Re: Elliott Algol - cctalk

21 Feb 2025

...
  On19 Feb 2025 18:39:08 -0500, Chuck Guzis via cctalk
wrote:

  One of most ingenious coding tricks to me was the
problem of saving and
 restoring all registers without resorting to an exchange jump.  We used
 that one as a test for applicants.  
 Argh... I know I've seen this trick, but it's been too many years.  How
 about a hint?  
 It uses the RJ instruction to record register content, bit-by-bit.
 Think about it--RJ is about the only instruction that can modify memory
 without fiddling with the A6 and A7 registers.

 Of course... I vaguely recalled there was a bit-by-bit save, but didn't 
 think of the RJ.  Thanks. 
A full example of this code is in the DEBUG package of CAL SNOBOL
<https://mcjones.org/CAL_SNOBOL/>, starting at label SAVEREG:

Original version: https://mcjones.org/CAL_SNOBOL/UArizona/SNOBOL.MAC.html

Revised version: https://mcjones.org/CAL_SNOBOL/UTexas/DEBUG.html