Unix services?

UNIX System Services allows Unix applications from other platforms to run on IBM mainframes. In many cases only a recompile is necessary, although additional effort may be advisable for z/OS integration (such as SMP/E installation). Binary programs using hardcoded ASCII numerical values need adjustment — z/OS architecture is based on EBCDIC. Programs running under USS have full access to the internal functions of z/OS. Database access (DB2 via Call Attach) is one example of how USS can access services found elsewhere in z/OS. Naturally such programs cannot be ported to non-mainframe platforms without rewriting should they use these z/OS-specific services. Conversely, if a program adheres to standards such as POSIX and ANSI C, it will be easier to port to the USS environment.