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>> [Daqq tal-mużika]

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DAVID J. Malan: Dan huwa simili
seminar freshman llum.

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KOLLOX SEW.

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Allura ħafna xita out.

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Dan x'aktarx li jseħħ nhar ta 'Erbgħa,
iżda kollha l-opportunità aktar

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għall-mistoqsijiet llum.

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Mela ejja nibdew off fil-fatt
mal-film fi ftit mument.

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Iżda aħna ser tibda grandly kif dejjem.

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>> Dan huwa CS50, u dan
hija t-tmiem tal-4 ġimgħa.

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Mela jekk inti stajt qatt jarah
TV jew fejn movie

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hemm xi esperti tal-kompjuter u
il-pulizija, jew FBI, jew xi aġenzija

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qed jippruvaw jaqbdu xi
avversarju, ukoll, inti stajt

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probabbilment jinstemgħu l-espressjoni "ittejjeb,"
fejn dik tekniku b'xi mod

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magically zooms fi infinitament
s'issa biex tara l-kriminali

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identità jew in-numru pjanċa liċenzja
anke l-shimmer ta 'mera

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jew l-glint ta 'għajnejn ta' xi ħadd.

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Allura fil-fatt, ejja tagħti ħarsa lejn
ftit xeni bħal dawn minn Hollywood.

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[Daqq video]

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-OK, Issa ejja tikseb ħarsa tajba fi inti.

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>> -Hold Dan.

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Mexxi dak lura.

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>> -Stenna minuta.

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Mur dritt.

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>> -Hemm, Friża dan.

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Screen Full.

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-OK, Friża dan.

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-Tighten Fuq dik, ser ikollok?

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-Vector F'dak is-
Guy mir-rota lura.

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-Zoom Fl-dritt hawn fuq dan il-post.

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-Bil L-apparat dritt, l-immaġni
jista 'jiġi estiż u inċiżiv.

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-Dak X'inhu?

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-Hija L programm titjib.

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-Jista Inti ċar li up xi?

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-I Do not know.

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Ejja ittejjeb dan.

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>> A6 -Enhance taqsima.

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>> -I Msaħħa l-dettall,
and-- Naħseb li hemm

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biżżejjed biex ittejjeb,
jgħadduha lill-iskrin tiegħi.

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-I Msaħħa l riflessjoni fl-għajnejn tagħha.

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>> -Let S run dan permezz
video titjib.

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-Edgar, Inti tista ttejjeb dan?

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>> -Żomm.

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>> -I've Ilhom jaħdmu fuq din ir-riflessjoni.

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>> Riflessjoni -Someone s.

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-Reflection.

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-Hemm L riflessjoni tal-wiċċ tar-raġel.

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Riflessjoni -Il.

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-Hemm L riflessjoni.

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-Zoom Fuq il-mera.

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'Tista' tara riflessjoni.

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-Jista Inti jsaħħu d-dehra minn hawn?

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-Jista Inti ittejjeb lilu dritt hawn?

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-Jista Inti ittejjeb dan?

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Inti tista 'ttejjeb it?

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>> -Jista Aħna ittejjeb dan?

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>> -Jista Inti ittejjeb dan?

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-Hold Fuq it-tieni, I ser itejbu.

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-Zoom Fuq il-bieb.

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-Times 10.

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-Zoom.

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-Move In.

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-Aktar.

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-Wait, Stop.

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Stop.

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-Pause Dan.

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Dawwar il us 75 gradi
madwar il-vertikali, jekk jogħġbok.

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Stop.

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Mur lura għall-parti
dwar il-bieb, għal darb'oħra.

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>> -Got Enhancer immaġni li jistgħu Bitmap?

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>> -Hey, Forsi nistgħu nużaw l Pradeep
Metodu sen biex tara fil-twieqi.

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Software -Dan huwa state of the art.

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>> -Il Eigenvalue huwa off.

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>> -Bil-Dritt
kombinazzjoni ta 'algorithm--

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>> Meħuda eliminazzjoni -He ta
algoritmi għal-livell li jmiss,

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u I jistgħu jużawhom biex
jsaħħu din ritratt.

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>> -Lock Fuq u tkabbar l-assi z.

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>> -Enhance.

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>> -Enhance.

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>> -Enhance.

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-Freeze U jtejbu.

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>> [END Daqq]

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>> DAVID J. Malan: Kull dritt, hekk
kollha ta 'dawn huma attwalment kliem.

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Huma qed biss midmum flimkien
mod li mhux attwalment sensibbli.

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U, fil-fatt, CS50 u korsijiet bhalu
tendenza li rovina ħafna TV u films

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għalik.

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Għaliex meta dawk l-esperti tal-kompjuter
huma jinstemgħu off termini u qal

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affarijiet fancy bħal
eigenvectors, u l-assi z,

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u kull numru ta 'ieħor
fil-fatt termini aktar tekniċi,

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dawn qed verament ftit stringing
kliem flimkien spiss.

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Hija li waħda mill tamiet tagħna hija li,
bħala effett sekondarju ta 'teħid korsijiet

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bħal dan, se aktar nies fil-
dinja effettivament ikun jista 'iżen fil

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u biss dejjem hekk ftit jinfluwenzaw il-
kwalità u l-preċiżjoni ta 'dawk il-films?

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>> Fil-fatt, ejja tagħti ħarsa lejn realtà.

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Allura hawnhekk huwa l-ritratt persunal ta '
Marija, wieħed mill-fellows tagħlim tagħna.

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U jissoponi hi
suspettati ta 'xi ħaġa.

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And yet, hemm glimmer ta
xi biċċa ta 'prova fl-għajnejn tagħha,

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jew fir-riflessjoni ta 'nuċċalijiet tagħha.

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Ukoll, jekk nagħmlu eżattament kif il-films
tipproponi, fejn aħna zoom u "jtejbu",

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dan huwa kemm l-informazzjoni
huwa fil-wiċċ Marija

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meta inti qbid immaġni
ma 'dik ir-riżoluzzjoni oriġinali.

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>> U, fil-fatt, tista 'tara dawn tikek.

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U dawn huma liema huma
imsejħa pixels, P-I-X-E-L-S,

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li huwa biss kwadru tipikament
li huwa dot li composés immaġini.

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U lura fil-ġurnata, u fil-fatt anke
illum ma 'wħud mill-lum LED TVs

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jew LCD TVs, jekk inti ħadthom ltqajna
wieħed fil-kamra tiegħek jew id-dar,

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jekk inti tmur up super qrib tiegħu, u
speċjalment jekk din hija TV kemmxejn anzjani,

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inti tista 'probabbilment anki tara dawn tikek
u dan huwa dak compose immaġini.

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>> Ukoll, mhemmx iktar
informazzjoni minn dan.

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Nistgħu "itejbu", fis-sens ta '
smoothing affarijiet aktar u tip ta '

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ddeduċiet tip ta ', sort ta' dak li
kulur għandu jkun ħdejn il-għajn Marija

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b'tali mod li mhuwiex fil-fatt hekk pixelated.

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Imma jekk I iżommu zooming, hemm
huwa l-Guy ħażina fl-għajnejn tagħha.

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Bħal dik hija l-
informazzjoni li għandna.

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Inti ma tistax toħloq
informazzjoni ta 'xejn.

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Hemm biss finit
numru ta 'bits hemmhekk.

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>> Għalhekk fl Problem Set 4, fejn
għandek l-opportunità

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jilagħbu ma 'dan it-tip tad-dinja.

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Fil Set 4 Problem, inti ser tesplora l-
dinja ta 'grafika, u l-forensika,

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u fil-fatt jikteb il-kodiċi
li jirkupra immaġini mitlufa.

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Int ser ikollok jikteb il-kodiċi li
jimmanipula immaġini eżistenti

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u finalment jifhmu x'hemm
għaddej taħt il-barnuża.

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>> U, jirriżulta, huwa attwalment
mhux kollha li ikkumplikata.

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Per eżempju, jekk ridna li
jirrappreżentaw wiċċ smiley fejn

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ma 'dawn pixels iswed,
jew dawn tikek suwed,

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ukoll, nistgħu sempliċiment jirrappreżentaw
bħala verament Bitmap.

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U jekk inti kienu qatt semgħu li
Bitmap espressjoni, forsi

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issa jibda jagħmel
ftit aktar sens illum.

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>> Aħna diġà jafu liema daqsxejn hu.

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Li għamilhom 0 jew 1.

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U mappa huwa biss xi ħaġa
bħal biċċa karta

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li jagħtik direzzjonijiet u għandha
forsi grilja ta 'x- u y-koordinati.

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Allura hawnhekk hija Bitmap.

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Huwa mappa ta 'bits
li biha 1 huwa apparentement

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ser jirrappreżenta pixel abjad, u
0 se jirrappreżenta pixel iswed.

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Iżda nistgħu ċertament flip madwar.

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Hija ma verament kwistjoni daqshekk
Sakemm aħna qed konsistenti.

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U hawn huwa kif, fil binary-- ġewwa
tal-memorja tal-kompjuter, jew saħansitra ġewwa

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ta 'fajl fuq hard tiegħek
drive-- tista int taħżen

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l-aktar sempliċi ta 'immaġini wiċċ smiley.

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Imma dak li aħna, naturalment,
nieqsa din id-dehra?

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Kulur, id-dritt?

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Huwa pass ovvju li jmiss jew
titjib biex ittejjeb din bil-kulur.

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Allura sfortunatament biss bi wieħed
bit, 0 jew 1, nistgħu jirrappreżentaw kulur.

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Dan jista 'jkun aħmar, jew blu, jew
iswed, jew abjad, jew aħdar, jew roża,

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jew xi pari ta 'kuluri.

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Iżda għall-finijiet ta 'sempliċità, aħna ser
biss wieħed jassumi iswed u abjad.

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>> Allura dak li loġikament għandna bżonn jekk irridu
jridu jimplimentaw kulur ta 'immaġni?

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What do għandna nagħmlu?

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Simili jekk il-fattur li jillimita hawn
hija li ma 'wieħed ftit inti tista' biss

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jirrappreżentaw żewġ stati, 0 jew 1, abjad
jew iswed, dak li inti trid tagħmel?

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Udjenza: Aktar data.

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DAVID J. Malan: Aktar bits,
yeah data aktar, aktar bits.

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U, tabilħaqq, dan huwa eżattament kif
immaġini bil-kulur huma rappreżentati.

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Pjuttost milli jużaw daqsxejn waħda,
0 jew 1 għal kull pixel, kull dot,

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inti biss tuża multiplu.

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Forsi l-użu 8, forsi, aktar komunement
użu 24, u tabilħaqq, fl Problem Set

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4, ser ikollok tilgħab ma 'fajl
format li juża 24 bits tipikament.

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>> Iżda ħafna inti probabilment
familjari ma 'JPEGs.

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Jekk inti stajt qatt jittieħdu
ritratt fuq il-mobile tiegħek,

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jew imtella jew jidhru xi ħaġa fuq
Facebook, jew Flickr, kwalunkwe numru

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ta 'websajts bbażati fuq ritratt, inti stajt
probabbilment jidhru immaġni JPEG qabel.

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U jirriżulta li, dan huwa l-fajl
format aħna qed tmur għall-użu fl PSet 4,

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fejn inti qed tmur biex
huma obbligati li jirkupraw stampi

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li stajt aċċidentalment mħassra minn
korrotta karta tal-memorja fil-camera,

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jekk inti se.

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>> U jirriżulta li għalkemm
JPEG hija pjuttost sophisticated--

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huwa ħafna aktar sofistikata
mill-tikek suwed u bojod

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rajna mument ilu, għaliex hemm
algoritmi attwalment fancy li

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huma użati biex jikkompressa JPEG, hekk
li inti jista 'jkollhom tassew sbieħ,

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stampa ta 'kwalità iżda bl-użu
relattivament ftit bits.

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U aħna ser terga 'lura għal
kompressjoni qabel fit-tul.

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Jirriżulta li l-ewwel
tliet bytes fil-image-- JPEG

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ebda kwistjoni dak li inti ħadt ritratt
of-- huma l-valuri 255, 216, 255.

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>> Fi kliem ieħor, jekk inti biss
tara li mudell ta 'bits,

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00:07:05,990 --> 00:07:09,180
rrappreżentati hawnhekk kif tlieta
bytes, jew 24 bits totali,

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00:07:09,180 --> 00:07:13,810
bi probabbiltà għolja tista 'tiddeduċi li
inti qiegħed tfittex lejn dan il--ewwel tliet

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bytes ta 'JPEG.

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U dan huwa dak magħruf
bħala l-iffirmar ta 'JPEG.

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00:07:18,040 --> 00:07:20,540
A lott ta 'formats tal-fajls
hemmhekk għandhom tendenza li tibda

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00:07:20,540 --> 00:07:23,735
ma 'ċerti mudelli ta' 0s u 1s,
hekk li l-Windows, u Mac OS, u IOS,

183
00:07:23,735 --> 00:07:28,272
u Android taf x'tip ta 'fajl li
huma, minbarra l-fajl hekk imsejħa

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estensjoni li ħafna ta 'fajls jkollhom.

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Jekk għandek jpg, li
clue ieħor għall-kompjuter.

186
00:07:32,590 --> 00:07:35,310
>> Mela ejja issa nħarsu lejn din
ftit aktar teknikament.

187
00:07:35,310 --> 00:07:37,390
Nafu l-deċimali
sistema hija 0 sa 9.

188
00:07:37,390 --> 00:07:38,740
Nafu binarju huwa ta '0 u 1.

189
00:07:38,740 --> 00:07:41,842
U jekk taħseb lura għall PSet
0, kellna inti wrestle ma ',

190
00:07:41,842 --> 00:07:43,800
għal xi ftit, xi ħaġa
imsejħa hexadeċimali,

191
00:07:43,800 --> 00:07:47,320
fejn inti għandek 16-il ċifra,
minflok 10 jew minflok 2.

192
00:07:47,320 --> 00:07:50,405
U dawk ċifri, b'konvenzjoni,
huma 0 sa 9 u mbagħad

193
00:07:50,405 --> 00:07:55,040
permezz f, fejn f jirrappreżenta dak
numru deċimali, biss bħala sanità malajr

194
00:07:55,040 --> 00:07:56,640
check?

195
00:07:56,640 --> 00:07:57,610
Allura, 15.

196
00:07:57,610 --> 00:08:01,390
U għandu jirrappreżenta 10, biss billi
natura tal-ordni li stajt mogħtija.

197
00:08:01,390 --> 00:08:04,350
Huwa biss konvenzjoni arbitrarja,
imma hija pjuttost standard.

198
00:08:04,350 --> 00:08:06,870
>> Mela jekk inħarsu lejn dan il-mudell
ta 'tlieta bytes-- ejja

199
00:08:06,870 --> 00:08:09,620
biss jibdew tħares lejn din fil
b'mod konsistenti mal-mod kif

200
00:08:09,620 --> 00:08:12,450
xjenzjati tal-kompjuter ġeneralment
tħares lejn u jaħsbu dwar fajls.

201
00:08:12,450 --> 00:08:15,580
Inti tista 'ċertament taħseb dwar
fajls fil 0s, u 1s, u ċifra deċimali,

202
00:08:15,580 --> 00:08:19,340
iżda fir-realtà, għandna t-tendenza li jużaw binarja
jew aktar li tipikament hexadecimal--

203
00:08:19,340 --> 00:08:20,760
lura mill PSet 0.

204
00:08:20,760 --> 00:08:25,857
So let me jipproponi li 255, 216, u 255
huma biss dawn it-tendenzi ta 0s u 1s.

205
00:08:25,857 --> 00:08:28,440
U inti tista 'tivverifika dan jekk inti
trid tagħmel l-matematika minn f'Ġimgħa 0.

206
00:08:28,440 --> 00:08:30,810
Iżda, għal issa, biss wieħed jassumi
li dan huwa verament korretta.

207
00:08:30,810 --> 00:08:33,850
Stajt biss miktuba mill-ġdid tliet deċimali
numri bħala tliet valuri binarja.

208
00:08:33,850 --> 00:08:36,100
Issa dak li jien ser tagħmel hu li
biss żid ftit spazju abjad,

209
00:08:36,100 --> 00:08:37,266
biss għall-finijiet leġibbiltà tal.

210
00:08:37,266 --> 00:08:39,940
U avviż, jien biss ser
li l-affarijiet jimxu bogħod minn xulxin.

211
00:08:39,940 --> 00:08:43,090
Allura qabel, wara, qabel, wara.

212
00:08:43,090 --> 00:08:46,180
Li qed nagħmel xejn interessanti oħra
minn sempliċiment tixrid affarijiet out hekk

213
00:08:46,180 --> 00:08:50,380
l-avviż kull sett ta 'tmien
bits issa huwa żewġ settijiet ta 'erba' bits.

214
00:08:50,380 --> 00:08:54,920
Dan huwa utli għaliex hexadeċimali
huwa partikolarment moda

215
00:08:54,920 --> 00:09:00,930
għax kull ħames figuri hexadeċimali 0 permezz
f, jew b'mod aktar speċifiku 0 permezz 15,

216
00:09:00,930 --> 00:09:03,430
jistax jiġi rappreżentat
b'eżattament erba bits.

217
00:09:03,430 --> 00:09:07,960
Fi kliem ieħor, f'hexadecimal jekk inti
tixtieq li jirrappreżentaw 0, huwa biss 0000,

218
00:09:07,960 --> 00:09:08,780
erba żerijiet.

219
00:09:08,780 --> 00:09:13,997
U jekk inti tixtieq li jirrapreżentaw 15,
huwa 1111, li huwa erba 'bits.

220
00:09:13,997 --> 00:09:16,080
U jekk inti tagħmel l-matematika,
jekk dan huwa l-post dawk,

221
00:09:16,080 --> 00:09:18,210
dan huwa l-post 16s,
li għaddej biex jagħti you--

222
00:09:18,210 --> 00:09:19,960
pjuttost li għaddej
to-- sorry, fil binarju,

223
00:09:19,960 --> 00:09:23,660
li għaddej biex jagħtuk 15, dawk il-post,
post twos, fours u eights post.

224
00:09:23,660 --> 00:09:26,821
So let me jipproponi li din
sett ta 'erba' bits fuq ix-xellug

225
00:09:26,821 --> 00:09:28,070
huwa dak li aħna qed tmur biex sejħa f.

226
00:09:28,070 --> 00:09:30,110
Hu l-akbar numru li
jista 'jirrappreżenta ma' erba 'bits.

227
00:09:30,110 --> 00:09:33,300
U aħna diġà jafu minn hexadecimal,
f huwa l-akbar ċifri f'hexadecimal.

228
00:09:33,300 --> 00:09:36,020
Imxejna ltqajna ieħor f hemmhekk,
żewġ aktar hemmhekk.

229
00:09:36,020 --> 00:09:38,980
U għal issa, ħu fuq il-fidi
li I għamlu d-dritt matematika

230
00:09:38,980 --> 00:09:41,890
u li l-nofs xellugi
ta 'dawk bits, 1101,

231
00:09:41,890 --> 00:09:43,980
huwa l-istess ħaġa bħat d f'hexadecimal.

232
00:09:43,980 --> 00:09:46,490
U l-lemin, 1000, huwa biss 8.

233
00:09:46,490 --> 00:09:48,140
>> U li wieħed faċli li wieħed jara, right?

234
00:09:48,140 --> 00:09:51,670
Il represents-- 8 huwa dritt
taħt dak il-post eights.

235
00:09:51,670 --> 00:09:56,040
Allura aħna għandna waħda fil-kolonna eights
u xejn fil-fours, twos jew dawk.

236
00:09:56,040 --> 00:09:59,830
Allura issa aktar konvenzjonalment, il-bnedmin għandhom tendenza
jiktbu ċifri hexadecimal bħal dan,

237
00:09:59,830 --> 00:10:03,000
inti biss squish lilhom flimkien,
u allura inti prefiss bl 0x.

238
00:10:03,000 --> 00:10:05,920
Dan ifisser xejn ħlief
a clue viżwali għal human--

239
00:10:05,920 --> 00:10:10,350
Hawnhekk jiġi value-- hexadeċimali għaliex
jista 'ma jkunx altrimenti tkun ovvja.

240
00:10:10,350 --> 00:10:13,629
>> Li jfisser, finalment, li
il-mudell ta 'żero u dawk,

241
00:10:13,629 --> 00:10:16,170
jew il-mudell ta 'hexadeċimali
ċifri ekwivalenti li int

242
00:10:16,170 --> 00:10:18,990
ser tibda 'tfittex għal
fil Problema Set 4 huwa this--

243
00:10:18,990 --> 00:10:22,120
u l-spec Problema Set 4 se jimxu
inti permezz ta 'dan f'aktar detail--

244
00:10:22,120 --> 00:10:25,344
iżda jirrealizzaw kif tip ta 'arcane bħala
dan tista 'tidher mad-daqqa t'għajn,

245
00:10:25,344 --> 00:10:27,010
int ser tibda tara dan il-lott.

246
00:10:27,010 --> 00:10:30,320
U fil-fatt, anki fil GDB, il-
debugger aħna introdotti nhar it-Tnejn

247
00:10:30,320 --> 00:10:35,440
u Dan jintroduċi fil PSet 3, va
li spiss nuruk valuri hexadeċimali

248
00:10:35,440 --> 00:10:39,910
sempliċiment minħabba li għandhom tendenza li jkunu aktar
konvenzjonali minn deċimali binarja jew

249
00:10:39,910 --> 00:10:41,157
fid-dinja tal-kompjuters.

250
00:10:41,157 --> 00:10:42,490
Issa ejja dan iseħħ fil-kuntest.

251
00:10:42,490 --> 00:10:48,040
Ħafna minnkom jista tiftakar dan
stampa hawn, li ġew minn dak?

252
00:10:48,040 --> 00:10:51,240
Vista, hekk anke qabel
li, Windows XP ma dan id-debutt.

253
00:10:51,240 --> 00:10:52,620
Allura dan huwa pajsaġġ sabiħa.

254
00:10:52,620 --> 00:10:55,940
U fil-fatt, jekk inti poke madwar online--
Naħseb li huwa artikolu Wikipedia,

255
00:10:55,940 --> 00:11:00,110
fejn xi ħadd amazingly ħafna marru out
jinstab dan post fid-dinja imwaqqaf

256
00:11:00,110 --> 00:11:02,240
tiegħu jew kamera tagħha fil
preċiżament il place-- dritt

257
00:11:02,240 --> 00:11:06,510
u dan illum jistenna like-- iżda
huwa eżattament l-istess setting.

258
00:11:06,510 --> 00:11:10,060
Din id-dehra, għalkemm, hi fil-fajl
format imsejħa Bitmap, b 'm-p.

259
00:11:10,060 --> 00:11:12,910
U aħna qed tmur biex tieħu super
t'għajn malajr fil dak li tfisser.

260
00:11:12,910 --> 00:11:17,770
>> Iżda Bitmap huwa biss mod differenti ta '
li jirrappreżentaw immaġini għadhom jużaw pixels

261
00:11:17,770 --> 00:11:19,580
fil 0s u 1s, finalment.

262
00:11:19,580 --> 00:11:23,282
Iżda fl t'għajn malajr, hija għandha
firma aktar interessanti

263
00:11:23,282 --> 00:11:24,490
fil-bidu tal-fajl.

264
00:11:24,490 --> 00:11:26,670
Huwa mhux biss tlieta
bytes, pjuttost hemm

265
00:11:26,670 --> 00:11:30,770
mazz sħiħ ta 'mudelli ta' bytes
li jkunu predeterminati tifsira.

266
00:11:30,770 --> 00:11:34,490
Per eżempju, x'imkien fil-
ewwel ftit bytes ta 'immaġni Bitmap

267
00:11:34,490 --> 00:11:37,440
se jkun id-daqs tal-
immaġni, il-wisa 'l-immaġini,

268
00:11:37,440 --> 00:11:40,390
l-għoli tad-dehra, hekk
metadata utli, jekk inti se.

269
00:11:40,390 --> 00:11:43,940
Informazzjoni utli li Photoshop
jew xi grafika programm inti qed tuża

270
00:11:43,940 --> 00:11:45,180
jistgħu attwalment kura dwar.

271
00:11:45,180 --> 00:11:47,170
>> Allura aktar dwar dan fil
Problema Set 4, iżda dan

272
00:11:47,170 --> 00:11:49,220
huwa biss li wieħed jgħid li
fl-aħħar tal-ġurnata

273
00:11:49,220 --> 00:11:52,390
l-formati tal-fajl inti kont qed tuża
għall years-- fajls Microsoft Word,

274
00:11:52,390 --> 00:11:55,820
Numri fajls, fajls Excel,
kwalunkwe numru ta 'formats tal-fajls

275
00:11:55,820 --> 00:11:57,770
li jista 'jkollhom xi
estensjoni fajl magħruf

276
00:11:57,770 --> 00:12:00,130
huma biss 0s u 1s taħtha il-barnuża.

277
00:12:00,130 --> 00:12:02,970
U l-bnedmin iddeċidejt
dak li l-konvenzjonijiet għandhom,

278
00:12:02,970 --> 00:12:08,340
liema mudelli ta '0s u 1s jirrappreżentaw
fajl Word versus fajl Excel,

279
00:12:08,340 --> 00:12:10,322
versus kull numru ta 'formats tal-fajls oħra.

280
00:12:10,322 --> 00:12:12,780
Għalhekk fl PSet 4, inti ser ikollhom
opportunità li tilgħab ma 'dak.

281
00:12:12,780 --> 00:12:14,405
>> Imma dak ma jfisser li jkollhom Istituzzjonjijiet.

282
00:12:14,405 --> 00:12:18,012
Dan huwa attwalment segue sbieħ issa
fis C, li għandha biss ftit

283
00:12:18,012 --> 00:12:20,220
karatteristiċi ta 'addizzjonali li
għadna ma ħares lejn s'issa.

284
00:12:20,220 --> 00:12:24,230
Huwa lingwa pretty żgħar u wieħed mill
il-karatteristiċi sbieħ dwar Ċ hija Istituzzjonjijiet.

285
00:12:24,230 --> 00:12:27,300
Per eżempju, jekk inti
riedu represent-- ejja

286
00:12:27,300 --> 00:12:33,690
jgħidu int riedu li jkollhom varjabbli li
jirrappreżenta student f'xi programm.

287
00:12:33,690 --> 00:12:37,330
Forsi inti kienu kitba ta 'kors
programm ta 'reġistrazzjoni, jew shopping qalba

288
00:12:37,330 --> 00:12:38,870
għodda, jew xi ħaġa bħal dik.

289
00:12:38,870 --> 00:12:42,922
Liema huma biċċiet ta 'data relatata ma'
lil student li jiġu f'moħħna?

290
00:12:42,922 --> 00:12:44,880
Bħal student huwa
rappreżentati ma 'dak valuri?

291
00:12:44,880 --> 00:12:45,732
Yeah?

292
00:12:45,732 --> 00:12:46,940
Għandek isem bħala student.

293
00:12:46,940 --> 00:12:48,900
X'iktar ma student tipiku jkollu?

294
00:12:48,900 --> 00:12:49,320
>> UDJENZA: [inaudible]

295
00:12:49,320 --> 00:12:50,200
>> DAVID J. Malan: Allura, sorry.

296
00:12:50,200 --> 00:12:50,660
>> UDJENZA: Età.

297
00:12:50,660 --> 00:12:52,980
>> DAVID J. Malan: An età jew
birthday b'mod ekwivalenti, Yep.

298
00:12:52,980 --> 00:12:53,557
X 'iktar?

299
00:12:53,557 --> 00:12:54,390
UDJENZA: numru ta 'identifikazzjoni?

300
00:12:54,390 --> 00:12:57,460
DAVID J. Malan: Allura numru ta 'identifikazzjoni, forsi
numru tat-telefon, forsi dorm, jew dar,

301
00:12:57,460 --> 00:12:58,670
jew kulleġġ, jew xi ħaġa bħal dik.

302
00:12:58,670 --> 00:13:01,820
Kull numru ta 'biċċiet ta' data li
inti jista 'jkollhom fil-lista kuntatti tiegħek

303
00:13:01,820 --> 00:13:03,890
huwa dak li jista 'jiddefinixxi student.

304
00:13:03,890 --> 00:13:08,490
Mela jekk ridna li tagħmel dan, fil-kodiċi,
nistgħu nagħmlu xi ħaġa sempliċi bħal dan.

305
00:13:08,490 --> 00:13:15,670
Aħna jista 'jkollhom programm sabiex
għandha ejja ngħidu, int prinċipali (vojt).

306
00:13:15,670 --> 00:13:18,920
U jekk irrid jirrappreżentaw
student I jista 'jkollhom, per eżempju,

307
00:13:18,920 --> 00:13:24,330
string imsejjaħ isem għal dak student,
string imsejjaħ dorm għal dak student,

308
00:13:24,330 --> 00:13:26,900
forsi int sejjaħ ID għal dak student.

309
00:13:26,900 --> 00:13:30,840
U għaliex jien jużaw string, I
bżonn li jmorru lura u mqiegħda CS50.h.

310
00:13:30,840 --> 00:13:33,300
Forsi jien ser bżonn stdio.h.

311
00:13:33,300 --> 00:13:38,190
So let me preemptively do dawn u jien
ser sejħa dan student.c għal issa

312
00:13:38,190 --> 00:13:40,080
u ħlief dan.

313
00:13:40,080 --> 00:13:44,206
>> U issa I tista 'tagħmel xi ħaġa
ma dawn il-varjabbli.

314
00:13:44,206 --> 00:13:46,830
U aħna qed biss ser jikteb
li bħala kumment fil-kodiċi psewdo,

315
00:13:46,830 --> 00:13:48,829
għaliex mhuwiex interessanti
dak li nagħmlu għal issa.

316
00:13:48,829 --> 00:13:51,242
OK, għalhekk dan huwa programm li
b'xi ħwienet student.

317
00:13:51,242 --> 00:13:53,450
What do I trid tagħmel jekk I
tixtieq li taħżen żewġ studenti?

318
00:13:53,450 --> 00:13:55,991
Allura l-ewwel istint tiegħi huwa għaddej
li jkun id-dritt, stenna minuta,

319
00:13:55,991 --> 00:14:01,920
jekk ikolli student ieħor għaliex ma I
biss tagħmel isem string 2, spag dorm 2,

320
00:14:01,920 --> 00:14:04,190
ID2 int.

321
00:14:04,190 --> 00:14:06,540
U aħna ghamilt marret
f'din it-triq qabel

322
00:14:06,540 --> 00:14:10,890
u dak li kien soluzzjoni tagħna għal dak li jidher
li jkun it-tip ta 'pejst kopja hackish

323
00:14:10,890 --> 00:14:11,555
xogħol hawn?

324
00:14:11,555 --> 00:14:12,346
UDJENZA: Firxa.

325
00:14:12,346 --> 00:14:13,830
DAVID J. Malan: Yeah,
nistgħu jużaw firxa.

326
00:14:13,830 --> 00:14:15,620
Dritt dan malajr ħafna
isir dens.

327
00:14:15,620 --> 00:14:18,453
Inti għandek biex issolvi tal arbitrarjament
tibda ismijiet kollha ta 'dawn il-varjabbli.

328
00:14:18,453 --> 00:14:22,190
U inti, il-bniedem, għandhom iżommu
track li jikkorrispondi name2 OK

329
00:14:22,190 --> 00:14:25,060
ma dorm2 tikkorrispondi mal ID2.

330
00:14:25,060 --> 00:14:26,200
Hija biss isir mess.

331
00:14:26,200 --> 00:14:29,350
Allura huwa ħafna aktar faċli,
jitlob lura mingħandhom ftit ġimgħat ilu,

332
00:14:29,350 --> 00:14:34,300
għal ftit ma jkollhom għalfejn imsejħa ismijiet string
u forsi tagħtina tlieta minn dawn.

333
00:14:34,300 --> 00:14:36,940
U allura forsi għandna
dorms spag u jkollhom

334
00:14:36,940 --> 00:14:41,900
tlieta minn dawn, jew ma 'kostanti,
int ids u jkollhom tlieta minn dawn.

335
00:14:41,900 --> 00:14:45,250
Iżda anke issa dan iħoss
ftit sloppy, right.

336
00:14:45,250 --> 00:14:49,440
Aħna qed jitkellem dwar l-istudenti u għadhom
Ninsab verament abitazzjoni fuq il-livell baxx

337
00:14:49,440 --> 00:14:50,470
dettalji tal-implimentazzjoni.

338
00:14:50,470 --> 00:14:52,790
L-istudent huwa isem u dorm u ID.

339
00:14:52,790 --> 00:14:59,814
>> Għaliex ma tistax I biss tiddikjara varjabbli
imsejħa student u sejħa hija s.

340
00:14:59,814 --> 00:15:02,230
U jekk irrid student ieħor,
għaliex ma I biss sejħa hija t.

341
00:15:02,230 --> 00:15:05,260
Jew jekk irrid mazz sħiħ
ta 'studenti, għaliex ma I biss

342
00:15:05,260 --> 00:15:09,740
jgħidu I jkollhom klassi kollha ta '
istudenti, u huwa tlieta minnhom.

343
00:15:09,740 --> 00:15:12,470
Fi kliem ieħor, għaliex ma nista jiġu
up ma 'tip data tiegħi stess, imsejħa

344
00:15:12,470 --> 00:15:15,641
Studenti, ġewwa minnhom hija
isem, huwa ID, huwa dorm,

345
00:15:15,641 --> 00:15:16,890
huwa kull numru ta 'oqsma oħra.

346
00:15:16,890 --> 00:15:19,030
U jirriżulta inti
tista 'tagħmel eżattament dan.

347
00:15:19,030 --> 00:15:21,850
>> Allura C din il-karatteristika imsejjaħ Istituzzjonjijiet.

348
00:15:21,850 --> 00:15:24,700
Li karatteristika lingwa li
jippermetti li jagħmlu eżattament dan.

349
00:15:24,700 --> 00:15:28,370
Jien ser jimxi 'l quddiem
u jiftħu structs.h

350
00:15:28,370 --> 00:15:32,299
fejn aħna qed tmur biex tara d-
wara definizzjoni ta 'student.

351
00:15:32,299 --> 00:15:35,215
Jirriżulta - u dan wieħed anki
sempliċi minn dik li jinvolvi ID

352
00:15:35,215 --> 00:15:36,080
mument ilu.

353
00:15:36,080 --> 00:15:39,120
Jekk inti tixtieq li toħroġ bi
tip tiegħek tad-data homemade,

354
00:15:39,120 --> 00:15:42,750
u barra minn hekk li int, u char u
float u dawn l-oħrajn kollha li jeżistu,

355
00:15:42,750 --> 00:15:45,810
inti tista 'tagħmel dan billi litteralment
miktub Struct typedef,

356
00:15:45,810 --> 00:15:47,880
imbagħad xi braces kaboċċi,
ġewwa ta 'li inti

357
00:15:47,880 --> 00:15:51,460
lista tal-varjabbli li trid
jassoċjaw ma 'din id-data custom ġodda

358
00:15:51,460 --> 00:15:55,670
tip bħal isem u dorm,
u mbagħad wara l-braces kaboċċi

359
00:15:55,670 --> 00:15:57,860
inti tagħti isem it-tip ta 'dejta ġdid.

360
00:15:57,860 --> 00:15:59,220
Allura, per eżempju, student.

361
00:15:59,220 --> 00:16:03,247
>> U x'hemm sbieħ dwar dan issa huwa li
jekk inħarsu lejn il-kodiċi korrispondenti,

362
00:16:03,247 --> 00:16:05,080
il-konvenzjoni, l-ewwel
ta 'kulħadd, huwa li tpoġġi din

363
00:16:05,080 --> 00:16:08,230
fil-fajl imsejħa xi ħaġa dot h,
fajl header, li aħna ma

364
00:16:08,230 --> 00:16:09,780
bdew jużaw nfusna wisq.

365
00:16:09,780 --> 00:16:12,120
Iżda aħna qed tmur biex tibda
użu pjuttost ftit issa.

366
00:16:12,120 --> 00:16:18,650
U x'nistgħu nagħmlu ma 'dan,
finalment, f'dawn ftit linji ta 'kodiċi

367
00:16:18,650 --> 00:16:22,130
huwa jiddikjara eżattament dan
tip ta 'data, student.

368
00:16:22,130 --> 00:16:23,230
U issa ejja jużawh.

369
00:16:23,230 --> 00:16:27,274
>> Jien ser issa jmorru fil
fajl imsejjaħ structs1.c.

370
00:16:27,274 --> 00:16:29,440
U ejja tagħti ħarsa lejn
ftit karatteristiċi hawn.

371
00:16:29,440 --> 00:16:32,250
Allura l-għalf up hawnhekk huwa
aktar familjari, u aħna ser

372
00:16:32,250 --> 00:16:35,040
terga 'lura għal dak li mhux
familjari fi ftit mument.

373
00:16:35,040 --> 00:16:39,880
Dan naturalment huwa inkluż tiegħi stess
fajl header, li huwa ġdid kif ukoll,

374
00:16:39,880 --> 00:16:42,580
ħlief għal PSet 3 fejn,
irtirar, għandna helpers.h.

375
00:16:42,580 --> 00:16:45,150
Allura inti tista 'recall helpers.h #include.

376
00:16:45,150 --> 00:16:49,381
>> Why am I għalkemm jużaw kwotazzjonijiet
minflok parentesi angolati?

377
00:16:49,381 --> 00:16:50,630
Meta nista jagħżlu bejniethom?

378
00:16:50,630 --> 00:16:52,310
Kważi dejjem I jidhru
għall-użu parentesi angolata.

379
00:16:52,310 --> 00:16:55,040
U mbagħad, kollha f'daqqa fuq
linja sitt Jien jużaw kwotazzjonijiet doppja.

380
00:16:55,040 --> 00:16:55,860
Għaliex jista 'jkun?

381
00:16:55,860 --> 00:16:56,700
Yeah?

382
00:16:56,700 --> 00:16:57,725
>> UDJENZA: [inaudible]

383
00:16:57,725 --> 00:16:59,350
DAVID J. Malan: Li reali, liema?

384
00:16:59,350 --> 00:17:00,559
UDJENZA: Li fil IDE tiegħek.

385
00:17:00,559 --> 00:17:02,475
DAVID J. Malan: Yeah,
li fil IDE attwali tiegħi.

386
00:17:02,475 --> 00:17:05,690
U ejja ma tiffokax fuq il-IDE, minħabba
li jinsab biss għodda li jien jużaw.

387
00:17:05,690 --> 00:17:08,119
Li fil kurrenti tiegħi
tad-direttorju, b'mod speċifiku.

388
00:17:08,119 --> 00:17:11,647
Allura structs.h huwa fajl tiegħi stess
mhux installat fil-IDE,

389
00:17:11,647 --> 00:17:14,480
fis-sistema operattiva nnifisha,
pjuttost huwa direttorju kurrenti tiegħi.

390
00:17:14,480 --> 00:17:16,910
Allura l-konvenzjoni hija jekk inti tixtieq
biex jinkludu fajl tiegħek header stess,

391
00:17:16,910 --> 00:17:18,200
inti biss tuża kwotazzjonijiet doppja.

392
00:17:18,200 --> 00:17:23,290
>> What do nitolbu dan ħaġa fil
linja 8, ġeneralment?

393
00:17:23,290 --> 00:17:25,200
Dan huwa dak?

394
00:17:25,200 --> 00:17:28,220
xi ħaġa #define.

395
00:17:28,220 --> 00:17:31,040
Dan jirrappreżenta kostanti, id-dritt?

396
00:17:31,040 --> 00:17:33,140
Jekk inti tixtieq li jkollok
valur fil-programm tiegħek

397
00:17:33,140 --> 00:17:35,110
li tuża sħiħ
mazz ta 'drabi, huwa

398
00:17:35,110 --> 00:17:39,330
konvenzjoni tajba għall-fattur it out,
tiddikjaraha, bis-simbolu hash

399
00:17:39,330 --> 00:17:43,340
jiddefinixxu, imbagħad, b'konvenzjoni, fl-
uppercase word-- għalkemm mhuwiex

400
00:17:43,340 --> 00:17:45,320
strettament meħtieġ, imma
huwa konvenzjoni tal-bniedem

401
00:17:45,320 --> 00:17:47,210
li tikkapitalizza kostanti
sabiex dawn jaqbżu

402
00:17:47,210 --> 00:17:50,380
fi inti visually-- ispazju u
allura l-valur inti tixtieq li tkun

403
00:17:50,380 --> 00:17:52,250
ekwivalenti għal isem li kostanti s.

404
00:17:52,250 --> 00:17:56,110
Nru punto virgola, imma inti sempliċiment
jirriżultax li mudell hemm.

405
00:17:56,110 --> 00:17:57,770
>> Allura dak am I tagħmel f'dan il-kodiċi attwali.

406
00:17:57,770 --> 00:18:00,660
Mela ejja tagħti ħarsa lejn
il-programm prinċipali hawnhekk.

407
00:18:00,660 --> 00:18:04,080
B'konformità 12 minħabba I
inkludew structs.h,

408
00:18:04,080 --> 00:18:06,492
I issa għandhom magically fil tiegħi
rimi ta 'tip ta' data ġdida.

409
00:18:06,492 --> 00:18:09,200
I ma biss ikollhom aċċess għall int,
u char, u float, u spag,

410
00:18:09,200 --> 00:18:10,060
u blu u oħrajn.

411
00:18:10,060 --> 00:18:12,470
I issa għandhom aċċess għal
tip data student.

412
00:18:12,470 --> 00:18:17,740
Dan b'konformità 12, jien kombinazzjoni ta 'żewġ
ideas-- wieħed tip data tad-dwana u tnejn,

413
00:18:17,740 --> 00:18:18,940
użu ta 'firxa.

414
00:18:18,940 --> 00:18:21,700
U hekk f'dan il-programm jekk
Irrid li attwalment jappoġġaw

415
00:18:21,700 --> 00:18:24,320
tliet studenti differenti
fil-programm tiegħi, I

416
00:18:24,320 --> 00:18:30,480
tista sempliċement jgħidu tagħti me a varjabbli
imsejħa studenti, li kull waħda minnhom

417
00:18:30,480 --> 00:18:32,970
huwa ta 'studenti tip, li
huwa tip ta 'data tad-dwana tiegħi.

418
00:18:32,970 --> 00:18:35,890
U, b'mod speċifiku, agħti lili
tlieta minn dawk fil-firxa tiegħi.

419
00:18:35,890 --> 00:18:37,750
>> Allura issa dak li nagħmlu f'dan il-programm?

420
00:18:37,750 --> 00:18:40,670
Hawn biss għall mtennija loop
0-3, minħabba li l

421
00:18:40,670 --> 00:18:42,110
dak il-valur ta 'studenti hu.

422
00:18:42,110 --> 00:18:44,420
Jien biss suġġeriment l-utent
tagħti me isem l-istudent.

423
00:18:44,420 --> 00:18:48,090
U mbagħad fil-linja 17, aħna
għandhom linja aktar familjari.

424
00:18:48,090 --> 00:18:50,370
Għandna ħabib antik tagħna
GetString fuq il-lemin.

425
00:18:50,370 --> 00:18:52,345
U dak biċċa sintassi
hija apparentement ġdid,

426
00:18:52,345 --> 00:18:55,130
jekk inti stajt qatt programmati C qabel,
u qatt ma użaw l-structs?

427
00:18:55,130 --> 00:18:55,510
Yeah?

428
00:18:55,510 --> 00:18:56,417
>> UDJENZA: Il .name.

429
00:18:56,417 --> 00:18:57,500
DAVID J. Malan: Il .name.

430
00:18:57,500 --> 00:19:01,220
Imma dan mhux wisq ta 'qabża,
minħabba li issa istudenti parentesi i

431
00:19:01,220 --> 00:19:02,590
jagħtik l-istudent numru i.

432
00:19:02,590 --> 00:19:04,730
U jekk inti tixtieq li adsa
ġewwa ta 'din l-istruttura,

433
00:19:04,730 --> 00:19:09,490
inti biss tuża perjodu wieħed u
allura l-isem tal-varjabbli ġewwa,

434
00:19:09,490 --> 00:19:11,900
jew il-proprjetà ġewwa li
inti tixtieq li tikseb aċċess għall.

435
00:19:11,900 --> 00:19:14,816
Bl-istess mod imbagħad, jekk I imbagħad fil-pront il-
utent, jagħtu me dorm l-istudent,

436
00:19:14,816 --> 00:19:18,390
inti tista 'bl-istess mod tinżamm din
string fil-varjabbli dorm ġewwa

437
00:19:18,390 --> 00:19:19,940
ta 'dik l-istruttura student.

438
00:19:19,940 --> 00:19:21,410
>> U issa l-affarijiet jiksbu fancy ftit.

439
00:19:21,410 --> 00:19:24,420
U dan se tħares
fi forsi ħafna pjuttost malajr.

440
00:19:24,420 --> 00:19:27,970
Imma inti taf tara dan ħafna iktar fil PSet
4, so ejja biss t'għajn lejn dan issa.

441
00:19:27,970 --> 00:19:33,364
Jirriżulta li fil-linja 23 permezz
38, x'taħseb qed nagħmel forsi?

442
00:19:33,364 --> 00:19:35,530
Stajt jitneħħew l-kummenti
għal-lum, iżda l-verżjoni

443
00:19:35,530 --> 00:19:38,660
tal-kodiċi online għall
referenza għandha kummenti kollha.

444
00:19:38,660 --> 00:19:40,171
What do I jidhru li tkun qiegħda tagħmel?

445
00:19:40,171 --> 00:19:42,530
>> UDJENZA: Iffrankar il-fajl ma 'l
l-informazzjoni li l-utent daħal.

446
00:19:42,530 --> 00:19:44,530
>> DAVID J. Malan: Yeah,
eżattament, dan huwa mod ġdid

447
00:19:44,530 --> 00:19:46,370
li aħna qed tara tnejn,
fattur ieħor ta 'C,

448
00:19:46,370 --> 00:19:48,700
li biha I tista 'toħloq fajls tiegħi stess.

449
00:19:48,700 --> 00:19:51,580
S'issa, kważi kull programm
inti stajt bil-miktub mingħajr Stat.

450
00:19:51,580 --> 00:19:53,334
Hekk kif dan isir taħdem, thats it.

451
00:19:53,334 --> 00:19:55,000
M'hemm l-ebda memorja jew rikollizzjoni ta 'dan.

452
00:19:55,000 --> 00:19:56,110
M'hemm l-ebda fajl ffrankati.

453
00:19:56,110 --> 00:19:58,120
Imma jekk inti tixtieq li
jiffranka input li għandha

454
00:19:58,120 --> 00:20:02,100
ġara, bħal fil-logħba jew programm
bħal dan, jirriżulta nistgħu nagħmlu hekk.

455
00:20:02,100 --> 00:20:04,360
U tkun taf tara dan aktar
fil PSet 4 u fit-Taqsima.

456
00:20:04,360 --> 00:20:08,661
Iżda din il-linja 23 essenzjalment
toħloq fajl imsejjaħ students.csv.

457
00:20:08,661 --> 00:20:10,160
U inti tista raw dan qabel.

458
00:20:10,160 --> 00:20:14,250
Anke jekk inti stajt qatt studjati CS qabel,
CSV huwa varjabbli mhux mifrudin comma.

459
00:20:14,250 --> 00:20:19,000
Huwa simili raġel fqir ħafna
Verżjoni ta 'fajl Excel,

460
00:20:19,000 --> 00:20:22,270
li jfisser li jista 'jinfetaħ
fl-Excel u Numri Apple,

461
00:20:22,270 --> 00:20:23,830
u għandu ringieli u kolonni.

462
00:20:23,830 --> 00:20:26,485
Imma din mhix proprjetarja
format bħal Microsoft jew Apple.

463
00:20:26,485 --> 00:20:29,840
Huwa biss virgoli jisseparaw l
valuri li aħna ser tara fil-mument.

464
00:20:29,840 --> 00:20:31,010
>> U ħu raden.

465
00:20:31,010 --> 00:20:33,480
F'konformità 23, fil-ħafna
aħħar, it-tieni argument tiegħi

466
00:20:33,480 --> 00:20:37,700
biex din il-funzjoni ġdida msejħa
f miftuħa għall-fajl miftuħ huwa w.

467
00:20:37,700 --> 00:20:39,430
Liema jista w juri?

468
00:20:39,430 --> 00:20:40,022
Yeah?

469
00:20:40,022 --> 00:20:41,260
>> UDJENZA: Hija ihallik jikteb lill-fajl?

470
00:20:41,260 --> 00:20:42,630
>> DAVID J. Malan: Hija tikri
tikteb għall-fajl.

471
00:20:42,630 --> 00:20:44,810
Allura hemm koppja ta 'varjanti
li nistgħu plagg fil hawn.

472
00:20:44,810 --> 00:20:47,184
Imma jekk inti biss tixtieq li taqra
il-fajl, jiġifieri tħares lejn din

473
00:20:47,184 --> 00:20:50,010
u taqrah fil-memorja, inti
biss użu quote unquote "r".

474
00:20:50,010 --> 00:20:53,110
Jekk inti tixtieq li jikteb lill-
fajl, tuża kwotazzjoni unquote "w".

475
00:20:53,110 --> 00:20:55,190
Hemm ukoll tehmeż u
koppja ta 'affarijiet oħra

476
00:20:55,190 --> 00:20:57,356
jekk inti tixtieq li timmodifika fajls eżistenti.

477
00:20:57,356 --> 00:21:00,480
Issa aħna qed tmur biex tibqa 'tara dan
ħaġa, allura aħna ser terga 'lura għal-linja 24.

478
00:21:00,480 --> 00:21:02,640
NULL, jirriżulta, huwa
valur speċjali li

479
00:21:02,640 --> 00:21:06,070
jistgħu jiġu rritornati minn ċerti funzjonijiet
jekk xi ħaġa marret wrong--

480
00:21:06,070 --> 00:21:08,490
jekk il-fajl ma teżistix,
jekk inti ħadthom jispiċċaw ta 'memorja,

481
00:21:08,490 --> 00:21:09,620
jew mazz ta 'żbalji oħra.

482
00:21:09,620 --> 00:21:13,470
Iżda għal issa, ejja biss wieħed jassumi li din
huwa iċċekkjar żball biss konvenzjonali.

483
00:21:13,470 --> 00:21:17,090
Hawnhekk fil-linja 26, jien mtennija
0-3 fuq l-istudenti kollha tiegħi.

484
00:21:17,090 --> 00:21:20,470
U dan huwa tip ta 'tip
ta 'funzjoni ġdida, fprintf,

485
00:21:20,470 --> 00:21:21,460
imma ħu raden.

486
00:21:21,460 --> 00:21:24,370
Jekk printf huwa biss print
string fformattjati,

487
00:21:24,370 --> 00:21:26,507
dak ma fprintf probabbilment jfisser?

488
00:21:26,507 --> 00:21:27,590
UDJENZA: Stampa għal fajl.

489
00:21:27,590 --> 00:21:29,290
DAVID J. Malan: Stampa a
string ifformattjat għall-fajl.

490
00:21:29,290 --> 00:21:31,180
Dak hu l-addizzjonali
f mezzi huwa fajl.

491
00:21:31,180 --> 00:21:36,420
U l-ewwel argument ġdida trid tiġi
il-varjabbli li tirrappreżenta fajl tiegħek.

492
00:21:36,420 --> 00:21:38,866
Imbagħad aħna biss ikollhom format
string bħad printf.

493
00:21:38,866 --> 00:21:40,740
U anki jekk dan
sintassi huwa ġdid, dan biss

494
00:21:40,740 --> 00:21:44,610
tfisser plagg fl-isem l-istudent,
-plagg fil-dorm student, u mbagħad

495
00:21:44,610 --> 00:21:47,160
ma fclose, agħlaq il-fajl.

496
00:21:47,160 --> 00:21:49,730
U allura lastly-- dan huwa ġdid
u aħna ser terga 'lura għal dan

497
00:21:49,730 --> 00:21:53,240
qabel long-- Jien ħelsien
l-istudent għal raġunijiet

498
00:21:53,240 --> 00:21:54,860
li ġara up hawn fuq hemmhekk.

499
00:21:54,860 --> 00:21:56,820
Iżda aħna ser terga 'lura
li li qabel long--

500
00:21:56,820 --> 00:21:59,820
dan għaliex ta 'kif GetString huwa
attwalment qed jaħdmu taħt il-barnuża.

501
00:21:59,820 --> 00:22:01,280
>> Mela ejja tagħti ħarsa hawn.

502
00:22:01,280 --> 00:22:04,380
Jekk I ls tip fl-direttorju tiegħi,
avviż li jien ma

503
00:22:04,380 --> 00:22:09,360
jkollhom fajl imsejjaħ students.csv,
biss ma jkunx hemm, ma teżistix.

504
00:22:09,360 --> 00:22:14,965
Mela jekk jien issa jiġbor dan il-programm,
jagħmlu structs-1,. / structs-1,

505
00:22:14,965 --> 00:22:20,570
u jien ser jimxi 'l quddiem u tip
Andi, li jgħix fi Berkeley fil-Yale.

506
00:22:20,570 --> 00:22:26,350
Aħna ser ikollhom Rob li
jgħix fil Thayer f'dawn il-jiem.

507
00:22:26,350 --> 00:22:33,760
U ejja toħroġ bi fejn
huwa, I think, Maria hija fil Mather,

508
00:22:33,760 --> 00:22:35,100
jekk ikolli mfakkar b'mod korrett.

509
00:22:35,100 --> 00:22:36,460
>> Allura xejn ma jidher li jiġri.

510
00:22:36,460 --> 00:22:40,680
Imma jekk jien ls-tip issa,
hemm students.csv.

511
00:22:40,680 --> 00:22:43,080
Ejja imorru quddiem u students.csv miftuħa.

512
00:22:43,080 --> 00:22:46,050
Dan ukoll ħafna
format tal-fajl ħfief.

513
00:22:46,050 --> 00:22:49,570
Imma stajt sempliċiment adotta konvenzjoni
li għandi żewġ ringieli u kolonni hawn.

514
00:22:49,570 --> 00:22:52,020
L-ewwel kolonna hija
ewwel ismijiet tan-nies.

515
00:22:52,020 --> 00:22:55,740
It-tieni kolonna hija l-istudent ta
dorm, jew kulleġġ, jew dar, jew whatnot.

516
00:22:55,740 --> 00:22:57,900
U issa stajt salvati dan
b'mod permanenti fil-fajl.

517
00:22:57,900 --> 00:22:59,280
>> Allura huwa mhux kollha li interessanti.

518
00:22:59,280 --> 00:23:02,980
Iżda din hija biss tarġa issa
li jkunu kapaċi jippersistu informazzjoni

519
00:23:02,980 --> 00:23:04,040
b'mod permanenti.

520
00:23:04,040 --> 00:23:08,340
Mela ejja ara issa liema aktar li nistgħu
ma 'dawn u oħrajn karatteristiċi.

521
00:23:08,340 --> 00:23:10,729
Iżda l-ewwel, xi mistoqsijiet?

522
00:23:10,729 --> 00:23:12,145
Dan kien ħafna, u li kien mgħaġġel.

523
00:23:12,145 --> 00:23:16,131
Imma inti taf tara ħafna
aktar fil PSet 4, kif ukoll.

524
00:23:16,131 --> 00:23:16,630
Yeah?

525
00:23:16,630 --> 00:23:19,360
>> UDJENZA: Hemm mod biex
tkompli żżid ismijiet mal dan il-fajl?

526
00:23:19,360 --> 00:23:19,880
>> DAVID J. Malan: Tajba kwistjoni.

527
00:23:19,880 --> 00:23:21,800
Hemm mod biex ikomplu
żżid ismijiet mal dan il-fajl?

528
00:23:21,800 --> 00:23:22,340
Iva.

529
00:23:22,340 --> 00:23:24,630
U, fil-fatt, jekk inti tispiċċa
up mill-ġdid jinfetaħ ir-reġistru,

530
00:23:24,630 --> 00:23:26,780
inti tuża quote
unquote "a" għal tehmeż,

531
00:23:26,780 --> 00:23:31,090
li kien biss żid linja ġdida,
linja ġdida għal darb'oħra u għal darb'oħra, eżattament.

532
00:23:31,090 --> 00:23:32,010
Tajba kwistjoni.

533
00:23:32,010 --> 00:23:32,950
Mistoqsijiet oħra?

534
00:23:32,950 --> 00:23:33,450
Yeah?

535
00:23:33,450 --> 00:23:35,580
UDJENZA: Jekk inti mexxa l-
programm ġdid dritt issa,

536
00:23:35,580 --> 00:23:38,000
ikun jidher ikompli jżid ismijiet għall-
fajl jew ikun jidher tiftaħ fajl ġdid?

537
00:23:38,000 --> 00:23:38,740
>> DAVID J. Malan: Ah, mistoqsija tajba.

538
00:23:38,740 --> 00:23:41,448
Jekk inti dam il-programm mill-ġdid dritt
issa, forsi ittajpjat fl-ismijiet ġodda,

539
00:23:41,448 --> 00:23:44,820
kieku dan iżid il-fajl
jew jissostitwixxu l-fajl?

540
00:23:44,820 --> 00:23:47,420
L-aħħar, għaliex jien
ma jużawx modalità tehmeż.

541
00:23:47,420 --> 00:23:49,930
U għaliex jien biss bl-addoċċ
ftuħ tal-fajl għall-kitba,

542
00:23:49,930 --> 00:23:51,310
huwa biss se jissostitwixxu l-fajl.

543
00:23:51,310 --> 00:23:54,570
So I tassew bżonn tagħmel hu tehmeż,
jekk irrid li għandhom attwalment fit-tul

544
00:23:54,570 --> 00:23:55,350
database.

545
00:23:55,350 --> 00:23:58,220
>> Issa CSV huwa utli, franchement, anki
simili għal jekk int writing--

546
00:23:58,220 --> 00:24:00,100
u aħna ser eventwalment tara dan
aktar tard fl-semestru meta

547
00:24:00,100 --> 00:24:01,455
nużaw CSVs għal skopijiet oħra.

548
00:24:01,455 --> 00:24:04,920
Jekk inti tixtieq li taħżen kollha tal-poplu
li jkunu rreġistraw għal xi avveniment,

549
00:24:04,920 --> 00:24:07,420
jew ffirmaw għall-istudenti tiegħek
grupp, jew xi ħaġa bħal dik,

550
00:24:07,420 --> 00:24:10,330
ħażna tad-data f'dan it-tip
ta 'format huwa super konvenjenti.

551
00:24:10,330 --> 00:24:12,580
Minħabba litteralment, jekk I
kienu biex tniżżel dan il-fajl.

552
00:24:12,580 --> 00:24:14,540
I tista 'double-- u
ejja fil-fatt jipprovaw dan

553
00:24:14,540 --> 00:24:16,720
jekk ikolli Excel jew Numri hawn fuq.

554
00:24:16,720 --> 00:24:19,130
>> Jien ser dritt ikklikkja
jew kontroll click fajl tiegħi.

555
00:24:19,130 --> 00:24:20,020
Whoops.

556
00:24:20,020 --> 00:24:21,830
Right-click jew kontroll click fajl tiegħi.

557
00:24:21,830 --> 00:24:24,960
Come on, ġurdien tiegħi hija ma tikkooperax.

558
00:24:24,960 --> 00:24:32,694
Download-- Jien ser
tniżżel il-fajls kollha hawn hekk

559
00:24:32,694 --> 00:24:33,860
biss hekk I tista 'grab dan wieħed.

560
00:24:33,860 --> 00:24:37,850
U ejja ara jekk dan jaħdem
ewwel darba students.csv--

561
00:24:37,850 --> 00:24:39,310
Stajt attivat.

562
00:24:39,310 --> 00:24:41,360
Issa li jridu jaraw kuntatti tiegħi.

563
00:24:41,360 --> 00:24:44,310
Issa, I bżonn jirreġistraw.

564
00:24:44,310 --> 00:24:47,620
Ara kemm huwa faċli biex jintuża CSVs?

565
00:24:47,620 --> 00:24:50,840
Iva, żżommha aġġornata.

566
00:24:50,840 --> 00:24:52,375
OK, issa aħna lesti għall-klassi.

567
00:24:52,375 --> 00:24:58,750

568
00:24:58,750 --> 00:25:00,370
OK, oh, x'hemm ġdid?

569
00:25:00,370 --> 00:25:02,920
OK, qrib.

570
00:25:02,920 --> 00:25:04,750
Dan kien maġika.

571
00:25:04,750 --> 00:25:07,280
OK, issa għandna biex taġġorna.

572
00:25:07,280 --> 00:25:10,890
U issa, huwa nesa dak
fajl I oriġinarjament miftuħa,

573
00:25:10,890 --> 00:25:13,090
imma dak a-- hemm immorru.

574
00:25:13,090 --> 00:25:16,341
OK, hekk issa għandna fajl Excel.

575
00:25:16,341 --> 00:25:18,290
Grazzi.

576
00:25:18,290 --> 00:25:20,764
>> OK, so dak li għamilt kienet il-parti faċli.

577
00:25:20,764 --> 00:25:23,930
Of course I setgħet installat minn qabel
Excel, jew Numri, jew kwalunkwe programm.

578
00:25:23,930 --> 00:25:25,846
Iżda dan huwa sbieħ, għaliex
issa I tista 'timmanipola

579
00:25:25,846 --> 00:25:28,090
id-dejta f'format standard.

580
00:25:28,090 --> 00:25:30,294
>> Kuntest Allura issa ejja
jaqilbu għal fejn aħna jitħalla 'off

581
00:25:30,294 --> 00:25:32,710
aħħar darba, li kellha tibda
jieħdu off roti ta 'taħriġ.

582
00:25:32,710 --> 00:25:34,543
Iżda l-ewwel, inti ma
tara dan ikla qabel

583
00:25:34,543 --> 00:25:38,150
għal darb'oħra qed jiġri hawn fuq nar u
Silġ Cambridge, Sitar fi New Haven.

584
00:25:38,150 --> 00:25:43,150
Sign up fuq il-websajt CS50s ASAP
biex jissieħbu istudenti CS50 u persunal.

585
00:25:43,150 --> 00:25:46,090
>> Allura aħna ħa roti ta 'taħriġ
off nhar it-Tnejn bħala follows--

586
00:25:46,090 --> 00:25:49,120
string ġie ddikjarat
CS50s librerija għal xi żmien.

587
00:25:49,120 --> 00:25:52,650
U huwa sbieħ, għaliex din tippermetti
ahna nitkellmu dwar varjabbli bħala

588
00:25:52,650 --> 00:25:54,660
kliem kompluta u sentenzi u aktar.

589
00:25:54,660 --> 00:25:56,710
Iżda jirriżulta string ma teżistix.

590
00:25:56,710 --> 00:26:00,200
Dan huwa biss sinonimu, jew alias,
li ħloqna xi ħaġa li

591
00:26:00,200 --> 00:26:03,780
fil-fatt huwa xi ftit aktar
teknika imsejħa char *.

592
00:26:03,780 --> 00:26:07,900
>> U fil-fatt, rajna eżempju
ta 'programm nhar it-Tnejn

593
00:26:07,900 --> 00:26:11,200
li ma jaġixxix pjuttost kif aħna mistennija.

594
00:26:11,200 --> 00:26:13,630
Dan kien il-fajl, iqabblu-0.

595
00:26:13,630 --> 00:26:17,910
U tfakkar li jqabblu-0, jekk
I recompile programm nhar it-Tnejn

596
00:26:17,910 --> 00:26:22,670
u run jqabblu '0 u tip mom fil
lowercase, u mom fl zghar mill-ġdid.

597
00:26:22,670 --> 00:26:25,320
Il-programm insista I
tip affarijiet differenti,

598
00:26:25,320 --> 00:26:29,210
anki jekk mom, kollha
lowercase, hija identika viżwalment.

599
00:26:29,210 --> 00:26:31,990
Allura dak li kien ir-risposta qasira
rigward għaliex ir kompjuter jaħseb

600
00:26:31,990 --> 00:26:34,500
dawn iż-żewġ kordi huma differenti?

601
00:26:34,500 --> 00:26:35,250
Yeah?

602
00:26:35,250 --> 00:26:36,534
>> UDJENZA: [inaudible]

603
00:26:36,534 --> 00:26:37,450
DAVID J. Malan: Dritt.

604
00:26:37,450 --> 00:26:39,600
Allura, mom, l-ewwel darba
I tip fil, qed

605
00:26:39,600 --> 00:26:42,710
maħżuna x'imkien fil-kompjuter tiegħi
memorja iżda f'post differenti

606
00:26:42,710 --> 00:26:44,690
mit-tieni darba I tip fil mom.

607
00:26:44,690 --> 00:26:46,580
Issa li ċertament tista 'tiġi ottimizzata.

608
00:26:46,580 --> 00:26:49,205
Il-kompjuter jista 'jkun intelliġenti u
jirrealizzaw dawn iż-żewġ kordi, ħej,

609
00:26:49,205 --> 00:26:49,954
dawn qed identiċi.

610
00:26:49,954 --> 00:26:51,520
Let me ma redundantly jaħżnu.

611
00:26:51,520 --> 00:26:54,229
Iżda kompjuters ma tagħmel dan
ottimizzazzjoni sakemm inti jgħidulhom li.

612
00:26:54,229 --> 00:26:56,061
Allura, awtomatikament, dawn qed
biss ser jispiċċaw

613
00:26:56,061 --> 00:26:57,670
f'żewġ postijiet differenti fil-memorja.

614
00:26:57,670 --> 00:27:01,570
U hekk li jkunu aktar ċari, meta
qabbilna-żewġ kordi,

615
00:27:01,570 --> 00:27:03,950
l-ewwel ġie imsejħa s,
it-tieni kienet imsejħa

616
00:27:03,950 --> 00:27:08,530
t, dak speċifikament kien I
tqabbil hawn fuq il-linja 13?

617
00:27:08,530 --> 00:27:09,494
Yeah.

618
00:27:09,494 --> 00:27:12,390
>> UDJENZA: Hu l-post fil-memorja
li l-varjabbli se jindika.

619
00:27:12,390 --> 00:27:14,900
>> DAVID J. Malan: Eżattament, I kien
tqabbel il-post fil-memorja

620
00:27:14,900 --> 00:27:16,300
li dawk il-varjabbli indikat.

621
00:27:16,300 --> 00:27:20,560
Allura speċifikament, jekk mom kien
Numru byte 1, u 2, u 3,

622
00:27:20,560 --> 00:27:24,020
u 4-- minħabba ftakar l-backslash
0 jeħtieġ li jkun it-triq kollha fl-aħħar.

623
00:27:24,020 --> 00:27:29,420
U l-każ ieħor ta 'mom, m-o-m,
kien fl-indirizz 10, 11, 12, u 13.

624
00:27:29,420 --> 00:27:33,100
I kien jqabbel 1, dak l-indirizz,
f'dak il-post fil-memorja,

625
00:27:33,100 --> 00:27:35,160
kontra 10, li hija
ovvjament mhux l-istess.

626
00:27:35,160 --> 00:27:36,260
1 mhix 10.

627
00:27:36,260 --> 00:27:39,620
>> Allura dan huwa sbieħ f'dak
huwa pjuttost sempliċi.

628
00:27:39,620 --> 00:27:42,870
Imma hija problematika sakemm
aħna ma jistgħux jidhru li jqabblu kordi.

629
00:27:42,870 --> 00:27:44,930
Allura fundamentally--
u f'dan il-livell baxx,

630
00:27:44,930 --> 00:27:47,300
jekk int riedu biex jimplimentaw
programm biex iqabblu

631
00:27:47,300 --> 00:27:50,270
żewġ kelmiet separati li l-
utent ikun ittajpjat fil għall-kwalità,

632
00:27:50,270 --> 00:27:53,944
ma huma linja up char għall
char, biss f'termini ġenerali,

633
00:27:53,944 --> 00:27:55,360
dak li rridu nagħmlu, apparentement?

634
00:27:55,360 --> 00:27:57,940
Huwa mhux biżżejjed biss biex
tħares lejn dawn iż-żewġ indirizzi.

635
00:27:57,940 --> 00:27:58,860
What do we bżonn tagħmel?

636
00:27:58,860 --> 00:27:59,360
Yeah?

637
00:27:59,360 --> 00:28:01,120
>> UDJENZA: jtenni permezz
l-sekwenza [inaudible].

638
00:28:01,120 --> 00:28:02,600
>> DAVID J. Malan: Yeah, ejja
jtenni permezz tal-sekwenza.

639
00:28:02,600 --> 00:28:05,808
Ejja jużaw għal loop, linja waqt, jew
tkun xi int l-aktar komdu magħhom.

640
00:28:05,808 --> 00:28:08,840
U jekk konna ltqajna żewġ kordi x'imkien
fil-memorja, ejja nħarsu lejn kull wieħed li

641
00:28:08,840 --> 00:28:11,770
ewwel karattru, allura kull tieni l
karattru, allura tielet, u r-raba,

642
00:28:11,770 --> 00:28:15,206
u l-ħames, sakemm aħna hit
liema valur sentinella speċjali?

643
00:28:15,206 --> 00:28:16,080
UDJENZA: [inaudible]

644
00:28:16,080 --> 00:28:18,800
DAVID J. Malan: Yeah, il-backslash
żero, f'liema punt jew string

645
00:28:18,800 --> 00:28:20,100
nistgħu tiddeċiedi li jinsab fiha.

646
00:28:20,100 --> 00:28:21,970
Have we mqabbla kull karattru wieħed?

647
00:28:21,970 --> 00:28:22,990
Jekk le, ritorn foloz.

648
00:28:22,990 --> 00:28:24,770
Jekk iva, ritorn veru.

649
00:28:24,770 --> 00:28:28,800
U hekk dan huwa eżattament dak li din il-verżjoni
tal-programm iqabblu-1.c ma.

650
00:28:28,800 --> 00:28:31,677
Huwa identiku għal dak li aħna
ħares lejn it-Tnejn ħlief li ħadthom I

651
00:28:31,677 --> 00:28:34,760
gotten rid tal-string-- kelma għalkemm
li m'għandha l-ebda impact-- funzjonali kollha

652
00:28:34,760 --> 00:28:37,450
Li qed nagħmel issa huwa li jitneħħa
xi roti ta 'taħriġ viżwali,

653
00:28:37,450 --> 00:28:40,880
iżda biex tara b'mod ċar li
iu t huma indirizzi.

654
00:28:40,880 --> 00:28:43,020
U dan huwa dak l-istilla,
l-asterisk, jirrappreżenta

655
00:28:43,020 --> 00:28:46,690
huwa indirizz, inkella magħruf
aktar teknikament bħala pointer.

656
00:28:46,690 --> 00:28:49,880
>> Allura meta I niddikjara s fuq
linja 9 u jgħidu char * i,

657
00:28:49,880 --> 00:28:52,160
dan ma jfissirx tagħti me a string.

658
00:28:52,160 --> 00:28:56,360
Dan ifisser jagħtu me varjabbli li
iskop fil-ħajja huwa li taħżen l-indirizz.

659
00:28:56,360 --> 00:29:00,400
Minħabba I am madwar biex tpoġġi l-
indirizz ta 'sekwenza inkorporat fih.

660
00:29:00,400 --> 00:29:03,500
U fil-fatt, GetString, li jkun
ċara, ma ritorn string.

661
00:29:03,500 --> 00:29:06,110
Ma ritorn mom
backslash żero, per se.

662
00:29:06,110 --> 00:29:10,005
Xi jfisser GetString speċifikament
u preċiż ritorn?

663
00:29:10,005 --> 00:29:10,880
UDJENZA: [inaudible]

664
00:29:10,880 --> 00:29:14,080
DAVID J. Malan: An indirizz, l-
indirizz ta 'l-ewwel karattru

665
00:29:14,080 --> 00:29:16,070
f'xi string hija gotten.

666
00:29:16,070 --> 00:29:19,250
U hekk issa aħna qed jaraw
keyword speċjali darb'oħra.

667
00:29:19,250 --> 00:29:20,640
U, I allużjoni għal din qabel.

668
00:29:20,640 --> 00:29:23,620
Dan se jkun konvenzjoni tajba
li aħna ser tara mill-ġdid u għal darb'oħra issa.

669
00:29:23,620 --> 00:29:27,540
Jien verifika biex jiġi żgurat li
i ma huwiex null u t mhix null.

670
00:29:27,540 --> 00:29:30,100
Minħabba bbażata fuq tiegħi verament
isemmu malajr qabel,

671
00:29:30,100 --> 00:29:35,510
dak li jista 'jfisser jekk GetString prospetti ma
indirizz iżda N-U-L-L, li hija għal darb'oħra,

672
00:29:35,510 --> 00:29:36,990
xi valur speċjali?

673
00:29:36,990 --> 00:29:37,890
>> UDJENZA: Żball.

674
00:29:37,890 --> 00:29:38,600
>> DAVID J. Malan: Huwa ta 'żball.

675
00:29:38,600 --> 00:29:39,550
Xi ħaġa li marret ħażin.

676
00:29:39,550 --> 00:29:41,341
U dak li tipikament
jista 'jiġri, speċjalment

677
00:29:41,341 --> 00:29:45,162
ma strings-- li tista 'tkun
ta 'tul mhux magħrufa advance--

678
00:29:45,162 --> 00:29:46,870
forsi l-kompjuters "
tal-memorja, forsi

679
00:29:46,870 --> 00:29:49,280
inti ittajpjat f'tali
kelma twil jew sentenza

680
00:29:49,280 --> 00:29:51,880
jew pasted tali essay enormi
hemm biss mhux memorja biżżejjed.

681
00:29:51,880 --> 00:29:55,340
U għalhekk GetString ma jistgħux jirritornaw
l-indirizz tal-ħaġa sħiħa,

682
00:29:55,340 --> 00:29:56,620
għalhekk jirritorna xejn.

683
00:29:56,620 --> 00:30:00,580
U jgħid żball kien ġara
billi jirritorna l-valur NULL speċjali.

684
00:30:00,580 --> 00:30:02,890
Hu l-indirizz żero, biex ngħidu hekk.

685
00:30:02,890 --> 00:30:06,157
>> Issa jirriżulta C tiġi flimkien ma '
funzjoni li ma li iterazzjoni.

686
00:30:06,157 --> 00:30:09,240
Aħna ma jkollhom biex jimplimentaw din ma
a għal loop jew loop waqt nfusna.

687
00:30:09,240 --> 00:30:11,150
Nistgħu nużaw funzjoni,
imsejħa konċiż,

688
00:30:11,150 --> 00:30:15,400
ħawwad comp, jew string iqabblu, li
iskop fil-ħajja huwa li tagħmel eżattament dan.

689
00:30:15,400 --> 00:30:19,990
Inti tagħti żewġ pointers, żewġ indirizzi,
u se jmorru lil dawk l-indirizzi

690
00:30:19,990 --> 00:30:23,130
u mbagħad iqabblu ittra għall
ittra għall-ittra għall-kwalità,

691
00:30:23,130 --> 00:30:26,610
waqfien biss meta dak li huwa veru?

692
00:30:26,610 --> 00:30:31,540
Meta intuwittivament għandhom ħawwad comp
stop mtennija, biss biex tkun ċara?

693
00:30:31,540 --> 00:30:35,400
Meta hits backslash 0 f'kull
spag, f'liema punt jista 'jiddeċiedi

694
00:30:35,400 --> 00:30:38,910
tkun kollox mqabbla, jew
kien hemm diskrepanza?

695
00:30:38,910 --> 00:30:42,740
>> Allura, jekk aħna run dan issa u jippruvaw
logħba tagħna kapitalizzazzjoni ftit,

696
00:30:42,740 --> 00:30:49,260
sabiex tagħmel iqabblu-1, ./compare-1, u
tip mom fl zghar kemm żminijiet.

697
00:30:49,260 --> 00:30:50,560
Issa huwa l-istess ħaġa.

698
00:30:50,560 --> 00:30:54,080
U jekk jien tagħmel dan mill-ġdid ma
zghar u mbagħad forsi uppercase.

699
00:30:54,080 --> 00:30:56,720
Issa tabilħaqq tiddistingwi
bejn fuq u zghar.

700
00:30:56,720 --> 00:31:00,440
Allura mhux kollha li diffiċli jew
maġika, iżda ma tispjegax issa

701
00:31:00,440 --> 00:31:03,140
x'inhu għaddej taħt il-barnuża.

702
00:31:03,140 --> 00:31:07,640
>> Allura dak li aktar jista aħna estratt
minn dan it-tip ta 'lezzjoni?

703
00:31:07,640 --> 00:31:08,980
Mela ejja tagħti ħarsa lejn dan.

704
00:31:08,980 --> 00:31:15,380
Jien ser jimxi 'l quddiem u jiktbu
programm quick hawn imsejħa kopja 0.

705
00:31:15,380 --> 00:31:21,594
U issa ejja imorru quddiem u fil-fatt
Ejja nagħmlu this-- ma 'kopja 0,

706
00:31:21,594 --> 00:31:23,010
tagħti ħarsa lejn dak li stajt ltqajna hawn.

707
00:31:23,010 --> 00:31:24,712
I ewwel tgħid l-utent, ngħid xi ħaġa.

708
00:31:24,712 --> 00:31:26,420
Imbagħad niġi string
u I maħżuna fil s.

709
00:31:26,420 --> 00:31:29,810
Imbagħad I jiċċekkjaw jekk i huwa ugwali
ugwali NULL, biss jirritorna 1.

710
00:31:29,810 --> 00:31:31,590
Allura dan huwa biss żball iċċekkjar standard.

711
00:31:31,590 --> 00:31:33,112
Xejn interessanti li ġara.

712
00:31:33,112 --> 00:31:36,320
U fil-fatt, jekk irridu jeħles mill-iżball
verifika, dan qisu ġimgħa 1 kodiċi

713
00:31:36,320 --> 00:31:36,985
fil-mument.

714
00:31:36,985 --> 00:31:39,110
Imma stajt bdiet tikseb
ftit aħjar dwar dan.

715
00:31:39,110 --> 00:31:43,340
>> Issa fil-linja 16, ġimgħa ilu, forsi
jiem anke koppja jew minuti ilu,

716
00:31:43,340 --> 00:31:46,720
inti jista 'jgħid linja 16 hija
ħolqien ta 'varjabbli imsejjaħ t

717
00:31:46,720 --> 00:31:48,219
u l-ikkupjar s fih.

718
00:31:48,219 --> 00:31:50,010
U li l-perfettament
takeaway raġonevoli.

719
00:31:50,010 --> 00:31:51,560
Imma jkun aktar preċiż issa.

720
00:31:51,560 --> 00:31:54,190
Dak li qed jiġri fil-linja 16?

721
00:31:54,190 --> 00:31:56,170
X'inhu jkollna kkupjata
minn lemin għax-xellug?

722
00:31:56,170 --> 00:31:56,669
Yeah?

723
00:31:56,669 --> 00:31:58,490
UDJENZA: Huwa t jkollna indirizz ta 'i?

724
00:31:58,490 --> 00:32:01,220
>> DAVID J. Malan: Eżattament, t
huwa jkollna l-indirizz ta 's.

725
00:32:01,220 --> 00:32:05,170
Allura biex tkun ċara issa, jekk immur
lura għal dak eżempju ta 'qabel

726
00:32:05,170 --> 00:32:08,520
u I tfassal l-ħaġa stajt ittajpjat fil.

727
00:32:08,520 --> 00:32:11,640
U dak li stajt ittajpjat
in-- hawnhekk i, u hawn

728
00:32:11,640 --> 00:32:15,830
huwa dak li stajt ittajpjat fil x'imkien fil
memorja, mom u mbagħad backslash

729
00:32:15,830 --> 00:32:17,840
0 thats miżjud għalija.

730
00:32:17,840 --> 00:32:23,060
What I maħżuna fil hawn, tfakkar,
dan huwa fil-post 1, 2, 3, 4,

731
00:32:23,060 --> 00:32:24,655
dan huwa dak li bħalissa s.

732
00:32:24,655 --> 00:32:29,220
Mela jekk on-line 16, I say jagħtu me
varjabbli imsejħa t-ieħor u jaħżnu

733
00:32:29,220 --> 00:32:33,590
f'mill-valur ta 'i, dak
gets maħżuna hawn mhux se mom

734
00:32:33,590 --> 00:32:35,480
iżda biss in-numru 1.

735
00:32:35,480 --> 00:32:38,520
>> Mela jekk inħarsu 'l quddiem f'dan il-programm
issa, dak li jiġri?

736
00:32:38,520 --> 00:32:40,690
Allura avviż li hemm
din il-funzjoni inti tista

737
00:32:40,690 --> 00:32:44,410
użaw dan xi żmien ilu għall Caesar,
jew Vigenere, jew forsi xejn affattu.

738
00:32:44,410 --> 00:32:48,170
I titlob bil printf tiegħi, jien
jmorru għall-kapitalizzazzjoni tal-kopja t.

739
00:32:48,170 --> 00:32:51,616
Ewwel linja 19, sanità malajr
jivverifikaw, kontrolli strlen-tul ta t.

740
00:32:51,616 --> 00:32:53,740
Minħabba I ma jridux
jippruvaw li tikkapitalizza xi ħaġa

741
00:32:53,740 --> 00:32:55,104
jekk hemm l-ebda string hemmhekk.

742
00:32:55,104 --> 00:32:57,520
Jekk l-utent biss hit Ikteb,
hemm xejn għall-kapitalizzazzjoni.

743
00:32:57,520 --> 00:33:01,100
So I ma trid tagħmel linja 21.

744
00:33:01,100 --> 00:33:05,758
Allura linja 21 huwa kapitalizzazzjoni
liema ittra, apparentement, f't?

745
00:33:05,758 --> 00:33:06,514
>> UDJENZA: m?

746
00:33:06,514 --> 00:33:08,722
DAVID J. Malan: Huwa jistenna
simili huwa ikkopjar liema waħda?

747
00:33:08,722 --> 00:33:09,486
UDJENZA: m.

748
00:33:09,486 --> 00:33:10,450
DAVID J. Malan: Uh, m.

749
00:33:10,450 --> 00:33:12,685
OK, hekk l-ewwel m,
għaliex avviż li jien

750
00:33:12,685 --> 00:33:14,935
tgħaddi biex toupper, li
jekk inti stajt qatt raw dan huwa

751
00:33:14,935 --> 00:33:16,980
biss funzjoni li
kapitalizzazzjoni bħala input tagħha.

752
00:33:16,980 --> 00:33:20,240
t bracket żero ifisser jagħtu
me-karattru żero ta t.

753
00:33:20,240 --> 00:33:22,550
U hekk kif ma dan
bidla stampa, li jkun ċar?

754
00:33:22,550 --> 00:33:25,490

755
00:33:25,490 --> 00:33:29,160
X'hemm bżonn li tikseb miktuba mill-ġdid jew mibdula
fir-rigward iu tu mom

756
00:33:29,160 --> 00:33:30,097
żero backslash.

757
00:33:30,097 --> 00:33:31,470
>> UDJENZA: [inaudible]

758
00:33:31,470 --> 00:33:34,030
>> DAVID J. Malan: Yeah,
għalhekk dan wieħed hawn sempliċiment

759
00:33:34,030 --> 00:33:40,860
teħtieġ li jiksbu mibdula to-- jiffissaw this--
jeħtieġ li jiksbu mibdula għal m kapital.

760
00:33:40,860 --> 00:33:44,330
Imma issa, tħares aktar tard fil-
programm, jekk I jistampa

761
00:33:44,330 --> 00:33:49,800
i u t bħala I tnaddaf hawn, watch x'hemm
jiġri stampar ta iu t.

762
00:33:49,800 --> 00:33:54,310
Sabiex tagħmel l-ikkupjar 0, ./copy-0.

763
00:33:54,310 --> 00:33:57,140
Let me imorru quddiem u t-tip
fil mom kollha lowercase.

764
00:33:57,140 --> 00:34:00,140
Avviż kemm l-oriġinali u
l-kopja ġew kapitalizzati.

765
00:34:00,140 --> 00:34:00,850
Għaliex?

766
00:34:00,850 --> 00:34:04,431
Well, iu t-tnejn huma tipponta lejn,
jekk inti se, l-istess blokki ta 'memorja.

767
00:34:04,431 --> 00:34:06,930
U franchement, dan huwa jkollna
verament uninteresting---fatt

768
00:34:06,930 --> 00:34:09,150
li aħna qed tuża indirizz żero hawn.

769
00:34:09,150 --> 00:34:11,719
I mean, I ma verament kura
fejn Jittieħed huwa fil-memorja.

770
00:34:11,719 --> 00:34:13,550
Jiddispjacini jien tħassir ftit wisq.

771
00:34:13,550 --> 00:34:15,674
Imma jien ma verament kura
fejn l-affarijiet huma fil-memorja.

772
00:34:15,674 --> 00:34:18,510
U għalhekk, tabilħaqq dak
programmaturi tendenza li jaħsbu dwar

773
00:34:18,510 --> 00:34:21,080
hija li meta tkellem dwar
indirizz, jew pointer,

774
00:34:21,080 --> 00:34:22,679
quién fejn huwa fl-memorja.

775
00:34:22,679 --> 00:34:24,989
I do not care jekk huwa fil
byte wieħed jew waħda biljun.

776
00:34:24,989 --> 00:34:27,920
I biss kura li dan
varjabbli hija effettivament

777
00:34:27,920 --> 00:34:29,620
tipponta lejn dak blokki ta 'memorja.

778
00:34:29,620 --> 00:34:33,350
U għalhekk, minn issa, aktar milli quibble
fuq indirizzi memorja arbitrarji, ejja

779
00:34:33,350 --> 00:34:36,710
biss jibdew tiġbed pointers
kif pointers, kif vleġeġ.

780
00:34:36,710 --> 00:34:39,340
Allura dak i u t verament huma,
skond dan il-programm,

781
00:34:39,340 --> 00:34:42,130
minħabba kif I maħluqa t,
huwa biss żewġ varjabbli separati

782
00:34:42,130 --> 00:34:43,840
tipponta fl-istess blokki ta 'memorja.

783
00:34:43,840 --> 00:34:45,215
U aħna ma 'kura fejn huma.

784
00:34:45,215 --> 00:34:47,130
Allura nistgħu astratt bogħod li dettall.

785
00:34:47,130 --> 00:34:48,780
>> Allura kif nista jiffissaw dan?

786
00:34:48,780 --> 00:34:54,120
Jekk irrid jikteb verżjoni tal-kopja
programm li attwalment kopji l spag

787
00:34:54,120 --> 00:34:56,840
u tikkapitalizza biss l
kopja, biss intuwittivament,

788
00:34:56,840 --> 00:34:59,766
dak ltqajna biex tkun
ingredjent li s-soluzzjoni tagħna?

789
00:34:59,766 --> 00:35:00,640
UDJENZA: [inaudible]

790
00:35:00,640 --> 00:35:01,420
DAVID J. Malan: Għandna bżonn liema?

791
00:35:01,420 --> 00:35:01,820
UDJENZA: Chunk tal-memorja.

792
00:35:01,820 --> 00:35:03,280
DAVID J. Malan: Għandna bżonn
blokki ieħor ta 'memorja, right?

793
00:35:03,280 --> 00:35:05,360
Ma nafux kif
tagħmel encore, neċessarjament.

794
00:35:05,360 --> 00:35:11,330
Imma I tip ta 'bżonn dan iseħħ hekk
li l-mom oriġinali f'ittri żgħar

795
00:35:11,330 --> 00:35:14,170
jispiċċa f'dak blokki żejda ta 'memorja.

796
00:35:14,170 --> 00:35:19,770
U mbagħad meta I jibdlu l-kopja, I
ma jridux bidla din il-kopja hawn.

797
00:35:19,770 --> 00:35:26,020
I minflok trid tibdel biss dan
Kopja sabiex il-oriġinal ma jinbidilx.

798
00:35:26,020 --> 00:35:27,980
>> Allura, ejja naraw kif nistgħu nagħmlu dan.

799
00:35:27,980 --> 00:35:31,800
Fil-1 kopja, li diġà
kienet tneħħietlu l-kumment,

800
00:35:31,800 --> 00:35:33,250
iżda huwa ikkummenta online.

801
00:35:33,250 --> 00:35:36,710
We minflok tagħmel l-following-- dawn
linji huma identiċi, jiksbu me string

802
00:35:36,710 --> 00:35:38,340
u sejħa hija s.

803
00:35:38,340 --> 00:35:43,500
Imma issa ejja nħarsu lejn wieħed mill-aktar tagħna
kumpless iżda l-aħħar tal-kumplessità

804
00:35:43,500 --> 00:35:47,340
għall awhile, linja 16 ma eżattament dan.

805
00:35:47,340 --> 00:35:49,400
Mela jekk comfy tiegħek mal-
stampa aħna biss drew--

806
00:35:49,400 --> 00:35:51,790
tagħti me blokki ġdid ta 'memorja,
kollox kopja fiha,

807
00:35:51,790 --> 00:35:53,730
ejja ara kif aħna tittraduċi dak li kodiċi.

808
00:35:53,730 --> 00:35:59,400
>> Allura linja 16, fuq in-naħa tax-xellug,
char * t tagħti me din il-kaxxa hawn fuq.

809
00:35:59,400 --> 00:36:00,230
Li kollox li tagħmel.

810
00:36:00,230 --> 00:36:03,240
Min-naħa tal-lemin,
ALLOC m, jew malloc,

811
00:36:03,240 --> 00:36:06,480
huwa allokazzjoni memorja, super fancy,
mod cryptic ta 'ftit qal

812
00:36:06,480 --> 00:36:07,640
tagħti me blokki ta 'memorja.

813
00:36:07,640 --> 00:36:09,290
Kemm memorja ħafna jeħtiġilna?

814
00:36:09,290 --> 00:36:10,910
Ukoll, huwa tip ta 'espressjoni big.

815
00:36:10,910 --> 00:36:12,570
Imma ejja ara dak li jgħid hawnhekk.

816
00:36:12,570 --> 00:36:15,940
Allura dan, naturalment, huwa jagħti
me tul sensiela ta 's.

817
00:36:15,940 --> 00:36:19,094
Allura, mom għandu jkun dak?

818
00:36:19,094 --> 00:36:21,010
Hekk biss tlieta, id-dritt?
mom huwa ta 'tliet karattri.

819
00:36:21,010 --> 00:36:22,830
Inti ma jgħoddux l-
backslash żero meta inti

820
00:36:22,830 --> 00:36:25,960
jitkellmu dwar it-tul ta 'sekwenza huwa
Attwalment l-ittri viżibbli tal-bniedem.

821
00:36:25,960 --> 00:36:28,020
Allura mom, għalhekk dan jagħti me 3.

822
00:36:28,020 --> 00:36:31,170
Iżda stenna minuta, jien issa żżid 1.

823
00:36:31,170 --> 00:36:34,861
Għaliex għandi attwalment jridu
jallokaw 4 bytes u mhux biss 3?

824
00:36:34,861 --> 00:36:35,360
Yeah?

825
00:36:35,360 --> 00:36:36,910
>> UDJENZA: Għall-valur sentinella?

826
00:36:36,910 --> 00:36:38,951
>> DAVID J. Malan: Eżattament,
għal dak il-valur sentinella.

827
00:36:38,951 --> 00:36:40,840
Għall-backslash żero,
I bżonn 4 bytes totali.

828
00:36:40,840 --> 00:36:42,870
So I bżonn it-tul
tas-sekwenza flimkien ma '1.

829
00:36:42,870 --> 00:36:45,400
U mbagħad biss għall measure-- tajba
anke jekk fuq din is-sistema,

830
00:36:45,400 --> 00:36:49,390
huwa dejjem se jkunu 1-- jien tgħid
immoltiplika dan mid-daqs ta 'char.

831
00:36:49,390 --> 00:36:51,552
Jinstabx sizeof huwa
operatur C li

832
00:36:51,552 --> 00:36:53,260
biss jgħidlek il
numru ta 'bytes li l-

833
00:36:53,260 --> 00:36:54,700
meħtieġa għal ċertu tip ta 'data.

834
00:36:54,700 --> 00:36:57,740
Hija ma taħdimx għall arrays,
tipikament, xi kultant ma.

835
00:36:57,740 --> 00:36:59,210
Iżda fil-każ ġenerali, l-ebda.

836
00:36:59,210 --> 00:37:02,330
Iżda se tgħidli kemm hemm bytes a
char huwa, li jirriżulta huwa dejjem 1.

837
00:37:02,330 --> 00:37:04,080
Allura dan huwa simili mmultiplikat b'1.

838
00:37:04,080 --> 00:37:05,900
>> Allura super cryptic linja tħares 'kodiċi.

839
00:37:05,900 --> 00:37:09,320
Iżda kollha ma huwa jagħti
me blokki ta 'memorja.

840
00:37:09,320 --> 00:37:13,590
Iżda ma jidhirx li jkun ikkupjar
xejn f'dak memorja?

841
00:37:13,590 --> 00:37:14,560
Mhux għalissa.

842
00:37:14,560 --> 00:37:22,040
U iva, liema do I fuq il-linja 22, u
23, 24, 25, ukoll, I sempliċiment tagħmel dan.

843
00:37:22,040 --> 00:37:23,760
U dan huwa tip ta '
Jittieħed iskola antika issa.

844
00:37:23,760 --> 00:37:26,010
Dan huwa simili PSet 2, fejn
int biss affarijiet jimxu

845
00:37:26,010 --> 00:37:28,620
madwar fil-memorja, jew pjuttost f'qatet.

846
00:37:28,620 --> 00:37:31,920
>> Hekk jien mtennija minn 0 sa
it-tul tas-sekwenza s.

847
00:37:31,920 --> 00:37:37,820
U jien ikkupjar il-karattru numru i
fl-i fil-karattru numru i f't.

848
00:37:37,820 --> 00:37:41,820
U minħabba I, il-programmer, magħmula
żgur li jallokaw eżattament kif ħafna bytes

849
00:37:41,820 --> 00:37:44,600
għandi bżonn, huwa perfett
one-to-one relazzjoni.

850
00:37:44,600 --> 00:37:47,060
U jien kopja mom fil
zghar għal dik ġdida.

851
00:37:47,060 --> 00:37:50,170
U mbagħad fl-aħħar, I do din il-linja.

852
00:37:50,170 --> 00:37:54,637
U għalhekk l-effett huwa biss
għall-kapitalizzazzjoni dan t hawn.

853
00:37:54,637 --> 00:37:56,470
Allura ħafna biex jassorbu, iżda
jekk inti biss tikkunsidra

854
00:37:56,470 --> 00:37:58,220
x'inhu verament għaddej
fuq taħt il-barnuża

855
00:37:58,220 --> 00:38:00,880
huwa biss dawn jimxu
bytes madwar, dak kollu li

856
00:38:00,880 --> 00:38:06,617
hija meħtieġa sabiex issolvi din il-problema hija
biss biex tagħtina din blokki ta 'memorja.

857
00:38:06,617 --> 00:38:08,450
Issa bir-riskju li
kbira, let me juru

858
00:38:08,450 --> 00:38:13,200
eżempju ieħor li kważi
identiċi, ħlief għal dan wieħed

859
00:38:13,200 --> 00:38:14,350
linja tal-kodiċi.

860
00:38:14,350 --> 00:38:18,870
Allura dan huwa l-verżjoni Hacker
ta 'dan il-programm, jekk inti se.

861
00:38:18,870 --> 00:38:21,050
Imma ejja biss jiddistillaw
fis x'inhu għaddej.

862
00:38:21,050 --> 00:38:28,920
Linja 24 użati biex tkun din t
bracket i gets bracket s i.

863
00:38:28,920 --> 00:38:33,370
Issa, jien jinbidlu dan
l ħafna aktar cryptic t star

864
00:38:33,370 --> 00:38:36,280
flimkien ma '1 ugwali star s plus 1.

865
00:38:36,280 --> 00:38:38,702
>> Allura x'inhu jiġri u għaliex
għandna karattru star?

866
00:38:38,702 --> 00:38:41,410
Rajna l-istilla qabel, u
huwa qed jintuża b'mod differenti hawn.

867
00:38:41,410 --> 00:38:45,490
Aħna diġà raw char *, issa jien jaraw
stilla fil-bidu, u li OK.

868
00:38:45,490 --> 00:38:48,190
Minħabba jirriżulta aħna
tista tip ta 'jiddeduċu biss

869
00:38:48,190 --> 00:38:50,280
minn dawk l-ewwel
prinċipji x'inhu għaddej.

870
00:38:50,280 --> 00:38:53,860
Hekk biss li jkun ċar, dak li huwa s?

871
00:38:53,860 --> 00:38:55,052
Last week, kien string.

872
00:38:55,052 --> 00:38:56,260
Dan mhuwiex biżżejjed jibqgħalu.

873
00:38:56,260 --> 00:38:57,690
X'inhu s, b'mod speċifiku?

874
00:38:57,690 --> 00:38:58,590
>> UDJENZA: [inaudible]

875
00:38:58,590 --> 00:38:59,881
>> DAVID J. Malan: Huwa pointer.

876
00:38:59,881 --> 00:39:02,610
Hu l-indirizz tal-
ewwel karattru aħna ittajpjat fil.

877
00:39:02,610 --> 00:39:04,780
OK, dak li huwa t?

878
00:39:04,780 --> 00:39:05,660
>> UDJENZA: [inaudible]

879
00:39:05,660 --> 00:39:07,950
>> DAVID J. Malan: Il-
indirizz ta 'l-ewwel byte

880
00:39:07,950 --> 00:39:10,490
f't, li blokki ta 'memorja riallokati.

881
00:39:10,490 --> 00:39:14,720
Għalhekk jirriżulta li meta aħna
jtenni minn 0 sa l-sekwenza

882
00:39:14,720 --> 00:39:17,424
length-- ewwel nett, i
jibda off fil-0, għaliex

883
00:39:17,424 --> 00:39:18,840
ta din l-iskola antika għal ħaġa loop.

884
00:39:18,840 --> 00:39:22,400
Hekk biss għas-sempliċità, ejja
jassumi li l-ewwel linja tal-kodiċi

885
00:39:22,400 --> 00:39:23,760
huwa verament biss dan, id-dritt.

886
00:39:23,760 --> 00:39:26,080
Jekk i huwa żero, u żżid żero
għal xi ħaġa preżumibbilment

887
00:39:26,080 --> 00:39:27,540
mhux se jkollhom effett.

888
00:39:27,540 --> 00:39:28,560
>> Allura dak li huwa dan qal?

889
00:39:28,560 --> 00:39:31,600
Jirriżulta li l-istilla
operatur f'dan il-kuntest

890
00:39:31,600 --> 00:39:33,700
huwa l-dereference
operatur, li huwa biss

891
00:39:33,700 --> 00:39:37,530
mod fancy ta 'tgħid tmur
f'dan l-indirizz.

892
00:39:37,530 --> 00:39:42,080
Mela jekk i huwa l-indirizz ta 'l-ewwel
karattru f'dan blokki ta 'memorja,

893
00:39:42,080 --> 00:39:43,630
* s mezzi jmorru hemm.

894
00:39:43,630 --> 00:39:45,630
U għaliex aħna ħadthom mfassla
l-istampa b'dan il-mod,

895
00:39:45,630 --> 00:39:47,430
inti tista 'tadotta l-
wara mudell mentali.

896
00:39:47,430 --> 00:39:51,030
Jekk dan huwa s, u inti tgħidli * i, * s
tip simili siġġijiet u slielem,

897
00:39:51,030 --> 00:39:54,540
jekk inti tiftakar il-logħba mit-tfulija,
huwa simili jirriżultax li vleġġa u jmorru

898
00:39:54,540 --> 00:39:55,570
fl-indirizz.

899
00:39:55,570 --> 00:39:57,080
>> * t huwa l-istess ħaġa.

900
00:39:57,080 --> 00:39:59,855
Allura tibda hawn, mur blokki tagħha.

901
00:39:59,855 --> 00:40:03,350
I tista 'mhux biss tibbaża fuq
dan l-iskrin li mod.

902
00:40:03,350 --> 00:40:05,560
* t ifisser li jmorru hawn.

903
00:40:05,560 --> 00:40:08,830
U mbagħad, il-loop huwa biss għall
qal jimxu dan il-karattru hawnhekk,

904
00:40:08,830 --> 00:40:11,330
jimxu dan il-karattru hawnhekk,
jimxu dan il-karattru hawnhekk.

905
00:40:11,330 --> 00:40:12,890
Imma kif nista 'nagħmlu incrementation?

906
00:40:12,890 --> 00:40:15,430
I-ħtieġa li jneħħu dak I biss mħassar.

907
00:40:15,430 --> 00:40:18,140
Dan huwa dak li ġeneralment jissejjaħ
aritmetika pointer, li

908
00:40:18,140 --> 00:40:20,040
ifisser matematika bl-indirizzi.

909
00:40:20,040 --> 00:40:22,460
>> Jekk, f'dan il-għal loop,
I iżommu inkrementazzjoni i,

910
00:40:22,460 --> 00:40:26,880
u s huwa indirizz u t huwa
indirizz, jekk I biss iżommu żżid 1,

911
00:40:26,880 --> 00:40:31,406
li sempliċiment ifisser iżommu miexja 'l quddiem,
u jibgħatu, u jibgħat fil-memorja.

912
00:40:31,406 --> 00:40:34,030
Huwa simili Oxford Street, il-
triq li l-bini CS huwa fuq.

913
00:40:34,030 --> 00:40:36,490
Il-bini CS huwa fil 33 Oxford Street.

914
00:40:36,490 --> 00:40:39,870
Mela jekk ġejt biex tagħmel 33
Oxford Street flimkien ma '1,

915
00:40:39,870 --> 00:40:42,870
li ġġib inti 34 Oxford
Street, allura Street 35 Oxford,

916
00:40:42,870 --> 00:40:46,380
imbagħad 36 Oxford Street, ikun x'ikun dawk
bini li huma effettivament huma - jekk dawn jeżistu.

917
00:40:46,380 --> 00:40:50,540
U għalhekk, li kollox li aħna qed tagħmel
hawn ma aritmetika pointer.

918
00:40:50,540 --> 00:40:53,820
>> Allura huwa mod super arcane
jesprimu nfusna.

919
00:40:53,820 --> 00:40:56,160
Iżda dak kollu li jiġri
taħt il-barnuża

920
00:40:56,160 --> 00:40:59,330
huwa biss wara dawn l-indirizzi,
bħal wara mappa, jekk inti se,

921
00:40:59,330 --> 00:41:02,692
jew wara vleġeġ bħall
konna mfassal fuq l-iskrin.

922
00:41:02,692 --> 00:41:04,910
OK, ħafna biex diġestiva.

923
00:41:04,910 --> 00:41:10,410
Kwalunkwe mistoqsija dwar sintassi, kunċetti,
pointers, malloc, jew affarijiet simili.

924
00:41:10,410 --> 00:41:11,480
Yeah, minn hawn ewwel.

925
00:41:11,480 --> 00:41:13,755
>> UDJENZA: Allura meta dik
jgħid * t ugwali toupper * t,

926
00:41:13,755 --> 00:41:15,575
huwa li jmorru għall-kapitalizzazzjoni
l-ittri jew just--

927
00:41:15,575 --> 00:41:17,283
>> DAVID J. Malan: Ah,
kwistjoni verament tajba.

928
00:41:17,283 --> 00:41:19,805
Allura f'dan il-linja hawnhekk, 31,
huwa dan se għall-kapitalizzazzjoni

929
00:41:19,805 --> 00:41:21,430
l-ewwel ittra jew kollha ta 'l-ittri.

930
00:41:21,430 --> 00:41:23,460
Mela ejja risposta għal din billi tmur
lura għall-ewwel prinċipji.

931
00:41:23,460 --> 00:41:26,168
U l-ewwel prinċipji hawn I jfissirx
biss jmorru għall-definizzjonijiet bażiċi

932
00:41:26,168 --> 00:41:27,000
ta 'dak involut.

933
00:41:27,000 --> 00:41:29,770
Allura toupper l b'funzjoni
li tikkapitalizza char.

934
00:41:29,770 --> 00:41:30,530
Dak kollox.

935
00:41:30,530 --> 00:41:36,740
* t ifisser tmur fil-first--
mur l-indirizz f't.

936
00:41:36,740 --> 00:41:40,350
Allura, fl-istampa, jekk dan huwa l-blokki
ta 'memorja aħna allokat malloc,

937
00:41:40,350 --> 00:41:43,310
u dan huwa t, * t ifisser mur hawn.

938
00:41:43,310 --> 00:41:46,710
>> Sadanittant, int tgħaddi
dan il-valur, zghar m

939
00:41:46,710 --> 00:41:50,040
li toupper, int jkollna lura
kapital M, fejn huma inti tqegħid?

940
00:41:50,040 --> 00:41:52,410
Int tqegħid fl-istess post.

941
00:41:52,410 --> 00:41:55,540
U hekk minn dak l-loġika ta 'dawk
definizzjonijiet bażiċi Huwa biss

942
00:41:55,540 --> 00:41:58,792
kapitalizzazzjoni-ewwel ittra
sakemm inti jtenni bil i jew

943
00:41:58,792 --> 00:42:02,000
għal loop jew loop waqt, mhuwiex ser
li tagħmel xejn aktar milli suppost jitlobha.

944
00:42:02,000 --> 00:42:02,583
Tajba kwistjoni.

945
00:42:02,583 --> 00:42:03,237
Yeah?

946
00:42:03,237 --> 00:42:05,369
>> UDJENZA: Għaliex ma tuża l-
dereference metodu pjuttost milli

947
00:42:05,369 --> 00:42:05,979
l-array?

948
00:42:05,979 --> 00:42:07,395
>> DAVID J. Malan: Ah, mistoqsija tajba.

949
00:42:07,395 --> 00:42:10,672
Għaliex kieku inti tuża l-dereference
metodu minflok il-metodu firxa?

950
00:42:10,672 --> 00:42:12,130
L-ebda raġuni partikolari, li tkun onest.

951
00:42:12,130 --> 00:42:15,290
U, fil-fatt, għal dan
tip ta 'eżempju, id-dritt,

952
00:42:15,290 --> 00:42:17,556
Jien biss argumenta jagħmlu l-
programm aktar ikkumplikati,

953
00:42:17,556 --> 00:42:19,680
għajnejn aktar qed glazing fuq,
nies huma iċċekkjar

954
00:42:19,680 --> 00:42:22,830
minħabba dan jistenna super arcane, iżda
anki jekk huwa qed jagħmel l-istess ħaġa.

955
00:42:22,830 --> 00:42:26,695
U għalhekk, franchement, dan huwa
Soluzzjoni bla bżonn viżwalment kumpless

956
00:42:26,695 --> 00:42:27,320
għall-problema.

957
00:42:27,320 --> 00:42:29,580
>> Huwa għadu disinn tajjeb,
ħamsa minn ħamsa għad-disinn,

958
00:42:29,580 --> 00:42:33,140
jekk fil-kategorija
notazzjoni jew in-notazzjoni pointer.

959
00:42:33,140 --> 00:42:36,299
But-- speċjalment meta nikbru
aktar tard fil-kors PSet 5

960
00:42:36,299 --> 00:42:39,340
meta nimplimentaw li dizzjunarju li
Stajt msemmija koppja ta 'times--

961
00:42:39,340 --> 00:42:42,300
aħna ser attwalment kura dwar l-
indirizzi memorja livell baxx

962
00:42:42,300 --> 00:42:44,140
li aħna verament jifhem
x'inhu għaddej.

963
00:42:44,140 --> 00:42:48,300
>> Iżda, għal issa, jirriżulta li din
linja ta 'kodiċi parentesi kwadri hawn

964
00:42:48,300 --> 00:42:49,900
ma tassew jeżistu.

965
00:42:49,900 --> 00:42:52,230
Dawn huma dak li sejjaħ
zokkor sintattika, li

966
00:42:52,230 --> 00:42:58,390
huwa biss mod weirdly jibred ta 'tgħid l-
kompilatur tikkonverti parentesi kwadri li jkun

967
00:42:58,390 --> 00:43:00,420
dik l-espressjoni matematika.

968
00:43:00,420 --> 00:43:02,660
Allura huwa konvenzjoni tal-bniedem
biex tkun tista 'tikteb biss

969
00:43:02,660 --> 00:43:04,220
dawn parentesi ħafna faċli għall-utent.

970
00:43:04,220 --> 00:43:06,850
Imma dak li l-kumpilatur, clang,
hu verament tagħmel kwalunkwe ħin

971
00:43:06,850 --> 00:43:10,970
tikteb dak li enfasizzat fil-linja
24, taħt il-barnuża huwa verament

972
00:43:10,970 --> 00:43:12,330
jikkonvertuha għal dan.

973
00:43:12,330 --> 00:43:16,200
Huwa biss aktar pleasurable bħala bniedem
jaqraw u jiktbu kodiċi bħal linja 24.

974
00:43:16,200 --> 00:43:18,530
Iżda eventwalment dawk
roti ta 'taħriġ wisq come off

975
00:43:18,530 --> 00:43:21,780
meta kumdità tiegħu stess gets aktar b'saħħitha.

976
00:43:21,780 --> 00:43:27,240
>> Kull dritt, hekk ifakkar allura li dan
kien il-tip ta 'akbar problema

977
00:43:27,240 --> 00:43:27,807
aħna dam fis.

978
00:43:27,807 --> 00:43:30,640
U dan huwa dak qanqal dan kollu
konverżazzjoni kkritikat dwar pointers,

979
00:43:30,640 --> 00:43:32,340
u l-indirizzi, u affarijiet ikkupjar.

980
00:43:32,340 --> 00:43:35,410
Kien għaliex aħna tripped fuq
dan stupid, il-kwistjoni stupid, fejn

981
00:43:35,410 --> 00:43:38,830
I implimentati logically-- ma Lauren
up here fuq il-demo u l meraq tal-larinġ

982
00:43:38,830 --> 00:43:43,770
fil-milk-- perfettament
funzjoni algorithmically korretta

983
00:43:43,770 --> 00:43:47,010
għall-iskambji żewġ varjabbli "
valuri, imma l-ħaġa kkritikat

984
00:43:47,010 --> 00:43:50,550
ma kellhomx xi persistenti, jew
permanenti, effett fuq kodiċi tiegħi.

985
00:43:50,550 --> 00:43:51,820
>> U għaliex kienet li?

986
00:43:51,820 --> 00:43:54,650
Fil-qosor, għaliex huwa dan
implimentazzjoni ta 'swap

987
00:43:54,650 --> 00:43:58,740
loġikament korrett, imma m'għandha ebda impatt
dwar il-varjabbli li huma mgħoddija lilha,

988
00:43:58,740 --> 00:44:01,119
bħall x uy għall prinċipali?

989
00:44:01,119 --> 00:44:02,410
Liema kienet l-gist tal-kwistjoni?

990
00:44:02,410 --> 00:44:02,909
Yeah?

991
00:44:02,909 --> 00:44:05,532
UDJENZA: Minħabba varjabbli magħmula
kopji ta 'varjabbli fl-pass

992
00:44:05,532 --> 00:44:06,240
permezz funzjoni.

993
00:44:06,240 --> 00:44:09,060
>> DAVID J. Malan: Eżattament, meta inti tgħaddi
varjabbli ġo funzjoni, jew argumenti

994
00:44:09,060 --> 00:44:11,030
fi funzjoni, dawn qed
għadda minn kopja, li

995
00:44:11,030 --> 00:44:14,770
tfisser ikollok identika tfittex
mudell ta 'bits kemm xuy,

996
00:44:14,770 --> 00:44:15,955
imsejħa hawn aub.

997
00:44:15,955 --> 00:44:18,080
U inti tista 'tagħmel xejn
trid ma dawk il-kopji,

998
00:44:18,080 --> 00:44:20,657
iżda dawn qed tmur biex ikollhom l-ebda
effett fuq il-funzjoni sejħa.

999
00:44:20,657 --> 00:44:22,990
U, fil-fatt, aħna ġibdet li
istampa fuq l-iskrin, irtirar

1000
00:44:22,990 --> 00:44:25,520
aħħar darba, fejn jekk inti
really think dwar x'hemm

1001
00:44:25,520 --> 00:44:28,570
għaddej taħt il hood-- jekk
dan huwa memorja tal-kompjuter tiegħek,

1002
00:44:28,570 --> 00:44:31,650
u 'l isfel hawnhekk huwa l-blokki ta'
memorja qed jintużaw għal prinċipali,

1003
00:44:31,650 --> 00:44:34,020
dan huwa l-blokki ta '
memorja qed jintużaw għal tpartit,

1004
00:44:34,020 --> 00:44:37,090
u għandu hekk anke jekk ewlenija
żewġ varjabbli, xuy,

1005
00:44:37,090 --> 00:44:41,840
tpartit jista 'jkollhom identiċi tfittex
valuri, it-tnejn li huma 1 u 2,

1006
00:44:41,840 --> 00:44:44,520
iżda dawn qed kompletament
biċċiet differenti ta 'memorja.

1007
00:44:44,520 --> 00:44:46,130
>> Għalhekk għandna bżonn soluzzjoni għal din.

1008
00:44:46,130 --> 00:44:51,580
U franchement, jidher li aħna issa
jkun hemm soluzzjoni għal din il-problema, id-dritt.

1009
00:44:51,580 --> 00:44:55,760
Jekk issa għandna l-ħila li
jimmanipulaw affarijiet permezz ta 'indirizzi

1010
00:44:55,760 --> 00:44:59,310
u, sort ta żrieżaq u slielem
stil, segwi dawn vleġeġ

1011
00:44:59,310 --> 00:45:02,820
u jmorru kullimkien rridu
fil-memorja, ma setgħux aħna

1012
00:45:02,820 --> 00:45:06,220
issolvi din il-problema billi
tgħaddi minn ewlenija tpartit

1013
00:45:06,220 --> 00:45:09,650
mhux il-valuri irridu
tpartit, imma biss intuwittivament

1014
00:45:09,650 --> 00:45:11,630
dak li nistgħu jgħaddu tpartit minflok?

1015
00:45:11,630 --> 00:45:12,620
>> [INTERPOSING VOICES]

1016
00:45:12,620 --> 00:45:15,244
>> DAVID J. Malan: Għaliex ma we biss
tgħaddiha l-indirizzi, id-dritt?

1017
00:45:15,244 --> 00:45:17,470
Għaliex ma we tagħti swap ta '
Mappa teżor, jekk inti se,

1018
00:45:17,470 --> 00:45:20,950
li twassal lill-
x valuri attwali u y.

1019
00:45:20,950 --> 00:45:24,340
Ejja tpartit, attwalment ibiddlu
dawk bits oriġinali, aktar milli

1020
00:45:24,340 --> 00:45:26,797
biss tgħaddi kopji tal-bits.

1021
00:45:26,797 --> 00:45:29,130
U għalhekk, fil-fatt, dan huwa dak l
se tkun is-soluzzjoni.

1022
00:45:29,130 --> 00:45:31,899
Din il-verżjoni hawnhekk hija
bad b'mod ċar u difettuż.

1023
00:45:31,899 --> 00:45:35,190
U issa, ewwel daqqa t'għajn, hija biss jistenna
bħal aħna miżjud mazz ta 'stilel saltwarjament

1024
00:45:35,190 --> 00:45:37,106
u qasmu idejna
li hija kienet ser tiġbor.

1025
00:45:37,106 --> 00:45:38,460
Iżda, issa se tiġbor.

1026
00:45:38,460 --> 00:45:40,090
>> Imma ejja ara dak dawn l-affarijiet jfisser.

1027
00:45:40,090 --> 00:45:43,990
U, sfortunatament, l-awturi ta
C setgħet għażlet simbolu ieħor

1028
00:45:43,990 --> 00:45:46,380
biex jagħmlu dan ftit
aktar ċara, iżda l-operatur istilla

1029
00:45:46,380 --> 00:45:48,610
għandu tifsira differenti
żewġ kuntesti differenti.

1030
00:45:48,610 --> 00:45:50,890
U Rajna tnejn,
imma ejja jiddistingwu.

1031
00:45:50,890 --> 00:45:55,310
>> Allura fil-quċċata hemm,
meta I nbidlu u b

1032
00:45:55,310 --> 00:46:00,470
milli s Int fil-ħażin
Verżjoni li int stilla, A u B,

1033
00:46:00,470 --> 00:46:01,740
qabel, kienu interi.

1034
00:46:01,740 --> 00:46:05,752
Liema huma u b issa fil
il-tajba, verżjoni aħdar?

1035
00:46:05,752 --> 00:46:06,900
Huma qed indirizzi.

1036
00:46:06,900 --> 00:46:09,610
Indirizzi ta 'dak, tkun ċara?

1037
00:46:09,610 --> 00:46:10,770
Indirizzi tan-numri interi.

1038
00:46:10,770 --> 00:46:12,520
Allura l-fatt li jien
qal star int mezzi

1039
00:46:12,520 --> 00:46:15,440
dan huwa l-indirizz ta '
integer, b'mod speċifiku.

1040
00:46:15,440 --> 00:46:19,120
>> Allura issa avviż fil-linji ta 'kodiċi,
xi ħaġa oħra inbidlet wisq.

1041
00:46:19,120 --> 00:46:22,770
TMP jibqa l-istess, minħabba li
huwa biss l-eqreb numru sħiħ temporanju,

1042
00:46:22,770 --> 00:46:24,110
ebda magic memorja hemmhekk.

1043
00:46:24,110 --> 00:46:26,370
Iżda issa jeħtieġ stilla.

1044
00:46:26,370 --> 00:46:28,560
U, fil-fatt, kull
Referenzi oħra au b,

1045
00:46:28,560 --> 00:46:31,780
avviż li dak kollu li
bidla minn aħmar għal aħdar

1046
00:46:31,780 --> 00:46:34,209
hija li jien prefiss
dawk il-varjabbli ma stilla.

1047
00:46:34,209 --> 00:46:35,750
Minħabba Ma rridx li kopja u b.

1048
00:46:35,750 --> 00:46:40,350
Għaliex jekk I biss kopja aub u swap
au b, dak li jien attwalment iskambji?

1049
00:46:40,350 --> 00:46:43,760
Just indirizzi, nixtieq li tpartit
x'hemm fil dawk l-indirizzi.

1050
00:46:43,760 --> 00:46:44,860
Irrid immur hemmhekk.

1051
00:46:44,860 --> 00:46:48,000
U għalhekk l-operatur istilla
ġewwa tal-funzjoni tiegħi,

1052
00:46:48,000 --> 00:46:51,700
mhux ġewwa tal-lista parametru,
ifisser li inti tmur għall dawk l-indirizzi

1053
00:46:51,700 --> 00:46:54,490
u fil-fatt tinbidel dawk il-valuri.

1054
00:46:54,490 --> 00:46:56,500
>> Allura dak ma l-istampa
issa look like minflok.

1055
00:46:56,500 --> 00:47:03,250
Ukoll, jekk minflok jien tgħaddi
fl għal aub mhux 1 u 2--

1056
00:47:03,250 --> 00:47:05,790
I attwalment bżonn li jiżdiedu
definizzjoni ieħor hawn.

1057
00:47:05,790 --> 00:47:09,030
Allura jissoponi li dan chunk
tal-memorja huwa fil-post 10.

1058
00:47:09,030 --> 00:47:12,960
>> Dan huwa fil-post 11, iżda dan
huwa daqsxejn ta 'simplifikazzjoni,

1059
00:47:12,960 --> 00:47:18,900
I issa għandhom żewġ għażliet do I jgħaddu x
uy jew għandi jgħaddu indirizzi tagħhom?

1060
00:47:18,900 --> 00:47:22,500
Jekk I jgħaddu l-indirizzi tagħhom
bħal dan, I biss

1061
00:47:22,500 --> 00:47:25,390
issa jeħtieġ li jiġu implimentati
tpartit kull l-kodiċi aħdar

1062
00:47:25,390 --> 00:47:29,080
hekk li meta jara u meta
jara b, ma biss kopja aub

1063
00:47:29,080 --> 00:47:30,540
u jimxu l-ħalib u meraq tal-larinġ.

1064
00:47:30,540 --> 00:47:32,664
Il-ħalib u meraq tal-larinġ
metafora issa jieqaf jaħdem,

1065
00:47:32,664 --> 00:47:35,060
għaliex dawk huma cups
ta 'mapep likwidi u mhux.

1066
00:47:35,060 --> 00:47:37,750
Għandna minflok bżonn biex tmur
biex jindirizzaw 10 u aħna

1067
00:47:37,750 --> 00:47:42,420
bżonn biex tmur biex jindirizzaw 11, u
mbagħad iwettqu l-loġika iskambji.

1068
00:47:42,420 --> 00:47:45,580
>> Allura l-loġika hija l-istess, iżda
għandna bżonn b'mod xi ftit differenti

1069
00:47:45,580 --> 00:47:47,160
ta 'aċċess dawk il-varjabbli.

1070
00:47:47,160 --> 00:47:52,400
U hekk fl-aħħar, dak li l-
programm għandu jħares bħal hija din.

1071
00:47:52,400 --> 00:47:56,610
Fil swap.c litteralment kkupjata
u pasted l-verżjoni aħdar.

1072
00:47:56,610 --> 00:47:58,450
Imma I bżonn tagħmel bidla waħda.

1073
00:47:58,450 --> 00:48:00,180
Huwa mhux biżżejjed biss biex jibdlu tpartit.

1074
00:48:00,180 --> 00:48:03,830
Liema linja oħra tal-kodiċi
għandi bżonn għall-bidla?

1075
00:48:03,830 --> 00:48:04,330
Yeah?

1076
00:48:04,330 --> 00:48:05,770
>> UDJENZA: każ li tieħu l-argumenti.

1077
00:48:05,770 --> 00:48:07,603
>> DAVID J. Malan: Fejn
li tieħu argument tagħha.

1078
00:48:07,603 --> 00:48:09,985
Mela jekk jien iscroll sa prinċipali, I
tista 'mhux biss jgħaddu fil xuy,

1079
00:48:09,985 --> 00:48:12,820
u, I wegħda, l-aħħar
biċċa sintassi ġdida llum.

1080
00:48:12,820 --> 00:48:17,200
I bżonn li tgħaddi l f'mhux x u
y iżda l-indirizz ta 'x uy.

1081
00:48:17,200 --> 00:48:20,400
U jirriżulta li, is-simbolu
li l-awturi ta 'C għażel

1082
00:48:20,400 --> 00:48:23,860
huwa jekk inti tuża ampersand hawn, ma
tiġi konfuża mal-ampersand bitwise,

1083
00:48:23,860 --> 00:48:27,130
jekk tuża ampersand
hawn u ampersand hawn,

1084
00:48:27,130 --> 00:48:29,570
dan figuri fl għalik,
x'inhu l-indirizz ta 'x,

1085
00:48:29,570 --> 00:48:31,740
forsi huwa 10, x'inhu l-
indirizz ta 'y, forsi huwa

1086
00:48:31,740 --> 00:48:35,400
11, u tgħaddi dawk minflok.

1087
00:48:35,400 --> 00:48:37,210
>> Allura ħafna biex jassorbu kollha f'daqqa.

1088
00:48:37,210 --> 00:48:40,190
Imma ejja naraw issa malajr
erba tagħna minuti fadal

1089
00:48:40,190 --> 00:48:42,150
fejn l-affarijiet jistgħu jmorru awry.

1090
00:48:42,150 --> 00:48:45,120
U bħala twarrib, fil-fatt
I ħa din l-istampa,

1091
00:48:45,120 --> 00:48:46,920
TF ħa din l-istampa sena jew tnejn ilu.

1092
00:48:46,920 --> 00:48:49,190
Allura dan huwa l-kantuniera ta 'wara
tal Eliot Dining Hall.

1093
00:48:49,190 --> 00:48:52,310
Pointers huma forsi l-agħar
tema li aħna ikopru b'mod CS50.

1094
00:48:52,310 --> 00:48:54,810
Mela jekk inti inkwetati-xorta
ta 'inklinazzjoni huwa simili forsi huwa

1095
00:48:54,810 --> 00:48:56,770
aktar ta 'stick hockey
bħal dan, tirrealizza

1096
00:48:56,770 --> 00:49:00,160
aħna qed tip ta kważi quċċata fil
termini tal-kumplessità kunċettwali.

1097
00:49:00,160 --> 00:49:02,300
>> U jien tqajjem din
ritratt, minħabba I naħlef

1098
00:49:02,300 --> 00:49:05,920
li god, fil-ħarifa 1996, meta I ħa
CS50 ma sħabi tagħlim tiegħi,

1099
00:49:05,920 --> 00:49:09,620
Nishat Mehta, hu sib me isfel fil-
rokna tad-Eliot D. Hall waqt l-ikel,

1100
00:49:09,620 --> 00:49:12,330
jew pranzu, jew xi ħaġa biex tipprova
għinni jifhmu pointers.

1101
00:49:12,330 --> 00:49:16,520
U dan huwa fejn I kien ġimgħat wara
ġie introdott fl lecture meta

1102
00:49:16,520 --> 00:49:18,170
I finalment mifhum pointers.

1103
00:49:18,170 --> 00:49:20,590
U jien tama li din
se ikklikkja bogħod kmieni għalik.

1104
00:49:20,590 --> 00:49:23,540
Iżda jirrealizzaw dan assolutament fost
is-suġġetti aktar sofistikati

1105
00:49:23,540 --> 00:49:24,420
konna ħares lejn.

1106
00:49:24,420 --> 00:49:25,819
Imma hija fost l-aktar qawwija.

1107
00:49:25,819 --> 00:49:28,860
U meta inti ġġibu, huwa verament kollha
biss se finalment jiltaqgħu flimkien.

1108
00:49:28,860 --> 00:49:31,460
Allura mistrieħ assigurat li ma
jeħtieġ li sink kollha fl-lum.

1109
00:49:31,460 --> 00:49:32,980
>> Allura hawnhekk-aħħar programm
aħna qed tmur biex tħares lejn.

1110
00:49:32,980 --> 00:49:35,605
U aħna qed tmur biex jispiċċa bil-
malajr tliet minuti ta 'claymation

1111
00:49:35,605 --> 00:49:37,030
magħmula mill ħabib tagħna, Nick Parlante.

1112
00:49:37,030 --> 00:49:41,440
Hawn programm, li fuq il-quċċata żewġ
linji jiddikjara x uy varjabbli.

1113
00:49:41,440 --> 00:49:44,780
Tnejn li huma indirizzi
tan-numri interi, pointers AKA.

1114
00:49:44,780 --> 00:49:48,125
Aħna mbagħad jalloka biżżejjed
memorja biex taħżen l int

1115
00:49:48,125 --> 00:49:51,344
u jaħżnu l-indirizz
ta 'dik memorja fil x.

1116
00:49:51,344 --> 00:49:53,260
Għalhekk, huwa saħansitra aktar sempliċi
mill-eżempju qabel.

1117
00:49:53,260 --> 00:49:56,100
Agħti me erba 'bytes ta' memorja,
dak l-daqs ta 'int,

1118
00:49:56,100 --> 00:49:58,000
u li jitqiegħdu indirizz x.

1119
00:49:58,000 --> 00:50:01,070
Din il-linja hawnhekk tfisser
mur l-indirizz x

1120
00:50:01,070 --> 00:50:05,270
u tpoġġi l-tifsira ta '
ħajja, in-numru 42 hemmhekk.

1121
00:50:05,270 --> 00:50:07,710
Iżda din il-linja inkwiet me.

1122
00:50:07,710 --> 00:50:12,620
Star y ifisser mur l-indirizz fil-y,
u n-numru unlucky 13 hemmhekk.

1123
00:50:12,620 --> 00:50:15,780
Għaliex huwa perikoluż, f'dan il-punt
fil-story-- għalkemm qal malajr

1124
00:50:15,780 --> 00:50:17,980
fil-minuti waning tagħna
here-- għaliex hi ħażina

1125
00:50:17,980 --> 00:50:19,660
għalija li ngħid, mur l-indirizz y?

1126
00:50:19,660 --> 00:50:21,077
>> UDJENZA: Inti għandek mhux [inaudible].

1127
00:50:21,077 --> 00:50:22,910
DAVID J. Malan: I ma jkunux
jitqiegħdu xejn y.

1128
00:50:22,910 --> 00:50:25,520
Allura x'inhi l-valur tal y,
f'dan il-punt fl-istorja?

1129
00:50:25,520 --> 00:50:26,570
Għandna l-ebda idea.

1130
00:50:26,570 --> 00:50:29,190
Huwa xi valur żibel
u lanqas ma Binky taf.

1131
00:50:29,190 --> 00:50:32,532
Jekk nistgħu tispiċċa fil din in-nota.

1132
00:50:32,532 --> 00:50:34,832
>> [Daqq video]

1133
00:50:34,832 --> 00:50:36,500
>> -Hey, Binky, tqum.

1134
00:50:36,500 --> 00:50:39,140
Wasal iż-żmien għall-gost pointer.

1135
00:50:39,140 --> 00:50:40,210
>> -Dak X'inhu?

1136
00:50:40,210 --> 00:50:41,690
Tgħallem dwar pointers?

1137
00:50:41,690 --> 00:50:43,570
Oh, Goody.

1138
00:50:43,570 --> 00:50:46,600
>> Well, li tibda, I raden aħna qed
ser jeħtieġu koppja pointers.

1139
00:50:46,600 --> 00:50:47,380
>> -KOLLOX SEW.

1140
00:50:47,380 --> 00:50:51,120
Dan il-kodiċi jalloka żewġ pointers
li jista 'jiġbed l interi.

1141
00:50:51,120 --> 00:50:53,557
>> -OK, Sew nara l
żewġ pointers, iżda dawn

1142
00:50:53,557 --> 00:50:55,140
ma jidhirx li jkun tipponta lejn xi ħaġa.

1143
00:50:55,140 --> 00:50:55,970
>> -Li Dritt.

1144
00:50:55,970 --> 00:50:58,100
Inizjalment Pointers
ma jurux xejn.

1145
00:50:58,100 --> 00:51:00,950
L-affarijiet li jindikaw li huma
imsejħa pointees u meta dawn jitwaqqfu

1146
00:51:00,950 --> 00:51:02,330
huwa pass separat.

1147
00:51:02,330 --> 00:51:03,210
>> -OH, Id-dritt, id-dritt.

1148
00:51:03,210 --> 00:51:03,940
Jien kont naf li.

1149
00:51:03,940 --> 00:51:05,730
Il pointees huma separati.

1150
00:51:05,730 --> 00:51:08,310
Allura kif taħseb li jallokaw pointee?

1151
00:51:08,310 --> 00:51:11,960
>> -OK, Ukoll dan jalloka kodiċi
a pointee ġdid numru sħiħ,

1152
00:51:11,960 --> 00:51:15,050
u dan parti settijiet x punt lilha.

1153
00:51:15,050 --> 00:51:16,240
>> -Hey, Li jistenna aħjar.

1154
00:51:16,240 --> 00:51:17,743
Sabiex tagħmel dan jagħmlu xi ħaġa.

1155
00:51:17,743 --> 00:51:23,580
>> -OK, I ser dereference l pointer x biex
jaħżnu l-għadd 42 fis pointee tagħha.

1156
00:51:23,580 --> 00:51:27,130
Għal dan trick, I bzonn tiegħi
bastun maġiku ta dereferencing.

1157
00:51:27,130 --> 00:51:30,200
>> Bastun maġiku -Your ta dereferencing?

1158
00:51:30,200 --> 00:51:32,310
Uh, li, li l-kbir.

1159
00:51:32,310 --> 00:51:34,270
>> -Dan Huwa dak l-kodiċi Dehra.

1160
00:51:34,270 --> 00:51:35,970
I ser biss twaqqaf in-numru and--

1161
00:51:35,970 --> 00:51:37,070
>> [POP ĦOSS]

1162
00:51:37,070 --> 00:51:39,140
>> -Hey, Tħares hemm din tmur.

1163
00:51:39,140 --> 00:51:43,980
Allura, tagħmel dereference fuq x ġej
il-vleġġa għall-aċċess pointee tagħha.

1164
00:51:43,980 --> 00:51:46,150
F'dan il-każ, li jaħżen 42 fil hemmhekk.

1165
00:51:46,150 --> 00:51:50,700
Ħej, ipprova uża dan biex jaħżnu l-għadd
13 permezz tal-pointer oħra, y.

1166
00:51:50,700 --> 00:51:51,840
>> -KOLLOX SEW.

1167
00:51:51,840 --> 00:51:56,270
I ser biss jmorru fuq hawn biex y,
u jiksbu n-numru 13 set up.

1168
00:51:56,270 --> 00:52:00,380
U mbagħad ħu l-bastun tal
dereferencing u just--

1169
00:52:00,380 --> 00:52:01,646
>> [Buzzer ĦOSS]

1170
00:52:01,646 --> 00:52:04,080
>> -OH, Ħej li ma ma taħdimx.

1171
00:52:04,080 --> 00:52:06,470
Say, uh, Binky, jien ma
think dereferencing

1172
00:52:06,470 --> 00:52:10,850
y hija idea tajba, għaliex twaqqif
l-pointee huwa pass separat.

1173
00:52:10,850 --> 00:52:12,480
U jien ma naħsibx we qatt ma kien.

1174
00:52:12,480 --> 00:52:14,620
>> -Hmm, Punt tajjeb.

1175
00:52:14,620 --> 00:52:19,810
>> -Yeah, Aħna allokati l pointer, y, iżda
aħna qatt tistabbilixxi li juru li hemm pointee.

1176
00:52:19,810 --> 00:52:21,590
>> -Hmm, Attent ħafna.

1177
00:52:21,590 --> 00:52:23,215
-Hey, Qed tfittex tajba hemmhekk, Binky.

1178
00:52:23,215 --> 00:52:26,390
Inti tista 'tiffissa lilha sabiex il-punti y
l-istess pointee bħala x.

1179
00:52:26,390 --> 00:52:29,290
>> -Sure, I-użu bastun maġiku tiegħi
ta 'assenjazzjoni pointer.

1180
00:52:29,290 --> 00:52:31,970
>> -Il Li ser tkun
problema, bħal qabel?

1181
00:52:31,970 --> 00:52:33,790
>> -Nru, Dan ma tmissx il-pointees.

1182
00:52:33,790 --> 00:52:35,840
Hija biss bidliet pointer wieħed
għall-punt li l-istess thing--

1183
00:52:35,840 --> 00:52:36,465
>> [Popping ĦOSS]

1184
00:52:36,465 --> 00:52:37,450
--as ieħor.

1185
00:52:37,450 --> 00:52:38,440
>> -OH, Nara.

1186
00:52:38,440 --> 00:52:41,200
Issa punti y għall-istess post bħall x.

1187
00:52:41,200 --> 00:52:42,950
Allura, stenna, issa y hija ffissata.

1188
00:52:42,950 --> 00:52:44,110
Hija għandha pointee.

1189
00:52:44,110 --> 00:52:47,779
Allura inti tista 'tipprova l-bastun tal
dereferencing darb'oħra biex jibagħtu l-13 fuq.

1190
00:52:47,779 --> 00:52:51,110
>> -OH, OK, hawnhekk tmur.

1191
00:52:51,110 --> 00:52:52,330
>> -Hey, Tħares lejn dak.

1192
00:52:52,330 --> 00:52:53,570
Issa dereferencing xogħlijiet fuq y.

1193
00:52:53,570 --> 00:52:57,900
U minħabba l-pointers huma qsim
li pointee wieħed, tnejn jaraw il-13.

1194
00:52:57,900 --> 00:52:59,952
>> -Yeah, Qsim, uh, ikun x'ikun.

1195
00:52:59,952 --> 00:53:01,535
Allura, aħna se jaqilbu postijiet issa?

1196
00:53:01,535 --> 00:53:03,730
>> -OH, Tħares we qed barra ta 'żmien.

1197
00:53:03,730 --> 00:53:04,660
>> -But--

1198
00:53:04,660 --> 00:53:06,520
>> Just remember-tliet regoli pointer.

1199
00:53:06,520 --> 00:53:09,550
Numru 1, l-istruttura bażika
huwa li inti għandek pointer,

1200
00:53:09,550 --> 00:53:11,630
u punti fuq għal pointee.

1201
00:53:11,630 --> 00:53:13,740
Iżda l-pointer u
pointee huma separati.

1202
00:53:13,740 --> 00:53:15,620
U l-iżball komuni
huwa li jitwaqqaf indikatur

1203
00:53:15,620 --> 00:53:18,000
iżda li tinsa biex tagħtiha pointee.

1204
00:53:18,000 --> 00:53:21,170
>> Numru 2, dereferencing pointer
jibda fil-pointer

1205
00:53:21,170 --> 00:53:24,020
u jsegwi vleġġa tagħha fuq
għall-aċċess pointee tagħha.

1206
00:53:24,020 --> 00:53:27,815
Kif nafu lkoll, dan jaħdem biss jekk ikun hemm
huwa pointee, liema tip ta 'gets lura

1207
00:53:27,815 --> 00:53:29,260
li tiddeċiedi numru 1.

1208
00:53:29,260 --> 00:53:31,990
>> Numru 3, pointer
assenjazzjoni jieħu pointer waħda

1209
00:53:31,990 --> 00:53:35,330
u bidliet li għall-punt li l-
istess pointee bħal pointer ieħor.

1210
00:53:35,330 --> 00:53:37,150
Allura wara l-assenjazzjoni,
iż-żewġ pointers

1211
00:53:37,150 --> 00:53:40,927
se jindika l-istess pointee,
kultant li sejjaħ qsim.

1212
00:53:40,927 --> 00:53:42,510
U li kollox hemm għaliha, verament.

1213
00:53:42,510 --> 00:53:43,130
Bye-bye issa.

1214
00:53:43,130 --> 00:53:43,475
>> [END Daqq]

1215
00:53:43,475 --> 00:53:44,830
>> DAVID J. Malan: Li lilha għall CS50.

1216
00:53:44,830 --> 00:53:46,246
Grazzi għall-Professur Nick Parlante.

1217
00:53:46,246 --> 00:53:47,730
Aħna ser tara int ġimgħa d-dieħla.

1218
00:53:47,730 --> 00:53:51,706

1219
00:53:51,706 --> 00:53:56,435
>> [Daqq tal-mużika ELETTRONIKA]

1220
00:53:56,435 --> 00:57:22,775