{"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\/ro\/blog\/administrirovanie\/pochemu-v-ebcdic-bukvy-idut-ne-podryad","title":{"rendered":"De ce literele \u00een EBCDIC nu sunt consecutive?","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Standardul ASCII a fost adoptat \u00een 1963, iar \u00een prezent, este pu\u021bin probabil ca cineva s\u0103 foloseasc\u0103 o codificare ale c\u0103rei prime 128 de caractere s\u0103 difere de ASCII. Cu toate acestea, p\u00e2n\u0103 la sf\u00e2r\u0219itul secolului trecut, EBCDIC a fost utilizat activ - o codificare standard pentru mainframe-urile IBM \u0219i clonele lor sovietice ES EVM. EBCDIC r\u0103m\u00e2ne codificarea principal\u0103 \u00een z\/OS - sistemul de operare standard pentru mainframe-urile moderne IBM Z.<\/p>\n

Ceea ce sare imediat \u00een ochi atunci c\u00e2nd ne uit\u0103m la EBCDIC este c\u0103 literele nu sunt consecutive: \u00eentre I<\/code> \u0219i J<\/code> \u0219i \u00eentre R<\/code> \u0219i S<\/code> au r\u0103mas pozi\u021bii neutilizate (pe ES EVM \u00een aceste intervale s-au distribuit<\/a><\/noindex> simboluri chirilice). Cui i-ar fi trecut prin minte s\u0103 codifice literele cu intervale inegale \u00eentre literele vecine?<\/p>\n

\"De<\/p>\n

Numele EBCDIC (\u201eExtended BCDIC\u201d) sugereaz\u0103 c\u0103 acest cod a fost creat, spre deosebire de ASCII, pe baza codului BCDIC cu \u0219ase bi\u021bi, folosit \u00eenc\u0103 din IBM 704<\/a><\/noindex> (1954):<\/p>\n

\"De<\/p>\n

Nu exist\u0103 o compatibilitate direct\u0103: un avantaj al BCDIC, pierdut \u00een tranzi\u021bia la EBCDIC, era c\u0103 cifrelor 0<\/code>\u20149<\/code> le corespund codurile 0-9. Cu toate acestea, deja existau lacune de \u0219apte coduri \u00eentre I<\/code> \u0219i J<\/code> \u0219i lacune de opt coduri \u00eentre R<\/code> \u0219i S<\/code> \u00een BCDIC. De unde au ap\u0103rut acestea?<\/p>\n

Istoria (E)BCDIC \u00eencepe simultan cu istoria IBM \u2014 cu mult \u00eenainte de computerele electronice. IBM a fost format\u0103 \u00een urma fuziunii a patru companii, dintre care cea mai avansat\u0103 tehnologic era \u201eTabulating Machine Company\u201d, fondat\u0103 \u00een 1896 de Hermann Hollerith \u2014 inventorul tabulatorului<\/a><\/noindex>. Primele tabulatoare num\u0103rau pur \u0219i simplu num\u0103rul de carduri perforate, b\u0103tute \u00eentr-un anumit loc; dar \u00een 1905, Hollerith a \u00eenceput produc\u021bia de tabulatoare zecimale.<\/em> Fiecare card pentru tabulatorul zecimal consta din c\u00e2mpuri de lungime arbitrar\u0103, iar numerele, scrise \u00een aceste c\u00e2mpuri \u00een forma decimal\u0103 obi\u0219nuit\u0103, erau sumarizate pe \u00eentreaga palet\u0103. \u00cemp\u0103r\u021birea cardului \u00een c\u00e2mpuri era definit\u0103 prin conectarea firelor pe panoul de comutare al tabulatorului. De exemplu, pe acest card perforat al lui Hollerith, p\u0103strat<\/a><\/noindex> \u00een Biblioteca Congresului, este evident c\u0103 num\u0103rul 23456789012345678 este b\u0103tut, nefiind clar cum a fost \u00eemp\u0103r\u021bit pe c\u00e2mpuri:<\/p>\n

\"De<\/p>\n

Cei mai aten\u021bi ar fi putut observa c\u0103 pe cardul lui Hollerith exist\u0103 12 r\u00e2nduri pentru g\u0103uri, de\u0219i pentru cifre sunt suficiente zece; iar \u00een BCDIC pentru fiecare valoare a celor dou\u0103 bi\u021bi cei mai semnificativi sunt folosi\u021bi doar 12 coduri din cele 16 posibile.<\/p>\n

Desigur, aceasta nu este o coinciden\u021b\u0103 \u00eent\u00e2mpl\u0103toare. Ini\u021bial, Hollerith a conceput r\u00e2ndurile suplimentare pentru \u201emarcaje speciale\u201d, care nu erau sumate, ci doar num\u0103rate \u2014 a\u0219a cum se \u00eent\u00e2mpla \u00een cele mai vechi tabulatoare. (Ast\u0103zi le-am numi \u201ec\u00e2mpuri de bi\u021bi\u201d.) \u00cen plus, printre \u201emarcajele speciale\u201d, se puteau stabili indicatori de grup: dac\u0103 la tabulare erau necesare nu doar sumele finale, ci \u0219i cele intermediare, tabulatorul se oprea atunci c\u00e2nd detecta modificarea oric\u0103rui dintre indicatorii de grup, iar operatorul trebuia s\u0103 transfere sumele intermediare de pe tabloul digital pe h\u00e2rtie, s\u0103 reseteze tabloul \u0219i s\u0103 reia tabularea. De exemplu, la calcularea soldurilor contabile, un grup de cartona\u0219e putea corespunde unei date sau unui contractor.<\/p>\n

P\u00e2n\u0103 \u00een 1920, c\u00e2nd Hollerith se pensionase deja, au \u00eenceput s\u0103 fie folosite \u201etabulatoare printante\u201d, care se conectau la teletype \u0219i puteau s\u0103 imprime singure sumele intermediare, f\u0103r\u0103 a necesita interven\u021bia operatorului. Complexitatea a constat acum \u00een a determina la ce se referea fiecare dintre numerele tip\u0103rite. \u00cen 1931, IBM a decis s\u0103 marcheze literele cu ajutorul \u201emarcajelor speciale\u201d: o marc\u0103 din r\u00e2ndul 12 indica litera de la A<\/code> la I<\/code>, din r\u00e2ndul 11 \u2014 de J<\/code> la R<\/code>, din r\u00e2ndul zero \u2014 de S<\/code> la Z<\/code>. Noua \u201etabulare alfabetic\u0103\u201d putea imprima numele fiec\u0103rui grup de cartona\u0219e \u00eempreun\u0103 cu sumele intermediare; \u00een acest caz, coloana neperforat\u0103 se transforma \u00eentr-un spa\u021biu \u00eentre simboluri. Observa\u021bi c\u0103 S<\/code> este marcat\u0103 de combina\u021bia g\u0103urilor 0+2, iar combina\u021bia 0+1 nu a fost utilizat\u0103 ini\u021bial din teama c\u0103 dou\u0103 g\u0103uri al\u0103turate \u00eentr-o singur\u0103 coloan\u0103 ar putea provoca probleme mecanice cititorului.<\/p>\n

\"De<\/p>\n

Acum, putem privi tabelul BCDIC dintr-o alt\u0103 perspectiv\u0103:<\/p>\n

\"De<\/p>\n

Cu excep\u021bia faptului c\u0103 0 \u0219i spa\u021biul sunt inverse, cele dou\u0103 bi\u021bi superiori determin\u0103 \u201emarcajul special\u201d, care din 1931 a fost perforat \u00een cartela de perforat pentru simbolul corespunz\u0103tor; iar cei patru bi\u021bi inferiori determin\u0103 cifra, perforat\u0103 \u00een partea principal\u0103 a c\u0103r\u021bii. Suportul simbolurilor & - \/<\/code> a fost introdus\u0103 \u00een tabulatorile IBM \u00een anii 1930, iar codificarea acestor simboluri \u00een BCDIC corespunde combina\u021biilor de g\u0103uri perforate. C\u00e2nd a fost nevoie de suport pentru un num\u0103r \u0219i mai mare de simboluri, a fost utilizat\u0103 o \u201emarc\u0103 special\u0103\u201d suplimentar\u0103, perfor\u00e2nd un r\u00e2nd 8 \u2014 astfel, \u00eentr-o coloan\u0103 puteau exista p\u00e2n\u0103 la trei g\u0103uri. Acest format de cartona\u0219e perforate a r\u0103mas practic neschimbat p\u00e2n\u0103 la sf\u00e2r\u0219itul secolului. \u00cen URSS, au fost p\u0103strate codific\u0103rile IBM pentru literele latine \u0219i semnele de punctua\u021bie, iar pentru literele chirilice au fost perforate mai multe \u201em\u0103rci speciale\u201d \u00een r\u00e2ndurile 12, 11, 0 \u2014 f\u0103r\u0103 a se limita la trei g\u0103uri \u00eentr-o singur\u0103 coloan\u0103.<\/p>\n

C\u00e2nd a fost creat computerul IBM 704, codificarea caracterelor pentru acesta nu a fost o problem\u0103 deosebit\u0103: a fost preluat\u0103 codificarea deja utilizat\u0103 \u00een cartona\u0219ele perforate, iar 0 a fost \u201eplasat la locul s\u0103u\u201d. \u00cen 1964, la trecerea de la BCDIC la EBCDIC, cele patru bi\u021bi inferiori ai fiec\u0103rui simbol au fost l\u0103sa\u021bi neschimba\u021bi, chiar dac\u0103 bi\u021bii superiori au fost pu\u021bin amesteca\u021bi. Astfel, formatul cartona\u0219ului perforat ales de Hollerith la \u00eenceputul secolului trecut a influen\u021bat arhitectura tuturor computerelor IBM, inclusiv IBM Z.<\/p>\n

Sursa: 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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