EBCDIC

Extended Binary Coded Decimal Interchange Code is an eight-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems. It descended from the code used with punched cards and the corresponding six-bit binary-coded decimal code used with most of IBM's computer peripherals of the late 1950s and early 1960s. It is supported by various non-IBM platforms, such as Fujitsu-Siemens' BS2000/OSD, OS-IV, MSP, and MSP-EX, the SDS Sigma series, Unisys VS/9, Unisys MCP and ICL VME.

History

EBCDIC 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 eight-bit character encoding, developed separately from the seven-bit ASCII encoding scheme. It was created to extend the existing Binary-Coded Decimal Interchange Code, or BCDIC, which itself was devised as an efficient means of encoding the two zone and number punches on punched cards into six bits. The distinct encoding of 's' and 'S' 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.
While IBM was a chief proponent of the ASCII standardization committee, the company did not have time to prepare ASCII peripherals to ship with its System/360 computers, so the company settled on EBCDIC. The System/360 became wildly successful, together with clones such as RCA Spectra 70, ICL System 4, and Fujitsu FACOM, thus so did EBCDIC.
All IBM's mainframe operating systems, and its IBM i operating system for midrange computers, use EBCDIC as their inherent encoding. Software can translate to and from encodings, and modern mainframes include processor instructions, at the hardware level, to accelerate translation between character sets. Modern z/OS compilers for the C and C++ languages on IBM Z mainframes, and earlier OS/390 C and C++ compilers on IBM System/390 mainframes, support a POSIX-compatible execution environment that makes use of ASCII by default.
Not all operating systems running on IBM hardware use EBCDIC; IBM AIX, Linux on IBM Z, and Linux on Power all use ASCII, as do all operating systems that run on the IBM Personal Computer and its successors.

Compatibility with ASCII

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 example would print the alphabet from A to Z if ASCII is used, but print 41 characters 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 that did not exist in EBCDIC, making translation to EBCDIC systems difficult. Workarounds such as trigraphs |trigraphs] were used. Conversely EBCDIC had some characters such as logical not, that were used on IBM systems and could not be translated to ASCII. The logical not character is used in the PL/I programming language, and some other IBM languages.
The EBCDIC character NL 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 a 36-bit word. On the PDP-11, bytes with the high bit set were treated as negative numbers, behavior that was copied to C, causing unexpected problems if the high bit was set. These all made it difficult to switch from ASCII to the 8-bit EBCDIC.
Code page layout

There are hundreds of EBCDIC code pages based on the original EBCDIC character encoding; there are a variety of EBCDIC code pages intended for use in different parts of the world, including code pages for non-Latin scripts such as Chinese, Japanese, Korean, and Greek. There is also a huge number of variations with the letters swapped around for no discernible reason.
The table below shows the "invariant subset" of EBCDIC, which are characters that should have the same assignments on all EBCDIC code pages that use the Latin alphabet. It also shows missing ASCII and EBCDIC punctuation, located where they are in Code Page 37. 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 the ISO basic Latin alphabet, such as English.

Definitions of non-ASCII EBCDIC controls

Following are the definitions of EBCDIC control characters which either do not map onto the ASCII 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.
Although the default mapping of New Line corresponds to the ISO/IEC 6429 Next Line character, most of these C1-mapped controls match neither those in the ISO/IEC 6429 C1 set, nor those in other registered C1 control sets such as ISO 6630. Although this effectively makes the non-ASCII EBCDIC controls a unique C1 control set, they are not among the C1 control sets registered in the ISO-IR registry, meaning that they do not have an assigned control set designation sequence.
Besides U+0085, the Unicode Standard does not prescribe an interpretation of C1 control characters, leaving their interpretation to higher level protocols, so this mapping is permissible in, but not specified by, Unicode.

Mnemonic	EBCDIC	CDRA pairing	Name	Description
SEL	04	009C	Select	Device control character taking a single-byte parameter.
PF	04	009C	Punch Off	Listed in this location by GOST 19768-93.
RNL	06	0086	Required New Line	Line-break resetting mode
LC	06	0086	Lower Case	Listed in this location by GOST 19768-93.
GE	08	0097	Graphic Escape	Non-locking shift that changes the interpretation of the following character. Compare ISO/IEC 6429's .
SPS	09	008D	Superscript	Begin superscript or undo subscript. Compare ISO/IEC 6429's .
RPT	0A	008E	Repeat	Switch to an operation mode repeating a print buffer
SMM	0A	008E	Start of Manual Message	Listed in this location by GOST 19768-93.
RES/ENP	14	009D	Restore, Enable Presentation	Resume output
NL	15	0085	New Line	Line break. Default mapping matches ISO/IEC 6429's. Mappings sometimes swapped with Line Feed in accordance with UNIX line breaking convention.
POC	17	0087	Program Operator Communication	Followed by two one-byte operators that identify the specific function, for example a light or function key. Contrast with ISO/IEC 6429's , and .
IL	17	0087	Idle	Listed in this location by GOST 19768-93.
UBS	1A	0092	Unit Backspace	A fractional backspace.
CC	1A	0092	Cursor Control	Listed in this location by GOST 19768-93.
CU1	1B	008F	Customer Use One	Not used by IBM; for customer use.
IUS/ITB	1F	001F	Interchange Unit Separator, Intermediate Transmission Block	Either used as an information separator to terminate a block called a "unit", or used as a transmission control code to delimit the end of an intermediate block.
DS	20	0080	Digit Select	Used by S/360 CPU edit instruction
SOS	21	0081	Start of Significance	Used by S/360 CPU edit instruction.
FS, FDS	22	0082	Field Separator	Used by S/360 CPU edit instruction.
WUS	23	0083	Word Underscore	Underscores the immediately preceding word. Contrast with ISO/IEC 6429's SGR.
BYP/INP	24	0084	Bypass, Inhibit Presentation	De-activates output, i.e. ignores all graphical characters and control characters besides transmission control codes and RES/ENP, until the next.
SA	28	0088	Set Attribute	Marks the beginning of a fixed-length device specific control sequence. Deprecated in favour of.
SFE	29	0089	Start Field Extended	Marks the beginning of a variable-length device specific control sequence. Deprecated in favour of.
SM/SW	2A	008A	Set Mode, Switch	Device specific control that sets a mode of operation, such as a buffer switch.
CU2	2B	008B	Customer Use Two	This appears in some specifications, such as GOST 19768-93; newer IBM specifications for EBCDIC control codes list only CU1 and CU3 as customer-use, and use this position for.
CSP	2B	008B	Control Sequence Prefix	Marks the beginning of a variable-length device specific control sequence. Followed by a class byte specifying a category of control function, a count byte giving the sequence length, a type byte identifying a control function within that category, and zero or more parameter bytes. Contrast with ISO/IEC 6429's and .
MFA	2C	008C	Modify Field Attribute	Marks the beginning of a variable-length device specific control sequence. Deprecated in favour of.
	30	0090	'	Reserved for future use by IBM
	31	0091	'	Reserved for future use by IBM
IR	33	0093	Index Return	Either move to start of next line, or terminate an information unit.
PP	34	0094	Presentation Position	Followed by two one-byte parameters to set the current position. Contrast with ISO/IEC 6429's CUP and HVP.
PN	34	0094	Punch On	Listed in this location by GOST 19768-93.
TRN	35	0095	Transparent	Followed by one byte parameter that indicates the number of bytes of transparent data that follow.
RST	35	0095	Reader Stop	Listed in this location by GOST 19768-93.
NBS	36	0096	Numeric Backspace	Move backward the width of one digit.
UC	36	0096	Upper Case	Listed in this location by GOST 19768-93.
SBS	38	0098	Subscript	Begin subscript or undo superscript. Compare ISO/IEC 6429's .
IT	39	0099	Indent Tab	Indents the current and all following lines, until or is encountered.
RFF	3A	009A	Required Form Feed	Page-break resetting mode.
CU3	3B	009B	Customer Use Three	Not used by IBM; for customer use.
	3E	009E		Reserved for future use by IBM
EO	FF	009F	Eight Ones	All ones character used as filler

Code pages with Latin-1 character sets

The following code pages have the full Latin-1 character set. The first column gives the original code page number. The second column gives the number of the code page updated with the euro sign replacing the universal currency sign
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 different code point values in different code pages. They are known as Country Extended Code Pages.

CCSID	Euro update	Countries
037	1140	Australia, Brazil, Canada, New Zealand, Portugal, South Africa, USA
273	1141	Austria, Germany
277	1142	Denmark, Norway
278	1143	Finland, Sweden
280	1144	Italy
284	1145	Latin America, Spain
285	1146	Ireland, United Kingdom
297	1147	France
500	1148	International
871	1149	Iceland
1047	924	Open Systems

Criticism and humor

advocate and software developer Eric S. Raymond writes in his Jargon File that EBCDIC was loathed by hackers, by which he meant members of a subculture of enthusiastic programmers. What is known as vendor lock-in today, is jokingly criticized in The Jargon File with the following definition:
EBCDIC design was the source of many jokes. One such joke, found in the Unix fortune file of 4.3BSD Reno went:
References to the EBCDIC character set are made in the 1979 computer game series Zork. In the "Machine Room" in Zork II, EBCDIC is used to imply an incomprehensible language:
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 an umlaut, which the bank omitted, and the customer filed a complaint citing the guarantee in the General [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 with diacritics. The appeals court ruled in favor of the customer.