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EBCDIC (Fully, "Extended Binary Coded Decimal Interchange Code") is an 8 bit character encoding used on IBM mainframes and AS/400s. It is descended from punched cards. Outside of such IBM systems, ASCII (and its descendants such as Unicode) are normally used instead; EBCDIC is generally considered an anachronism.

EBCDIC takes up eight bits, which are divided in two pieces. The first four bits are called the zone and represent the category of the character, whereas the last four bits are the called the digit and identify the specific character. There are a number of different versions of EBCDIC, customised for different countries.


EBCDIC was devised in 1963-1964 timeframe by IBM and announced with the release of the IBM System/360 line of mainframe computers at the apex of IBM’s mainframe monopoly. It was designed to be better than ASCII, i.e. different and make it difficult for IBM customers to port their data to non-IBM machines. It was an 8 bit encoding, vs. the 7 bit encoding of ASCII and included encodings for all possible punch card codes—an important feature at the time. But the Roman alphabet characters were non-contiguous, a great annoyance.

All IBM mainframe peripheralss and operating systems used EBCDIC. Their only lip service to ASCII was to provide an ASCII mode for reading magnetic tapes.

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