{"id":96211,"date":"2020-10-09T07:42:43","date_gmt":"2020-10-09T05:42:43","guid":{"rendered":"https:\/\/prohoster.info\/blog\/administrirovanie\/pochemu-v-ebcdic-bukvy-idut-ne-podryad"},"modified":"2020-10-09T07:42:43","modified_gmt":"2020-10-09T05:42:43","slug":"pochemu-v-ebcdic-bukvy-idut-ne-podryad","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sk\/blog\/administrirovanie\/pochemu-v-ebcdic-bukvy-idut-ne-podryad","title":{"rendered":"Pre\u010do v EBCDIC p\u00edsmen\u00e1 id\u00fa neporiadku?","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\u0160tandard ASCII bol prijat\u00fd v roku 1963 a dnes sotva niekto pou\u017e\u00edva k\u00f3dovanie, ktor\u00e9ho prv\u00fdch 128 znakov by sa od ASCII l\u00ed\u0161ilo. Napriek tomu do konca minul\u00e9ho storo\u010dia sa akt\u00edvne pou\u017e\u00edval EBCDIC \u2013 \u0161tandardn\u00e9 k\u00f3dovanie pre mainframe IBM a ich sovietske klony ES EVM. EBCDIC zost\u00e1va hlavn\u00fdm k\u00f3dovan\u00edm v z\/OS \u2013 \u0161tandardnom OS pre modern\u00e9 mainframe IBM Z.<\/p>\n

To, \u010do okam\u017eite udiera do o\u010d\u00ed pri poh\u013eade na EBCDIC, je to, \u017ee p\u00edsmen\u00e1 nie s\u00fa za sebou: medzi I<\/code> a J<\/code> a medzi R<\/code> a S<\/code> zostali nevyu\u017eit\u00e9 poz\u00edcie (na ES EVM sa medzi t\u00fdmito medzerami distribuovali<\/a><\/noindex> znaky cyrilice). Koho mohlo napadn\u00fa\u0165 k\u00f3dova\u0165 p\u00edsmen\u00e1 s nerovn\u00fdmi rozstupmi medzi susedn\u00fdmi p\u00edsmenami?<\/p>\n

\"Pre\u010do<\/p>\n

Sama n\u00e1zov EBCDIC («Extended BCDIC») nazna\u010duje, \u017ee t\u00e1to k\u00f3dovanie \u2014 na rozdiel od ASCII \u2014 bola vytvoren\u00e1 na z\u00e1klade \u0161es\u0165bitovej k\u00f3dovania BCDIC, ktor\u00e1 sa pou\u017e\u00edvala od IBM 704<\/a><\/noindex> (1954):<\/p>\n

\"Pre\u010do<\/p>\n

Priama sp\u00e4tn\u00e1 kompatibilita neexistuje: pohodlnou vlastnos\u0165ou BCDIC, ktor\u00e1 sa stratila pri prechode na EBCDIC, bolo to, \u017ee \u010d\u00edslam 0<\/code>\u20149<\/code> zodpovedaj\u00fa k\u00f3dy 0-9. Napriek tomu u\u017e existovali medzery v siedmich k\u00f3doch medzi I<\/code> a J<\/code> a v \u00f4smich k\u00f3doch medzi R<\/code> a S<\/code> v BCDIC. Odkia\u013e sa teda vzali?<\/p>\n

Hist\u00f3ria (E)BCDIC za\u010d\u00edna s\u00fa\u010dasne s hist\u00f3riou IBM \u2014 d\u00e1vno pred elektronick\u00fdmi po\u010d\u00edta\u010dmi. IBM vznikla zl\u00fa\u010den\u00edm \u0161tyroch spolo\u010dnost\u00ed, z ktor\u00fdch najtechnologicky vyspel\u0161ou bola «Tabulating Machine Company», zalo\u017een\u00e1 v roku 1896 Hermanom Holleritom \u2014 vyn\u00e1lezcom tabul\u00e1tora<\/a><\/noindex>. Prv\u00e9 tabul\u00e1tory jednoducho po\u010d\u00edtali po\u010det perforovan\u00fdch kariet, ktor\u00e9 boli prebodnut\u00e9 na ur\u010ditom mieste; ale v roku 1905 Hollerith za\u010dal v\u00fdrobu desiatkov\u00fdch<\/em> tabul\u00e1torov. Ka\u017ed\u00e1 karta pre desiatkov\u00fd tabul\u00e1tor pozost\u00e1vala z pol\u00ed \u013eubovo\u013enej d\u013a\u017eky a \u010d\u00edsla zap\u00edsan\u00e9 v t\u00fdchto poliach v be\u017enej desiatkovej forme sa s\u010d\u00edtavali cez cel\u00fa k\u00f4pku. Rozdelenie karty na polia sa ur\u010dovalo spojom vodi\u010dov na prep\u00edna\u010dovej doske tabul\u00e1tora. Napr\u00edklad na tejto perforovanej karte Holleritha, uchov\u00e1vanej<\/a><\/noindex> v Kni\u017enici Kongresu, je jasne vyrazen\u00e9 \u010d\u00edslo 23456789012345678, nezn\u00e1mo ako rozdelen\u00e9 na polia:<\/p>\n

\"Pre\u010do<\/p>\n

Najpozornej\u0161\u00ed si mohli v\u0161imn\u00fa\u0165, \u017ee na karte Holleritha je 12 radov pre otvory, hoci pre \u010d\u00edsla sta\u010d\u00ed desa\u0165; a v BCDIC sa pre ka\u017ed\u00fa hodnotu najvy\u0161\u0161\u00edch dvoch bitov pou\u017e\u00edva len 12 k\u00f3dov z 16 mo\u017en\u00fdch.<\/p>\n

Samozrejme, nie je to n\u00e1hodn\u00e9. P\u00f4vodne ich Hollerit ur\u010dil na «\u0161peci\u00e1lne zna\u010dky», ktor\u00e9 sa nes\u010d\u00edtavali, ale len po\u010d\u00edtali \u2014 ako v najprv\u0161\u00edch tabu\u013e\u00e1toroch. (Dnes by sme ich nazvali «bitov\u00fdmi po\u013eami».) Okrem toho bolo mo\u017en\u00e9 medzi «\u0161peci\u00e1lnymi zna\u010dkami» nastavi\u0165 skupinov\u00e9 indik\u00e1tory: ak sa pri tabu\u013eovan\u00ed vy\u017eadovali nielen kone\u010dn\u00e9 s\u00fa\u010dty, ale aj medzistupne, tabu\u013e\u00e1tor sa zastavil, ke\u010f zistil zmenu niektor\u00e9ho z skupinov\u00fdch indik\u00e1torov, a oper\u00e1tor musel prep\u00edsa\u0165 medzistupne z digit\u00e1lnych displejov na papier, nulova\u0165 displeje a obnovi\u0165 tabu\u013eovanie. Napr\u00edklad, pri v\u00fdpo\u010dte \u00fa\u010dtovn\u00fdch zostatkov mohla skupina kariet zodpoveda\u0165 jedn\u00e9mu d\u00e1tumu alebo jedn\u00e9mu partnerovi.<\/p>\n

Do roku 1920, ke\u010f sa Hollerit u\u017e posunul do d\u00f4chodku, sa dostali do obiehania «tla\u010dov\u00e9 tabu\u013e\u00e1tory», ktor\u00e9 sa prip\u00e1jali k teletype a mohli samy tla\u010di\u0165 medzistupne, bez potreby z\u00e1sahu obsluhy. Zlo\u017eitostou teraz bolo ur\u010di\u0165, k \u010domu sa ka\u017ed\u00e9 z vytla\u010den\u00fdch \u010d\u00edsiel vz\u0165ahuje. V roku 1931 sa IBM rozhodla ozna\u010dova\u0165 p\u00edsmen\u00e1 pomocou «\u0161peci\u00e1lnych zna\u010diek»: zna\u010dka v 12. riadku znamenala p\u00edsmeno od A<\/code> do I<\/code>, v 11. \u2014 od J<\/code> do R<\/code>, v nultom \u2014 od S<\/code> do Z<\/code>. Nov\u00fd «abecedn\u00fd tabu\u013e\u00e1tor» mohol tla\u010di\u0165 n\u00e1zov ka\u017edej skupiny kariet spolu s medzistup\u0148ov\u00fdmi s\u00fa\u010dty; pritom neprebit\u00e9 st\u013apec sa premenil na medzeru medzi znakmi. V\u0161imnite si, \u017ee S<\/code> sa ozna\u010duje kombin\u00e1ciou otvorov 0+2, zatia\u013e \u010do kombin\u00e1cia 0+1 sa p\u00f4vodne nepou\u017e\u00edvala z obavy, \u017ee dva otvory ved\u013ea seba v jednom st\u013apci m\u00f4\u017eu sp\u00f4sobi\u0165 mechanick\u00e9 probl\u00e9my v \u010d\u00edta\u010dke.<\/p>\n

\"Pre\u010do<\/p>\n

Teraz sa na tabu\u013eku BCDIC m\u00f4\u017eeme pozrie\u0165 z trochu in\u00e9ho uhla:<\/p>\n

\"Pre\u010do<\/p>\n

S v\u00fdnimkou toho, \u017ee 0 a medzera s\u00fa prehoden\u00e9, vy\u0161\u0161ie dva bity ur\u010duj\u00fa «\u0161peci\u00e1lnu zna\u010dku», ktor\u00fa od roku 1931 preb\u00edjali v perforovanej karte pre pr\u00edslu\u0161n\u00fd symbol; a ni\u017e\u0161ie \u0161tyri bity ur\u010duj\u00fa \u010d\u00edslo, preb\u00edjan\u00e9 v hlavnej \u010dasti karty. Podpora symbolov & - \/<\/code> Pridala sa do tabuliek IBM v 30. rokoch a k\u00f3dovanie t\u00fdchto znakov v BCDIC zodpoved\u00e1 priechodn\u00fdm kombin\u00e1ci\u00e1m otvorov. Ke\u010f bola potrebn\u00e1 podpora e\u0161te v\u00e4\u010d\u0161ieho po\u010dtu znakov, ako \u010fal\u0161ia \u201e\u0161peci\u00e1lna zna\u010dka\u201c sa za\u010dali vyr\u00e1ba\u0165 otvory v rade 8 - takto mohli by\u0165 v jednom st\u013apci a\u017e tri otvory. Tento form\u00e1t diernych \u0161t\u00edtkov zostal prakticky nezmenen\u00fd a\u017e do konca storo\u010dia. V ZSSR zostali IBM-ovsk\u00e9 k\u00f3dovania latinky a interpunkcie, a pre cyrilsk\u00e9 p\u00edsmen\u00e1 sa vyr\u00e1balo naraz nieko\u013eko \u201e\u0161peci\u00e1lnych zna\u010diek\u201c v radoch 12, 11, 0 - bez obmedzenia na tri otvory v jednom st\u013apci.<\/p>\n

Ke\u010f sa vytv\u00e1ral po\u010d\u00edta\u010d IBM 704, dlho sa neuva\u017eovalo o k\u00f3dovan\u00ed znakov pre neho: prevzali k\u00f3dovanie, ktor\u00e9 sa u\u017e vtedy pou\u017e\u00edvalo v diernych \u0161t\u00edtkoch, a len 0 \u201edali na miesto\u201c. V roku 1964, pri prechode od BCDIC k EBCDIC, spodn\u00e9 \u0161tyri bity ka\u017ed\u00e9ho znaku zostali nezmenen\u00e9, hoci sa tro\u0161ku premie\u0161ali horn\u00e9 bity. Tak\u017ee form\u00e1t diernych \u0161t\u00edtkov, ktor\u00fd vybral Hollerith na za\u010diatku minul\u00e9ho storo\u010dia, mal vplyv na architekt\u00faru v\u0161etk\u00fdch po\u010d\u00edta\u010dov IBM, vr\u00e1tane IBM Z.<\/p>\n

Zdroj: habr.com<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0421\u0442\u0430\u043d\u0434\u0430\u0440\u0442 ASCII \u0431\u044b\u043b \u043f\u0440\u0438\u043d\u044f\u0442 \u0432 1963, \u0438 \u0441\u0435\u0439\u0447\u0430\u0441 \u0432\u0440\u044f\u0434 \u043b\u0438 \u043a\u0442\u043e-\u043d\u0438\u0431\u0443\u0434\u044c \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u0443\u0435\u0442 \u043a\u043e\u0434\u0438\u0440\u043e\u0432\u043a\u0443, \u043f\u0435\u0440\u0432\u044b\u0435 128 \u0441\u0438\u043c\u0432\u043e\u043b\u043e\u0432 \u043a\u043e\u0442\u043e\u0440\u043e\u0439 \u043e\u0442\u043b\u0438\u0447\u0430\u043b\u0438\u0441\u044c \u0431\u044b \u043e\u0442 ASCII. \u0422\u0435\u043c \u043d\u0435 \u043c\u0435\u043d\u0435\u0435, \u0434\u043e \u043a\u043e\u043d\u0446\u0430 \u043f\u0440\u043e\u0448\u043b\u043e\u0433\u043e \u0432\u0435\u043a\u0430 \u0430\u043a\u0442\u0438\u0432\u043d\u043e \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043b\u0430\u0441\u044c EBCDIC \u2014 \u0441\u0442\u0430\u043d\u0434\u0430\u0440\u0442\u043d\u0430\u044f \u043a\u043e\u0434\u0438\u0440\u043e\u0432\u043a\u0430 \u0434\u043b\u044f \u043c\u0435\u0439\u043d\u0444\u0440\u0435\u0439\u043c\u043e\u0432 IBM \u0438 \u0438\u0445 \u0441\u043e\u0432\u0435\u0442\u0441\u043a\u0438\u0445 \u043a\u043b\u043e\u043d\u043e\u0432 \u0415\u0421 \u042d\u0412\u041c. 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