On 2013-07-31 15:01, Gerhard Postpischil wrote: > On 7/31/2013 1:44 PM, Bernd Oppolzer wrote: >> When I came to the site where I am actually working 25 years ago, >> I was very surprised that they use RA to RF for 10 to 15 - I never met >> that before, but you get accustomed to that very quickly. It's always >> two characters, after all ... > > I first came across this form in the OS/360 reader/interpreter. > Personally I don't like it because searches on RB and RE get many more > false hits than R11 and R14. > And, of course, since there's no standard, the system macros must use pure numeric designators. And with a mixture of conventions, XREF doesn't reliably list register references. IATYREGS is somewhat unusual among IBM macros in that it sets a flag so it can exit if it's used twice, and some other JES3 macros invoke IATYREGS so they _can_ use register mnemonics.
I think I've also seen GR0-GR15, which likewise reduces the likelihood of false hits in searches. CDC 6600 et al. made the register names predefined, reserved, and mandatory. It was impossible to confuse L and LR; the operands distinguish them. And no need for unintuitive conventions such as "7" means constant 7 and "(7)" means register 7 in macro arguments. It was "7" or "X7". So, no need for such as IHBINRRA. And less incentive to print macro expansions; they did what they appeared to from the call. -- gil
