EBCDIC

EBCDIC stands for Extended Binary Coded Decimal Interchange Code. It is an 8-bit character encoding used primarily on IBM mainframe and midrange computers, including systems such as z/OS and IBM i. It originated in the 1960s as a successor to BCDIC and was designed to support business data processing with decimal digits and punctuation in a way aligned to punched-card practices. Unlike ASCII, EBCDIC is not ASCII-compatible; each code page has its own mapping from byte values to characters, and there is no single universal mapping between EBCDIC and other encodings.

Because many IBM systems use different code pages—often referred to as CCSIDs—the assignment of characters to byte values varies by language and system. EBCDIC defines 256 possible codes for each code page, with variations that accommodate different alphabets and symbols. This means that the same byte value can represent different characters on different systems, complicating data exchange without proper translation.

In practice, EBCDIC is still used for data storage and processing on IBM platforms, and legacy COBOL/PL/I programs often rely on it. Interfacing with ASCII-based environments or networks typically requires translation tools or conversion steps. Modern IBM environments may support Unicode internally while still storing or transferring data in EBCDIC, converting as needed on input or output. Despite its age, EBCDIC remains in use due to backward compatibility and the presence of large volumes of legacy data on IBM systems.