52,390
Huwa initialized għal 0.

652
00:28:52,390 --> 00:28:55,670
>> U mbagħad, jidher qisu
aħna qed tgħaddi printf, valur.

653
00:28:55,670 --> 00:28:58,000
U, fil-fatt, I għamel typo ftit hawn.

654
00:28:58,000 --> 00:28:59,850
Iżda li faċilment fiss.

655
00:28:59,850 --> 00:29:02,390
Let me żid in, i hawn.

656
00:29:02,390 --> 00:29:06,150
Issa għandna printf benesseri
għadda dak il-valur placeholder.

657
00:29:06,150 --> 00:29:08,299
U x'inhu għaddej biex jingħaddu up permezz?

658
00:29:08,299 --> 00:29:08,840
UDJENZA: 50.

659
00:29:08,840 --> 00:29:09,340
50.

660
00:29:09,340 --> 00:29:10,160
49..

661
00:29:10,160 --> 00:29:10,910
DAVID J Malan: 49.

662
00:29:10,910 --> 00:29:13,340
Allura 50, ewwel daqqa t'għajn, jidher dritt.

663
00:29:13,340 --> 00:29:16,990
Iżda dan, jirriżulta, se tkun
kundizzjoni tagħna li aħna żżomm kontroll.

664
00:29:16,990 --> 00:29:21,740
U aħna qed tmur biex tieqaf ladarba
i m'għadux inqas minn 50.

665
00:29:21,740 --> 00:29:24,920
Allura dan loop, għall-kuntrarju, jekk
tesegwixxi, sakemm i huwa inqas minn 50.

666
00:29:24,920 --> 00:29:28,891
Iżda hekk kif din issir 50, jew 51,
jew agħar, hija għandha tieqaf awtomatikament.

667
00:29:28,891 --> 00:29:29,390
Kull dritt.

668
00:29:29,390 --> 00:29:31,200
>> Allura x'inhu dak li attwalment jiġri hawn?

669
00:29:31,200 --> 00:29:33,160
Allura dan huwa l-ordni ta '
operazzjonijiet għal loop.

670
00:29:33,160 --> 00:29:35,440
Wieħed, inti għandek l-
hekk imsejħa inizjalizzazzjoni.

671
00:29:35,440 --> 00:29:38,264
Dan blokki enfasizzat isfar
tal-kodiċi jkun ikkompilat ewwel,

672
00:29:38,264 --> 00:29:40,930
u għandha l-effett li, għal kull
L-Erbgħa, inti probabilment timmaġina.

673
00:29:40,930 --> 00:29:45,500
Hija toħloq varjabbli imsejjaħ i u
ħwienet f'dak varjabbli-valur 0.

674
00:29:45,500 --> 00:29:47,560
Hekk i huwa 0 f'dan il-punt fl-istorja.

675
00:29:47,560 --> 00:29:49,680
>> Il-ħaġa li jmiss li
jiġri f'dan tibni,

676
00:29:49,680 --> 00:29:51,540
huwa li l-kundizzjoni gets ċċekkjati.

677
00:29:51,540 --> 00:29:54,325
So I check immedjatament,
huwa i inqas minn 50?

678
00:29:54,325 --> 00:29:57,700
U naturalment, ir-risposta
għal issa huwa, ċertament, iva.

679
00:29:57,700 --> 00:30:00,710
Iva, għaliex i huwa 0, u
li l-żgur inqas minn 50.

680
00:30:00,710 --> 00:30:03,866
Imbagħad x'jiġri, hija li dan
linja tal-kodiċi gets esegwiti.

681
00:30:03,866 --> 00:30:06,740
U fil-fatt, jekk ikun hemm multipli
linji ta 'kodiċi f'dawk ċineg kaboċċi,

682
00:30:06,740 --> 00:30:09,020
dawn kollha jiksbu esegwiti wara xulxin.

683
00:30:09,020 --> 00:30:11,450
>> U fl-effett hawn, huwa
apparentement, li jistampa

684
00:30:11,450 --> 00:30:15,365
l-i numru, li se
jkun 0, u mbagħad 1, u mbagħad 2.

685
00:30:15,365 --> 00:30:15,865
Iżda għaliex?

686
00:30:15,865 --> 00:30:17,410
Għaliex ma jiksbu inkrementat?

687
00:30:17,410 --> 00:30:20,680
Ukoll, il-ħaġa raba li
li jiġri huwa li dan sintassi

688
00:30:20,680 --> 00:30:22,610
gets esegwiti, wara l-virgola.

689
00:30:22,610 --> 00:30:27,506
i ++ huwa mod shorthand ta 'tgħid;
tieħu l-valur ta 'i, u żid 1 miegħu;

690
00:30:27,506 --> 00:30:30,380
u allura l-ħin li jmiss madwar, żid
1 lilha; u l-ħin li jmiss madwar,

691
00:30:30,380 --> 00:30:31,330
żid 1 miegħu.

692
00:30:31,330 --> 00:30:33,640
>> Allura jekk aħna jibqgħu għaddejjin,
x'inhu jiġri

693
00:30:33,640 --> 00:30:35,890
li jmiss huwa Jien ma jmur biex
initialize i qatt darb'oħra.

694
00:30:35,890 --> 00:30:38,290
Jekk I tinżamm initializing
i għal 0, dan l-eżempju

695
00:30:38,290 --> 00:30:41,110
qatt ma tispiċċa minħabba
Inkun mwaħħla f'0.

696
00:30:41,110 --> 00:30:43,870
Imma dak li jiġri huwa
li l-kondizzjoni ser jiġu kkontrollati,

697
00:30:43,870 --> 00:30:54,280
il-linja ta 'kodiċi se tikseb eżegwit,
l-i se jkun inkrementat,

698
00:30:54,280 --> 00:30:56,970
kundizzjoni se jiġu kkontrollati,
kodiċi se tikseb esegwiti.

699
00:30:56,970 --> 00:30:59,790
U jinżamm ċikliżmu mill-ġdid,
u għal darb'oħra, u għal darb'oħra,

700
00:30:59,790 --> 00:31:03,340
sakemm i ++ jinduċi valur ta '50.

701
00:31:03,340 --> 00:31:05,870
>> Il-kundizzjoni mbagħad jgħid,
hija 50 inqas minn 50?

702
00:31:05,870 --> 00:31:09,360
It-tweġiba, naturalment, l-ebda, u
sabiex il-kodiċi kollha waqfiet eżekuzzjoni.

703
00:31:09,360 --> 00:31:13,020
U jekk ikollok aktar kodiċi fuq l-iskrin
stabbiliti hawn taħt, dan huwa dak li jiġri li jmiss.

704
00:31:13,020 --> 00:31:17,530
Pops out ta 'dawn ċineg kaboċċi u
tkompli jistampaw aktar wara dik.

705
00:31:17,530 --> 00:31:20,470
>> Allura Joke issa, minn Foxtrot, li
inti ser forsi issa jifhmu.

706
00:31:20,470 --> 00:31:30,810

707
00:31:30,810 --> 00:31:31,560
Huwa dejjem umoristiċi.

708
00:31:31,560 --> 00:31:34,110
Huwa simili l-chuckles
tip ta 'saffi,

709
00:31:34,110 --> 00:31:38,370
u allura inti tirrealizza inti m'għandekx
tkun laughing Humer bħal dan.

710
00:31:38,370 --> 00:31:41,160
Iżda hemm xi takeaway
hawn, pedagoġika, wisq.

711
00:31:41,160 --> 00:31:43,577
Għalhekk jirriżulta li jien
nieqsa biċċa sintassi,

712
00:31:43,577 --> 00:31:45,410
jew ta foxtrot nieqsa
biċċa sintassi hawn.

713
00:31:45,410 --> 00:31:48,076
X'hemm nieqes, li aħna kellna
f'kull każ ieħor, s'issa?

714
00:31:48,076 --> 00:31:51,599

715
00:31:51,599 --> 00:31:53,390
Ritorn, hemm, so
dan huwa xi ħaġa oħra,

716
00:31:53,390 --> 00:31:54,440
li aħna ser terga 'lura għal qabel twil.

717
00:31:54,440 --> 00:31:55,398
X'hemm nieqes, għalkemm?

718
00:31:55,398 --> 00:31:55,908
Yeah.

719
00:31:55,908 --> 00:31:58,150
>> Udjenza membru: Il-
inizjalizzazzjoni ta '[inaudible].

720
00:31:58,150 --> 00:31:58,470
>> DAVID J Malan: OK.

721
00:31:58,470 --> 00:31:58,980
So yeah.

722
00:31:58,980 --> 00:32:03,210
Allura fil-fatt, dan is-- Well,
u l-għadd huwa initialized

723
00:32:03,210 --> 00:32:05,470
up fuq, jew minflok, iddikjarat up hawn fuq.

724
00:32:05,470 --> 00:32:06,960
Allura dan huwa mod ieħor ta 'kif isir dan.

725
00:32:06,960 --> 00:32:08,685
Iżda mhux f'sensiela waħda huwa validu għalkemm.

726
00:32:08,685 --> 00:32:09,310
Kif dwar hawn?

727
00:32:09,310 --> 00:32:10,196
>> Udjenza membru: Huwa l-braces kaboċċi?

728
00:32:10,196 --> 00:32:10,640
>> DAVID J Malan: Yeah.

729
00:32:10,640 --> 00:32:12,080
Allura l-braces kaboċċi huma nieqsa.

730
00:32:12,080 --> 00:32:15,495
Iżda dan il-kodiċi, I mean, għall-kreditu tagħhom,
huwa attwalment, sintattikament valida.

731
00:32:15,495 --> 00:32:17,610
Jirriżulta, inti ma
bżonn l-braces kaboċċi

732
00:32:17,610 --> 00:32:21,691
jekk inti biss għandek linja waħda tal-kodiċi li
inti tixtieq li tesegwixxi ġewwa tal-linja.

733
00:32:21,691 --> 00:32:24,190
Issa aħna dejjem, fil-klassi u fid
kollha tal-kodiċi ta 'distribuzzjoni tagħna,

734
00:32:24,190 --> 00:32:26,730
jinkludu l-braces kaboċċi
xorta waħda, biss f'ġieħ iċ-ċarezza.

735
00:32:26,730 --> 00:32:29,010
Iżda jirrealizzaw li fil-kotba
u eżempji onlajn,

736
00:32:29,010 --> 00:32:31,300
inti tista 'tajjeb ħafna' tara kaboċċi
ċingi nieqsa f'xi.

737
00:32:31,300 --> 00:32:34,850
U li OK, jekk dak li
jkunu inċiża u maħsuba

738
00:32:34,850 --> 00:32:38,650
huwa biss linja waħda tal-kodiċi, u ma
diversi linji ta 'kodiċi, potenzjalment.

739
00:32:38,650 --> 00:32:39,150
Kull dritt.

740
00:32:39,150 --> 00:32:44,500
Allura relatati mal-kwistjoni tal
impreċiżjoni, hija kwistjoni ta 'overflow,

741
00:32:44,500 --> 00:32:48,560
fis-sens li, b'mod simili,
do interi għandhom limiti għalihom

742
00:32:48,560 --> 00:32:49,970
bħad f'wiċċ l-ilma valuri tal-punti?

743
00:32:49,970 --> 00:32:53,120
Fid-dinja punt floating
Valuri, nistgħu nkunu tant preċiżi biss,

744
00:32:53,120 --> 00:32:55,710
wara li, xi kultant
affarijiet ħżiena jista 'jiġri,

745
00:32:55,710 --> 00:32:57,760
u programmi tagħna tista 'tiġi Buggy u żball.

746
00:32:57,760 --> 00:33:00,050
Issa anke ma interi,
inti tista 'tiffaċċja problemi.

747
00:33:00,050 --> 00:33:03,820
Issa integer ma jkollux
punt deċimali jew numri wara dan.

748
00:33:03,820 --> 00:33:07,130
Huwa biss numru naturali, tipikament.

749
00:33:07,130 --> 00:33:09,430
Allura dak li tista 'tmur ħażin ma' int?

750
00:33:09,430 --> 00:33:12,210
Jekk jien jużaw int biex
għadd, dak li tista 'tmur ħażin?

751
00:33:12,210 --> 00:33:13,230
Jidher ħafna aktar sempliċi.

752
00:33:13,230 --> 00:33:13,873
Yeah.

753
00:33:13,873 --> 00:33:16,240
>> Udjenza membru: Jekk il-
Numru gets [inaudible]

754
00:33:16,240 --> 00:33:17,073
>> DAVID J Malan: Yeah.

755
00:33:17,073 --> 00:33:20,820
X'jiġri jekk inti għadd tant għoli, li inti
ma jistgħux jesprimu dak in-numru verament kbir.

756
00:33:20,820 --> 00:33:21,320
Dritt?

757
00:33:21,320 --> 00:33:23,910
F'xi punt, int ser
li jaqbżu l-konfini

758
00:33:23,910 --> 00:33:27,077
ta 'valur 32-bit jew valur 64-bit.

759
00:33:27,077 --> 00:33:29,410
Issa mill-ġdid, M'inix ċert kif
jippronunzja valur 64-bit,

760
00:33:29,410 --> 00:33:32,230
imma naf bi 32-bit numru sħiħ,
l-akbar valur jista 'jkun,

761
00:33:32,230 --> 00:33:35,490
jekk huwa biss pożittiv
Valuri, huwa bejn wieħed u ieħor 4 biljun.

762
00:33:35,490 --> 00:33:39,000
Mela jekk jien nipprova għodd sa 5 biljun,
xi ħaġa jiġri.

763
00:33:39,000 --> 00:33:41,050
Imma ejja ara dak, fil-fatt, jista 'jiġri.

764
00:33:41,050 --> 00:33:44,570
Fid-dinja tal numru sħiħ
overflow, fejn inti, f'ċertu sens,

765
00:33:44,570 --> 00:33:48,270
overflow il-kapaċità ta '
numru sħiħ, dak li jista 'jiġri?

766
00:33:48,270 --> 00:33:51,190
>> Allura hawnhekk numru binarju,
huwa throwback għal 0.

767
00:33:51,190 --> 00:33:54,630
Huwa kollu 1, u l-placeholders
hemm, huma setgħat ta '2,

768
00:33:54,630 --> 00:33:55,980
għalhekk dan huwa binarja.

769
00:33:55,980 --> 00:33:59,416
Allura dawn huma 8, 1 bits fuq l-iskrin.

770
00:33:59,416 --> 00:34:01,290
U jekk inti recall jew
inti malajr tagħmel l-matematika,

771
00:34:01,290 --> 00:34:06,074
liema valur qiegħed ikun rappreżentat
hawn ma 'dawn it-tmien 1 bits?

772
00:34:06,074 --> 00:34:06,950
255.

773
00:34:06,950 --> 00:34:09,260
U anki jekk inti ma kinux pjuttost ċert
tal-matematika, inti tista 'tagħmel dan out.

774
00:34:09,260 --> 00:34:10,550
Jew inti tista 'biss tip
tar-raġuni permezz tagħha,

775
00:34:10,550 --> 00:34:12,633
stenna minuta, jekk jien
tirrappreżenta valur 8 bit,

776
00:34:12,633 --> 00:34:17,750
u stajt ltqajna 256 valuri possibbli,
iżda l-ewwel waħda minnhom huwa ta '0,

777
00:34:17,750 --> 00:34:19,909
I biss jafu li l-
akbar se tkun 255,

778
00:34:19,909 --> 00:34:21,510
u dan huwa dak li dan wieħed jista 'jkun.

779
00:34:21,510 --> 00:34:26,060
>> So I jissoponi tipprova żżid 1 ta 'dan il-valur.

780
00:34:26,060 --> 00:34:28,750
What would you do fil-grad
iskola meta żżid 1, u

781
00:34:28,750 --> 00:34:31,139
ma verament tajbin għax
inti għandek twettaq l-1 ta '?

782
00:34:31,139 --> 00:34:34,380
X'inhu dan in-numru jmorru
li ssir meta inti żid 1?

783
00:34:34,380 --> 00:34:37,030
Huwa ser isiru 0.

784
00:34:37,030 --> 00:34:37,530
Dritt?

785
00:34:37,530 --> 00:34:41,139
Għaliex jekk inti kellhom aktar bits-- u jien ser
jippruvaw, tip ta ', it-tip out here--

786
00:34:41,139 --> 00:34:44,710
jekk kellna aktar bits, dak li aħna
tista 'tagħmel hawnhekk huwa jżid il-1,

787
00:34:44,710 --> 00:34:47,370
u mbagħad aħna'd jiksbu dan.

788
00:34:47,370 --> 00:34:48,739
Whoops.

789
00:34:48,739 --> 00:34:52,250
Aħna'd jkollhom 1 bit-triq kollha madwar hawn.

790
00:34:52,250 --> 00:34:55,530
>> Imma jekk dan huwa finite
valur, huwa biss 8 bits,

791
00:34:55,530 --> 00:34:57,480
u li l-pre-determinat
mill-kompjuter,

792
00:34:57,480 --> 00:34:59,370
li 1 huwa effettivament ma jkunx hemm.

793
00:34:59,370 --> 00:35:00,980
Hija biss tip ta 'jaqa off a cliff.

794
00:35:00,980 --> 00:35:05,480
U hekk jekk inti żid minn 1 sa 255, dak
valur do you apparentement nirċievi?

795
00:35:05,480 --> 00:35:06,180
0.

796
00:35:06,180 --> 00:35:09,700
U għalhekk numri aċċidentalment,
u forsi, mhux intenzjonalment,

797
00:35:09,700 --> 00:35:12,040
jispiċċaw tgeżwir madwar bħal dan.

798
00:35:12,040 --> 00:35:14,079
Allura dak li tista 'tkun l-implikazzjoni ta' din?

799
00:35:14,079 --> 00:35:15,620
Ukoll, hemm ftit affarijiet differenti.

800
00:35:15,620 --> 00:35:18,751
Allura wieħed, ma jispiċċaw ifittxu
bħal 0, mhux intenzjonalment,

801
00:35:18,751 --> 00:35:20,750
imma int tista 'tip ta' tara,
anki fid-dinja reali,

802
00:35:20,750 --> 00:35:23,416
għall-aħjar jew għall-agħar,
manifestazzjonijiet ta 'din l-idea ta' limitu.

803
00:35:23,416 --> 00:35:26,630
Per eżempju, kull minnkom li
qatt lagħbu Lego Star Wars,

804
00:35:26,630 --> 00:35:28,880
ħadd ma jiġri li tkun taf
l-għadd massimu ta 'muniti

805
00:35:28,880 --> 00:35:32,032
inti tista 'tiġbor fil Lego Star Wars?

806
00:35:32,032 --> 00:35:35,640
Ħu raden bbażata fuq
mistoqsijiet ewlenin tal-lum.

807
00:35:35,640 --> 00:35:39,140
Huwa akbar minn 256 jew 255.

808
00:35:39,140 --> 00:35:40,330
Huwa 4 biljun.

809
00:35:40,330 --> 00:35:42,080
Għalhekk jirriżulta li, u
hemm xi people--

810
00:35:42,080 --> 00:35:46,080
xi googling aħħar night-- kkonfermat
gotten 4 biljun muniti tad-deheb,

811
00:35:46,080 --> 00:35:47,730
jew whatnot, fil Lego Star Wars.

812
00:35:47,730 --> 00:35:49,860
Għalkemm apparentement, hemm
mod li trick-logħba,

813
00:35:49,860 --> 00:35:53,222
hemm bug jew karatteristika, li ihallik
biss jakkumulaw lottijiet u lottijiet ta 'punti.

814
00:35:53,222 --> 00:35:54,930
Iżda l-akbar possibbli
valur, skond

815
00:35:54,930 --> 00:35:58,360
li dan l-iskrin sparatura ta 'xi ħadd I
misjuba online, huwa tabilħaqq, 4 biljun.

816
00:35:58,360 --> 00:35:59,240
>> Issa għaliex huwa li?

817
00:35:59,240 --> 00:36:03,040
Huwa preċiżament 4 biljun,
probabbilment minħabba xi ħadd iddeċieda,

818
00:36:03,040 --> 00:36:05,500
li kien miktub din il-logħba,
li huma jistgħu jagħmlu 4 biljun,

819
00:36:05,500 --> 00:36:07,340
xi ħaġa, xi ħaġa, xi ħaġa,
bħall-valur I impoġġija

820
00:36:07,340 --> 00:36:10,256
mal-kalkulatur qabel, iżda
huwa biss ftit aktar nadifa għall-bnedmin

821
00:36:10,256 --> 00:36:12,610
jiġifieri l-għadd massimu
tal coins-- jew studs,

822
00:36:12,610 --> 00:36:14,860
kif huma jitolbu them-- li inti
tista 'tiġbor huwa ta' 4 biljun.

823
00:36:14,860 --> 00:36:16,290
U għalhekk, għaliex huwa dan?

824
00:36:16,290 --> 00:36:20,310
Kif huwa l-logħba LEGO
implimentazzjoni tal-counter

825
00:36:20,310 --> 00:36:23,420
li l-issorveljar ta 'l-
numru ta 'muniti li għandek?

826
00:36:23,420 --> 00:36:24,266
Huma qed tuża liema?

827
00:36:24,266 --> 00:36:26,390
Udjenza membru: Huwa jwaqqaf
għadd wara 4 biljun.

828
00:36:26,390 --> 00:36:27,720
DAVID J Malan: Huwa jwaqqaf
għadd wara 4 biljuni,

829
00:36:27,720 --> 00:36:29,525
li jfisser li inti tista '
jiddeduċu, bħala programmer,

830
00:36:29,525 --> 00:36:31,960
li dawn qed probabbilment
użu ta '32 bit numru sħiħ.

831
00:36:31,960 --> 00:36:35,380
Bħall-programmer litteralment biss
ttajpjata, int, fil-kodiċi tiegħu jew tagħha,

832
00:36:35,380 --> 00:36:39,620
u dak l-tip ta 'varjabbli li
li qed jużaw biex jaħżnu kodiċi ta 'xi ħadd.

833
00:36:39,620 --> 00:36:42,230
Allura hemm manifestazzjonijiet oħra
ta 'dawn it-tipi ta' limiti.

834
00:36:42,230 --> 00:36:45,063
>> So I ma lagħbu din game--
u I kien qari fuq l-istorja

835
00:36:45,063 --> 00:36:48,470
biex tikkonferma kif much-- iżda fil-
verżjoni oriġinali tal-ċiviltà, fejn

836
00:36:48,470 --> 00:36:53,240
inti apparentement jinteraġixxu ma 'kull
xulxin u jistgħu pagi gwerra jew ikollok paċi,

837
00:36:53,240 --> 00:36:56,590
Gandhi kien suppost li tkun waħda mill
l-karattri l-aktar paċifiċi, kif I

838
00:36:56,590 --> 00:36:59,280
jifhimha, fl-ewwel
Verżjoni tal-ċiviltà.

839
00:36:59,280 --> 00:37:03,250
U fil-fatt, fuq skala minn 1 sa 10,
aggressività tiegħu kienet biss 1.

840
00:37:03,250 --> 00:37:05,620
Allura dejjem hekk ħafif
aggressivi, apparentement.

841
00:37:05,620 --> 00:37:11,590
>> Iżda f'xi punt, inti tista apparentement
jinstallaw demokrazija fil-ġeografija tiegħek.

842
00:37:11,590 --> 00:37:14,900
U jekk inti jinstallaw demokrazija
fil-verżjoni tiegħek tal-logħba,

843
00:37:14,900 --> 00:37:17,320
imbagħad livell aggressjoni tiegħek jinżel.

844
00:37:17,320 --> 00:37:18,460
Hija ħaġa tajba.

845
00:37:18,460 --> 00:37:20,890
In-nies huma aktar tranquil
apparentement, f'dik is-sitwazzjoni.

846
00:37:20,890 --> 00:37:23,190
Imma apparentement, xi ħadd ma
ma jkollhomx, jekk, kundizzjoni

847
00:37:23,190 --> 00:37:24,780
fil-verżjoni oriġinali tar-kodiċi.

848
00:37:24,780 --> 00:37:30,650
>> Allura livell aggressjoni Gandhi marru minn
pożittiv 1, minus 2, ma 'riżultati negattivi 1,

849
00:37:30,650 --> 00:37:33,840
iżda l-logħba ma
jifhmu numri negattivi.

850
00:37:33,840 --> 00:37:38,680
Allura dak li ġara kien aggressjoni Gandhi
livell marru minn 1, għal 0, ma 'riżultati negattivi 1,

851
00:37:38,680 --> 00:37:40,900
li kellu l-effett ta '
tgeżwir madwar li jkunu

852
00:37:40,900 --> 00:37:44,690
-karattru aktar aggressiva
fil-logħba, b'valur ta '255,

853
00:37:44,690 --> 00:37:46,630
fuq skala minn 1 sa 10.

854
00:37:46,630 --> 00:37:49,887
U minn dakinhar, hemm kien
aktar incarnations ta din il-logħba,

855
00:37:49,887 --> 00:37:51,720
u ħadthom miżmuma bħala
tip ta 'bajd tal-Għid,

856
00:37:51,720 --> 00:37:53,870
li Gandhi hija apparentement
hekk terriblement aggressivi.

857
00:37:53,870 --> 00:37:56,740
Iżda dan kien ir-riżultat ta '
żball programmazzjoni sempliċi ħafna

858
00:37:56,740 --> 00:37:58,630
f'dak verżjoni bikrija ħafna tal-logħba.

859
00:37:58,630 --> 00:38:02,860
>> Issa aktar disturbingly, aktar
reċentement, il-Boeing 787

860
00:38:02,860 --> 00:38:05,720
kien dokumentat bħala li
bug, mhux it-tip ta 'apparat

861
00:38:05,720 --> 00:38:07,340
inti partikolarment tixtieq li jkollok bug.

862
00:38:07,340 --> 00:38:10,130
U s-sintomi, li I taf taqra
hawn, minn online artiklu,

863
00:38:10,130 --> 00:38:13,840
kien dan, mudell 787 ajruplan
li ġiet imħaddma kontinwament

864
00:38:13,840 --> 00:38:18,030
għall 248 jiem tista 'titlef kollha
kurrent alternanti, AC,

865
00:38:18,030 --> 00:38:20,850
enerġija elettrika, minħabba
l-unitajiet ta 'kontroll ġeneratur,

866
00:38:20,850 --> 00:38:23,330
GCUs, fl-istess ħin
tgħaddi għall-modalità fail-safe.

867
00:38:23,330 --> 00:38:26,790
Allura dan kien twissija maħruġa
meta din il-problema ġiet skoperta.

868
00:38:26,790 --> 00:38:28,750
Din il-kondizzjoni hija kkawżata
minn software counter,

869
00:38:28,750 --> 00:38:32,230
interna għall-GCUs, hekk
numru sħiħ jew varjabbli,

870
00:38:32,230 --> 00:38:36,850
li se overflow wara 248
ġranet ta 'enerġija kontinwa.

871
00:38:36,850 --> 00:38:40,350
Boeing tinsab fil-proċess ta '
iżvilupp ta 'software GCU upgrade li

872
00:38:40,350 --> 00:38:42,350
se jirrimedjaw il-kundizzjoni mhux sigura.

873
00:38:42,350 --> 00:38:44,226
>> Allura ħafna bħall-missili
xenarju, fejn

874
00:38:44,226 --> 00:38:46,850
huma kellhom xi tip ta 'varjabbli
li kien qed jgħodd, u l-għadd,

875
00:38:46,850 --> 00:38:50,720
u l-għadd, iżda overflowing gradwalment
il-konfini tal-kapaċità tagħha,

876
00:38:50,720 --> 00:38:54,890
bl-istess mod ma 'l-ajruplan kkritikat
jkollhom overflow varjabbli

877
00:38:54,890 --> 00:38:56,410
wara żmien biżżejjed ta 'tmexxija.

878
00:38:56,410 --> 00:38:59,240
U għalhekk l-mod tongue-in-cheek
ta 'xogħol madwar din il-kwistjoni

879
00:38:59,240 --> 00:39:04,400
huwa li verament, reboot, pjan tiegħek kull
247 ġurnata, sabiex il-memorja gets jintilfu

880
00:39:04,400 --> 00:39:06,100
u l-varjabbli tmur lura għal 0.

881
00:39:06,100 --> 00:39:09,410
Iżda realizzata, din hija ferm
Inkarnazzjoni kbir ta 'software,

882
00:39:09,410 --> 00:39:14,070
iżda speċjalment kif aħna jisimgħu dwar Apple
sistemi operattivi nidħlu karozzi,

883
00:39:14,070 --> 00:39:18,030
u l-karozzi self-sewqan minn Google, u
kwalunkwe numru ta 'incarnations ta' softwer

884
00:39:18,030 --> 00:39:21,000
Fil-ħajja tagħna ta 'kuljum, it-televiżjonijiet
u arloġġi, u aktar,

885
00:39:21,000 --> 00:39:24,950
tirrealizza kienu mdawra permezz ta 'softwer,
li kollha huwa miktub minn us bnedmin.

886
00:39:24,950 --> 00:39:28,150
>> U kif aħna ser kollha dalwaqt jiskopru,
huwa faċli ħafna u tipiku ħafna

887
00:39:28,150 --> 00:39:30,250
li jagħmlu żbalji meta tikteb software.

888
00:39:30,250 --> 00:39:32,745
U jekk inti ma jaqbduhom,
xi affarijiet ħżiena jista 'jiġri.

889
00:39:32,745 --> 00:39:35,400
Issa xi kultant, xi
affarijiet umoristiċi jista 'jiġri,

890
00:39:35,400 --> 00:39:38,280
jew għall-inqas xi kultant aħna
taf li jistennew xi badness.

891
00:39:38,280 --> 00:39:41,550
Allura 0 diviż bil 0, mill-grad
iskola, huwa ġeneralment ħaġa ħażina.

892
00:39:41,550 --> 00:39:43,050
Huwa undefined.

893
00:39:43,050 --> 00:39:46,440
U jirriżulta out-- u ejja ara jekk
mic tiegħi tista 'pick dan up-- li Apple

894
00:39:46,440 --> 00:39:47,790
kellhom xi gost ma 'dan l-aħħar.

895
00:39:47,790 --> 00:39:48,850
So I jkollhom iPhone hawn.

896
00:39:48,850 --> 00:39:54,160
Jien ser jitkellmu ma Siri u jistaqsu tagħha
li tagħti me-risposta għal 0 diviż bil 0.

897
00:39:54,160 --> 00:39:55,850
X'inhu 0 diviż bil 0?

898
00:39:55,850 --> 00:39:59,350

899
00:39:59,350 --> 00:40:02,230
>> Siri: Immaġina li inti għandek 0
cookies, u inti maqsuma minnhom indaqs

900
00:40:02,230 --> 00:40:03,540
fost 0 ħbieb.

901
00:40:03,540 --> 00:40:05,810
Kemm cookies ma 'kull persuna nirċievi?

902
00:40:05,810 --> 00:40:06,350
Ara?

903
00:40:06,350 --> 00:40:07,660
Ma jagħmilx sens.

904
00:40:07,660 --> 00:40:10,540
U Monster cookie huwa imdejjaq
li ma jkunx hemm cookies.

905
00:40:10,540 --> 00:40:13,987
U inti diqa li
ikollok ebda ħbieb.

906
00:40:13,987 --> 00:40:15,570
DAVID J Malan: Huwa tip ta 'obnoxious.

907
00:40:15,570 --> 00:40:17,550
Allura dan huwa dak li kien biss qal hemmhekk.

908
00:40:17,550 --> 00:40:21,380
Huwa indeterminat, mhuwiex iddefinit,
u fil-fatt, lingwi ta 'programmar ħafna

909
00:40:21,380 --> 00:40:24,950
jew, tassew, kompilaturi se
jiskopru meta inti, fi programm,

910
00:40:24,950 --> 00:40:27,050
jippruvaw jaqsmu 0 0.

911
00:40:27,050 --> 00:40:29,830
Gost aktar minn dan għalkemm, hi
li apparentement, Monster cookie

912
00:40:29,830 --> 00:40:31,270
hija fuq Twitter f'dawn il-jiem.

913
00:40:31,270 --> 00:40:37,610
U hu wieġeb għal dan, ma 'dan,
li huwa assolutament adorable.

914
00:40:37,610 --> 00:40:40,110
Imma ejja tagħti ħarsa lejn
ftit constructs oħra,

915
00:40:40,110 --> 00:40:43,459
u mbagħad iwettqu xi ftit minn dan
kodiċi li tuża, modi tajba.

916
00:40:43,459 --> 00:40:45,250
Għalhekk jirriżulta li, minbarra
għal-linji, hemm

917
00:40:45,250 --> 00:40:49,174
xi ħaġa imsejħa loop waqt, li
jistenna differenti u huwa implimentat

918
00:40:49,174 --> 00:40:51,590
a differently-- ftit u
aħna ser eventwalment tara examples--

919
00:40:51,590 --> 00:40:53,500
imma f'ċertu sens,
huwa aktar sempliċi minħabba li

920
00:40:53,500 --> 00:40:56,670
ma jippermettu li inti initialize u
taġġorna fi ħdan il-konfini tal-linja.

921
00:40:56,670 --> 00:40:57,794
Inti xorta tista jimplimentawha.

922
00:40:57,794 --> 00:41:01,219
Allura inti tista 'tagħmel l-istess affarijiet eżatt
bil-loop waqt, bħala ma 'għall loop,

923
00:41:01,219 --> 00:41:03,260
iżda sintassi tiegħek, ultimately--
kif aħna ser eventwalment

924
00:41:03,260 --> 00:41:04,551
see-- se tkun differenti.

925
00:41:04,551 --> 00:41:07,450
Hemm anki do filwaqt loop, li
huwa attwalment ftit differenti,

926
00:41:07,450 --> 00:41:09,640
f'dak billi għal loop
u loop filwaqt dejjem

927
00:41:09,640 --> 00:41:13,005
iċċekkja kundizzjoni tagħhom l-ewwel, jekk
inti taqra dan ħaġa fuq għal isfel,

928
00:41:13,005 --> 00:41:16,440
it-tip ta 'qisu li għaddej biex
check s kundizzjoni aħħar għaliex dan huwa

929
00:41:16,440 --> 00:41:17,910
verament l-aħħar linja tal-kodiċi.

930
00:41:17,910 --> 00:41:20,580
U fil-fatt, li għaddej biex tkun utli
f'ċerti programmi li aħna tikteb,

931
00:41:20,580 --> 00:41:23,746
jekk inti tixtieq li biss bl-addoċċ jagħmel xi ħaġa
u eventwalment tivverifika l-kundizzjoni.

932
00:41:23,746 --> 00:41:25,205
Li mhux neċessarjament ħaġa ħażina.

933
00:41:25,205 --> 00:41:27,912
Jekk irridu varjabbli, nistgħu nagħmlu
dan fi ftit ta 'modi differenti.

934
00:41:27,912 --> 00:41:30,290
U rajna fil-Foxtrot
cartoons, mod wieħed kif isir dan,

935
00:41:30,290 --> 00:41:33,400
fejn inti tiddikjara varjabbli tiegħek,
bħal int counter punto virgola,

936
00:41:33,400 --> 00:41:36,570
u mbagħad later-- forsi li jmiss
linja, forsi 10 linji later--

937
00:41:36,570 --> 00:41:37,800
inti fil-fatt initialize dan.

938
00:41:37,800 --> 00:41:42,230
Allura dawn 2 linji ta 'kodiċi
tiddikjara varjabbli ta 'int tip

939
00:41:42,230 --> 00:41:44,930
u sejħa hija counter, u għalhekk tagħti
me bits biżżejjed li jkollhom int.

940
00:41:44,930 --> 00:41:48,230
U allura eventwalment, li tqiegħed
il-valur 0 f'dak varjabbli.

941
00:41:48,230 --> 00:41:51,250
Jipprovdi l għamilhom 0 u 1 fil-
mudell, li nafu mill-aħħar ġimgħa,

942
00:41:51,250 --> 00:41:53,260
jirrappreżenta n-numru nafu kif 0.

943
00:41:53,260 --> 00:41:56,920
Jew franchement, inti tista 'tagħmel dan ħafna
aktar konċiż, bħad dan.

944
00:41:56,920 --> 00:41:59,390
>> Issa irridu wkoll il-
abbiltà li sejħa funzjonijiet.

945
00:41:59,390 --> 00:42:03,070
U fil-fatt, hawnhekk linja 2
programm, jew silta tiegħu,

946
00:42:03,070 --> 00:42:06,157
li jippermetti li attwalment
jikteb xi kodiċi li

947
00:42:06,157 --> 00:42:08,990
gets string mill-user-- ħafna
bħal voluntier tagħna mument ago--

948
00:42:08,990 --> 00:42:11,320
ħażna r-riżultat
varjabbli imsejħa isem,

949
00:42:11,320 --> 00:42:15,470
u then-- simili ħafna ma 'voluntier tagħna
prints printf-- barra dawk il-valuri

950
00:42:15,470 --> 00:42:19,180
billi jgħaddu f'żewġ argumenti, il-
spag, segwita mill-varjabbli

951
00:42:19,180 --> 00:42:20,781
imsejħa, l-isem, hija stess.

952
00:42:20,781 --> 00:42:23,155
Mela ejja tagħti ħarsa, qabel
aħna terga 'lura għal Mario hemmhekk,

953
00:42:23,155 --> 00:42:26,010
fi ftit issa, eżempji ta 'dan.

954
00:42:26,010 --> 00:42:30,537
>> Jien ser jimxi 'l quddiem u miftuħa
up, ejja ngħidu, funzjoni 0.c.

955
00:42:30,537 --> 00:42:33,120
U kif dejjem, dan il-kodiċi huwa
disponibbli fuq il-websajt tal-kors, l

956
00:42:33,120 --> 00:42:35,660
sabiex inti tista 'tilgħab flimkien fuq
dar u tħares lejn din aktar tard.

957
00:42:35,660 --> 00:42:40,400
Iżda hawn l-programm huwa
Essenzjalment, mil-linja 17 sa 22.

958
00:42:40,400 --> 00:42:43,270
Il-programm prinċipali huwa fejn il-
programm huwa dejjem se tibda.

959
00:42:43,270 --> 00:42:46,980
Dan il-programm, apparentement, va
biex jistampa l-isem tiegħek, kolon.

960
00:42:46,980 --> 00:42:50,320
Huwa mbagħad ser sejħa GetString,
bħad għamilna mal-voluntiera tagħna.

961
00:42:50,320 --> 00:42:53,365
U allura, dan huwa interessanti,
li għaddej biex sejħa PrintName.

962
00:42:53,365 --> 00:42:56,490
Jirriżulta, dan il-ħin, hemm
jidher li huwa funzjoni msejħa PrintName.

963
00:42:56,490 --> 00:42:57,614
Li tistampa isem ta 'xi ħadd.

964
00:42:57,614 --> 00:43:01,210
Aħna ma bżonn tuża printf minn
imgħoddi, hemm PrintName.

965
00:43:01,210 --> 00:43:03,500
>> Imma dak li qarrieqa
minħabba PrintName ma

966
00:43:03,500 --> 00:43:06,760
jiġu mal C. Nies ma
jivvintaw dan madwar 40 jew 50 sena ilu,

967
00:43:06,760 --> 00:43:07,990
I did, minflok.

968
00:43:07,990 --> 00:43:10,330
U fil-fatt, jekk I iscroll
down aktar, avviż

969
00:43:10,330 --> 00:43:14,200
kif Kapaċi nikteb tiegħi stess
funzjonijiet C. Aħna ser eventwalment

970
00:43:14,200 --> 00:43:16,319
jispjega għaliex inżommu qal,
vojt, fi ftit postijiet,

971
00:43:16,319 --> 00:43:18,110
iżda għal-lum, ejja
biss ħarsa lejn l-isem.

972
00:43:18,110 --> 00:43:20,905
>> Fuq il-linja 24, jekk inti tixtieq li
joħolqu funzjoni tiegħek stess,

973
00:43:20,905 --> 00:43:22,780
inti litteralment tikteb il-
isem tal-funzjoni.

974
00:43:22,780 --> 00:43:24,340
I għażlet PrintName.

975
00:43:24,340 --> 00:43:26,159
Fil-parentesi, inti
imbagħad jispeċifikaw liema tipi

976
00:43:26,159 --> 00:43:28,450
ta 'inputs, u kemm inti
tixtieq din il-funzjoni li tieħu.

977
00:43:28,450 --> 00:43:31,906
F'dan il-każ, I tixtieq li tieħu
1 varjabbli imsejħa, l-isem,

978
00:43:31,906 --> 00:43:34,030
u li għaddej biex tkun ta '
tip, spag, hekk li għaddej

979
00:43:34,030 --> 00:43:35,780
li jkun hemm xi sekwenza ta 'karattri.

980
00:43:35,780 --> 00:43:39,170
U mbagħad, dan program--
ferm simili fl Scratch,

981
00:43:39,170 --> 00:43:42,590
inti jista 'jkollhom puzzle custom pieces--
huwa se jkollu din l-imġiba tad-dwana.

982
00:43:42,590 --> 00:43:46,760
Huwa ser sejħa printf
tgħaddi fi, hello, placeholder,

983
00:43:46,760 --> 00:43:49,110
u allura huwa għaddej biex timla
fi kwalunkwe utent imsejħa.

984
00:43:49,110 --> 00:43:51,450
>> Allura dan huwa eżempju ta 'dak li
xjenzat kompjuter kieku

985
00:43:51,450 --> 00:43:55,090
estrazzjoni sejħa jew funzjonali
dekompożizzjoni, li huma biss

986
00:43:55,090 --> 00:43:58,110
modi fancy ta saying-- hija jekk
inti bħal din l-idea livell għoli,

987
00:43:58,110 --> 00:44:01,569
bħal Irrid funzjonalità li
stampi isem ta 'xi ħadd, assolutament inti

988
00:44:01,569 --> 00:44:04,360
jistgħu litteralment jiktbu printf u mbagħad
jgħaddu l-argumenti li trid,

989
00:44:04,360 --> 00:44:07,340
u l-programm se taħdem,
kif għamlet sa mill-Erbgħa.

990
00:44:07,340 --> 00:44:10,510
Imma inti tista 'tibda biex astratta bogħod
il-kunċett ta 'stampar isem.

991
00:44:10,510 --> 00:44:13,270
Inti tista 'tagħtiha isem,
bħall PrintName, u dan

992
00:44:13,270 --> 00:44:15,280
hija din idea ta saffi minn ġimgħa 0.

993
00:44:15,280 --> 00:44:19,910
>> Minn issa, I u inti ma għandekx tkun taf
jew kura kif PrintName tiġi implimentata.

994
00:44:19,910 --> 00:44:22,470
Iva hija tuża printf, forsi
ma, li jaf liema juża?

995
00:44:22,470 --> 00:44:23,410
Quién?

996
00:44:23,410 --> 00:44:26,034
Issa jien jitkellem up here,
minflok stabbiliti hawn.

997
00:44:26,034 --> 00:44:28,700
U fil-fatt, bħala programmi tagħna jiksbu
aktar avvanzati u sofistikati,

998
00:44:28,700 --> 00:44:32,550
aħna qed tmur biex tkompli tieħu għall mogħtija
li l-biċċiet puzzle livell aktar baxx jeżistu.

999
00:44:32,550 --> 00:44:34,780
Għaliex aħna kiteb minnhom
jew xi ħadd ieħor ma, so

1000
00:44:34,780 --> 00:44:36,910
li nistgħu mbagħad jibnu fuq wiċċ minnhom.

1001
00:44:36,910 --> 00:44:39,430
Ejja tagħti ħarsa lejn din
varjant, funzjoni waħda.

1002
00:44:39,430 --> 00:44:41,780
>> Allura dan wieħed l-ftit aktar
avvanzati, iżda jirriżulta

1003
00:44:41,780 --> 00:44:44,570
li fil-librerija CS50, l
hemm biss funzjoni GetInt.

1004
00:44:44,570 --> 00:44:47,720
Aħna ma naħsibx, snin ilu, li
timplimenta funzjoni GetPositiveInt.

1005
00:44:47,720 --> 00:44:50,970
U li ftit annoying għaliex jekk
inti guys qed tikteb programm wherein

1006
00:44:50,970 --> 00:44:53,325
inti tixtieq li tikseb pożittiv
numru sħiħ mill-utent,

1007
00:44:53,325 --> 00:44:55,010
inti tista 'assolutament tuża GetInt.

1008
00:44:55,010 --> 00:44:57,840
U inti tista 'assolutament tiċċekkja mal
il-kondizzjoni u forsi loop

1009
00:44:57,840 --> 00:45:00,320
jekk dan int huwa akbar
minn 0 u Yell fil-utent

1010
00:45:00,320 --> 00:45:02,699
jekk hu jew hi ma jagħtix
inti numru pożittiv.

1011
00:45:02,699 --> 00:45:04,740
Imma ejja jinbena dan
bini blokk lilna nfusna, a,

1012
00:45:04,740 --> 00:45:06,555
biċċa Scratch custom, jekk inti se.

1013
00:45:06,555 --> 00:45:08,680
Jien ser jkollhom programm
hawn li finalment, I

1014
00:45:08,680 --> 00:45:11,780
tixtieq li jkunu jistgħu jsejħu
GetPositiveInt, u nixtieq li tkun

1015
00:45:11,780 --> 00:45:14,200
kapaċi li jistampa kwalunkwe li int hu.

1016
00:45:14,200 --> 00:45:16,240
Iżda dan huwa estratt bogħod issa.

1017
00:45:16,240 --> 00:45:19,050
Huwa biss ġie mogħti livell għoli
isem li tgħid dak li tagħmel,

1018
00:45:19,050 --> 00:45:21,780
li huwa wunderbare għaliex dan huwa
ħafna intuwittivi issa biex jinqara.

1019
00:45:21,780 --> 00:45:24,710
U jekk jien care x'hemm taħt
il-barnuża, let me iscroll isfel.

1020
00:45:24,710 --> 00:45:27,140
U huwa ftit intimidanti
fl-ewwel, speċjalment

1021
00:45:27,140 --> 00:45:29,470
jekk dan huwa l-ewwel programm tiegħek,
imma ejja tagħti ħarsa.

1022
00:45:29,470 --> 00:45:32,860
>> Jien m'għadhomx qal, null,
għaliex jirriżulta funzjonijiet,

1023
00:45:32,860 --> 00:45:34,777
ferm simili GetString, jista
ritorn valur lili.

1024
00:45:34,777 --> 00:45:36,610
Huma ma biss għandhom
li jistampaw l-iskrin,

1025
00:45:36,610 --> 00:45:38,410
huma jkunu effettivament jistgħu idejn
me xi ħaġa lura.

1026
00:45:38,410 --> 00:45:41,535
U billi qabel PrintName,
I ma bżonn xi ħaġa lura.

1027
00:45:41,535 --> 00:45:44,160
I meħtieġa l-effett sekondarju ta '
xi ħaġa li juru up fuq l-iskrin,

1028
00:45:44,160 --> 00:45:46,570
imma jien ma bżonn uman
għall-idejn me xi ħaġa lura.

1029
00:45:46,570 --> 00:45:48,840
Hawnhekk, ma GetPositiveInt,
bħal ma GetInt,

1030
00:45:48,840 --> 00:45:50,640
Irrid li jingħataw xi ħaġa lura.

1031
00:45:50,640 --> 00:45:53,220
Hekk jien tgħid le, null,
fuq il-linja 23, iżda int,

1032
00:45:53,220 --> 00:45:55,570
li jgħid, din il-funzjoni
li nikteb,

1033
00:45:55,570 --> 00:45:58,860
imsejħa GetPositiveInt se
idejn lili lura integer, mhux xejn,

1034
00:45:58,860 --> 00:45:59,890
mhux nulli.

1035
00:45:59,890 --> 00:46:03,280
>> Sadanittant, li għaddej biex jieħu l-ebda
inputs, hekk stajt, tip ta ', maqluba dan.

1036
00:46:03,280 --> 00:46:08,280
Jien mhux qed jagħti GetPositiveInt ebda
input, I tixtieq li tagħti me output tagħha.

1037
00:46:08,280 --> 00:46:09,800
U allura x'jiġri issa?

1038
00:46:09,800 --> 00:46:11,640
Allura hawnhekk kif I tista 'tiddikjara varjabbli.

1039
00:46:11,640 --> 00:46:15,090
I ghamilt barra mill-linja,
għal raġunijiet aħna ser eventwalment tara,

1040
00:46:15,090 --> 00:46:17,700
iżda dan biss jagħti
me 32 bits imsejħa, n,

1041
00:46:17,700 --> 00:46:20,952
u stajt pre-determinazzjoni
biex jaħżnu numru sħiħ.

1042
00:46:20,952 --> 00:46:23,660
U hawnhekk li, tagħmel waqt tibni,
u dan huwa għaliex huwa utli.

1043
00:46:23,660 --> 00:46:26,700
Litteralment tagħmel dan,
filwaqt n huwa inqas minn 1.

1044
00:46:26,700 --> 00:46:28,030
Mela ejja ara dak li jiġri.

1045
00:46:28,030 --> 00:46:30,760
I jistampa, jekk jogħġbok
tagħti me a int pożittiv.

1046
00:46:30,760 --> 00:46:34,300
I imbagħad nikseb int, bl-użu tal CS50
jiffunzjonaw u maħżuna n.

1047
00:46:34,300 --> 00:46:38,990
>> U mbagħad, liema linja tal-kodiċi probabbilment
gets esegwiti jmiss, loġikament?

1048
00:46:38,990 --> 00:46:41,890
Liema linja numru?

1049
00:46:41,890 --> 00:46:42,571
Yeah, hekk 31.

1050
00:46:42,571 --> 00:46:45,320
Inti ma tkunx taf dan sakemm inti stajt
qallek jew tip ta 'jiddeduċu li,

1051
00:46:45,320 --> 00:46:45,986
iżda dan huwa veru.

1052
00:46:45,986 --> 00:46:48,280
Hija tmur fuq għal isfel
u mbagħad jżomm tirrepeti.

1053
00:46:48,280 --> 00:46:55,840
Mela jekk jien ittajpjat fil ngħidu aħna, in-numru
negattiv 1, hija n anqas minn negattiv 1?

1054
00:46:55,840 --> 00:46:56,340
Yeah.

1055
00:46:56,340 --> 00:46:58,470
Minħabba negattiv 1 huwa inqas minn 1.

1056
00:46:58,470 --> 00:46:59,510
Allura dak li jiġri?

1057
00:46:59,510 --> 00:47:03,260
Jien ser tagħmel dan
filwaqt n huwa inqas minn 1,

1058
00:47:03,260 --> 00:47:05,760
hekk jien se jmorru lura għal-linja 28.

1059
00:47:05,760 --> 00:47:09,530
>> U kull time-- u ejja jimxu this--
jagħmlu funzjoni 1 li josservawha,

1060
00:47:09,530 --> 00:47:11,340
u issa dot slash funzjoni 1.

1061
00:47:11,340 --> 00:47:14,280
Jekk tip I negattiv 1, huwa
ser iżommu yelling fil lili

1062
00:47:14,280 --> 00:47:17,530
sal I jikkoperaw minħabba li kull
ta 'inputs tiegħi huwa inqas minn 1

1063
00:47:17,530 --> 00:47:20,070
u jekk huwa filwaqt li inqas minn 1,
Jien ser tkompli tagħmel dan.

1064
00:47:20,070 --> 00:47:24,240
Jekk I finalment jagħtiha numru simili 50,
Thankfully, jgħid, grazzi għall-50.

1065
00:47:24,240 --> 00:47:24,970
Għaliex?

1066
00:47:24,970 --> 00:47:30,640
Minħabba hekk kif n ma jkunx inqas minn
1, I stop jkollna staġnati f'dan loop,

1067
00:47:30,640 --> 00:47:33,840
u dan il-keyword ġdida llum,
ritorn, litteralment ma dan.

1068
00:47:33,840 --> 00:47:36,800
Hekk stajt biss implimentati, b'mod
sens, l-ekwivalenti ta 'GetString,

1069
00:47:36,800 --> 00:47:40,590
fejn jien għoti lura lill
min qed tuża me, xi valur.

1070
00:47:40,590 --> 00:47:42,820
Ma għandhom ikunu
string, huwa ta 'int.

1071
00:47:42,820 --> 00:47:44,990
Allura sempliċi, ta 'malajr
eżempju, iżda aħna ser dalwaqt

1072
00:47:44,990 --> 00:47:47,930
tara ftit aktar sofistikati
Verżjonijiet għadhom.

1073
00:47:47,930 --> 00:47:53,882
Fil-fatt, ejja tagħti ħarsa lejn
wieħed numerika, li huwa msejjaħ return.c.

1074
00:47:53,882 --> 00:47:55,590
U dan wieħed fil-fatt
ftit aktar sempliċi.

1075
00:47:55,590 --> 00:47:59,010
Allura iskop dan il-programm fil
life-- ejja tiġbor u run,

1076
00:47:59,010 --> 00:48:03,090
sabiex tagħmel ritorn, dot
slash, avviż return--

1077
00:48:03,090 --> 00:48:05,530
il-programm sempliċiment kubi il-valur 2.

1078
00:48:05,530 --> 00:48:08,410
Huwa pretty stupid, huwa diffiċli
kodiċi, dan ma jieħux xi inputs,

1079
00:48:08,410 --> 00:48:12,220
iżda ma juru ieħor
funzjoni li stajt bil-miktub myself.

1080
00:48:12,220 --> 00:48:15,760
So here, stajt ddikjarat
varjabbli, imsejħa x, ta 'int tip,

1081
00:48:15,760 --> 00:48:17,840
ugwali għan-numru 2,
kompletament arbitrarja.

1082
00:48:17,840 --> 00:48:19,530
Dan huwa biss xi stampar fluffy.

1083
00:48:19,530 --> 00:48:23,070
Hija tgħid x Huwa issa, tali u
tali, cubing dot dot dot.

1084
00:48:23,070 --> 00:48:26,390
U l-magic hija apparentement konformi 21.

1085
00:48:26,390 --> 00:48:30,120
Jien ssejjaħ funzjoni msejħa, kubi,
Jien Teħodha folja ta 'karta

1086
00:48:30,120 --> 00:48:32,890
bin-numru 2 bil-miktub dwar dan,
u liema valur, matematikament,

1087
00:48:32,890 --> 00:48:34,860
do Irrid li toħroġ minnha?

1088
00:48:34,860 --> 00:48:36,570
Just bħala verifika sanità?

1089
00:48:36,570 --> 00:48:37,070
8.

1090
00:48:37,070 --> 00:48:37,570
Dritt?

1091
00:48:37,570 --> 00:48:40,160
I tixtieq 2 kubiku lura, 2 għal
il-qawwa ta '3, hekk 8 lura.

1092
00:48:40,160 --> 00:48:42,570
>> Għalhekk, fejn huwa kubu implimentat?

1093
00:48:42,570 --> 00:48:44,349
Ukoll, avviż huwa implimentat stabbiliti hawn.

1094
00:48:44,349 --> 00:48:47,140
U bħad qabel, loġikament,
anki jekk il-sintassi hija probabbilment

1095
00:48:47,140 --> 00:48:49,320
ferm ġdida ħafna minnkom,
Irrid din il-funzjoni

1096
00:48:49,320 --> 00:48:51,780
għall-idejn me lura folja ta
karta ma 'int fuqha.

1097
00:48:51,780 --> 00:48:53,990
So I jkollhom int, il
isem huwa arbitrarju,

1098
00:48:53,990 --> 00:48:55,530
iżda konvenjenti imsejħa kubu.

1099
00:48:55,530 --> 00:48:58,430
L-input għal dan, huwa n ta
tip numru sħiħ, b'tali mod li

1100
00:48:58,430 --> 00:49:00,800
kif I jistgħu jgħaddu fin-numru
2 fuq folja tal-karta.

1101
00:49:00,800 --> 00:49:03,910
U allura jirriżulta jappoġġja C
matematika, sabiex inti ma għandekx x għas drabi,

1102
00:49:03,910 --> 00:49:06,680
inti biss tuża l-asterisk
għat-tkattir.

1103
00:49:06,680 --> 00:49:11,070
U dan jirritorna drabi n żminijiet n
n, li hija sempliċement valur kubiku.

1104
00:49:11,070 --> 00:49:12,840
>> Għalhekk, fejn aħna se kollha ta 'dan?

1105
00:49:12,840 --> 00:49:14,570
Dan żgur huwa
tour whirlwind, mistrieħ assigurat,

1106
00:49:14,570 --> 00:49:16,410
li fit-taqsimiet super
u fil-problema sett 1,

1107
00:49:16,410 --> 00:49:18,368
inti ser tkun mixi permezz
dan kollu l-aktar.

1108
00:49:18,368 --> 00:49:22,490
U fil-problema stabbilixxa l-1, aħna ser transizzjoni
mid-dinja grafika ta Scratch

1109
00:49:22,490 --> 00:49:25,640
għal xi ħaġa aktar linja tal-kmand
fil C. Iżda aħna ser jieħdu l-ispirazzjoni

1110
00:49:25,640 --> 00:49:27,680
minn dan hawn logħba
minn imgħoddi, fejn

1111
00:49:27,680 --> 00:49:31,591
użu C u l-edizzjoni standard tal-
sett p inti ser timplimenta piramida Mario.

1112
00:49:31,591 --> 00:49:34,340
U fil-Hacker edizzjoni tal-
sett p, jekk hekk jagħżlu li jeleġġu,

1113
00:49:34,340 --> 00:49:38,280
inti ser timplimenta daqsxejn aktar
sfida piramida żewġ quċċati.

1114
00:49:38,280 --> 00:49:41,239
Int ser ikollok jimplimentaw ukoll
algoritmu, algoritmu greedy.

1115
00:49:41,239 --> 00:49:43,030
Jirriżulta hemm
xi loġika interessanti

1116
00:49:43,030 --> 00:49:45,640
wara l-proċess ta '
tmexxija istazzjon ta 'kaxxier

1117
00:49:45,640 --> 00:49:47,410
u fil-fatt għoti
xi ħadd bidla lura.

1118
00:49:47,410 --> 00:49:50,410
Hemm algoritmu li pjuttost
sempliċi, li inti tista 'anki

1119
00:49:50,410 --> 00:49:53,576
jaħtfu intuwittivament meta inti l-ewwel taqra
it-- jirrealizzaw dan huwa dak I stajt dejjem

1120
00:49:53,576 --> 00:49:57,110
jsir kwalunkwe ħin stajt mogħtija lil xi ħadd xi
back-- flus li jippermetti li inti dejjem

1121
00:49:57,110 --> 00:50:00,679
jimminimizzaw in-numru ta '
noti tal-karta jew muniti tal-metall

1122
00:50:00,679 --> 00:50:02,220
li int għoti lura lill-utent.

1123
00:50:02,220 --> 00:50:04,610
U dan, naturalment, huwa konvinċenti
għaliex jekk inti tmur biex CVS jew whatnot,

1124
00:50:04,610 --> 00:50:06,430
inti ma tridx tkun mogħtija
mazz sħiħ ta 'dawk

1125
00:50:06,430 --> 00:50:07,596
jew mazz sħiħ ta 'pennies.

1126
00:50:07,596 --> 00:50:10,120
Trid li l-inqas numru
muniti, probabbilment, ikun possibbli.

1127
00:50:10,120 --> 00:50:13,070
>> Fl-aħħarnett, inti ser jintalbu wkoll
dabble fid-dinja ta 'ilma

1128
00:50:13,070 --> 00:50:17,220
u fil-fatt tikseb apprezzament
għal immappjar bejn ir-rati ta 'fluss,

1129
00:50:17,220 --> 00:50:19,890
ta 'prodotti simili, ilma fil-doċċa,
kemm kemm ilma huwa użat.

1130
00:50:19,890 --> 00:50:22,640
U l-allużjoni fih,
se jkun dan il-klipp hawn,

1131
00:50:22,640 --> 00:50:24,840
li aħna ser jispiċċaw fuq għal
biss 60 sekonda, li

1132
00:50:24,840 --> 00:50:29,070
żebgħa stampa ta '
rjus tad-doċoċ-fluss baxxa.

1133
00:50:29,070 --> 00:50:30,886
>> [Daqq video]

1134
00:50:30,886 --> 00:50:31,385
-kull Dritt.

1135
00:50:31,385 --> 00:50:32,774
Sibt kollox hawn.

1136
00:50:32,774 --> 00:50:35,800
Sibt l-F Series Ċiklun,
Hydra, Jetflow, Stokkolma

1137
00:50:35,800 --> 00:50:37,660
Supersteam, inti isem li bih.

1138
00:50:37,660 --> 00:50:39,265
>> -u Liema do you jirrakkomandaw?

1139
00:50:39,265 --> 00:50:40,460
>> Liema huma inti tfittex?

1140
00:50:40,460 --> 00:50:41,300
>> Bniedem -Power.

1141
00:50:41,300 --> 00:50:42,285
Power.

1142
00:50:42,285 --> 00:50:42,910
-SIMILI Silkwood.

1143
00:50:42,910 --> 00:50:44,520
-Li S għar-radjazzjoni.

1144
00:50:44,520 --> 00:50:46,335
-Li Dritt.

1145
00:50:46,335 --> 00:50:48,275
-Issa Dak li huwa dan?

1146
00:50:48,275 --> 00:50:49,704
-Li Hija l-Commando 450.

1147
00:50:49,704 --> 00:50:50,620
I ma jbiegħux li wieħed.

1148
00:50:50,620 --> 00:50:51,700
>> -Imma dan huwa dak li rridu.

1149
00:50:51,700 --> 00:50:52,680
Huwa comando 450.

1150
00:50:52,680 --> 00:50:53,882
>> -Ebda Nemmen lili.

1151
00:50:53,882 --> 00:50:55,090
Huwa użat biss fil-ċirku.

1152
00:50:55,090 --> 00:50:56,512
Huwa għal iljunfanti.

1153
00:50:56,512 --> 00:50:59,356
>> -I'll Tħallas xejn.

1154
00:50:59,356 --> 00:51:01,252
>> Liema dwar Jerry?

1155
00:51:01,252 --> 00:51:02,760
>> -He Ma tista 'timmaniġġja dan.

1156
00:51:02,760 --> 00:51:04,910
Hu delikat.

1157
00:51:04,910 --> 00:51:05,750
Oh yeah.

1158
00:51:05,750 --> 00:51:36,737

1159
00:51:36,737 --> 00:51:37,320
[END Daqq]

1160
00:51:37,320 --> 00:51:37,700
DAVID J Malan: Kull dritt.

1161
00:51:37,700 --> 00:51:38,820
Li jekk għal CS50.

1162
00:51:38,820 --> 00:51:40,050
Aħna ser tara int ġimgħa d-dieħla.

1163
00:51:40,050 --> 00:51:45,910

1164
00:51:45,910 --> 00:51:49,029
>> SPEAKER 1: [? Scully?], [? Ian,?]
safejn dan il-proġett outro,

1165
00:51:49,029 --> 00:51:50,362
dak li jkollu guys toħroġ bi?

1166
00:51:50,362 --> 00:51:51,990
>> SPEAKER 2: Well, konna mogħtija
dan varjetà tal-ħsieb,

1167
00:51:51,990 --> 00:51:53,250
u naħsbu li l-aħjar mod to--

1168
00:51:53,250 --> 00:51:53,660
>> SPEAKER 3: Mejju I?

1169
00:51:53,660 --> 00:51:54,326
>> SPEAKER 2: Yeah.

1170
00:51:54,326 --> 00:51:56,360
Bil-mezzi kollha, fil-fatt.

1171
00:51:56,360 --> 00:51:59,425
>> SPEAKER 3: So I think
nistgħu qosor idea tagħna

1172
00:51:59,425 --> 00:52:05,450
għall-Outros ma xejn word-- wieħed.

1173
00:52:05,450 --> 00:52:08,950

1174
00:52:08,950 --> 00:52:10,409
>> DAVID J Malan: Xejn?

1175
00:52:10,409 --> 00:52:11,200
SPEAKER 3: Xejn.

1176
00:52:11,200 --> 00:52:12,990
DAVID J Malan: Xi jfisser?

1177
00:52:12,990 --> 00:52:16,260
SPEAKER 3: Il-Outros huma dwar xejn.

1178
00:52:16,260 --> 00:52:21,720
SPEAKER 2: Well, I mean, fil-filosofija,
I mean, xejn huwa dejjem xi ħaġa.

1179
00:52:21,720 --> 00:52:24,200
SPEAKER 1: Allura what's--
x'inhu l-premessa?

1180
00:52:24,200 --> 00:52:25,720
SPEAKER 3: Allura huwa bħall-ħajja.

1181
00:52:25,720 --> 00:52:26,680
OK.

1182
00:52:26,680 --> 00:52:28,294
What did you do illum?

1183
00:52:28,294 --> 00:52:31,811
>> DAVID J Malan: I ltqajna up, kellhom
kolazzjon, u waslet biex jaħdmu.

1184
00:52:31,811 --> 00:52:34,056
>> SPEAKER 3: C'est outro.

1185
00:52:34,056 --> 00:52:36,806
SPEAKER 2: Iżda, I mean, m'għandhomx
xi ħaġa jiġri lilu fuq the--

1186
00:52:36,806 --> 00:52:37,889
SPEAKER 3: No, no, no, no.

1187
00:52:37,889 --> 00:52:40,220
Xejn jiġri.

1188
00:52:40,220 --> 00:52:42,910
>> SPEAKER 1: Allura għaliex aħna jaraw?

1189
00:52:42,910 --> 00:52:46,956
>> SPEAKER 3: Minħabba
huwa ta 'outro għall CS50.

1190
00:52:46,956 --> 00:52:48,652
>> DAVID J Malan: Għadu mhux.

1191
00:52:48,652 --> 00:52:49,151