[TUHS] who invented the link register

Bakul Shah bakul at iitbombay.org
Wed Oct 26 08:24:01 AEST 2022

On Oct 12, 2022, at 12:01 PM, ron minnich <rminnich at gmail.com> 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.

Zuse Z4 had instructions to jump to a subprogram and back. Unclear if they were in the original Z4 (1945) or were added later. Or how it was done.


Turing's ACE (1946) computer had BURY and UNBURY that push and pop a subroutine's return address from a ptr held in TS31. TS1..TS32 were "temporary storage" registers each in a recirculating memory (mercury delay line?) with a cycle time of 32┬Ás. The paper referenced below says BURY and UNBURY were subroutines but I wonder if they were macros.

From the "Turing and ACE, Lessons from a 1946 Computer Design" <https://cds.cern.ch/record/263304/files/p230.pdf> paper, "Inventing this concept in late 1945 was a truly amazing achievement, perhaps inspired by the recursive function theory which Turing had learnt from the work of Church, and by a slight knowledge of the nineteenth century work of Babbage."

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