EBCDIC
The character encoding mainframes use, where letters and numbers are stored as different byte values than on a laptop.
Also written character encoding
EBCDIC, or Extended Binary Coded Decimal Interchange Code, is the scheme mainframes use to represent text as numbers. Most other computing settled on ASCII and later Unicode; IBM mainframes have used EBCDIC since the 1960s and kept it for compatibility.
The practical consequence is that the same letter has a different numeric value depending on the system. That matters in two situations. The first is sorting: in EBCDIC, lowercase letters sort before uppercase, and digits sort after letters, which is the opposite of what ASCII does. A sorted report can therefore come out in an order that surprises you. The second is moving data between systems, where a file transferred without translation arrives as unreadable characters.
Most of the time the tools handle the conversion for you and you never think about it. It becomes relevant when you are transferring files to or from another platform, or debugging why a comparison or a sort is not behaving the way you expected.
Learn the acronym early. It gets used casually and rarely explained.
Related terms
- z/OSThe main operating system that runs on IBM mainframes, in the same way Windows or Linux runs on a laptop or server.
- DatasetWhat a mainframe calls a file: a named collection of records with a defined structure, rather than a loose stream of bytes.
- File transferMoving data between the mainframe and other systems, where character encoding and record structure both need attention.