{"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\/hr\/blog\/administrirovanie\/pochemu-v-ebcdic-bukvy-idut-ne-podryad","title":{"rendered":"Za\u0161to u EBCDIC-u slova nisu uzastopna?","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

ASCII standard was adopted in 1963, and now hardly anyone uses a character encoding where the first 128 characters differ from ASCII. Nevertheless, until the end of the last century, EBCDIC was actively used \u2014 the standard encoding for IBM mainframes and their Soviet clones \u0415\u0421 \u042d\u0412\u041c. EBCDIC remains the primary encoding in z\/OS \u2014 the standard OS for modern IBM Z mainframes.<\/p>\n

What immediately catches the eye when looking at EBCDIC is that the letters do not run in sequence: between I<\/code> i J<\/code> and between R<\/code> i S<\/code> there are unused positions (on \u0415\u0421 \u042d\u0412\u041c, characters of Cyrillic were distributed<\/a><\/noindex> in these gaps). Who could have thought of encoding letters with unequal spaces between adjacent letters?<\/p>\n

\"Za\u0161to<\/p>\n

Sama naziv EBCDIC («Extended BCDIC») sugerira da je ova kodna shema \u2014 za razliku od ASCII \u2014 razvijena ne na praznom mjestu, ve\u0107 na osnovi \u0161estobitne kodne sheme BCDIC, koja se koristila od IBM 704<\/a><\/noindex> (1954):<\/p>\n

\"Za\u0161to<\/p>\n

There is no direct backward compatibility: a convenient feature of BCDIC, lost when transitioning to EBCDIC, was that the digits 0<\/code>\u20149<\/code> correspond to codes 0-9. However, there were already gaps of seven codes between I<\/code> i J<\/code> and eight codes between R<\/code> i S<\/code> in BCDIC. Where did they come from?<\/p>\n

Povijest (E)BCDIC po\u010dinje istovremeno s povijesti IBM-a \u2014 davno prije elektroni\u010dkih ra\u010dunala. IBM je osnovan spajanjem \u010detiri kompanije, od kojih je tehnolo\u0161ki najnaprednija bila «Tabulating Machine Company», koju je 1896. godine osnovao Herman Hollerith \u2014 izumitelj the tabulator<\/a><\/noindex>. The first tabulators simply counted the number of punch cards perforated in a certain place; but in 1905, Hollerith began manufacturing decimal<\/em> tabulators. Each card for the decimal tabulator consisted of fields of arbitrary length, and numbers recorded in these fields in a familiar decimal form were summed across the entire deck. The breakdown of the card into fields was determined by connecting wires on the tabulator's control panel. For example, on this punch card of Hollerith's, stored<\/a><\/noindex> in the Library of Congress, the number 23456789012345678 is clearly marked, though how it was split into fields is unknown:<\/p>\n

\"Za\u0161to<\/p>\n

The most attentive may notice that Hollerith's card has 12 rows for holes, although only ten are enough for digits; while in BCDIC, only 12 codes from the 16 possible are used for each value of the top two bits.<\/p>\n

Naravno, to nije slu\u010dajna podudarnost. U po\u010detku je Hollerith namijenio dodatne redove za «posebne oznake», koje se nisu zbrajale, ve\u0107 su se jednostavno brojale \u2014 kao u najranijim tabulatorima. (Danas bismo ih nazvali «bitnim poljima».) Osim toga, me\u0111u «posebnim oznakama» mogli su se postaviti group indicators: ako su prilikom tabulacije bile potrebne ne samo kona\u010dne sume, ve\u0107 i me\u0111usume, tabulator se zaustavljao kada je otkrio promjenu bilo kojeg od group indicators, a operater je morao prepisati me\u0111usume s digitalnih displeja na papir, poni\u0161titi displej i nastaviti tabulaciju. Na primjer, kod izra\u010dunavanja ra\u010dunovodstvenih bilanci grupa kartica mogla je odgovarati jednom datumu ili jednom klijentu.<\/p>\n

Do 1920. godine, kada je Hollerith ve\u0107 oti\u0161ao u mirovinu, u uporabu su u\u0161li «ispisni tabulatori», koji su se povezivali s teletipom i mogli su sami ispisivati me\u0111usume, ne zahtijevaju\u0107i intervenciju operatera. Slo\u017eenost je sada bila odrediti na \u0161to se odnosi svaki od ispisanih brojeva. Godine 1931. IBM je odlu\u010dio da pomo\u0107u «posebnih oznaka» ozna\u010dava slova: oznaka u 12. redu ozna\u010davala je slovo od A<\/code> do I<\/code>, u 11. redu \u2014 od J<\/code> do R<\/code>, u nultom \u2014 od S<\/code> do Z<\/code>. Novi «alfabetski tabulator» mogao je ispisivati naziv svake grupe kartica zajedno s me\u0111usumama; pri tom, neprobijen stupac pretvarao se u razmak izme\u0111u simbola. Imajte na umu da S<\/code> ozna\u010dava kombinaciju rupa 0+2, dok se kombinacija 0+1 prvotno nije koristila zbog straha da bi dva otvora blizu zajedno u jednom stupcu mogla prouzro\u010diti mehani\u010dke probleme u \u010dita\u010du.<\/p>\n

\"Za\u0161to<\/p>\n

Sada na tablicu BCDIC mo\u017eemo pogledati iz malo druga\u010dije perspektive:<\/p>\n

\"Za\u0161to<\/p>\n

Osim \u0161to su 0 i razmak zamijenjeni, gornja dva bita odre\u0111uju «posebnu oznaku», koju su od 1931. probijali u perforiranoj kartici za odgovaraju\u0107i simbol; a donja \u010detiri bita odre\u0111uju broj, koji se probijao u glavnom dijelu kartice. Podr\u0161ka za simbole & - \/<\/code> dodana u tabulatore IBM 1930-ih, a kodiranje tih simbola u BCDIC odgovara probijenim kombinacijama rupa za njih. Kada je postojala potreba za podr\u0161kom za jo\u0161 ve\u0107i broj simbola, kao dodatna 'specijalna oznaka' po\u010deli su probijati red 8 \u2013 tako da je u jednom stupcu moglo biti do tri rupe. Ovaj format perforiranih kartica odr\u017eao se prakti\u010dki nepromijenjen do kraja stolje\u0107a. U SSSR-u su zadr\u017eali IBM-ove kodiranja latini\u010dnog pisma i interpunkcije, dok su za \u0107irili\u010dna slova probijali odmah nekoliko 'specijalnih oznaka' u redovima 12, 11, 0 \u2013 ne ograni\u010davaju\u0107i se na tri rupe u jednom stupcu.<\/p>\n

Kada je osmi\u0161ljen ra\u010dunar IBM 704, dugo se nije razmi\u0161ljalo o kodiranju simbola za njega: uzeta je kodiranja koja su ve\u0107 tada kori\u0161\u0107ena u perforiranim karticama, a samo je 0 'stavljen na mesto'. Godine 1964, prilikom prelaska sa BCDIC na EBCDIC, donji \u010detiri bita svakog simbola ostala su nepromijenjena, iako su malo promije\u0161ani gornji bitovi. Tako je format perforiranih kartica, koji je izabrao Hollerith po\u010detkom pro\u0161log stolje\u0107a, utjecao na arhitekturu svih IBM-ovih ra\u010dunara, uklju\u010duju\u0107i IBM Z.<\/p>\n

Izvor: 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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