History
EBCDIC ( /ˈɛbsɨdɪk/) was devised in 1963 and 1964 by IBM and was announced with the release of the IBM System/360 line of mainframe computers. It is an 8-bit character encoding, in contrast to, and developed separately from, the 7-bit ASCII encoding scheme. It was created to extend the existing binary-coded decimal (BCD) interchange code, or BCDIC, which itself was devised as an efficient means of encoding the two zone and number punches on punched cards into 6 bits.
While IBM was a chief proponent of the ASCII standardization committee, they did not have time to prepare ASCII peripherals (such as card punch machines) to ship with its System/360 computers, so the company settled on EBCDIC. The System/360 became wildly successful, and together with clones such as RCA Spectra, ICL System 4, and Fujitsu Facom, thus so did EBCDIC.
All IBM mainframe and midrange peripherals and operating systems use EBCDIC as their inherent encoding, but AIX running on the iSeries, Linux running on the zSeries, and the IBM PC and its descendants use ASCII. Software and many hardware peripherals can translate to and from encodings, and modern mainframes (such as IBM zSeries) include processor instructions, at the hardware level, to accelerate translation between character sets.
EBCDIC has no technical advantage compared to ASCII-based code pages such as the ISO-8859 series or Unicode except for the inclusion of the "¢" (cent) character. While EBCDIC, like ASCII, has one bit flagging upper or lower case, unlike ASCII the EBCDIC alphabet is non-contiguous, interleaved with unassigned characters which may or may not be in use. Data portability is hindered by a lack of many symbols commonly used in programming and in network communications. The collating sequence of upper case alphabetic characters is higher than lower case and numerics are higher still — the exact opposite of ASCII. As with single-byte extended ASCII codepages, EBCDIC codepages are language-dependent with no nomenclature or internal mechanism to denote non-"standard" usage.
Where true support for multilingual text is desired, a system supporting far more characters is needed. Generally this is done with some form of Unicode support. There is an EBCDIC Unicode Transformation Format called UTF-EBCDIC proposed by the Unicode consortium, but it is not intended to be used in open interchange environments and, even on EBCDIC-based systems, it is almost never used. IBM mainframes support UTF-16, but they do not support UTF-EBCDIC natively.
Arabic EBCDIC versions are typically in left-to-right presentation order as displayed by older mainframes and line printers rather than in the right-to-left logical order used by later encodings such as Unicode.
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