[TUHS] who invented the link register

[Angelo Papenhoff]

On 12/10/22, ron minnich wrote:
> I know branch and link was in the 360; was it earlier? And ... anybody know
> who invented it?
> 
> This came up in a risc-v meeting just now :-) My claim is that if anybody
> knows, they will  be in this group.

The Whirlwind used the A register for this purpose. The jump (sp =
sub-program) and conditional jump (cp = conditional sub-program)
instructions set A to the return address. The first instruction at the
target can then use ta (transfer A to storage) to write to the address
part of the return-sp instruction. It would look like this:

	sp foo		; call foo
ret,	...		; come back here

foo,	ta foo1		; store return address
	...
foo1,	sp .		; will return to ret

Might be earlier than this, I just happen to know the Whirlwind somewhat
well. It's late 40s machine, so you probably won't find anything *much*
older.

Cheers,
aap