1 00:00:00,000 --> 00:00:00,940 2 00:00:00,940 --> 00:00:05,440 >> [Daqq ta mużika] 3 00:00:05,440 --> 00:00:11,577 4 00:00:11,577 --> 00:00:12,660 DAVID J. Malan: Kull dritt. 5 00:00:12,660 --> 00:00:15,590 Dan huwa CS50, u dan huwa l-bidu ta 'ġimgħatejn. 6 00:00:15,590 --> 00:00:19,120 Mela ejjew tibda llum ma bug. 7 00:00:19,120 --> 00:00:20,974 A bug, naturalment, huwa żball fi programm, 8 00:00:20,974 --> 00:00:22,890 u int ser tingħata ħafna familjari ma 'dan il-kunċett 9 00:00:22,890 --> 00:00:26,050 jekk inti stajt qatt programmati qabel. pset0 u issa pset1. 10 00:00:26,050 --> 00:00:29,280 Imma ejja jikkunsidraw xi ħaġa sempliċi ftit fl-ewwel. 11 00:00:29,280 --> 00:00:32,189 Dan il-programm hawn li I threw flimkien bil-quddiem, 12 00:00:32,189 --> 00:00:37,280 u I jsostnu li dan għandu jistampa 10 istilel fuq il-iskrin bl-użu printf, 13 00:00:37,280 --> 00:00:41,020 imma hija apparentement Buggy b'xi mod. 14 00:00:41,020 --> 00:00:45,370 >> Minħabba li l-ispeċifikazzjoni li għandu jistampa istilel 10, 15 00:00:45,370 --> 00:00:50,230 iżda ma apparentement, liema kieku inti titlob hija l-bug? 16 00:00:50,230 --> 00:00:52,004 Yeah? 17 00:00:52,004 --> 00:00:54,420 Allura huwa off minn żball wieħed, u liema taħseb jfisser minn dak? 18 00:00:54,420 --> 00:01:00,991 19 00:01:00,991 --> 00:01:01,490 OK. 20 00:01:01,490 --> 00:01:09,820 21 00:01:09,820 --> 00:01:10,410 Eċċellenti. 22 00:01:10,410 --> 00:01:13,930 Allura aħna ve speċifikata bidu valur ta 'żero għall i, 23 00:01:13,930 --> 00:01:18,399 u konna speċifikati valur n ta '10, imma aħna ħadthom użati inqas minn jew ugwali għal. 24 00:01:18,399 --> 00:01:21,190 U r-raġuni li dan huwa żewġ karattri u mhux biss simbolu wieħed, 25 00:01:21,190 --> 00:01:22,630 bħal fi ktieb matematika, hija li inti ma għandekx 26 00:01:22,630 --> 00:01:24,880 mezz li jesprimu l- karattru ekwivalenti wieħed. 27 00:01:24,880 --> 00:01:28,450 >> Allura dan ifisser inqas minn, iżda jekk tibda għadd għal żero, 28 00:01:28,450 --> 00:01:31,690 imma inti jgħoddu it-triq kollha up permezz ta 'u ugwali għal 10, 29 00:01:31,690 --> 00:01:34,170 int naturalment se għadd 11 affarijiet b'kollox. 30 00:01:34,170 --> 00:01:35,900 U hekk int ser jistampaw 11 istilel. 31 00:01:35,900 --> 00:01:37,990 Allura dak li jista 'jkun jiffissaw għal dan? 32 00:01:37,990 --> 00:01:39,970 Yeah? 33 00:01:39,970 --> 00:01:43,980 >> Hekk biss taġġusta l-inqas minn jew daqs jkun biss inqas minn, 34 00:01:43,980 --> 00:01:46,250 u hemm, I jsostnu, forsi soluzzjoni oħra, wisq. 35 00:01:46,250 --> 00:01:47,210 Liema jista inkella inti tagħmel? 36 00:01:47,210 --> 00:01:48,590 Yeah? 37 00:01:48,590 --> 00:01:53,660 >> Allura tibda daqs li 1, u jħallu l-inqas minn jew ugwali għal. 38 00:01:53,660 --> 00:01:56,187 U franchement I ser jargumenta li, għal bniedem tipiku, 39 00:01:56,187 --> 00:01:57,770 dan huwa probabbilment aktar sempliċi. 40 00:01:57,770 --> 00:02:00,280 Ibda għadd f'1 u għadd up permezz 10. 41 00:02:00,280 --> 00:02:01,690 Essenzjalment tagħmel dak li jfisser. 42 00:02:01,690 --> 00:02:04,010 >> Iżda r-realtà hija fil- programmazzjoni, kif aħna stajt tidher, 43 00:02:04,010 --> 00:02:07,598 xjenzjati tal-kompjuter u programmaturi ġeneralment ma jibdew jingħaddu fuq iż-żero. 44 00:02:07,598 --> 00:02:09,389 U hekk li l-multa ladarba inti jidraw lilha. 45 00:02:09,389 --> 00:02:12,640 Kundizzjoni tiegħek se ġeneralment jkun xi ħaġa bħal inqas minn. 46 00:02:12,640 --> 00:02:14,910 Allura sempliċiment loġiku żball li nistgħu issa 47 00:02:14,910 --> 00:02:17,990 tiffissa u finalment recompile dan u tikseb biss 10. 48 00:02:17,990 --> 00:02:19,610 >> Ukoll kif dwar dan bug hawn? 49 00:02:19,610 --> 00:02:24,200 Hawnhekk, għal darb'oħra, I jsostnu li għandi għan ta 'l-istampar 10 stars-- 50 00:02:24,200 --> 00:02:28,140 waħda għal kull linja f'dan il-ħin, iżda ma. 51 00:02:28,140 --> 00:02:30,940 Qabel ma aħna tipproponi liema l-jiffissaw huwa, dak ma dan 52 00:02:30,940 --> 00:02:34,640 jistampaw viżwalment jekk kienu I biex jikkompilaw u run dan il-programm taħseb? 53 00:02:34,640 --> 00:02:35,140 Yeah? 54 00:02:35,140 --> 00:02:38,360 55 00:02:38,360 --> 00:02:38,860 >> Star. 56 00:02:38,860 --> 00:02:41,690 Allura l-istilel fuq il- istess linja huwa dak I smajt, 57 00:02:41,690 --> 00:02:43,391 u allura l-karattru linja ġdida. 58 00:02:43,391 --> 00:02:44,140 Mela ejja jippruvaw dan. 59 00:02:44,140 --> 00:02:48,710 Allura make-Buggy 1, jidħlu, u nara l-kmand clang 60 00:02:48,710 --> 00:02:50,090 li tkellimna dwar aħħar darba. 61 00:02:50,090 --> 00:02:55,180 ./buggy-1, u tabilħaqq nara kollha istilel 10 fuq l-istess linja anki jekk I pretensjoni 62 00:02:55,180 --> 00:02:58,690 fl-ispeċifikazzjoni tiegħi biss kumment atop il-kodiċi li I maħsuba biex tagħmel kull wieħed 63 00:02:58,690 --> 00:02:59,230 linja. 64 00:02:59,230 --> 00:03:00,580 Iżda dan jistenna d-dritt. 65 00:03:00,580 --> 00:03:04,620 >> Issa linja 15 jidher qisu jien istampar stilla, u mbagħad linja 16 66 00:03:04,620 --> 00:03:06,620 jidher qisu jien istampar karattru linja ġdida, 67 00:03:06,620 --> 00:03:09,560 u dawn qed kemm inċiża hekk Jien ġewwa tal-loop b'mod ċar. 68 00:03:09,560 --> 00:03:13,610 Allura mhux għandi tkun qiegħda tagħmel stilla, l-ġdida linja, star, linja ġdida, star, linja ġdida? 69 00:03:13,610 --> 00:03:14,110 Iva? 70 00:03:14,110 --> 00:03:18,430 71 00:03:18,430 --> 00:03:21,240 >> Yeah, b'differenza lingwa bħal Python, jekk int familjari, 72 00:03:21,240 --> 00:03:23,540 indentazzjoni ma kwistjoni għall-kompjuter. 73 00:03:23,540 --> 00:03:25,280 Hija biss kwistjonijiet lill-bniedem. 74 00:03:25,280 --> 00:03:29,860 Allura linji billi here stajt ivvintat 15 u 16-- li jistenna sbieħ, 75 00:03:29,860 --> 00:03:31,330 iżda l-kompjuter ma care. 76 00:03:31,330 --> 00:03:34,640 Il-kompjuter cares dwar attwalment jkollhom braces kaboċċi 77 00:03:34,640 --> 00:03:36,310 madwar dawn il-linji ta 'kodiċi. 78 00:03:36,310 --> 00:03:39,520 >> Allura li huwa clear-- eżatt bħal fil Scratch-- li dawn iż-żewġ linji ta 'kodiċi 79 00:03:39,520 --> 00:03:40,450 għandhom jiġu esegwiti. 80 00:03:40,450 --> 00:03:44,390 Bħal wieħed minn dawk puzzle Scratch isfar biċċiet ġdid u għal darb'oħra u għal darb'oħra. 81 00:03:44,390 --> 00:03:50,920 >> Allura issa mmexxija mill-ġdid jekk I dan program-- ./buggy-2-- Hm. 82 00:03:50,920 --> 00:03:51,770 I jkollhom żball issa. 83 00:03:51,770 --> 00:03:54,212 What did I tinsa tagħmel? 84 00:03:54,212 --> 00:03:55,420 Yeah, so I ma josservawha. 85 00:03:55,420 --> 00:03:56,740 Allura make-Buggy 2. 86 00:03:56,740 --> 00:03:59,840 Nru file tali minħabba I ma attwalment jikkompilaw-tieni verżjoni. 87 00:03:59,840 --> 00:04:04,860 Allura issa interessanti mhux iddikjarat variable-- mhux 2. 88 00:04:04,860 --> 00:04:05,510 Aħna qed tagħmel 1. 89 00:04:05,510 --> 00:04:11,050 Jagħmlu Buggy-1---./buggy 1-- u issa kull wieħed minnhom huwa fuq l-istess linja. 90 00:04:11,050 --> 00:04:13,880 >> Issa hemm eċċezzjoni għal dan suppost pretensjoni ta 'minjiera 91 00:04:13,880 --> 00:04:15,520 li għandek bżonn dawn ċingi kaboċċi. 92 00:04:15,520 --> 00:04:20,160 Meta huwa attwalment OK-- jekk inti stajt innotati fis-sezzjoni jew textbooks-- 93 00:04:20,160 --> 00:04:22,130 li jħalli barra l-braces kaboċċi? 94 00:04:22,130 --> 00:04:22,630 Yeah? 95 00:04:22,630 --> 00:04:26,290 96 00:04:26,290 --> 00:04:26,870 >> Eżattament. 97 00:04:26,870 --> 00:04:28,940 Meta jkun hemm biss wieħed linja tal-kodiċi li inti 98 00:04:28,940 --> 00:04:32,830 jridu jkunu assoċjati mal- loop bħal fl-ewwel eżempju tagħna. 99 00:04:32,830 --> 00:04:36,380 Huwa perfettament leġittimu li jħalli barra l-braces kaboċċi 100 00:04:36,380 --> 00:04:40,310 biss bħala tip ta 'konvenjenza mill-kompilatur lilek. 101 00:04:40,310 --> 00:04:40,810 Yeah? 102 00:04:40,810 --> 00:04:43,347 103 00:04:43,347 --> 00:04:43,930 Mistoqsija tajba. 104 00:04:43,930 --> 00:04:45,500 Ikun jitqies bħala żball stil? 105 00:04:45,500 --> 00:04:49,340 Nixtiequ promote-- bħal fil CS50 Gwida tal-Istil, il-URL li għalih 106 00:04:49,340 --> 00:04:51,926 huwa pset1-- li dejjem tuża l-braces kaboċċi. 107 00:04:51,926 --> 00:04:53,550 Ċertament jekk int ġodda għall-ipprogrammar. 108 00:04:53,550 --> 00:04:56,800 Ir-realtà hija aħna mhux qed ser jipprojbixxu lilek 109 00:04:56,800 --> 00:04:58,680 milli jagħmlu dawn latrini. 110 00:04:58,680 --> 00:05:00,846 Imma jekk int biss jkollna fil-swing ta 'affarijiet, 111 00:05:00,846 --> 00:05:04,020 assolutament biss dejjem jużaw l-kaboċċi ċingi sakemm ikollok l-hang minnha. 112 00:05:04,020 --> 00:05:04,640 Mistoqsija tajba. 113 00:05:04,640 --> 00:05:05,320 >> Kull dritt. 114 00:05:05,320 --> 00:05:07,660 Allura li mbagħad kienet bug. 115 00:05:07,660 --> 00:05:09,190 Mill-inqas xi ħaġa pjuttost sempliċi. 116 00:05:09,190 --> 00:05:11,260 And yet inti tista 'taħseb dan huwa pjuttost rudimentali, id-dritt? 117 00:05:11,260 --> 00:05:13,635 Dan huwa tip ta 'l-ewwel ġimgħa tħares lejn il-lingwa 118 00:05:13,635 --> 00:05:14,890 bħal, ara bugs tiegħek hemmhekk. 119 00:05:14,890 --> 00:05:17,250 Iżda r-realtà dawn huma attwalment rappreżentant 120 00:05:17,250 --> 00:05:20,310 ta 'xi problemi pretty biża li jistgħu jinqalgħu fid-dinja reali. 121 00:05:20,310 --> 00:05:23,530 >> Allura xi wħud minnkom tista 'recall jekk inti ssegwi aħbarijiet tech, 122 00:05:23,530 --> 00:05:25,740 jew forsi anke maqbuda riħ ta 'dan fi Frar 123 00:05:25,740 --> 00:05:29,434 ta 'din is-sena passat li Apple kellha magħmula daqsxejn ta 'żball fiż-żewġ IOS, 124 00:05:29,434 --> 00:05:31,350 is-sistema operattiva fuq mowbajls tagħhom, u wkoll 125 00:05:31,350 --> 00:05:34,220 Mac OS, is-sistema operattiva fuq desktops tagħhom u laptops. 126 00:05:34,220 --> 00:05:36,480 U inti raw dawn aħbarijiet bħal dan. 127 00:05:36,480 --> 00:05:41,120 U wara dan, Apple wiegħed li jiffissaw dan bug, 128 00:05:41,120 --> 00:05:45,950 u malajr ħafna ma tiffissa lilha fil IOS, iżda mbagħad finalment iffissat fil Mac OS 129 00:05:45,950 --> 00:05:46,810 kif ukoll. 130 00:05:46,810 --> 00:05:50,370 >> Issa ebda waħda minn dawn aħbarijiet waħdu verament jiżvelaw x'inhi l-problema sottostanti kienet, 131 00:05:50,370 --> 00:05:55,640 iżda l-bug kien finalment imnaqqas għal bug fil SSL, saff sockets siguri. 132 00:05:55,640 --> 00:05:57,390 U l-istorja twila fil-qosor, dan huwa l-software 133 00:05:57,390 --> 00:06:01,030 li browsers tagħna u oħrajn softwer użat biex jagħmlu dak? 134 00:06:01,030 --> 00:06:04,090 135 00:06:04,090 --> 00:06:06,860 >> Jekk I qal li SSL huwa involuti, kull meta inti 136 00:06:06,860 --> 00:06:13,920 żur URL li jibda bil HTTPS, X'inhu allura jista SSL jkunu relatati mal? 137 00:06:13,920 --> 00:06:14,580 Encryption. 138 00:06:14,580 --> 00:06:16,470 Allura aħna ser nitkellmu dwar dan fil-jiem li ġejjin. 139 00:06:16,470 --> 00:06:18,750 Encryption, l-arti tal- scrambling informazzjoni. 140 00:06:18,750 --> 00:06:22,200 >> Iżda l-istorja twila fil-qosor, Apple f'xi ilu kienet għamlet żball 141 00:06:22,200 --> 00:06:25,970 fl-implimentazzjoni tagħhom tal SSL, l- software li finalment timplimenta 142 00:06:25,970 --> 00:06:30,120 URLs bħal HTTPS jew max Konnessjonijiet hemm wisq. 143 00:06:30,120 --> 00:06:32,850 Ir-riżultat ta 'liema huwa li tiegħek konnessjonijiet jistgħu potenzjalment 144 00:06:32,850 --> 00:06:33,920 jiġu interċettati. 145 00:06:33,920 --> 00:06:37,130 U l-konnessjonijiet tiegħek kienu mhux neċessarjament encrypted 146 00:06:37,130 --> 00:06:40,350 jekk kellek xi Guy ħażina fl bejn inti u l-website destinazzjoni li 147 00:06:40,350 --> 00:06:42,170 kien jaf kif tieħu vantaġġ ta 'dan. 148 00:06:42,170 --> 00:06:45,090 >> Issa Apple finalment stazzjonati a jiffissaw għal dan finalment, 149 00:06:45,090 --> 00:06:46,920 u d-deskrizzjoni tal jiffissaw tagħhom kienet din. 150 00:06:46,920 --> 00:06:49,878 Trasport Secure naqas milli jivvalidaw l-awtentiċità tal-konnessjoni. 151 00:06:49,878 --> 00:06:52,920 Il-kwistjoni ġiet indirizzata mill- restawr nieqsa passi validazzjoni. 152 00:06:52,920 --> 00:06:57,250 >> Allura dan huwa spjegazzjoni immewġin ħafna idejn għal sempliċiment tgħid li aħna invitat up. 153 00:06:57,250 --> 00:07:00,920 Hemm litteralment wieħed linja ta 'kodiċi li kien Buggy 154 00:07:00,920 --> 00:07:05,130 fl-implimentazzjoni tagħhom tal-SSL, u jekk inti tmur online u tfittxija għal dan 155 00:07:05,130 --> 00:07:07,210 inti tista 'attwalment issib il-kodiċi tas-sors oriġinali. 156 00:07:07,210 --> 00:07:11,960 Per eżempju, dan huwa maqtul screen ta biss porzjon ta 'fajl pjuttost kbir, 157 00:07:11,960 --> 00:07:15,965 iżda dan huwa funzjoni apparentement imsejjaħ SSL jivverifika server sinjal iskambju ċavetta. 158 00:07:15,965 --> 00:07:17,840 U li tieħu mazz ta ' argumenti u inputs. 159 00:07:17,840 --> 00:07:20,298 U aħna mhux qed tmur biex tiffoka wisq fuq il-minutia hemmhekk, 160 00:07:20,298 --> 00:07:24,390 imma jekk inti tiffoka fuq il-kodiċi ġewwa ta 'dak topmost function-- ejja 161 00:07:24,390 --> 00:07:25,590 zoom fl fuq dak. 162 00:07:25,590 --> 00:07:28,140 Inti tista 'diġà suspett dak l-iżball jista 163 00:07:28,140 --> 00:07:31,230 jkun saħansitra jekk ma jkollok ebda idea finalment dak li qed tfittex fuq. 164 00:07:31,230 --> 00:07:35,924 Hemm tip ta 'anomalija hawnhekk, li huwa dak? 165 00:07:35,924 --> 00:07:38,940 >> Yeah, I ma verament simili il-ħarsa ta 'żewġ goto jonqos. 166 00:07:38,940 --> 00:07:42,060 Franchement, I ma verament jafu liema goto jonqsu mezzi, iżda li tnejn minnhom 167 00:07:42,060 --> 00:07:42,810 lura lura. 168 00:07:42,810 --> 00:07:45,290 Li biss tip ta 'rubs me intellettwalment il-mod żbaljat, 169 00:07:45,290 --> 00:07:48,910 u tabilħaqq jekk aħna zoom fl fuq biss dawk il-linji, dan huwa C. 170 00:07:48,910 --> 00:07:52,220 >> Allura ħafna ta 'kodiċi Apple hija nnifisha miktub fl C, 171 00:07:52,220 --> 00:07:55,780 u dan apparentement huwa verament equivalent-- 172 00:07:55,780 --> 00:07:59,060 mhux għal dik indentazzjoni pretty verżjoni, iżda jekk inti tirrikonoxxi l-fatt 173 00:07:59,060 --> 00:08:02,560 li hemm ebda ċingi kaboċċi, liema Apple verament kiteb kien kodiċi li jistenna 174 00:08:02,560 --> 00:08:03,540 bħal dan. 175 00:08:03,540 --> 00:08:07,080 So I ve żżomjati out u I biss stabbilixxa l-indentazzjoni fis-sens 176 00:08:07,080 --> 00:08:10,690 li jekk hemm l-ebda ċingi kaboċċi, li tieni goto jonqsu li fil isfar 177 00:08:10,690 --> 00:08:12,500 se tesegwixxi x'ikun. 178 00:08:12,500 --> 00:08:15,540 Huwa mhux assoċjat mal l-jekk il-kundizzjoni hawn fuq. 179 00:08:15,540 --> 00:08:19,590 >> Għalhekk anki darb'oħra, jekk inti ma pjuttost jifhmu dak li dan jista 'possibilment 180 00:08:19,590 --> 00:08:23,230 tkun qiegħda tagħmel, jafu li kull wieħed minn dawn conditions-- kull wieħed minn dawn il-linji 181 00:08:23,230 --> 00:08:26,180 huwa pass importanti ħafna fil-proċess ta 'verifika 182 00:08:26,180 --> 00:08:28,350 jekk id-data tiegħek huwa fil-fatt encrypted. 183 00:08:28,350 --> 00:08:31,710 Allura taqbeż is-site waħda minn dawn passi, mhux l-aħjar idea. 184 00:08:31,710 --> 00:08:34,840 >> Iżda għaliex għandna dan tieni goto jonqsu fl-isfar, 185 00:08:34,840 --> 00:08:36,840 u minħabba li ladarba aħna tip ta 'estetikament 186 00:08:36,840 --> 00:08:40,480 jġorrhom lejn ix-xellug fejn loġikament huwa fil-mument, liema 187 00:08:40,480 --> 00:08:43,230 jfisser dan għall-linja tal-kodiċi taħt dak it-tieni goto 188 00:08:43,230 --> 00:08:46,480 jonqsu kieku inti taħseb? 189 00:08:46,480 --> 00:08:48,860 Huwa dejjem se tkun skipped. 190 00:08:48,860 --> 00:08:52,100 Allura gotos huma ġeneralment frowned fuq għal raġunijiet aħna mhux se verament jmorru fi, 191 00:08:52,100 --> 00:08:54,940 u tabilħaqq fil CS50 għandna t-tendenza ma biex jgħallmu dan Goto dikjarazzjoni, 192 00:08:54,940 --> 00:08:58,130 imma int tista 'taħseb goto jonqsu fis-sens go jaqbżu 193 00:08:58,130 --> 00:08:59,600 ma 'xi parti oħra tal-kodiċi. 194 00:08:59,600 --> 00:09:03,120 >> Fi kliem ieħor jaqbżu fuq dan l-aħħar linja għal kollox, 195 00:09:03,120 --> 00:09:07,420 u għalhekk ir-riżultat ta 'din stupid żball sempliċi li kien biss 196 00:09:07,420 --> 00:09:10,330 riżultat ta 'xi ħadd probabbilment ikkupjar u pasta wieħed wisq 197 00:09:10,330 --> 00:09:14,150 ħafna drabi kienet li l-kollu sigurtà tal-IOS u Mac OS 198 00:09:14,150 --> 00:09:18,240 kien vulnerabbli għall-interċettazzjoni billi guys ħżiena għal żmien pjuttost twil. 199 00:09:18,240 --> 00:09:19,940 Sakemm Apple finalment fiss dan. 200 00:09:19,940 --> 00:09:23,100 >> Issa jekk xi wħud minnkom huma attwalment running verżjonijiet qodma ta 'IOS jew Mac OS, 201 00:09:23,100 --> 00:09:27,250 inti tista 'tmur gotofail.com li hija website li xi ħadd imwaqqaf 202 00:09:27,250 --> 00:09:29,190 biex jiddeterminaw essenzjalment programmatically 203 00:09:29,190 --> 00:09:30,980 jekk il-kompjuter tiegħek għadu vulnerabbli. 204 00:09:30,980 --> 00:09:33,600 U franchement, jekk huwa, huwa probabbilment idea tajba 205 00:09:33,600 --> 00:09:36,870 biex taġġorna telefon tiegħek jew Mac tiegħek f'dan il-punt. 206 00:09:36,870 --> 00:09:40,120 Iżda hemm, biss xhieda kemm apprezzament ta 'dawn f'livell aktar baxx 207 00:09:40,120 --> 00:09:42,400 dettalji u ġust ideat sempliċi tista 'verament 208 00:09:42,400 --> 00:09:44,590 jissarraf deċiżjonijiet u problemi li 209 00:09:44,590 --> 00:09:47,320 affected-- f'dan case-- miljuni ta 'nies. 210 00:09:47,320 --> 00:09:49,107 >> Issa kelma fuq l-amministrazzjoni. 211 00:09:49,107 --> 00:09:50,690 Taqsima se tibda dan il-Ħadd li ġejjin. 212 00:09:50,690 --> 00:09:53,360 Inti ser tirċievi email mill- weekend dwar taqsima, f'liema punt 213 00:09:53,360 --> 00:09:55,290 il-proċess resectioning se tibda jekk inti stajt 214 00:09:55,290 --> 00:09:56,998 realizzati issa għandek xi kunflitti ġodda. 215 00:09:56,998 --> 00:10:00,180 Allura dan jiġri kull sena, u aħna se jakkomodaw fil-jiem li ġejjin. 216 00:10:00,180 --> 00:10:02,430 >> Uffiċċju hours-- do żżomm għajnejk fuq din l-iskeda hawn. 217 00:10:02,430 --> 00:10:05,100 Bidliet ftit din il-ġimgħa, partikolarment il-ħin tal-bidu 218 00:10:05,100 --> 00:10:08,180 u l-post, hekk do jikkonsulta li qabel l-intestatura għall ħinijiet tal-uffiċċju 219 00:10:08,180 --> 00:10:09,520 kwalunkwe mill-erba 'iljieli li jmiss. 220 00:10:09,520 --> 00:10:12,680 U issa kelma dwar il-valutazzjoni, partikolarment kif inti adsa fis-problema 221 00:10:12,680 --> 00:10:14,350 settijiet wieħed u lil hinn. 222 00:10:14,350 --> 00:10:17,070 >> Allura kull l-ispeċifikazzjoni, dawn huma ġeneralment 223 00:10:17,070 --> 00:10:20,360 l-assi flimkien li aħna jivvalutaw ix-xogħol tiegħek. 224 00:10:20,360 --> 00:10:23,170 Ambitu tirreferi għal dak estent timplimenta kodiċi tiegħek 225 00:10:23,170 --> 00:10:25,690 il-karatteristiċi meħtieġa bi speċifikazzjoni tagħna. 226 00:10:25,690 --> 00:10:28,290 Fi kliem ieħor, kemm ta ' sett biċċa ma inti gidma off. 227 00:10:28,290 --> 00:10:30,440 Ridt tagħmel terz ta 'dan, nofs ta 'dan, 100% ta' dan. 228 00:10:30,440 --> 00:10:33,000 Anki jekk mhuwiex korrett, kemm ma inti tipprova? 229 00:10:33,000 --> 00:10:35,290 Allura li jaqbad l-livell tal-isforz u l-ammont 230 00:10:35,290 --> 00:10:38,260 li inti daqsxejn off l- problemi sett problema'S. 231 00:10:38,260 --> 00:10:40,690 >> Correctness-- dan wieħed, li liema punt, huwa kodiċi tiegħek 232 00:10:40,690 --> 00:10:43,150 konsistenti mal tagħna ispeċifikazzjonijiet u ħielsa minn bugs. 233 00:10:43,150 --> 00:10:44,770 Allura taħdem b'mod korrett? 234 00:10:44,770 --> 00:10:48,700 Jekk aħna jagħtuh xi input, ma tagħtina l-output li nistennew? 235 00:10:48,700 --> 00:10:52,570 Design-- issa dan huwa l-ewwel ta ' dawk partikolarment kwalitattivi, 236 00:10:52,570 --> 00:10:56,180 jew dawk li jeħtieġu ġudizzju uman. 237 00:10:56,180 --> 00:10:59,690 U fil-fatt, dan huwa għaliex għandna persunal ta 'hekk ħafna fellows tagħlim u kors 238 00:10:59,690 --> 00:11:00,350 assistenti. 239 00:11:00,350 --> 00:11:03,480 Sa liema punt huwa tiegħek kodiċi miktub tajjeb? 240 00:11:03,480 --> 00:11:05,810 >> U għal darb'oħra dan huwa ħafna valutazzjoni kwalitattiva 241 00:11:05,810 --> 00:11:09,100 li se jaħdmu miegħek fuq bi-direzzjonalment fil-ġimgħat li ġejjin. 242 00:11:09,100 --> 00:11:12,060 Allura li meta ikollok ma biss punteġġi numeriċi, iżda wkoll 243 00:11:12,060 --> 00:11:16,682 punteġġi miktub, jew feedback ittajpjat, jew feedback bil-miktub fi kliem Ingliż. 244 00:11:16,682 --> 00:11:19,640 Dak hu li aħna ser tuża biex issuq int lejn attwalment kitba kodiċi aħjar. 245 00:11:19,640 --> 00:11:23,320 U fil lecture u t-taqsima, aħna ser nippruvaw għall-punt out-- spiss kemm aħna can-- 246 00:11:23,320 --> 00:11:26,420 dak li jagħmel programm mhux biss korretta u funzjonalment tajba, 247 00:11:26,420 --> 00:11:28,200 iżda wkoll mfassla tajjeb. 248 00:11:28,200 --> 00:11:31,850 L-aktar effiċjenti jista 'jkun, jew anke l-aktar sbieħ jista 'jkun. 249 00:11:31,850 --> 00:11:33,100 >> Li twassalna għall-istil. 250 00:11:33,100 --> 00:11:36,876 Style finalment, huwa sentenza estetika. 251 00:11:36,876 --> 00:11:38,750 Ridt tagħżel tajba ismijiet għal varjabbli tiegħek? 252 00:11:38,750 --> 00:11:40,330 Have you inċiża kodiċi tiegħek kif suppost? 253 00:11:40,330 --> 00:11:44,010 Ma ħarsa tajba, u għalhekk, huwa faċli għall-bniedem ieħor 254 00:11:44,010 --> 00:11:46,550 biex taqra rispettiv tiegħek ta 'korrettezza tagħha. 255 00:11:46,550 --> 00:11:50,300 >> Issa ġeneralment per-sillabu, aħna punteġġ dawn l-affarijiet fuq skala punt ħamsa. 256 00:11:50,300 --> 00:11:53,640 U let me martell dar il-punt li tlieta huwa tabilħaqq tajba. 257 00:11:53,640 --> 00:11:55,550 Malajr ħafna do folks tibda tagħmel aritmetika. 258 00:11:55,550 --> 00:11:58,133 Meta huma jiksbu tlieta minn hamsa fuq korrettezza għal xi pset 259 00:11:58,133 --> 00:12:02,040 u jaħsbu kkritikat, I se 60% li huwa essenzjalment D jew E. 260 00:12:02,040 --> 00:12:03,980 >> Li mhux il-mod aħna think ta 'dawn in-numri. 261 00:12:03,980 --> 00:12:06,880 A tliet huwa tabilħaqq tajba, u dak li aħna ġeneralment jistennew fil-bidu 262 00:12:06,880 --> 00:12:09,820 tat-terminu hija li jekk int jkollna mazz ta three's-- forsi koppja 263 00:12:09,820 --> 00:12:12,540 ta 'fieri, koppja ta' fours-- jew ftit twos koppja, koppja ta 'fours-- 264 00:12:12,540 --> 00:12:13,748 li l-post tajjeb biex tibda. 265 00:12:13,748 --> 00:12:16,320 U sakemm naraw trajettorja fuq matul iż-żmien, 266 00:12:16,320 --> 00:12:18,540 int f'post partikolarment tajba. 267 00:12:18,540 --> 00:12:20,752 >> Il-formula nużaw biex affarijiet piż huwa essenzjalment 268 00:12:20,752 --> 00:12:22,710 dan per-sillabu, li ifisser biss li aħna 269 00:12:22,710 --> 00:12:24,750 jagħtu aktar piż lill korrettezza. 270 00:12:24,750 --> 00:12:27,930 Għaliex dan huwa ħafna drabi korrettezza li tieħu l-ħin l-aktar. 271 00:12:27,930 --> 00:12:28,760 Trust me issa. 272 00:12:28,760 --> 00:12:31,190 Inti se find-- inqas fil pset-- wieħed li inti 273 00:12:31,190 --> 00:12:36,790 jonfqu 90% tal-ħin tiegħek taħdem fuq 10% tal-problema. 274 00:12:36,790 --> 00:12:39,320 >> U kollox tip ta 'xogħlijiet ħlief għal wieħed jew tnejn bugs, 275 00:12:39,320 --> 00:12:41,570 u dawk huma l-bugs li inti żżomm up tard bil-lejl. 276 00:12:41,570 --> 00:12:43,380 Dawk huma dawk li tip ta 'ħarba inti. 277 00:12:43,380 --> 00:12:45,560 Iżda wara irqad fuqha, jew li jattendu ħinijiet tal-uffiċċju 278 00:12:45,560 --> 00:12:48,844 jew tistaqsi mistoqsijiet online, huwa meta ikollok biex din il-mira ta '100%, 279 00:12:48,844 --> 00:12:50,760 u huwa għalhekk li għandna piż Korrettezza l-aktar. 280 00:12:50,760 --> 00:12:54,102 Disinn ta 'ftit inqas, u stil ftit inqas minn dik. 281 00:12:54,102 --> 00:12:56,060 Iżda jżomm fl-istil mind-- huwa forsi l-eħfef 282 00:12:56,060 --> 00:12:58,890 minn dawn li gidma off kif fis-Gwida tal-Istil. 283 00:12:58,890 --> 00:13:01,580 >> U issa, aktar serja nota dwar onestà akkademika. 284 00:13:01,580 --> 00:13:05,000 CS50 għandha d-distinzjoni sfortunati ta ' huma l-akbar produttur ta 'Ad Bord 285 00:13:05,000 --> 00:13:07,330 każijiet kważi kull sena storikament. 286 00:13:07,330 --> 00:13:11,012 Dan mhux minħabba l-istudenti iqarrqu fil CS50 kwalunkwe aktar minn kull klassi oħra, 287 00:13:11,012 --> 00:13:13,720 iżda minħabba min-natura tax-xogħol, il-fatt li huwa elettronika, 288 00:13:13,720 --> 00:13:16,636 il-fatt li aħna tfittex għal dan, u il-fatt aħna xjenzjati tal-kompjuter, 289 00:13:16,636 --> 00:13:20,570 Nista 'ngħid aħna sfortunatament tajba ħafna lejn is-sejbien dan. 290 00:13:20,570 --> 00:13:22,710 >> Allura dak li jfisser dan f'termini reali? 291 00:13:22,710 --> 00:13:24,820 Għalhekk, per-sillabu, filosofija tal-kors tal- 292 00:13:24,820 --> 00:13:28,090 verament ma jsarrafx biss fl raġonevoli. 293 00:13:28,090 --> 00:13:31,684 Hemm din il-linja bejn tagħmel xogħol wieħed fuq tiegħek 294 00:13:31,684 --> 00:13:34,100 u jkollna xi ftit ta ' għajnuna raġonevoli minn ħabib, 295 00:13:34,100 --> 00:13:38,020 u outright tagħmel li x-xogħol għall tiegħek ħabib, jew jibgħat lilu jew lilha kodiċi tiegħek 296 00:13:38,020 --> 00:13:41,080 sabiex hu jew hi tista 'sempliċement tieħu jew tissellef out dritt. 297 00:13:41,080 --> 00:13:43,580 U li jaqsam il-linja li aħna mfassla fil-klassi. 298 00:13:43,580 --> 00:13:45,410 >> Ara, il-sillabu finalment għal-linji 299 00:13:45,410 --> 00:13:48,209 li aħna tiġbed bħala raġonevoli u l-imġieba irraġonevoli, 300 00:13:48,209 --> 00:13:50,000 imma verament ma għalli isfel għall-essenza 301 00:13:50,000 --> 00:13:53,980 tax-xogħol tiegħek bżonn li jkun tiegħek stess fl-aħħar. 302 00:13:53,980 --> 00:13:56,230 Issa ma 'dak imsemmi, hemm heuristic. 303 00:13:56,230 --> 00:13:58,980 Għaliex kif inti tista imagine-- minn ħinijiet tal-uffiċċju u l-visuals 304 00:13:58,980 --> 00:14:01,060 u l-videos konna muri CS50 b'hekk far-- 305 00:14:01,060 --> 00:14:04,530 tabilħaqq maħsub li jkun bħala kollaborattiv u bħala kooperattiva u bħala soċjali 306 00:14:04,530 --> 00:14:06,450 kemm jista 'jkun. 307 00:14:06,450 --> 00:14:08,570 Kif kollaborattiv kif inhi rigoruża. 308 00:14:08,570 --> 00:14:11,314 >> Iżda ma 'dan qal, il-heuristic, kif tkun taf tara fil-sillabu, 309 00:14:11,314 --> 00:14:12,980 hija li meta int wara xi problema. 310 00:14:12,980 --> 00:14:16,470 Inti għandek xi bug fil-kodiċi tiegħek li inti ma tistax issolvi, huwa raġonevoli għalik 311 00:14:16,470 --> 00:14:18,039 biex juru kodiċi tiegħek lil xi ħadd ieħor. 312 00:14:18,039 --> 00:14:21,080 Ħabib anke fil-klassi, ħabib seduta li jmiss lilek fil-ħinijiet tal-uffiċċju, 313 00:14:21,080 --> 00:14:22,680 jew membru tal-persunal. 314 00:14:22,680 --> 00:14:25,810 Iżda huma ma jistgħux juru kodiċi tagħhom lilek. 315 00:14:25,810 --> 00:14:27,710 >> Fi kliem ieħor, l- iwieġeb għall question-- tiegħek 316 00:14:27,710 --> 00:14:29,940 I bżonn help-- mhix oh, hawnhekk kodiċi tiegħi. 317 00:14:29,940 --> 00:14:32,440 Agħti ħarsa lejn dan u dedott minnha dak li inti se. 318 00:14:32,440 --> 00:14:34,580 Issa, naturalment, hemm mod ċar għall-kaċċa 319 00:14:34,580 --> 00:14:37,760 din is-sistema li biha I ser nuruk kodiċi tiegħi qabel ma kwistjoni. 320 00:14:37,760 --> 00:14:40,150 You urini tiegħi kodiċi tiegħek qabel li jkollhom mistoqsija. 321 00:14:40,150 --> 00:14:45,870 Iżda tara l-sillabu ġdid għall- dettalji ifjen ta 'fejn din il-linja huwa. 322 00:14:45,870 --> 00:14:50,606 >> Just biex issa żebgħa l-istampa u l- jaqsmu kemm trasparenti kemm jista 'jkun 323 00:14:50,606 --> 00:14:53,480 fejn ninsabu fil fis-snin riċenti, dan huwa n-numru ta 'każijiet Ad Bord 324 00:14:53,480 --> 00:14:56,260 li CS50 kellu matul l-aħħar seba 'snin. 325 00:14:56,260 --> 00:14:58,717 Ma '14-il każ dan it-tnaqqis l-aktar riċenti. 326 00:14:58,717 --> 00:15:01,300 F'termini ta 'l-istudenti involuti, kien 20 xi studenti fard 327 00:15:01,300 --> 00:15:02,490 dan it-tnaqqis fil-passat. 328 00:15:02,490 --> 00:15:05,670 Intlaħqet quċċata ta '33 istudenti xi snin ilu. 329 00:15:05,670 --> 00:15:08,830 Ħafna minnhom huma sfortunatament m'għadhomx hawn fuq il-kampus. 330 00:15:08,830 --> 00:15:13,100 >> Studenti involuti bħala perċentwali tal- klassi storikament kienu jvarjaw minn 0% 331 00:15:13,100 --> 00:15:17,300 għal 5.3%, li huwa biss li jgħidu dan huwa kull sena sfida. 332 00:15:17,300 --> 00:15:20,390 U lejn dak il-għan, liema li rridu nagħmlu hu twassal wieħed 333 00:15:20,390 --> 00:15:24,310 li aħna dd-- biss FYI-- tqabbel fuq a ekwità lil dawk l-istudenti li 334 00:15:24,310 --> 00:15:26,520 Dawn li ġejjin huma l-linja kif xieraq. 335 00:15:26,520 --> 00:15:29,620 We do jqabblu attwali kollha sottomissjonijiet kontra-missjonijiet kollha tal-passat 336 00:15:29,620 --> 00:15:30,840 mill-ħafna snin li għaddew. 337 00:15:30,840 --> 00:15:33,620 >> Nafu wisq kif Google madwar u jsibu repożitorji kodiċi 338 00:15:33,620 --> 00:15:36,360 onlajn, fora ta 'diskussjoni online, siti tax-xogħol onlajn. 339 00:15:36,360 --> 00:15:41,580 Jekk student tistax issib li, nistgħu żgur jsibuha kemm aħna b'dispjaċir do. 340 00:15:41,580 --> 00:15:45,330 Allura dak li inti ser tara fil-sillabu għalkemm huwa din il-klawżola dispjaċir. 341 00:15:45,330 --> 00:15:47,500 I jista 'ċertament japprezzaw, u aħna kollha għandu 342 00:15:47,500 --> 00:15:50,870 persunal wara li jsir il-kors simili dan, jew dan wieħed innifsu matul iż-żmien, 343 00:15:50,870 --> 00:15:53,997 ċertament taf dak li huwa simili meta ħajja gets fil-mod meta jkollok 344 00:15:53,997 --> 00:15:56,080 xi tard bil-lejl deadline-- mhux biss f'din il-klassi, 345 00:15:56,080 --> 00:15:58,660 imma another-- meta int kompletament eżawriti, enfasizzat, 346 00:15:58,660 --> 00:16:00,659 ikollhom numru eċċessiv ta 'affarijiet oħra li jagħmlu. 347 00:16:00,659 --> 00:16:03,660 Inti se tagħmel f'xi punt fil- ħajja ċertament ħażina, forsi tard 348 00:16:03,660 --> 00:16:04,620 deċiżjoni lejl. 349 00:16:04,620 --> 00:16:06,520 >> Allura kull l-sillabu, hemm din il-klawżola, 350 00:16:06,520 --> 00:16:10,629 tali li jekk fi żmien 72 siegħa ta 'teħid xi deċiżjoni foqra, inti stess sa dan 351 00:16:10,629 --> 00:16:12,670 u jilħqu lili u wieħed mill-kapijiet tal-kors tal- 352 00:16:12,670 --> 00:16:14,300 u aħna se jkollhom konverżazzjoni. 353 00:16:14,300 --> 00:16:16,220 Aħna se jimmaniġġjaw l-affarijiet internament fit-tamiet 354 00:16:16,220 --> 00:16:18,770 ta 'dan li jsir aktar ta' mument tagħlim jew lezzjoni tal-ħajja, 355 00:16:18,770 --> 00:16:22,120 u mhux xi ħaġa ma ramifikazzjonijiet partikolarment drastiku 356 00:16:22,120 --> 00:16:24,570 kif inti tista 'tara fuq dawn il-mapep hawn. 357 00:16:24,570 --> 00:16:26,540 >> Allura dak tone serja ħafna. 358 00:16:26,540 --> 00:16:29,960 Let us nieqaf għal ftit ftit sekondi biex jiksru l-tensjoni. 359 00:16:29,960 --> 00:16:34,442 >> [Daqq ta mużika] 360 00:16:34,442 --> 00:17:17,768 361 00:17:17,768 --> 00:17:20,250 >> DAVID J. Malan: Kull dritt, hekk kif kien li għal segue? 362 00:17:20,250 --> 00:17:22,059 Biex suġġetti primarji lum. 363 00:17:22,059 --> 00:17:23,859 L-ewwel waħda minnhom hija estrazzjoni. 364 00:17:23,859 --> 00:17:26,900 Ieħor ta 'liema se tkun l- rappreżentazzjoni ta 'data, li franchement 365 00:17:26,900 --> 00:17:31,640 huwa mod verament xott ta 'tgħid kif nistgħu tmur dwar soluzzjoni ta 'problemi u l-ħsieb 366 00:17:31,640 --> 00:17:33,250 dwar soluzzjoni ta 'problemi? 367 00:17:33,250 --> 00:17:37,285 Allura inti stajt tidher fl Scratch, u inti stajt dehru forsi diġà fis pset1 ma 'C 368 00:17:37,285 --> 00:17:39,930 li inti mhux biss tista 'tuża funzjonijiet, bħal printf, 369 00:17:39,930 --> 00:17:42,770 li nies oħra fil aħħar snin kiteb għalik. 370 00:17:42,770 --> 00:17:45,340 Tista 'wkoll tikteb funzjonijiet tiegħek stess. 371 00:17:45,340 --> 00:17:48,440 >> U anki jekk inti jista 'ma jkollhomx għamlu dan fis-C, u franchement fl pset1 372 00:17:48,440 --> 00:17:51,866 inti ma verament bżonn jiktbu tiegħek funzjoni stess minħabba l-problem-- 373 00:17:51,866 --> 00:17:53,990 filwaqt li forsi kbar fl- ewwel glance-- tkun taf tara 374 00:17:53,990 --> 00:17:57,910 jistgħu finalment jiġu solvuti bi mhux kollha li ħafna linji ta 'kodiċi. 375 00:17:57,910 --> 00:18:01,140 Iżda ma 'dak imsemmi, f'termini tal-kitba funzjoni tiegħek stess, 376 00:18:01,140 --> 00:18:03,570 tirrealizza li C ma jagħtu inti din il-kapaċità. 377 00:18:03,570 --> 00:18:06,940 >> Jien se jmorru fil-kodiċi sors tal-lum, li huwa disponibbli diġa online, 378 00:18:06,940 --> 00:18:10,900 u jien ser jimxi 'l quddiem u miftuħa up programm imsejjaħ 0.C funzjoni, 379 00:18:10,900 --> 00:18:14,620 u fil-funzjoni żero Ser naraw ftit affarijiet. 380 00:18:14,620 --> 00:18:19,160 Fl-ewwel linji 18 permezz 23 hija l-funzjoni prinċipali tiegħi. 381 00:18:19,160 --> 00:18:22,414 U issa li aħna qed jibdew jaqraw kodiċi li aħna mhux qed miktub fuq il-fly, 382 00:18:22,414 --> 00:18:25,080 iżda minflok stajt bil-miktub bil-quddiem jew li inti fil-problema sett 383 00:18:25,080 --> 00:18:27,910 tista 'tirċievi jkollhom ġew miktuba bil-quddiem. 384 00:18:27,910 --> 00:18:30,040 A mod tajjeb biex tibda qari kodiċi xi ħadd ieħor 385 00:18:30,040 --> 00:18:31,400 hija tfittex l-funzjoni prinċipali. 386 00:18:31,400 --> 00:18:34,420 Insemmu fejn dak id-dħul punt huwa li jmexxu l-programm, 387 00:18:34,420 --> 00:18:36,580 u mbagħad segwi dan loġikament minn hemm. 388 00:18:36,580 --> 00:18:40,190 >> Allura dan programm apparentement prints isem tiegħek segwit minn kolon. 389 00:18:40,190 --> 00:18:42,490 Aħna mbagħad jużaw GetString mill-bibljoteka CS50 390 00:18:42,490 --> 00:18:46,050 biex tikseb string, jew kelma jew frażi mill-utent fuq il-keyboard. 391 00:18:46,050 --> 00:18:48,390 U allura hemm dan Ħaġa PrintName here--. 392 00:18:48,390 --> 00:18:51,420 >> Issa PrintName mhix funzjoni li jiġi ma C. 393 00:18:51,420 --> 00:18:52,970 Mhuwiex fl io.h. standard 394 00:18:52,970 --> 00:18:55,570 Mhuwiex fl CS50.h. 395 00:18:55,570 --> 00:18:57,880 Huwa pjuttost fl-istess fajl. 396 00:18:57,880 --> 00:19:01,000 Avviż jekk I iscroll linji bit-- 25 sa 27-- 397 00:19:01,000 --> 00:19:05,330 huwa biss mod pretty ta 'kummentarju kodiċi tiegħek billi tuża l-istilel u slashes. 398 00:19:05,330 --> 00:19:07,320 Din hija multi-line jikkummentaw, u dan huwa biss 399 00:19:07,320 --> 00:19:10,570 Deskrizzjoni tiegħi fil-blu ta ' liema din il-funzjoni ma. 400 00:19:10,570 --> 00:19:14,530 >> Minħabba fil-linji 28 permezz 31, Stajt bil-miktub funzjoni super sempliċi 401 00:19:14,530 --> 00:19:16,280 isem tagħha huwa PrintName. 402 00:19:16,280 --> 00:19:19,560 Huwa jieħu kemm argumenti would you say? 403 00:19:19,560 --> 00:19:25,120 Allura wieħed argument-- għaliex hemm wieħed argument elenkat ġewwa l-parentesi. 404 00:19:25,120 --> 00:19:27,000 It-tip ta 'liema hija String. 405 00:19:27,000 --> 00:19:30,240 Liema jiġifieri PrintName huwa simili din il-kaxxa sewda 406 00:19:30,240 --> 00:19:32,910 jew il-funzjoni li jieħu bħala input string. 407 00:19:32,910 --> 00:19:35,730 >> U l-isem ta 'dik String konvenjenti se jkun Isem. 408 00:19:35,730 --> 00:19:37,840 Mhux S, mhux N, iżda isem. 409 00:19:37,840 --> 00:19:41,090 Allura dak li ma PrintName do? 410 00:19:41,090 --> 00:19:42,210 Huwa sempliċi sbieħ. 411 00:19:42,210 --> 00:19:45,390 Just bħala linja waħda tal-kodiċi għall l printf, imma apparentement dan 412 00:19:45,390 --> 00:19:47,950 prints out "Hello," hekk u hekk. 413 00:19:47,950 --> 00:19:50,070 Fejn l-hekk u hekk ġej mill-argument. 414 00:19:50,070 --> 00:19:52,300 >> Issa dan mhuwiex innovazzjoni enormi hawn. 415 00:19:52,300 --> 00:19:56,710 Really, I ħadt programm li jista ġew miktuba b'linja waħda tal-kodiċi 416 00:19:56,710 --> 00:20:00,190 billi dan up hawn, u nbidel għal xi ħaġa 417 00:20:00,190 --> 00:20:04,920 li jinvolvi xi sitt jew seba 'jew hekk linji ta 'kodiċi it-triq kollha stabbiliti hawn. 418 00:20:04,920 --> 00:20:08,190 >> Imma hija l-prattikanti ta ' prinċipju magħruf bħala estrazzjoni. 419 00:20:08,190 --> 00:20:12,550 Tip ta 'siġillar ġewwa ta' sistema ġdida funzjoni li għandha isem, u aħjar 420 00:20:12,550 --> 00:20:14,590 għadhom dak l-isem litteralment jgħid dak li tagħmel. 421 00:20:14,590 --> 00:20:16,880 I tfisser printf-- li mhux partikolarment deskrittiva. 422 00:20:16,880 --> 00:20:18,932 Jekk irrid li joħolqu biċċa puzzle, jew jekk I 423 00:20:18,932 --> 00:20:21,140 tixtieq toħloq funzjoni li prints isem ta 'xi ħadd, 424 00:20:21,140 --> 00:20:23,230 l-sbuħija ta 'kif isir dan hija li nista attwalment 425 00:20:23,230 --> 00:20:27,170 tagħti dik il-funzjoni isem li jiddeskrivi dak li tagħmel. 426 00:20:27,170 --> 00:20:29,844 >> Issa jieħu fir input li Stajt arbitrarju imsejħa isem, 427 00:20:29,844 --> 00:20:32,760 iżda li wisq huwa wonderfully deskrittiv Minflok ma jiġu aktar ftit 428 00:20:32,760 --> 00:20:36,140 ġeneriku bħal S. U null, għal issa, ifisser biss 429 00:20:36,140 --> 00:20:38,330 li din il-funzjoni ma idejn me lura xejn. 430 00:20:38,330 --> 00:20:41,127 Mhuwiex simili GetString li litteralment idejn me back string 431 00:20:41,127 --> 00:20:43,960 bħal għamilna mal-biċċiet tal-karti mal-klassi tiegħek aħħar ġimgħa, 432 00:20:43,960 --> 00:20:45,990 iżda hija biss għandha effett sekondarju. 433 00:20:45,990 --> 00:20:48,080 Hija prints xi ħaġa għall-iskrin. 434 00:20:48,080 --> 00:20:53,880 >> Għalhekk fl-aħħar tal-ġurnata, jekk I do make-funzjoni 0, ./function 0, 435 00:20:53,880 --> 00:20:55,450 aħna ser tara li hija tistaqsi għall-isem tiegħi. 436 00:20:55,450 --> 00:20:58,150 I tip David, u t-tipi out isem tiegħi. 437 00:20:58,150 --> 00:21:01,080 Jekk nagħmel dan mill-ġdid ma 'Rob, li għaddej biex jgħidu "Hello, Rob." 438 00:21:01,080 --> 00:21:04,280 Allura idea sempliċi, imma forsi estrapolati minn dan mentalment 439 00:21:04,280 --> 00:21:06,750 li bħala programmi tiegħek tikseb ftit aktar kumplikata, 440 00:21:06,750 --> 00:21:10,290 u inti tixtieq li jiktbu blokki ta ' kodiċi u sejħa li code-- jinvokaw 441 00:21:10,290 --> 00:21:13,270 li code-- minn xi deskrittiva isem bħal PrintName, 442 00:21:13,270 --> 00:21:15,600 C ma jaffordjaw us din il-kapaċità. 443 00:21:15,600 --> 00:21:17,660 >> Hawn eżempju ieħor sempliċi. 444 00:21:17,660 --> 00:21:22,940 Per eżempju, jekk I jiftħu fajl mil-lum imsejħa return.c, 445 00:21:22,940 --> 00:21:24,270 Avviż dak I ghamilt hawn. 446 00:21:24,270 --> 00:21:26,330 Ħafna minn din il-funzjoni ewlenija hija printf. 447 00:21:26,330 --> 00:21:30,360 I ewwel arbitrarjament initialize a varjabbli msejħa x biex in-numru 2. 448 00:21:30,360 --> 00:21:34,110 I mbagħad jistampa "x issa hija % I "tgħaddi fil-valur ta 'x. 449 00:21:34,110 --> 00:21:35,500 So jien biss qal dak li hu. 450 00:21:35,500 --> 00:21:37,208 >> Issa jien biss boldly titlob bil printf. 451 00:21:37,208 --> 00:21:42,050 I am cubing li l-valur x, u jien jagħmlu dan billi ssejjaħ il-funzjoni 452 00:21:42,050 --> 00:21:45,590 imsejħa tgħaddi kubu fil x bħala l-argument, 453 00:21:45,590 --> 00:21:49,300 u mbagħad iffrankar l-output fil-varjabbli innifsu, x. 454 00:21:49,300 --> 00:21:51,340 So jien clobbering-valur ta 'x. 455 00:21:51,340 --> 00:21:53,380 Jien sorpassata l- valur ta 'x bi kwalunkwe 456 00:21:53,380 --> 00:21:56,510 ir-riżultat ta 'sejħa din il-funzjoni kubu huwa. 457 00:21:56,510 --> 00:21:59,530 U mbagħad I biss print out xi wħud Jittieħed fluffy hawn tgħid dak li għamilt. 458 00:21:59,530 --> 00:22:01,600 >> Allura dak allura huwa kubu? 459 00:22:01,600 --> 00:22:03,510 Avviż x'hemm fundamentalment differenti hawn. 460 00:22:03,510 --> 00:22:05,540 Stajt minħabba l-funzjoni isem bħal qabel. 461 00:22:05,540 --> 00:22:08,270 Stajt speċifikat isem sabiex argument. 462 00:22:08,270 --> 00:22:11,650 Din id-darba huwa msejjaħ n minflok l-isem, imma I jistgħu sejħa hija xi ħaġa I trid. 463 00:22:11,650 --> 00:22:12,650 Iżda din hija differenti. 464 00:22:12,650 --> 00:22:14,080 Dan ħaġa fuq ix-xellug. 465 00:22:14,080 --> 00:22:16,290 Preċedentement kien dak keyword? 466 00:22:16,290 --> 00:22:16,870 Boys. 467 00:22:16,870 --> 00:22:18,580 Issa huwa ovvjament int. 468 00:22:18,580 --> 00:22:20,630 >> Allura x'hemm forsi l take away? 469 00:22:20,630 --> 00:22:24,090 Billi ifisser null tip ta ' nothingness, u li kien il-każ. 470 00:22:24,090 --> 00:22:25,970 PrintName lura xejn. 471 00:22:25,970 --> 00:22:27,942 Hija għamlet xi ħaġa, iżda hija ma idejn lili lura 472 00:22:27,942 --> 00:22:30,650 xi ħaġa li I tista 'tpoġġi fuq il- naħa tax-xellug ta 'sinjal ugwali 473 00:22:30,650 --> 00:22:32,460 bħal I ghamilt hawn fuq il-linja 22. 474 00:22:32,460 --> 00:22:36,780 >> Mela jekk jien ngħid fis on line 30, X'hemm li probabbilment jimplikaw 475 00:22:36,780 --> 00:22:38,610 dwar dak kubu ma għalija? 476 00:22:38,610 --> 00:22:41,110 Yeah? 477 00:22:41,110 --> 00:22:42,310 Dan jirritorna integer. 478 00:22:42,310 --> 00:22:44,590 Għalhekk idejn me lura, għal Pereżempju, biċċa karta 479 00:22:44,590 --> 00:22:46,580 li fuqha jkun miktub it-tweġiba. 480 00:22:46,580 --> 00:22:50,130 2 kubiku, jew 3 kubiku, jew 4 cubed-- kwalunkwe I għadda fi, 481 00:22:50,130 --> 00:22:51,540 u kif għamlet I timplimenta din? 482 00:22:51,540 --> 00:22:54,810 Well, just n ħinijiet n żminijiet n huwa kif I jista 'kubu valur. 483 00:22:54,810 --> 00:22:57,110 Għalhekk għal darb'oħra, super sempliċi idea, iżda dimostrattiv 484 00:22:57,110 --> 00:23:00,100 issa kif nistgħu jiktbu funzjonijiet li attwalment kellu lura lilna 485 00:23:00,100 --> 00:23:02,380 valuri li jistgħu jkunu ta 'interess. 486 00:23:02,380 --> 00:23:05,740 >> Ejja nħarsu lejn eżempju l-aħħar wieħed hawnhekk imsejħa funzjoni waħda. 487 00:23:05,740 --> 00:23:08,530 F'dan l-eżempju, jibda biex tikseb aktar konvinċenti. 488 00:23:08,530 --> 00:23:12,400 Allura fil-funzjoni waħda, dan avviż program-- finalment 489 00:23:12,400 --> 00:23:14,920 jitlob funzjoni msejħa GetPositiveInt. 490 00:23:14,920 --> 00:23:17,800 GetPositiveInt mhix funzjoni fil-librerija CS50, 491 00:23:17,800 --> 00:23:20,400 imma aħna iddeċieda li aħna tixtieq li jeżistu. 492 00:23:20,400 --> 00:23:24,550 >> Allura jekk aħna iscroll aktar tard fil-fajl, avviż kif I marru dwar implimentazzjoni 493 00:23:24,550 --> 00:23:26,560 nikseb int pożittiv, u I jgħidu huwa aktar konvinċenti 494 00:23:26,560 --> 00:23:28,992 minħabba li din hija deċenti numru ta 'linji ta' kodiċi. 495 00:23:28,992 --> 00:23:30,700 Huwa mhux biss iblah programm ġugarell ftit. 496 00:23:30,700 --> 00:23:33,870 Huwa fil-fatt ltqajna xi żball iċċekkjar u tagħmel xi ħaġa aktar utli. 497 00:23:33,870 --> 00:23:38,470 >> Mela jekk inti stajt ma bbenefikawx l-walkthrough videos li għandna integrati fil pset1, 498 00:23:38,470 --> 00:23:42,350 taf li dan huwa tip ta ' loop fis-C, simili fl-ispirtu 499 00:23:42,350 --> 00:23:44,270 għal tipi ta 'affarijiet Scratch jistgħu jagħmlu. 500 00:23:44,270 --> 00:23:46,320 U ma jgħid tagħmel dan. 501 00:23:46,320 --> 00:23:47,500 Stampa din out. 502 00:23:47,500 --> 00:23:51,860 Imbagħad imorru quddiem u jiksbu n-- tikseb int u jaħżen fil n, 503 00:23:51,860 --> 00:23:55,760 u jżomm tagħmel dan mill-ġdid u għal darb'oħra u darb'oħra sakemm n huwa inqas minn wieħed. 504 00:23:55,760 --> 00:23:58,720 >> Allura n se tkun inqas minn wieħed biss jekk il-bniedem mhuwiex kkooperaw. 505 00:23:58,720 --> 00:24:01,980 Jekk hu jew hi qed ittajpjar fl 0 jew -1 jew -50, 506 00:24:01,980 --> 00:24:04,790 dan loop se żżomm eżekuzzjoni għal darb'oħra u għal darb'oħra. 507 00:24:04,790 --> 00:24:07,549 U finalment avviż, I sempliċement lura l-valur. 508 00:24:07,549 --> 00:24:09,590 Allura issa għandna funzjoni li kieku stajt kien sbieħ 509 00:24:09,590 --> 00:24:14,040 jekk CS50 ikun implimentat fil CS50.h u CS50.c għalik, 510 00:24:14,040 --> 00:24:16,520 iżda hawnhekk nistgħu issa jimplimentaw dan nfusna. 511 00:24:16,520 --> 00:24:19,230 >> Iżda żewġ kummenti dwar xi dettalji ewlenin. 512 00:24:19,230 --> 00:24:24,390 One-- għaliex ma Niddikjara int n, taħseb, fuq il-linja 29 513 00:24:24,390 --> 00:24:27,139 minflok sempliċiment tagħmel dan hawnhekk, li hija 514 00:24:27,139 --> 00:24:28,930 aktar konsistenti mal- dak li għamilna ġimgħa li għaddiet? 515 00:24:28,930 --> 00:24:29,430 Yeah? 516 00:24:29,430 --> 00:24:34,485 517 00:24:34,485 --> 00:24:35,110 A ħasbu tajba. 518 00:24:35,110 --> 00:24:37,080 Mela jekk konna biex tqiegħed lilha hawn, huwa kif jekk aħna 519 00:24:37,080 --> 00:24:39,110 iżommu tiddikjara mill-ġdid u għal darb'oħra. 520 00:24:39,110 --> 00:24:42,000 Dan fih innifsu huwa mhux problematiku, per se, 521 00:24:42,000 --> 00:24:43,940 għaliex għandna bżonn biss il-valur darba u mbagħad 522 00:24:43,940 --> 00:24:45,330 aħna qed tmur biex tikseb waħda ġdida xorta waħda. 523 00:24:45,330 --> 00:24:45,940 Iżda riflessjoni tajba. 524 00:24:45,940 --> 00:24:46,440 Yeah? 525 00:24:46,440 --> 00:24:52,770 526 00:24:52,770 --> 00:24:53,330 >> Agħlaq. 527 00:24:53,330 --> 00:24:59,030 So għaliex stajt iddikjarata n fuq linja 29 barra mill-linja, 528 00:24:59,030 --> 00:25:01,390 huwa aċċessibbli matul din il-funzjoni kollu. 529 00:25:01,390 --> 00:25:05,400 Mhux l-funzjonijiet l-oħra minħabba n għadu ġewwa minn dawn kaboċċi 530 00:25:05,400 --> 00:25:06,470 ċingi hawn. 531 00:25:06,470 --> 00:25:07,940 So-- żgur. 532 00:25:07,940 --> 00:25:12,430 533 00:25:12,430 --> 00:25:12,940 >> Eżattament. 534 00:25:12,940 --> 00:25:14,356 Allura dan huwa saħansitra aktar lejn il-punt. 535 00:25:14,356 --> 00:25:18,600 Jekk aħna minflok iddikjarata n dritt hawn fuq il-linja 32, 536 00:25:18,600 --> 00:25:22,340 huwa problematiku għaliex raden fejn inkella I bżonn li jkollhom aċċess għaliha? 537 00:25:22,340 --> 00:25:25,620 On-line 34, u l- regola sempliċi ta 'thumb huwa 538 00:25:25,620 --> 00:25:30,060 li tista 'tuża biss varjabbli ġewwa taċ-ċingi kaboċċi aktar riċenti 539 00:25:30,060 --> 00:25:31,420 fejn inti ddikjarat lilha. 540 00:25:31,420 --> 00:25:35,230 >> Sfortunatament, linja 34 hija linja waħda tard wisq, 541 00:25:35,230 --> 00:25:38,560 għaliex stajt diġà magħluqa il-Brace kaboċċi fuq il-linja 33 542 00:25:38,560 --> 00:25:41,220 li jikkorrispondi għall- Brace kaboċċi fuq il-linja 30. 543 00:25:41,220 --> 00:25:44,180 U hekk dan huwa mod ta 'tgħid li dan int varjabbli huwa scoped, 544 00:25:44,180 --> 00:25:46,970 biex ngħidu hekk, biss ġewwa ta 'dawk ċingi kaboċċi. 545 00:25:46,970 --> 00:25:48,910 Hija biss ma jeżistu barra minnhom. 546 00:25:48,910 --> 00:25:51,580 >> Għalhekk tabilħaqq, jekk nagħmel dan ħażin, let me isalva l-kodiċi 547 00:25:51,580 --> 00:25:53,530 kif is-- b'mod żbaljat miktub. 548 00:25:53,530 --> 00:25:57,990 Let me imorru quddiem u ma jagħmlu funzjoni 1, u żball notice--. 549 00:25:57,990 --> 00:26:03,502 Użu ta 'mhux iddikjarat identifikatur n fuq il-linja 35, li huwa dritt hawn. 550 00:26:03,502 --> 00:26:05,210 U jekk aħna iscroll aktar, ieħor. 551 00:26:05,210 --> 00:26:08,750 Użu ta 'mhux iddikjarat identifikatur n fuq il-linja 34. 552 00:26:08,750 --> 00:26:11,200 >> Allura l-kumpilatur, Clang, huwa jinnota li hija biss 553 00:26:11,200 --> 00:26:13,720 ma teżistix anki jekk b'mod ċar huwa hemmhekk viżwalment. 554 00:26:13,720 --> 00:26:16,090 Allura jiffissaw sempliċi hija tiddikjara hemmhekk. 555 00:26:16,090 --> 00:26:18,790 >> Issa let me iscroll biex il-quċċata tal-fajl. 556 00:26:18,790 --> 00:26:21,080 What jumps fil inti bħala tkun ftit differenti 557 00:26:21,080 --> 00:26:23,070 mill-għalf ħarisna lejn l-aħħar ġimgħa? 558 00:26:23,070 --> 00:26:26,990 Mhux biss do I jkollhom isem, mhux biss do Għandi xi sharp jinkludi top up, 559 00:26:26,990 --> 00:26:29,340 I ikollhom xi ħaġa jien ssejjaħ prototip. 560 00:26:29,340 --> 00:26:36,100 Issa li jistenna awfully simili għal dak aħna biss raw mument ilu fuq il-linja 27. 561 00:26:36,100 --> 00:26:39,230 >> Mela ejja jiddeduċu minn differenti messaġġ ta 'żball għaliex I ghamilt dan. 562 00:26:39,230 --> 00:26:42,050 Let me imorru quddiem u tħassar dawn il-linji hemmhekk. 563 00:26:42,050 --> 00:26:44,240 U hekk aħna nafu xejn dwar prototip. 564 00:26:44,240 --> 00:26:45,430 Remake dan il-fajl. 565 00:26:45,430 --> 00:26:46,890 Jagħmlu funzjoni waħda. 566 00:26:46,890 --> 00:26:48,090 U issa, kkritikat, erba 'żbalji. 567 00:26:48,090 --> 00:26:50,220 Ejja iscroll sa l-ewwel waħda. 568 00:26:50,220 --> 00:26:55,070 >> Dikjarazzjoni impliċitu tal-funzjoni nikseb int pożittiv huwa invalidu C99. 569 00:26:55,070 --> 00:26:57,780 C99 ifisser biss l-1999 verżjoni tal-lingwa 570 00:26:57,780 --> 00:26:59,710 C, li huwa dak li aħna qed tabilħaqq jużaw. 571 00:26:59,710 --> 00:27:01,050 Allura dak li jfisser dan? 572 00:27:01,050 --> 00:27:05,250 Well C-- u b'mod aktar speċifiku C compilers-- huma programmi pretty mutu. 573 00:27:05,250 --> 00:27:07,420 Huma biss jafu liema inti stajt qaltilhom, u li l- 574 00:27:07,420 --> 00:27:08,960 attwalment tematika mill-aħħar ġimgħa. 575 00:27:08,960 --> 00:27:12,910 >> Il-problema hija li jekk immur dwar implimentazzjoni isem up here, 576 00:27:12,910 --> 00:27:17,640 u I call funzjoni msejħa GetPositiveInt hawn fuq il-linja 20, 577 00:27:17,640 --> 00:27:22,520 dik il-funzjoni teknikament ma teżisti sakemm l-kumpilatur jara linja 27. 578 00:27:22,520 --> 00:27:25,450 Sfortunatament, il-kompilatur hija nagħmlu l-affarijiet top, isfel, xellug, lemin, 579 00:27:25,450 --> 00:27:29,580 hekk għaliex ma raw l- implimentazzjoni ta 'GetPositiveInt, 580 00:27:29,580 --> 00:27:32,400 iżda jara inti tipprova biex jużaw it up here, 581 00:27:32,400 --> 00:27:35,810 huwa biss se bail-- Yell fil inti ma żball message-- forsi 582 00:27:35,810 --> 00:27:38,440 cryptic, u mhux fil-fatt jikkompilaw il-fajl. 583 00:27:38,440 --> 00:27:41,940 >> Allura hekk imsejħa prototip up hawnhekk huwa ċertament żejda. 584 00:27:41,940 --> 00:27:47,870 Litteralment, I niżlet hawn u I kkupjati u pasted dan, u I poġġih up here. 585 00:27:47,870 --> 00:27:51,020 Null tkun aktar xierqa, hekk aħna ser litteralment kopja u paste dan iż-żmien. 586 00:27:51,020 --> 00:27:52,854 I litteralment kkupjati u pasted dan. 587 00:27:52,854 --> 00:27:54,270 Verament biss bħala bħal Frak tal-ħobż. 588 00:27:54,270 --> 00:27:56,260 >> A ftit clue għall-kompilatur. 589 00:27:56,260 --> 00:27:58,860 I do not know dak li dan ma s'issa, iżda jien promettenti lilek 590 00:27:58,860 --> 00:28:00,260 li se jeżistu eventwalment. 591 00:28:00,260 --> 00:28:04,010 U hu għalhekk li din line-- fl linja 16-- tispiċċa bil-punto virgola. 592 00:28:04,010 --> 00:28:05,486 Huwa hija żejda permezz tad-disinn. 593 00:28:05,486 --> 00:28:05,986 Iva? 594 00:28:05,986 --> 00:28:11,340 595 00:28:11,340 --> 00:28:14,360 >> Jekk inti ma rabta librerija tiegħek li the-- oh, mistoqsija tajba. 596 00:28:14,360 --> 00:28:17,350 Sharp jinkludi inklużjonijiet fajl header. 597 00:28:17,350 --> 00:28:20,040 Ħtieġa li be-- għandhom kważi dejjem ikunu fil-quċċata ħafna 598 00:28:20,040 --> 00:28:23,270 tal-fajl għal similar-- għall eżattament l-istess raġuni, iva. 599 00:28:23,270 --> 00:28:26,430 Minħabba fl-istandard io.h hu litteralment linja 600 00:28:26,430 --> 00:28:30,560 bħal dan, iżda bil-printf kelma, u b'argumenti tagħha u t-tip ritorn tagħha. 601 00:28:30,560 --> 00:28:33,310 U hekk billi tagħmel sharp jinkludu sa hawn, dak li int litteralment tagħmel 602 00:28:33,310 --> 00:28:36,380 hija li jikkopjaw u pasta l-kontenut xi ħadd ieħor kiteb up top. 603 00:28:36,380 --> 00:28:39,660 B'hekk cluing kodiċi tiegħek fil lill- fatt li jeżistu dawk il-funzjonijiet. 604 00:28:39,660 --> 00:28:40,160 Yeah? 605 00:28:40,160 --> 00:28:47,520 606 00:28:47,520 --> 00:28:48,260 >> Assolutament. 607 00:28:48,260 --> 00:28:51,690 Allura ħafna għaqlija u korretta soluzzjoni tkun, inti taf liema? 608 00:28:51,690 --> 00:28:53,760 I do not know dak li prototip huwa, imma naf 609 00:28:53,760 --> 00:28:56,390 jekk Nifhem li C huwa biss mutu u rethinks fuq għal isfel. 610 00:28:56,390 --> 00:28:57,820 Well ejja tagħtiha dak li trid. 611 00:28:57,820 --> 00:29:01,650 Ejja maqtugħin istess kodiċi, paste up top, u issa imbotta prinċipali stabbiliti hawn taħt. 612 00:29:01,650 --> 00:29:03,470 Dan ukoll ssolvix il-problema. 613 00:29:03,470 --> 00:29:07,409 >> Iżda int tista 'faċilment toħroġ bi f'xenarju li fih A bżonn tirrikorri B, 614 00:29:07,409 --> 00:29:10,075 u forsi B jitlob lura għall A. Dan hija xi ħaġa imsejħa recursion, 615 00:29:10,075 --> 00:29:11,370 u aħna ser terga 'lura għal dan. 616 00:29:11,370 --> 00:29:13,911 U jista 'jew ma jista' jkun tajjeb ħaġa, imma inti tista 'definittivament 617 00:29:13,911 --> 00:29:15,110 break din is-soluzzjoni. 618 00:29:15,110 --> 00:29:17,690 >> U barra minn hekk, nixtieq pretensjoni stylistically, 619 00:29:17,690 --> 00:29:20,760 speċjalment meta programmi tiegħek jsiru dan twil u dan twil, 620 00:29:20,760 --> 00:29:23,064 huwa biss super konvenjenti li jpoġġi prinċipali fil-quċċata 621 00:29:23,064 --> 00:29:25,730 għaliex dan huwa l-aktar ħaġa programmaturi huma ser jimpurtahom. 622 00:29:25,730 --> 00:29:28,150 U dan huwa aktar nadifa ftit, forsi, biex tagħmel dan il-mod 623 00:29:28,150 --> 00:29:30,380 I oriġinarjament ma kien ma 'prototip anke 624 00:29:30,380 --> 00:29:33,396 għalkemm jidher ftit superfluwi ewwel daqqa t'għajn. 625 00:29:33,396 --> 00:29:33,895 Yeah? 626 00:29:33,895 --> 00:29:36,472 627 00:29:36,472 --> 00:29:37,680 Jiddispjacini, inti tista jgħidu li louder? 628 00:29:37,680 --> 00:29:45,650 629 00:29:45,650 --> 00:29:49,580 >> Jekk taqleb l-postijiet tal- implimentazzjoni u l-prototip? 630 00:29:49,580 --> 00:29:51,270 Allura li hija mistoqsija tajba. 631 00:29:51,270 --> 00:29:53,780 Jekk għandek terġa 'tiddikjara dan l isfel hawn, ejja ara dak li jiġri. 632 00:29:53,780 --> 00:29:55,530 Mela jekk nressaq dan isfel hawn, inti qed tgħid. 633 00:29:55,530 --> 00:29:57,860 634 00:29:57,860 --> 00:29:58,360 Oh, sorry. 635 00:29:58,360 --> 00:29:58,859 Louder? 636 00:29:58,859 --> 00:30:02,000 637 00:30:02,000 --> 00:30:04,011 Anke louder. 638 00:30:04,011 --> 00:30:04,760 Oh, mistoqsija tajba. 639 00:30:04,760 --> 00:30:05,860 Ikun tinvalida l-funzjoni? 640 00:30:05,860 --> 00:30:08,901 You know, wara dawn is-snin kollha, I qatt ma tpoġġi prototip wara. 641 00:30:08,901 --> 00:30:13,810 Mela ejja ma jagħmlu funzjoni-1 wara li tagħmel dan. 642 00:30:13,810 --> 00:30:15,279 >> [Muttering] 643 00:30:15,279 --> 00:30:16,320 DAVID J. Malan: Oh, stenna. 644 00:30:16,320 --> 00:30:17,944 Għad għandna biex tpoġġi kollox top up. 645 00:30:17,944 --> 00:30:21,400 Mela ejja tagħmel dan up hawn, jekk jien fehim mistoqsija tiegħek b'mod korrett. 646 00:30:21,400 --> 00:30:24,700 Jien tqegħid kollox, inkluż il-prototip ta 'hawn fuq prinċipali, 647 00:30:24,700 --> 00:30:28,180 imma jien tqegħid tal-prototip taħt l-implimentazzjoni. 648 00:30:28,180 --> 00:30:33,190 >> Mela jekk jien jagħmlu waħda, jien jkollna lura n varjabbli mhux użati error--. 649 00:30:33,190 --> 00:30:37,280 650 00:30:37,280 --> 00:30:37,860 Oh, hemm. 651 00:30:37,860 --> 00:30:38,360 Grazzi. 652 00:30:38,360 --> 00:30:39,430 Ejja naraw, aħna teħles minn dan. 653 00:30:39,430 --> 00:30:41,304 Li l-bug differenti, hekk ejja jinjoraw dik. 654 00:30:41,304 --> 00:30:43,910 Ejja verament malajr remake dan. 655 00:30:43,910 --> 00:30:48,100 >> OK, hekk argument data mhux użati mill String format 656 00:30:48,100 --> 00:30:52,310 n-- oh, dan għaliex I mibdula għal dawn hawn. 657 00:30:52,310 --> 00:30:55,885 Kull dritt, nafu liema l-risposta huwa għaddej to-- id-dritt, here we go. 658 00:30:55,885 --> 00:31:00,560 Ah, grazzi għall-pożittiv. 659 00:31:00,560 --> 00:31:03,430 Kull dritt, I se jiffissaw dan il-kodiċi after-- jinjora dan bug partikolari 660 00:31:03,430 --> 00:31:08,300 peress li dan was-- jaħdem huwa l-risposta. 661 00:31:08,300 --> 00:31:11,560 >> Allura dan ma jissostitwixxu dak li inti stajt biss isir. 662 00:31:11,560 --> 00:31:14,800 Nissuspetta l-kumpilatur huwa miktub b'tali mod 663 00:31:14,800 --> 00:31:18,420 li qed jinjora prototip tiegħek għaliex il-korp, biex ngħidu hekk, 664 00:31:18,420 --> 00:31:20,922 tal-funzjoni diġà ġew implimentati ogħla sa. 665 00:31:20,922 --> 00:31:23,380 I jkollhom biex effettivament jikkonsulta il-manwal tal-kompilatur 666 00:31:23,380 --> 00:31:26,171 biex jifhmu jekk ikun hemm xi oħra implikazzjoni, iżda fl-ewwel daqqa t'għajn 667 00:31:26,171 --> 00:31:29,290 biss billi tipprova u jesperimentaw, jidher li hemm ebda impatt. 668 00:31:29,290 --> 00:31:30,730 Mistoqsija tajba. 669 00:31:30,730 --> 00:31:33,660 >> Mela ejja nimxu 'l quddiem issa, li jiċċaqalqu bogħod mill-effetti sekondarji li 670 00:31:33,660 --> 00:31:36,660 huma funzjonijiet li jagħmlu xi ħaġa bħal viżwalment fuq l-iskrin ma printf, 671 00:31:36,660 --> 00:31:38,090 iżda ma jirritornawx valur. 672 00:31:38,090 --> 00:31:41,550 U funzjonijiet li jkollhom ritorn Valuri bħal aħna biss raw ftit ta. 673 00:31:41,550 --> 00:31:45,350 Aħna diġà raw dan il-kunċett ta 'ambitu, u aħna ser tara dan ġdid u għal darb'oħra. 674 00:31:45,350 --> 00:31:47,210 Iżda għal issa, għal darb'oħra, jużaw ir-regola ta 'thumb 675 00:31:47,210 --> 00:31:51,410 li varjabbli jistgħu jintużaw biss ġewwa mill-aktar riċentement fetaħ 676 00:31:51,410 --> 00:31:54,350 u braces kaboċċi magħluqa kif aħna raw f'dak eżempju partikolari. 677 00:31:54,350 --> 00:31:56,910 >> U kif inti enfasizzat, hemm ability-- 678 00:31:56,910 --> 00:32:00,040 inti tista 'ssolvi xi wħud minn dawn il-problemi billi jpoġġi varjabbli globalment 679 00:32:00,040 --> 00:32:01,290 fuq nett ta 'fajl. 680 00:32:01,290 --> 00:32:03,630 Iżda kważi fil-każijiet kollha aħna se frown fuq li, 681 00:32:03,630 --> 00:32:06,170 u tabilħaqq ma anki jmorru f'dak soluzzjoni għal issa. 682 00:32:06,170 --> 00:32:09,890 Allura għal issa, il-takeaway hija li varjabbli jkollhom dan il-kunċett ta 'ambitu. 683 00:32:09,890 --> 00:32:13,430 >> Imma issa ejja nħarsu lejn ieħor mod xott tal-fatt tfittex 684 00:32:13,430 --> 00:32:15,810 f'xi pretty interessanti dettalji tal-implimentazzjoni. 685 00:32:15,810 --> 00:32:17,810 Kif nistgħu jirrappreżentaw informazzjoni. 686 00:32:17,810 --> 00:32:20,370 U aħna diġà ħares lejn dan fl-ewwel ġimgħa tal-klassi. 687 00:32:20,370 --> 00:32:23,320 Ħarsa lejn binaries, u fakkruha lilna nfusna ta 'informazzjoni. 688 00:32:23,320 --> 00:32:28,310 >> Iżda recall minn aħħar ġimgħa li C għandha tipi ta 'data differenti u għenieqed aktar, 689 00:32:28,310 --> 00:32:30,600 iżda dawk l-aktar utli għal issa jista 'jkun dawn. 690 00:32:30,600 --> 00:32:36,030 A char, jew il-karattru, li jiġri li jkun byte wieħed, jew tmien total bits. 691 00:32:36,030 --> 00:32:40,060 U li li jgħidu li d-daqs ta 'char huwa biss wieħed byte. 692 00:32:40,060 --> 00:32:45,370 A byte huwa tmien bits, għalhekk dan ifisser li nistgħu jirrappreżentaw kemm karattri ħafna. 693 00:32:45,370 --> 00:32:47,320 Kemm l-ittri jew simboli fuq il-tastiera 694 00:32:47,320 --> 00:32:49,210 jekk ikollna byte wieħed jew tmien bits. 695 00:32:49,210 --> 00:32:51,546 Think lura għal żero ġimgħa. 696 00:32:51,546 --> 00:32:53,420 Jekk għandek tmien bits, kemm il-valuri totali 697 00:32:53,420 --> 00:32:55,503 inti tista 'tirrappreżenta ma mudelli ta 'żerijiet u dawk? 698 00:32:55,503 --> 00:32:58,170 699 00:32:58,170 --> 00:33:00,260 One-- aktar minn dak. 700 00:33:00,260 --> 00:33:03,490 Mela 256 total, jekk inti jibdew jingħaddu minn żero. 701 00:33:03,490 --> 00:33:07,120 Mela jekk għandek tmien bits-- hekk jekk irridu kellhom basal binarja tagħna up here għal darb'oħra, 702 00:33:07,120 --> 00:33:12,180 nistgħu dawran dawk bozoz tad-dawl fuq u off fi kwalunkwe ta '256 mudelli uniċi. 703 00:33:12,180 --> 00:33:13,640 >> Issa dan huwa daqsxejn problematika. 704 00:33:13,640 --> 00:33:16,857 Mhux tant għall-Ingliż u lingwi rumanz, iżda ċertament 705 00:33:16,857 --> 00:33:19,190 meta inti jintroduċu, għal pereżempju, il-lingwi Asjatiċi, li 706 00:33:19,190 --> 00:33:22,580 jkollhom simboli ferm aktar minn like 26 ittri tal-alfabett. 707 00:33:22,580 --> 00:33:24,390 Għandna attwalment jista 'jkollok bżonn aktar minn byte wieħed. 708 00:33:24,390 --> 00:33:28,240 U Thankfully fl snin riċenti għandha soċjetà 709 00:33:28,240 --> 00:33:31,040 adottati standards oħra li jużaw byte aktar minn wieħed għal kull ħlas. 710 00:33:31,040 --> 00:33:34,210 >> Iżda għal issa fis-C, l-inadempjenza huwa biss byte wieħed jew tmien bits. 711 00:33:34,210 --> 00:33:38,195 Integer, sadanittant, hija erbgħa bytes, inkella magħruf bħala 32 bits. 712 00:33:38,195 --> 00:33:41,320 Li jfisser x'inhu l-akbar possibbli numru nistgħu jirrappreżentaw ma 'int 713 00:33:41,320 --> 00:33:41,820 apparentement? 714 00:33:41,820 --> 00:33:44,426 715 00:33:44,426 --> 00:33:45,050 Bil biljun. 716 00:33:45,050 --> 00:33:46,760 Allura huwa erba 'biljun jagħtu jew jieħu. 717 00:33:46,760 --> 00:33:49,840 2 għall-qawwa 32th, jekk aħna jassumu l-ebda numri negattivi 718 00:33:49,840 --> 00:33:52,530 u biss użu kollha pożittivi numri, huwa erba 'biljun 719 00:33:52,530 --> 00:33:53,730 jagħtu jew jieħu possibbiltajiet. 720 00:33:53,730 --> 00:33:57,890 A float, sadanittant, hija tip differenti tat-tip tad-data fil C. Huwa għadu numru, 721 00:33:57,890 --> 00:33:58,990 imma hija numru reali. 722 00:33:58,990 --> 00:34:00,660 Xi ħaġa ma 'punt deċimali. 723 00:34:00,660 --> 00:34:03,000 U jirriżulta li C tuża wkoll erba 'bytes 724 00:34:03,000 --> 00:34:05,340 biex jirrappreżentaw valuri b'punt li jvarja ta. 725 00:34:05,340 --> 00:34:09,420 >> Sfortunatament kemm f'wiċċ l-ilma valuri tal-punti huma hemmhekk fid-dinja? 726 00:34:09,420 --> 00:34:11,582 Kemm in-numri reali ħafna hemm? 727 00:34:11,582 --> 00:34:13,540 Hemm xi infinita numru, u għal dik il-kwistjoni 728 00:34:13,540 --> 00:34:15,164 hemm numru infinit ta 'interi. 729 00:34:15,164 --> 00:34:18,070 Allura aħna qed diġà tip ta ' tħaffir nfusna toqba hawn. 730 00:34:18,070 --> 00:34:21,780 Li biha apparentament computers-- fi inqas programmi bil-miktub fis-C fuq them-- 731 00:34:21,780 --> 00:34:24,110 tista 'biss jgħoddu bħala għoli daqs erba 'biljun jagħtu jew jieħu, 732 00:34:24,110 --> 00:34:26,260 u floating valuri tal-punti tista 'biss apparentement 733 00:34:26,260 --> 00:34:28,330 għandhom xi ammont finit ta 'preċiżjoni. 734 00:34:28,330 --> 00:34:30,810 Biss tant ċifri wara punt deċimali tagħhom. 735 00:34:30,810 --> 00:34:32,822 >> Minħabba, naturalment, jekk inti biss għandek 32 bits, 736 00:34:32,822 --> 00:34:36,030 I do not know kif aħna qed tmur biex jmorru dwar jirrappreżenta numbers-- reali probabbilment 737 00:34:36,030 --> 00:34:37,409 ma 'tipi differenti ta' mudelli. 738 00:34:37,409 --> 00:34:40,030 Iżda hemm żgur finit numru ta 'tali mudelli, 739 00:34:40,030 --> 00:34:41,830 hekk hawn, wisq, dan huwa problematiku. 740 00:34:41,830 --> 00:34:43,710 >> Issa nistgħu evitata l-problema kemmxejn. 741 00:34:43,710 --> 00:34:45,710 Jekk inti ma jużawx float, inti tista 'tuża double 742 00:34:45,710 --> 00:34:50,230 fis-C, li tagħtik tmien bytes, li huwa mudelli mod aktar possibbli ta 'żerijiet 743 00:34:50,230 --> 00:34:50,730 u dawk. 744 00:34:50,730 --> 00:34:55,199 Iżda huwa għadu finit, li se li jkun problematiku jekk tikteb software 745 00:34:55,199 --> 00:34:57,670 għall-grafika jew għal fancy formuli matematiċi. 746 00:34:57,670 --> 00:35:00,410 Allura inti tista 'fil-fatt tixtieq li jgħoddu up akbar minn dak. 747 00:35:00,410 --> 00:35:05,640 A twil long-- stupidly named-- huwa wkoll tmien bytes, jew 64 bits, 748 00:35:05,640 --> 00:35:10,260 u dan huwa darbtejn sakemm bħala int, u huwa għal valur sħiħ twil. 749 00:35:10,260 --> 00:35:15,655 >> Pjaċir fact-- jekk int huwa erba bytes, kemm żmien huwa twil fis-C tipikament? 750 00:35:15,655 --> 00:35:18,290 751 00:35:18,290 --> 00:35:21,560 Ukoll erba bytes, iżda twil twil huwa tmien bytes, 752 00:35:21,560 --> 00:35:23,050 u dan huwa għal raġunijiet storiċi. 753 00:35:23,050 --> 00:35:26,450 >> Iżda l-takeaway issa huwa biss li data għandha 754 00:35:26,450 --> 00:35:29,625 li jkunu rappreżentati fil-computer-- li l- mezz fiżiku bl-elettriku, 755 00:35:29,625 --> 00:35:32,190 huwa ġeneralment sewqan dawk żerijiet u ones-- 756 00:35:32,190 --> 00:35:34,320 b'ammonti finit ta 'preċiżjoni. 757 00:35:34,320 --> 00:35:35,620 Allura x'inhu l-problema allura? 758 00:35:35,620 --> 00:35:37,480 >> Ukoll hemm problema ta 'overflow numru sħiħ. 759 00:35:37,480 --> 00:35:39,780 Mhux biss fil-C, iżda kompjuters b'mod ġenerali. 760 00:35:39,780 --> 00:35:42,590 Per eżempju, jekk dan huwa byte jiswew bit-- 761 00:35:42,590 --> 00:35:45,120 hekk jekk dan huwa tmienja bit-- kollha li huma n-numru wieħed. 762 00:35:45,120 --> 00:35:47,300 X'inhu numru huwa dan tirrappreżenta jekk nassumu 763 00:35:47,300 --> 00:35:50,730 huwa valuri pożittivi kollha fl binarju? 764 00:35:50,730 --> 00:35:54,410 >> 255, u mhuwiex 256, għaliex żero hija l-inqas numru. 765 00:35:54,410 --> 00:35:56,760 Allura 255 huwa l-ogħla wieħed, iżda l-problema 766 00:35:56,760 --> 00:36:00,330 huwa wieħed jissoponi li xtaqt li inkrement dan il-varjabbli li 767 00:36:00,330 --> 00:36:04,030 qed tuża tmien bits total jekk irrid li inkrement lilha. 768 00:36:04,030 --> 00:36:07,160 >> Ukoll malli I żid wieħed għal kulħadd ta 'dawn dawk, 769 00:36:07,160 --> 00:36:10,500 inti tista 'forsi timmaġina visually-- biss simili jġorru l-wieħed juża decimals-- 770 00:36:10,500 --> 00:36:12,300 xi ħaġa għaddej biex fluss lejn ix-xellug. 771 00:36:12,300 --> 00:36:15,590 U fil-fatt, jekk I żid l-għadd wieħed għal dan, dak li jiġri fil-binarju 772 00:36:15,590 --> 00:36:17,670 huwa li tifwir lura għal żero. 773 00:36:17,670 --> 00:36:21,730 >> Mela jekk inti biss use-- mhux int, iżda byte wieħed biex jingħaddu interi 774 00:36:21,730 --> 00:36:27,170 fi programm, billi default-- hekk kif ikollok biex 250, 251, 252, 253, 254, 775 00:36:27,170 --> 00:36:32,710 255-- 0 wasal wara 255, li probabbilment ma jkunx dak 776 00:36:32,710 --> 00:36:34,790 utent se tistenna. 777 00:36:34,790 --> 00:36:39,620 >> Issa sadanittant fil-galleġġjanti punt dinja, inti ukoll għandek problema simili. 778 00:36:39,620 --> 00:36:42,670 Mhux daqshekk mal-akbar number-- għalkemm dan għadu kwistjoni. 779 00:36:42,670 --> 00:36:45,360 Imma bl-ammont ta 'preċiżjoni li inti tista 'tirrappreżenta. 780 00:36:45,360 --> 00:36:49,490 Mela ejja tagħti ħarsa lejn dan l-eżempju hawn ukoll minn sors code-- lum 781 00:36:49,490 --> 00:36:52,070 -float 0.c. 782 00:36:52,070 --> 00:36:54,280 >> U avviż huwa super programm sempliċi li 783 00:36:54,280 --> 00:36:56,580 għandhom apparentement jistampa liema valur? 784 00:36:56,580 --> 00:37:00,777 785 00:37:00,777 --> 00:37:04,110 What do you wager dan se jistampaw anke jekk kien hemm daqsxejn ta 'sintassi ġdida 786 00:37:04,110 --> 00:37:05,540 hawn? 787 00:37:05,540 --> 00:37:06,700 Allura nisperaw 0.1. 788 00:37:06,700 --> 00:37:10,000 Allura l-ekwivalenti ta 'wieħed minn għaxra għaliex jien tagħmel 1 maqsum f'10. 789 00:37:10,000 --> 00:37:12,430 Jien ħażna ir-risposta fi varjabbli msejħa f. 790 00:37:12,430 --> 00:37:15,850 Dan il-varjabbli huwa tat-tip float, li huwa keyword I biss propost eżista. 791 00:37:15,850 --> 00:37:18,910 >> Imxejna ma bbenefikawx dan qabel, imma dan huwa tip ta 'mod pulita fil printf 792 00:37:18,910 --> 00:37:22,110 li jispeċifikaw kif ħafna numri inti trid tara wara punt deċimali. 793 00:37:22,110 --> 00:37:25,020 Allura dan notazzjoni ifisser biss li hawnhekk placeholder. 794 00:37:25,020 --> 00:37:27,900 Huwa għal floating point valur, u oh, mill-mod, 795 00:37:27,900 --> 00:37:31,389 juru li dan ma 'l-punt deċimali ma numru wieħed wara l-punt deċimali. 796 00:37:31,389 --> 00:37:33,180 Allura dak in-numru tal figuri sinifikanti, 797 00:37:33,180 --> 00:37:34,650 biex ngħidu hekk, li inti tista 'tixtieq. 798 00:37:34,650 --> 00:37:40,450 >> So let me go quddiem u jagħmlu make-float 0, ./float-0, 799 00:37:40,450 --> 00:37:46,660 u apparentement 1 maqsum f'10 hija 0.0. 800 00:37:46,660 --> 00:37:47,760 Issa għaliex huwa dan? 801 00:37:47,760 --> 00:37:51,380 >> Ukoll għal darb'oħra, il-kompjuter qed tieħu me litteralment, u ktibtu 1 802 00:37:51,380 --> 00:37:56,680 u I miktub 10, u tieħu raden liema huwa t-tip tad-data preżunta għal dawk iż-żewġ 803 00:37:56,680 --> 00:37:58,440 Valuri? 804 00:37:58,440 --> 00:38:00,970 An int, huwa teknikament xi ftit differenti. 805 00:38:00,970 --> 00:38:04,150 Huwa tipikament twil, imma hija finalment valur integrali. 806 00:38:04,150 --> 00:38:06,030 Mhux valur punt f'wiċċ l-ilma. 807 00:38:06,030 --> 00:38:09,456 >> Li huwa li jgħidu li jekk dan huwa int u dan huwa int, 808 00:38:09,456 --> 00:38:11,830 il-problema hija li l-kompjuter ma jkollu l-abbiltà 809 00:38:11,830 --> 00:38:13,680 li anki jaħżnu dik punt deċimali. 810 00:38:13,680 --> 00:38:16,430 Allura meta inti tagħmel 1 maqsuma b'10 jużaw interi 811 00:38:16,430 --> 00:38:20,950 kemm għall-numeratur u l- denominatur, ir-risposta għandha tkun 0.1. 812 00:38:20,950 --> 00:38:24,930 Iżda l-computer-- minħabba dawk huma integers-- 813 00:38:24,930 --> 00:38:27,430 ma jafu x'għandhom jagħmlu ma 'l-0.1. 814 00:38:27,430 --> 00:38:30,010 >> Allura x'inhu tagħmel b'mod ċar? 815 00:38:30,010 --> 00:38:33,120 Huwa biss jitfg bogħod, u dak li jien jaraw finalment 816 00:38:33,120 --> 00:38:38,830 huwa 0.0 biss minħabba I insista li printf urini punt deċimali wieħed. 817 00:38:38,830 --> 00:38:41,740 Iżda l-problema hija li jekk inti jaqsam integer minn integer, 818 00:38:41,740 --> 00:38:44,347 inti ser get-- b'definizzjoni ta C-- integer. 819 00:38:44,347 --> 00:38:46,680 U huwa mhux se jagħmlu xi ħaġa sabiħa u konvenjenti 820 00:38:46,680 --> 00:38:49,040 bħal round f'idejn l- eqreb wieħed up jew 'l isfel. 821 00:38:49,040 --> 00:38:51,860 Huwa ser truncate kollox wara l-deċimali. 822 00:38:51,860 --> 00:38:54,030 >> Hekk biss intuwittivament, x'hemm probabbilment tiffissa? 823 00:38:54,030 --> 00:38:55,351 X'hemm l-jiffissaw sempliċi hawn? 824 00:38:55,351 --> 00:38:55,850 Yeah? 825 00:38:55,850 --> 00:39:00,570 826 00:39:00,570 --> 00:39:01,100 Eżattament. 827 00:39:01,100 --> 00:39:04,200 Għaliex ma aħna biss jittrattaw dawn kif f'wiċċ l-ilma valuri point effettiv 828 00:39:04,200 --> 00:39:05,860 b'hekk jissarfu kannizzati jew jirdoppja. 829 00:39:05,860 --> 00:39:10,500 U issa jekk I do jagħmlu sufruni-0, jew jekk I jikkompilaw sufruni-1, 830 00:39:10,500 --> 00:39:12,570 li huwa identiku għall dak li kien biss proposta. 831 00:39:12,570 --> 00:39:16,400 U issa I do sufruni-0, issa niġi 0.1 tiegħi. 832 00:39:16,400 --> 00:39:17,234 >> Issa dan huwa aqwa. 833 00:39:17,234 --> 00:39:19,441 Imma issa jien se tagħmel xi ftit differenti. 834 00:39:19,441 --> 00:39:22,280 Jien kurjużi biex tara x'hemm verament tmur fuq taħt il-barnuża, 835 00:39:22,280 --> 00:39:26,050 u jien ser Stampa din out għal 28 postijiet deċimali. 836 00:39:26,050 --> 00:39:29,730 I tixtieq li verament tara 0.1000-- l infinite-- 837 00:39:29,730 --> 00:39:32,710 [Inaudible] 27 żerijiet wara dik 0.1. 838 00:39:32,710 --> 00:39:34,740 >> Well ejja ara jekk dan huwa dak I tabilħaqq nikseb. 839 00:39:34,740 --> 00:39:39,430 Jagħmlu sufruni-0 istess fajl. 840 00:39:39,430 --> 00:39:41,150 ./floats-0. 841 00:39:41,150 --> 00:39:44,380 Ejja zoom fl fuq ir-risposta drammatika. 842 00:39:44,380 --> 00:39:49,980 Dan il-ħin, inti kont qed taħseb 1 maqsum f'10 huwa ta '10%, jew 0.1. 843 00:39:49,980 --> 00:39:50,810 Mhuwiex. 844 00:39:50,810 --> 00:39:53,210 Mill-inqas safejn l- tal kkonċernata kompjuter. 845 00:39:53,210 --> 00:39:57,060 >> Issa why-- OK, dan huwa komplet jimteddu 1 maqsum f'10 hija 0.1. 846 00:39:57,060 --> 00:39:59,710 Iżda why-- li mhuwiex illum il-takeaway. 847 00:39:59,710 --> 00:40:04,010 Allura għaliex ma l-kompjuter think, b'differenza lkoll fil-kamra, 848 00:40:04,010 --> 00:40:06,870 li 1 maqsum f'10 huwa attwalment dak il-valur crazy? 849 00:40:06,870 --> 00:40:10,620 X'hemm-kompjuter tagħmel apparentement? 850 00:40:10,620 --> 00:40:12,490 X'hemm li? 851 00:40:12,490 --> 00:40:13,785 >> Mhuwiex jfur, per se. 852 00:40:13,785 --> 00:40:15,910 Overflow hija tipikament meta inti wrap madwar valur. 853 00:40:15,910 --> 00:40:18,970 Huwa din il-kwistjoni ta 'nuqqas ta' preċiżjoni fil-valur tal-punt floating 854 00:40:18,970 --> 00:40:22,220 fejn inti biss għandek 32 jew forsi anke 64 bit. 855 00:40:22,220 --> 00:40:25,230 Imma jekk hemm xi infinita numru ta 'numbers-- reali 856 00:40:25,230 --> 00:40:27,940 numri bil-punti deċimali u n-numri thereafter-- żgur 857 00:40:27,940 --> 00:40:29,380 inti ma tistax tirrappreżenta kull wieħed minnhom. 858 00:40:29,380 --> 00:40:32,870 Allura l-kompjuter għandha tingħata lilna l-logħba eqreb 859 00:40:32,870 --> 00:40:37,090 għall-valur li tista 'tirrappreżenta użu li ħafna bits għall-valur attwalment I trid, 860 00:40:37,090 --> 00:40:38,690 li hija 0.1. 861 00:40:38,690 --> 00:40:40,685 >> Sfortunatament, jekk inti jibdew jagħmlu matematika, jew inti 862 00:40:40,685 --> 00:40:44,360 jibdew jinvolvu dawn it-tipi ta 'f'wiċċ l-ilma Valuri punt fl programs-- importanti 863 00:40:44,360 --> 00:40:46,770 software finanzjarji, xejn software-- militari 864 00:40:46,770 --> 00:40:49,090 fejn perċezzjoni hija probabbilment pretty importanti. 865 00:40:49,090 --> 00:40:51,520 U inti tibda żżid numri bħal dan, u bidu 866 00:40:51,520 --> 00:40:54,050 running li softwer bil inputs verament kbar 867 00:40:54,050 --> 00:40:56,890 jew għal lottijiet ta 'sigħat jew lottijiet ta 'jiem jew lottijiet ta' snin, 868 00:40:56,890 --> 00:41:01,060 dawn l-iżbalji ftit żgħira żgur tista 'żżid maż-żmien. 869 00:41:01,060 --> 00:41:04,252 >> Issa bħala twarrib, jekk inti stajt qatt tidher Superman 3 jew l-Uffiċċju Ispazju 870 00:41:04,252 --> 00:41:05,960 u inti tista 'recall kif dawk guys seraq 871 00:41:05,960 --> 00:41:08,668 ħafna ta 'flus mill-kompjuter tagħhom billi jużaw valuri b'punt li jvarja 872 00:41:08,668 --> 00:41:11,290 u jingħadd il-ftit fdalijiet, nisperaw li movie 873 00:41:11,290 --> 00:41:12,390 issa jagħmel aktar sens. 874 00:41:12,390 --> 00:41:14,930 Dan huwa dak li kienu jalludi f'dak movie. 875 00:41:14,930 --> 00:41:16,710 Il-fatt li ħafna kumpaniji ma look 876 00:41:16,710 --> 00:41:18,600 wara ċertu numru ta 'postijiet deċimali, 877 00:41:18,600 --> 00:41:20,009 iżda dawk huma frazzjonijiet ta 'ċenteżmi. 878 00:41:20,009 --> 00:41:22,550 Allura inti tibda żżid lilhom up, inti tibda tagħmel ħafna ta 'flus 879 00:41:22,550 --> 00:41:23,424 fil-kont bankarju tiegħek. 880 00:41:23,424 --> 00:41:25,160 Allura dak Office Space spjegat. 881 00:41:25,160 --> 00:41:28,220 >> Issa sfortunatament lil hinn Uffiċċju Ispazju, hemm 882 00:41:28,220 --> 00:41:31,794 huma wħud leġittimament inkwetanti u impatti sinifikanti 883 00:41:31,794 --> 00:41:33,710 ta 'dawn it-tipi ta' deċiżjonijiet tad-disinn sottostanti, 884 00:41:33,710 --> 00:41:35,990 u tabilħaqq waħda mir-raġunijiet nużaw C fil-kors 885 00:41:35,990 --> 00:41:39,640 huwa hekk li inti verament ikollhom din ir-raġuni up fehim ta 'kif il-kompjuters jaħdmu, 886 00:41:39,640 --> 00:41:42,440 kif software xogħlijiet, u ma tieħu xejn għall mogħtija. 887 00:41:42,440 --> 00:41:45,820 >> U fil-fatt sfortunatament, anke ma li l-fehim fundamentali, 888 00:41:45,820 --> 00:41:47,370 aħna bnedmin jagħmlu żbalji. 889 00:41:47,370 --> 00:41:51,310 U dak li ħsibt I d jaqsmu huwa dan il-video tmien minuti hawn jittieħdu 890 00:41:51,310 --> 00:41:56,980 minn episodju marvels Moderna, li hija juru edukattiv dwar kif jaħdmu l-affarijiet 891 00:41:56,980 --> 00:42:00,370 li ż-żebgħa żewġ stampi ta meta l-użu mhux xieraq 892 00:42:00,370 --> 00:42:02,540 u l-fehim ta ' f'wiċċ l-ilma valuri point 893 00:42:02,540 --> 00:42:05,610 wassal għal xi sinifikanti riżultati sfortunati. 894 00:42:05,610 --> 00:42:06,363 Ejja tagħti ħarsa. 895 00:42:06,363 --> 00:42:07,029 [Daqq ta 'video] 896 00:42:07,029 --> 00:42:11,290 -Aħna Issa jirritorna għal "Inġinerija Diżastri "fuq marvels moderna. 897 00:42:11,290 --> 00:42:12,940 Kompjuters. 898 00:42:12,940 --> 00:42:15,580 Imxejna kollha waslu li jaċċettaw l- problemi ta 'spiss frustranti li 899 00:42:15,580 --> 00:42:20,960 ltqajna bil them-- bugs, viruses, u Softwer glitches-- għall-prezzijiet żgħar 900 00:42:20,960 --> 00:42:23,100 li tħallas għall-konvenjenza. 901 00:42:23,100 --> 00:42:27,770 Iżda fil teknoloġija għolja u l-veloċità għolja applikazzjonijiet programm spazjali militari u, 902 00:42:27,770 --> 00:42:32,780 l-iżgħar problema tista jiġu eżaltat fil-diżastru. 903 00:42:32,780 --> 00:42:38,880 >> 4 Ġunju, 1996, xjentisti ppreparati biex tniedi mingħajr ekwipaġġ Ariane 5 rokit. 904 00:42:38,880 --> 00:42:41,190 Kien jġorru xjentifika satelliti mfassla 905 00:42:41,190 --> 00:42:44,570 biex tistabbilixxi preċiżament kif l- Jinteraġixxi Dinja qasam manjetiku 906 00:42:44,570 --> 00:42:47,380 mal-irjieħ solari. 907 00:42:47,380 --> 00:42:50,580 Il rokit kienet mibnija għall l-Aġenzija Spazjali Ewropea, 908 00:42:50,580 --> 00:42:54,400 u tintrefa 'mill-faċilità tagħha fuq il-kosta tal-Gujana Franċiża. 909 00:42:54,400 --> 00:42:57,520 >> -At Madwar 37 għal sekondi fis it-titjira, huma l-ewwel 910 00:42:57,520 --> 00:42:59,070 xi ħaġa ndunat kien tmur ħażina. 911 00:42:59,070 --> 00:43:02,240 Li l-żennuni kienu swiveling b'mod li verament ma għandu. 912 00:43:02,240 --> 00:43:06,550 Madwar 40 sekonda fil-titjira, b'mod ċar il-vettura kien fl-inkwiet, 913 00:43:06,550 --> 00:43:08,820 u li meta huma jkunu għamlu id-deċiżjoni li tiddistruġġih. 914 00:43:08,820 --> 00:43:12,370 L-uffiċjal tas-sigurtà firxa, ma imsaren tremenda, ippressat-buttuna 915 00:43:12,370 --> 00:43:18,030 u nefaħ l-rokit qabel ma setgħet issir periklu għas-sigurtà pubblika. 916 00:43:18,030 --> 00:43:21,010 >> -Dan Kien il-xebba vjaġġ tal-5 Ariane, 917 00:43:21,010 --> 00:43:23,920 u l-qerda tagħha ħa poġġi minħabba l-difett 918 00:43:23,920 --> 00:43:25,932 inkorporati fis-software tal-rokit li. 919 00:43:25,932 --> 00:43:27,640 -Il Problema fuq il- Ariane kienet li hemm 920 00:43:27,640 --> 00:43:30,500 kien numru dak meħtieġ 64 bits biex jesprimu, 921 00:43:30,500 --> 00:43:33,560 u riedu li jikkonvertu li numru 16-bit. 922 00:43:33,560 --> 00:43:36,820 Huma jassumi li n-numru qatt ma kienet se tkun kbar ħafna. 923 00:43:36,820 --> 00:43:40,940 Li aktar ta 'dawk ċifri fil in-numru 64-bit kienu żerijiet. 924 00:43:40,940 --> 00:43:42,450 Huma kienu żbaljati. 925 00:43:42,450 --> 00:43:45,000 >> -Il Inabbiltà ta 'wieħed programm tas-software li jaċċetta 926 00:43:45,000 --> 00:43:49,460 it-tip ta 'numru iġġenerat mill ieħor kien fil-għerq tan-nuqqas. 927 00:43:49,460 --> 00:43:54,260 Iżvilupp Software kienet saret parti jiswew ħafna ta 'teknoloġija ġdida. 928 00:43:54,260 --> 00:43:57,060 Il rokit Ariane 4 kellhom suċċess kbir. 929 00:43:57,060 --> 00:44:01,600 Tant ta 'l-software maħluqa għall kien ukoll użat fil-Ariane 5. 930 00:44:01,600 --> 00:44:04,790 >> -Il Problema bażika kienet li l-Ariane 5. 931 00:44:04,790 --> 00:44:11,200 Was faster-- aċċellerat aktar mgħaġġla, u l-software ma ammontaw għal dak. 932 00:44:11,200 --> 00:44:14,910 >> -Il Qerda tal-rokit kien hemm diżastru finanzjarju enormi. 933 00:44:14,910 --> 00:44:18,630 Kollha minħabba żball software minuta. 934 00:44:18,630 --> 00:44:21,160 Iżda dan ma kienx l-ewwel problemi ta 'konverżjoni data fil-ħin 935 00:44:21,160 --> 00:44:24,770 kien infestat teknoloġija rokit moderna. 936 00:44:24,770 --> 00:44:28,020 >> -Fil 1991 bil-bidu ta 'l-ewwel Gwerra tal-Golf, 937 00:44:28,020 --> 00:44:30,540 l-missili Patriot esperjenzaw tip simili 938 00:44:30,540 --> 00:44:32,465 ta 'problema konverżjoni numru. 939 00:44:32,465 --> 00:44:36,760 U bħala riżultat 28 people-- 28 Soldiers-- Amerikani kienu maqtula, 940 00:44:36,760 --> 00:44:39,010 u madwar mitt oħrajn midruba. 941 00:44:39,010 --> 00:44:42,830 Meta l-Patriot, li suppost kellha biex jipproteġu kontra Scuds deħlin, 942 00:44:42,830 --> 00:44:45,780 naqas milli nar missili. 943 00:44:45,780 --> 00:44:51,610 >> -Meta Iraq invadiet Kuwajt, u l-Amerika imnedija Maltempata deżert kmieni fl-1991, 944 00:44:51,610 --> 00:44:55,720 Batteriji missili Patriot kienu skjerati biex jipproteġu l-Għarabja Sawdita u l-Iżrael 945 00:44:55,720 --> 00:44:59,180 minn attakki bil-missili Scud Iraqini. 946 00:44:59,180 --> 00:45:03,080 Il Patriot hija ta 'medda medja Istati Uniti wiċċ to-air sistema 947 00:45:03,080 --> 00:45:06,530 manifatturati mill-kumpanija Raytheon. 948 00:45:06,530 --> 00:45:09,500 >> -Il Daqs tal-Patriot interċetturi itself-- 949 00:45:09,500 --> 00:45:14,705 Huwa dwar madwar 20 pied fit-tul, u li jiżen madwar 2,000 liri. 950 00:45:14,705 --> 00:45:19,090 U din twettaq warhead ta 'madwar, Naħseb li huwa bejn wieħed u ieħor 150 £. 951 00:45:19,090 --> 00:45:23,880 U l-warhead innifsu huwa hija splussiv għolja, li 952 00:45:23,880 --> 00:45:26,700 għandha frammenti madwar lilu. 953 00:45:26,700 --> 00:45:31,630 Allura l-casing tal-warhead huwa disinjata sabiex taġġixxi bħal buckshot. 954 00:45:31,630 --> 00:45:34,040 >> -Il Missili huma mwettqa erba 'għal kull kontenitur, 955 00:45:34,040 --> 00:45:37,170 u huma trasportati bil-karru semi. 956 00:45:37,170 --> 00:45:44,880 >> Sistema -Il Patriot kontra l-missili tmur lura għall-inqas 20 snin issa. 957 00:45:44,880 --> 00:45:48,380 Din kienet oriġinarjament iddisinjata bħala missili difiża arja 958 00:45:48,380 --> 00:45:50,810 biex rimja fl ajruplani ghadu. 959 00:45:50,810 --> 00:45:54,410 Fl-ewwel Gwerra tal-Golf meta dik gwerra daħal jilgħab 960 00:45:54,410 --> 00:45:59,650 l-Armata riedu jużawh biex rimja fl Scuds, mhux ajruplani. 961 00:45:59,650 --> 00:46:03,580 Il Air Force Iraqi kien mhux tant ta 'problema, 962 00:46:03,580 --> 00:46:06,590 iżda l-Armata kien inkwetat dwar Scuds. 963 00:46:06,590 --> 00:46:10,120 U għalhekk huma ppruvaw jaġġornaw il-Patriot. 964 00:46:10,120 --> 00:46:12,740 >> -Intercepting Ghadu missili jivvjaġġaw lejn Mach 5 965 00:46:12,740 --> 00:46:15,670 kienet se tkun sfida biżżejjed. 966 00:46:15,670 --> 00:46:18,440 Iżda meta l-Patriot kien ġrew fis-servizz, 967 00:46:18,440 --> 00:46:22,580 l-Armata ma kienx konxju ta ' modifika Iraqi li 968 00:46:22,580 --> 00:46:25,880 magħmula scuds tagħhom kważi impossibbli għaliha. 969 00:46:25,880 --> 00:46:30,690 >> Liema-ġara huwa l-Scuds li kienu ġejjin fil kienu instabbli. 970 00:46:30,690 --> 00:46:32,000 Huma kienu wobbly. 971 00:46:32,000 --> 00:46:37,210 Ir-raġuni għal dan kienet l-Iraqis-- sabiex tikseb 600 kilometru out 972 00:46:37,210 --> 00:46:41,680 ta 'firxa missile-- 300 kilometru ħa piż barra mill-warhead quddiem, 973 00:46:41,680 --> 00:46:43,340 u għamel l-warhead eħfef. 974 00:46:43,340 --> 00:46:48,490 Allura issa l-tal-Patriot tipprova toħroġ fil-Scud, u ħafna mill-time-- 975 00:46:48,490 --> 00:46:52,880 il-maġġoranza kbira tal- time-- ikun biss jtiru mill-Scud. 976 00:46:52,880 --> 00:46:57,120 >> -Once L-operaturi tas-sistema Patriot realizzati l-Patriot qbiżt mira tagħha, 977 00:46:57,120 --> 00:47:01,630 huma jisplodu warhead l-Patriot tal biex jevitaw diżgrazzji possibbli jekk hija 978 00:47:01,630 --> 00:47:04,440 kien permess li jaqgħu l-art. 979 00:47:04,440 --> 00:47:08,700 >> -li Kien dak li ħafna nies raw bħala fireballs kbar fil-sema, 980 00:47:08,700 --> 00:47:14,180 u ħażin bħala interċettazzjonijiet ta 'testati Scud. 981 00:47:14,180 --> 00:47:18,020 >> -Although Fil-smewwiet lejl, Patriots dehru li jeqirdu b'suċċess 982 00:47:18,020 --> 00:47:23,280 Scuds, fil Dhahran jista 'jkun hemm l-ebda żball dwar ir-rendiment tagħha. 983 00:47:23,280 --> 00:47:27,930 Hemm sistema radar tal-Patriot tal track mitlufa ta 'Scud dieħla 984 00:47:27,930 --> 00:47:30,260 u qatt nediet dovut għal difett software. 985 00:47:30,260 --> 00:47:34,060 986 00:47:34,060 --> 00:47:38,880 >> Kien l-Iżraeljani li l-ewwel skoperti li l-aktar is-sistema kienet fuq, 987 00:47:38,880 --> 00:47:41,130 l-akbar il diskrepanza ħin sar. 988 00:47:41,130 --> 00:47:44,770 Minħabba arloġġ integrati fil-kompjuter tas-sistema. 989 00:47:44,770 --> 00:47:48,190 >> -About Ġimgħatejn qabel l-traġedja fl Dhahran, 990 00:47:48,190 --> 00:47:50,720 l-Iżraeljani rrapportati lill id-Dipartiment tad-Difiża 991 00:47:50,720 --> 00:47:52,410 li s-sistema kienet jitilfu l-ħin. 992 00:47:52,410 --> 00:47:54,410 Wara madwar tmien sigħat tat-tmexxija, huma ndunat 993 00:47:54,410 --> 00:47:57,690 li s-sistema tal-isiru notevoli inqas preċiż. 994 00:47:57,690 --> 00:48:01,850 Id-Dipartiment tad-Difiża wieġbet billi javżak kollha tal-batteriji Patriot 995 00:48:01,850 --> 00:48:04,800 biex ma jħallux is-sistemi fuq għal żmien twil. 996 00:48:04,800 --> 00:48:06,980 Huma qatt ma qal dak żmien twil kien. 997 00:48:06,980 --> 00:48:09,140 8 sigħat, 10 siegħa, elf sigħat. 998 00:48:09,140 --> 00:48:11,300 Ħadd ma kien jaf. 999 00:48:11,300 --> 00:48:13,320 >> -Il Batterija Patriot stazzjonati fuq il-barracks 1000 00:48:13,320 --> 00:48:18,310 fil Dhahran u interna difettuż tiegħu arloġġ kienet ilha għaddejja aktar minn 100 sigħat 1001 00:48:18,310 --> 00:48:21,520 dwar il-lejl ta 'Frar 25. 1002 00:48:21,520 --> 00:48:25,792 >> -Hija Tracked ħin bi preċiżjoni ta 'madwar wieħed minn għaxra ta' sekonda. 1003 00:48:25,792 --> 00:48:27,950 Issa wieħed minn għaxra ta 'sekonda huwa numru interessanti 1004 00:48:27,950 --> 00:48:31,850 minħabba li ma tistax tiġi espressa fl binarju eżattament, liema 1005 00:48:31,850 --> 00:48:36,500 ifisser li ma tistax tiġi espressa eżattament fi kwalunkwe kompjuter diġitali moderna. 1006 00:48:36,500 --> 00:48:41,070 Huwa diffiċli li wieħed jemmen, iżda jużaw dan bħala eżempju. 1007 00:48:41,070 --> 00:48:43,420 >> Ejja jieħdu l-tielet numru wieħed. 1008 00:48:43,420 --> 00:48:47,330 Terz ma tistax tkun espressi deċimali eżattament. 1009 00:48:47,330 --> 00:48:52,060 Terz huwa 0.333 għaddej għal infinità. 1010 00:48:52,060 --> 00:48:56,420 M'hemm l-ebda mod biex tagħmel dan ma eżattezza assoluta fil deċimali. 1011 00:48:56,420 --> 00:48:59,530 Dik hija eżattament it-tip ta 'problema li ġara fil-Patriot. 1012 00:48:59,530 --> 00:49:04,040 L-itwal-sistema dam, il- agħar l-iżball ħin sar. 1013 00:49:04,040 --> 00:49:08,840 >> -After 100 siegħa ta 'tħaddim, l- żball fil-ħin kien biss madwar terz 1014 00:49:08,840 --> 00:49:10,440 ta 'sekonda. 1015 00:49:10,440 --> 00:49:14,150 Iżda f'termini ta immirar ta ' missili jivvjaġġaw Mach 5, 1016 00:49:14,150 --> 00:49:18,560 dan irriżulta traċċar żball ta 'aktar minn 600 metru. 1017 00:49:18,560 --> 00:49:21,870 Ikun żball fatali għall-suldati fil Dhahran. 1018 00:49:21,870 --> 00:49:28,455 >> Liema-ġara huwa tnedija Scud kien skoperti mis-satelliti ta 'twissija bikrija, 1019 00:49:28,455 --> 00:49:32,710 u dawn kienu jafu Scud kien ġejjin fid-direzzjoni ġenerali tagħhom. 1020 00:49:32,710 --> 00:49:35,150 Huma ma jafux fejn kien ġejjin. 1021 00:49:35,150 --> 00:49:38,210 Kien issa sa l-radar komponent tas-sistema Patriot 1022 00:49:38,210 --> 00:49:43,150 tiddefendi Dhahran biex jinstabu u jżommu track tal-missili ghadu dieħla. 1023 00:49:43,150 --> 00:49:44,561 >> -Il Radar kien intelliġenti ħafna. 1024 00:49:44,561 --> 00:49:46,560 Hija fil-fatt track il-pożizzjoni tal-Scud 1025 00:49:46,560 --> 00:49:48,930 u mbagħad previżjoni fejn probabbilment ikun 1026 00:49:48,930 --> 00:49:51,380 il-ħin li jmiss il- radar bagħtet polz out. 1027 00:49:51,380 --> 00:49:53,040 Dan kien jissejjaħ il-gate firxa. 1028 00:49:53,040 --> 00:49:57,620 >> -Then Ladarba l-Patriot jiddeċiedi ħin biżżejjed għandha 1029 00:49:57,620 --> 00:50:02,400 mgħoddija li jmorru lura u jivverifika l-li jmiss post għal dan l-oġġett skoperti 1030 00:50:02,400 --> 00:50:03,550 din tmur lura. 1031 00:50:03,550 --> 00:50:07,820 Allura meta marru lura lill-ħażin post, imbagħad jara l-ebda oġġett. 1032 00:50:07,820 --> 00:50:10,360 U huwa jiddeċiedi li ma kien hemm ebda oġġett. 1033 00:50:10,360 --> 00:50:13,630 Li kien hemm kxif falza u qtar il-binarju. 1034 00:50:13,630 --> 00:50:16,970 >> -Il Scud deħlin sparixxew mill-iskrin tar-radar, 1035 00:50:16,970 --> 00:50:20,200 u sekondi wara, slammed fil-kwartieri. 1036 00:50:20,200 --> 00:50:22,570 Il Scud maqtula 28. 1037 00:50:22,570 --> 00:50:26,110 Kien l-aħħar wieħed sparati matul l-ewwel Gwerra tal-Golf. 1038 00:50:26,110 --> 00:50:31,920 Traġikament, il-software aġġornat waslu fuq dawn l-għada. 1039 00:50:31,920 --> 00:50:34,870 Il difett softwer kellhom ġie ffissat, għeluq 1040 00:50:34,870 --> 00:50:39,150 kapitolu wieħed fil-mnikkta istorja tal-missili Patriot. 1041 00:50:39,150 --> 00:50:40,030 >> [END daqq ta 'video] 1042 00:50:40,030 --> 00:50:41,488 >> DAVID J. Malan: Li lilha għall CS50. 1043 00:50:41,488 --> 00:50:42,820 Aħna se tara int nhar l-Erbgħa. 1044 00:50:42,820 --> 00:50:46,420 1045 00:50:46,420 --> 00:50:50,370 >> [Daqq ta mużika] 1046 00:50:50,370 --> 00:54:23,446