Service_name

The name that assembler understands is the name of a module in the form BPX1xxx, where xxx is a three-character symbol unique to the service. AMODE 64 callers use the form BPX4xxx.

Modules are invoked in one of the following ways:

A program can load a module first and then branch to the address where it was loaded.
When you are link-editing a program, you can link to the linkage stub. The program can issue a call.
You can include in the code the system control offset to the callable service. See System control offsets to callable services for information about how to use this linkage.