1. Ordinarily, when a function is invoked, branch or call instruction . 2. The code may be processed by an call instructions . 3. ;Trampolines : Many CPUs have smaller subroutine call instructions to access low memory. 4. Instead it is accessed by other programs and subsystems typically via a CALL instruction . 5. Some smaller instruction classes include the shift / rotate instructions and the procedure call instructions . 6. The canonical implementation is a register load of a constant followed by a call instruction . 7. The original instruction set did not have a subroutine call instruction and could only address one bank of memory. 8. This was accomplished using an MVS emulator that intercepted system calls at the Supervisor Call instruction ( SVC ) level. 9. With inlining, control drops through directly to the code for the function, without a branch or call instruction . 10. Instead the hardware and the OS provide a " gate " that may be the target of a Call instruction .
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