⟩ How are data passed from JCL parm to assembler program. And how is data passed from a calling program to an assembler called program?
By convention, general purpose register 1 will have the
address of the parameter list. The list will be a list of
pointers (addresses) to individual parameters. The CALL
macro does this, but you can bypass the CALL macro and be
creative on how you set up the parameter list. Don't forget
the parameter must be on a fullword boundary.