Extended Binary Coded Decimal Interchange Code^[1][2] (EBCDIC;^[1]/ˈɛbsɪdɪk/) is an eight-bitcharacter encoding used mainly onIBM mainframe andIBMmidrange computer operating systems. It descended from the code used withpunched cards and the correspondingsix-bit binary-coded decimal code used with most of IBM'scomputer peripherals of the late 1950s and early 1960s.^[3] It is supported by various non-IBM platforms, such asFujitsu-Siemens'BS2000/OSD, OS-IV, MSP, and MSP-EX, theSDS Sigma series,UnisysVS/9, UnisysMCP andICLVME.

EBCDIC was devised in 1963 and 1964 byIBM and was announced with the release of theIBM System/360 line of mainframecomputers. It is an eight-bit character encoding, developed separately from the seven-bitASCII encoding scheme. It was created to extend the existingBinary-Coded Decimal (BCD) Interchange Code, orBCDIC, which itself was devised as an efficient means of encoding the twozone andnumber punches onpunched cards into six bits. The distinct encoding of 's' and 'S' (using position 2 instead of 1) was maintained from punched cards where it was desirable not to have hole punches too close to each other to ensure the integrity of the physical card.^{[4][failed verification]}

While IBM was a chief proponent of the ASCII standardization committee,^[5] the company 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.^[3] The System/360 became wildly successful, together with clones such asRCA Spectra 70,ICL System 4, and Fujitsu FACOM, thus so did EBCDIC.

All IBM's mainframeoperating systems, and itsIBM i operating system formidrange computers, use EBCDIC as their inherent encoding^[6] (with toleration for ASCII, for example,ISPF inz/OS can browse and edit both EBCDIC and ASCII encoded files). Software can translate to and from encodings, and modern mainframes (such asIBM Z) include processor instructions, at the hardware level, to accelerate translation between character sets. Modern z/OS compilers for the C and C++ languages onIBM Z mainframes, and earlierOS/390 C and C++ compilers onIBM System/390 mainframes, support a POSIX-compatible execution environment that makes use of ASCII by default.^[7]

Not all operating systems running on IBM hardware use EBCDIC;IBM AIX,Linux on IBM Z, andLinux on Power all use ASCII, as do all operating systems that run on theIBM Personal Computer and its successors.

There were numerous difficulties to writing software that would work in both ASCII and EBCDIC.

• The gaps between letters made simple code that worked in ASCII fail on EBCDIC. For examplefor(c='A';c<='Z';++c)putchar(c); would print the alphabet from A to Z if ASCII is used, but print 41 characters (including a number of unassigned ones) in EBCDIC.
• Sorting EBCDIC put lowercase letters before uppercase letters and letters before numbers, exactly the opposite of ASCII.
• Most programming languages and file formats and network protocols designed for ASCII used available punctuation marks (such as carat^, tilde~, square brackets, and the curly braces{ and}) that did not exist in EBCDIC, making translation to EBCDIC systems difficult. Workarounds such astrigraphs were used.^[8] Conversely EBCDIC had some characters such as¬ logical not,¢ (US cent) that were used on IBM systems and could not be translated to ASCII. The logical not character is used in thePL/I programming language, and some other IBM languages.
• The EBCDIC character NL (next line) was best treated as the ASCII LF, but as EBCDIC also contains a character called LF this was not always done consistently.
• If seven-bit ASCII was used, there was an "unused" high bit in 8-bit bytes, and many pieces of software stored other information there. Software would also pack the seven bits and discard the eighth, such as packing five seven-bit ASCII characters in a36-bit word.^[9] On thePDP-11, bytes with the high bit set were treated as negative numbers, behavior that was copied toC, causing unexpected problems if the high bit was set. These all made it difficult to switch from ASCII to the 8-bit EBCDIC (and also made it difficult to switch to 8-bitextended ASCII encodings).

There are hundreds of EBCDIC code pages based on the original EBCDIC character encoding; there are a variety of EBCDICcode pages intended for use in different parts of the world, including code pages for non-Latin scripts such as Chinese, Japanese (e.g., EBCDIC 930, JEF, and KEIS), Korean, and Greek (EBCDIC 875). There is also a huge number of variations with the letters swapped around for no discernible reason.^{[citation needed]}

The table below shows the "invariant subset"^[10] of EBCDIC, which are characters thatshould have the same assignments on all EBCDIC code pages that use the Latin alphabet. (This includes most of theISO/IEC 646 invariant repertoire, except theexclamation mark.) It also shows (in gray) missing ASCII and EBCDIC punctuation, located where they are in Code Page 37 (one of the code page variants of EBCDIC). The blank cells are filled with region-specific characters in the variants, but the characters in gray are often swapped around or replaced as well. Like ASCII, the invariant subset works only for languages using only theISO basic Latin alphabet, such as English.

Following are the definitions of EBCDIC control characters which either do not map onto theASCII control characters, or have additional uses. When mapped to Unicode, these are mostly mapped to C1 control character codepoints in a manner specified by IBM's Character Data Representation Architecture (CDRA).^[11][12]

Although the default mapping of New Line (NL) corresponds to the ISO/IEC 6429 Next Line character (NEL, U+0085, the behaviour of which is also specified, but not required, in Unicode Annex 14),^[13] most of these C1-mapped controls match neither those in theISO/IEC 6429 C1 set, nor those in other registered C1 control sets such asISO 6630.^[14] Although this effectively makes the non-ASCII EBCDIC controls a unique C1 control set, they are not among the C1 control sets registered in theISO-IR registry,^[15] meaning that they do not have an assigned control set designation sequence (as specified byISO/IEC 2022, and optionally permitted inISO/IEC 10646 (Unicode)).^[16]

Besides U+0085 (Next Line), the Unicode Standard does not prescribe an interpretation of C1 control characters, leaving their interpretation to higher level protocols (it suggests, but does not require, their ISO/IEC 6429 interpretations in the absence of use for other purposes),^[17] so this mapping is permissible in, but not specified by, Unicode.

The following code pages have the fullLatin-1 character set (ISO/IEC 8859-1). The first column gives the original code page number. The second column gives the number of the code page updated with theeuro sign (€) replacing the universalcurrency sign (¤) (or in the case of EBCDIC 924, with the set changed to matchISO 8859-15)

Different countries have different code pages because these code pages originated as code pages with country-specific character repertoires, and were later expanded to contain the entire ISO 8859-1 repertoire, meaning that a given ISO 8859-1 character may have differentcode point values in different code pages. They are known asCountry Extended Code Pages (CECPs).^[21]

Open-source software advocate and software developerEric S. Raymond writes in hisJargon File that EBCDIC was loathed by hackers, by which he meant^[22] members of a subculture of enthusiastic programmers. The Jargon File 4.4.7 gives the following definition:^[23]

EBCDIC: /eb´s@·dik/, /eb´see`dik/, /eb´k@·dik/, n.[abbreviation, Extended Binary Coded Decimal Interchange Code] An alleged character set used on IBM dinosaurs. It exists in at least six mutually incompatible versions, all featuring such delights as non-contiguous letter sequences and the absence of several ASCII punctuation characters fairly important for modern computer languages (exactly which characters are absent varies according to which version of EBCDIC you're looking at). IBM adapted EBCDIC from punched card code in the early 1960s and promulgated it as a customer-control tactic (seeconnector conspiracy), spurning the already established ASCII standard. Today, IBM claims to be anopen-systems company, but IBM's own description of the EBCDIC variants and how to convert between them is still internally classified top-secret, burn-before-reading. Hackers blanch at the veryname of EBCDIC and consider it a manifestation of purest evil.

— The Jargon file 4.4.7

EBCDIC design was also the source of many jokes. One such joke, found in the Unixfortune file of4.3BSD Reno (1990)^[24] went:

Professor: "So the American government went to IBM to come up with anencryption standard, and they came up with—"
Student: "EBCDIC!"

References to the EBCDIC character set are made in the 1979 computer game seriesZork. In the "Machine Room" inZork II, EBCDIC is used to imply an incomprehensible language:

This is a large room full of assorted heavy machinery, whirring noisily. The room smells of burned resistors. Along one wall are three buttons which are, respectively, round, triangular, and square. Naturally, above these buttons are instructions written in EBCDIC...

In 2021, it became public that a Belgian bank was still using EBCDIC internally in 2019. A customer insisted that the correct spelling of his surname included anumlaut, which the bank omitted, and the customer filed a complaint citing the guarantee in theGeneral Data Protection Regulation of the right to timely "rectification of inaccurate personal data." The bank's argument included the fact that their system used EBCDIC, as well as that it did not support letters withdiacritics (or lower case, for that matter). The appeals court ruled in favor of the customer.^[25][26]

• UTF-EBCDIC

• IBM-related:
  • Character Data Representation Architecture (CDRA) from IBM at theWayback Machine (archived 2018-05-13). Contains IBM's official information on code pages and character sets.
    • Code page 37 at theWayback Machine (archived 2015-06-19)
    • Code page 1047 at theWayback Machine (archived 2015-06-07)
  • Host Code Page Reference from IBM, shows code charts for several single-byte IBM EBCDIC pages.
  • ICU Converter Explorer Contains more information about EBCDIC derived from IBM's CDRA, including DBCS EBCDIC (Double Byte Character Set EBCDIC)
  • "Code Pages".IBM. from"IBM i globalization".IBM.
• XHCS V2.0 manual, shows code charts for several single-byteSiemens/Fujitsu (as opposed to IBM) EBCDIC pages used on theBS2000.
• EBCDIC character list, including decimal and hex values, symbolic name, and character/function at theWayback Machine (archived 2016-03-03)
• EBCDIC-code pages with Latin-1-charset (JavaScript) at theWayback Machine (archived 2018-04-18)
• All EBCDIC code pages and 3270 graphics escape codes at theWayback Machine (archived August 27, 2016)
• ICU Character Set Mapping Tables Contains computer readable Unicode mapping tables for EBCDIC and many other character sets