I interpreted "might have taken pages of assembler instructions" as referring 
to GETMAIN, FREEMAIN and linkage needed in conjunction with the BALR. With 
PC/PR the registers are saved and restored with no additional user code.


--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3


________________________________________
From: IBM Mainframe Discussion List <[email protected]> on behalf of 
Peter Relson <[email protected]>
Sent: Friday, August 30, 2019 8:24 AM
To: [email protected]
Subject: Re: Assembler :- PC Instruction

<snip>
>From what I understood of the PC instruction: with 1 instruction you can
now execute a 'function' that might have taken pages of assembler
instructions before.
</snip>

I'm not sure where this thought comes from. The PC instruction is not
magic. It does not execute a "function" beyond the function of the
instruction itself.
It passes control somewhere, may change state, may create an entry on the
linkage stack.

Peter Relson
z/OS Core Technology Design


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