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EBCDIC is an 8-bit code developed by IBM in 1963 as an extension of the Binary Coded Decimal (BCD) standard, allowing for encoding of letters, formatting codes, and communication controls. It has been expanded to 16- and 32-bit variants for non-Latin character sets and is still supported by IBM mainframe computers for legacy applications.
EBCDIC, Extended Binary Coded Decimal Interchange Code, was developed in 1963 by IBM as an extension of the older Binary Coded Decimal (BCD) standard. BCD encodes the 10 digits of the standard counting system using 4 binary counters, or bits, where a single bit can be either a 1 or a 0.
BCD for numeric characters
Cipher
EBCDIC
0/0000
1/0001
2/0010
3/0011
4/0100
5/0101
6/0110
7/0111
8/1000
9/1001
By establishing BCD as a standard, IBM allowed users to move shared data between computers with the use of punch cards. The roots of BCD lie, in fact, in the row and column arrangement of IBM’s original computer punch cards. With EBCDIC, IBM has extended the 8-bit approach, enabling encoding of not only digits, but also uppercase and lowercase letters, formatting codes such as headers and carriage returns, and basic communication controls such as Request, Acknowledge and Bell . This allowed IBM mainframe computer users to share not only data, but the actual programming code as well.
EBCDIC is eight bits or one byte wide. Each byte consists of two nibbles, each four bits wide. The first four bits define the class of the character, while the second nibble defines the specific character within that class. For example, setting the first nibble to all ones, 1111, defines the character as a number and the second nibble defines which number is encoded.
In recent years, EBCDIC has been expanded to 16- and 32-bit variants to allow for the representation of large non-Latin character sets. Each EBCDIC variant is known as a codepage, identified by its Coded Character Set Identifier or CCSID. EBCDIC code pages were created for a number of important writing scripts, including complex ones such as Chinese, Korean and Japanese.
All IBM mainframe computers, even the latest models, continue to support EBCDIC so that legacy applications can run without modification.
