Tasks that z/OS UNIX application programmers do

Application programmers are likely to do the following when creating UNIX-compliant application programs:

Design, code, and test the programs on their workstations using XPG4 UNIX-conforming systems.
Send the source modules from the workstation to z/OS.
Copy the source modules from the MVS™ data sets to z/OS® UNIX files.
Compile the source modules and link-edit them into executable programs.
Test the application programs.
Use the application programs.

A z/OS UNIX program can be run interactively from a shell in the foreground or background, run as an MVS batch job, or called from another program.

The following types of applications exist in z/OS UNIX:

Strictly conforming XPG4-conforming applications
Applications using only kernel services
Applications using both kernel and MVS services
Applications using only MVS services

A z/OS program submitted through the job stream or as a job from a TSO/E session can request kernel services through the following:

C/C++ functions
Shell commands, after invoking the shell
Callable services

At the first request for a kernel service, the system dubs the program as a z/OS UNIX process. C/C++ applications that use RUNOPT 'POSIX(ON)' are always dubbed implicitly. POSIX(OFF) or non-C/C++ applications are not dubbed until an explicit kernel service request is issued.