In a program unit you can also issue subprogram calls, e.g. C/C++ functions or COBOL subprograms. These subprograms may contain subprogram calls themselves. Using subprogram calls you call programs via their program name (in C/C++: function name) and not via their transaction code.
Subprograms can also be written in a programming language other than that of the calling program.
For BS2000 systems, the points that then need to be taken into account and the compilers and runtime systems that are required are described in openUTM manual “Using UTM Applications on BS2000 Systems”.
You will find more information on subprogram calls in the section "C/C++ program units as subroutines" and section "COBOL program units as subroutines".
The program run must either return to the program unit or be terminated in a subprogram using the PEND call.