design that continues to work with earlier versions of a language, program or hardware.
The program or hardware is compatible with the older versions of the same product.
A system is backward compatible if it is compatible with (e.g. can share data with) earlier versions of itself, or sometimes other earlier systems, particularly systems it intends to supplant. For example, WordPerfect 6.0 can read WordPerfect 5.1 files, so it is backward compatible. Source: Foldoc: Free On-line Dictionary of Computing
A design that continues to work with earlier versions of a language, program, etc.
Allows using pervious versions of hardware and software.