J.R.
1. "The comma"
And, by the way, I never stopped using the comma between index and base
registers, so I never had to restart when AR-mode came along. Good
practice never goes out of style.
By which I expect you mean you never stopped using the comma in order to
indicate that you wanted the register in the address to be the base register
rather than the index register.
I brought this up as recently as a fortnight ago[1] as an excuse to recall a
story about the famous comma and Wayne Driscoll was kind enough to add his
comment that it indeed mattered still.
2. Register Equates
After using register equates for forty years, instructions just don't look
right without them.
When I started doing some serious Assembler long, long ago, I decided that
the R0-R15 register equates were not really going far enough in terms of
assisting documentation of the program. I decided a character string that
gave some idea what the register was doing was more appropriate - although I
always retained the leading "R" - innate conservatism I suppose.
I discovered another benefit in using this approach. I no longer had to
bother solving my problem - some would say "issue" these days[2] - alongside
worrying about assigning numbers to registers. The routine got written and
then I bothered about the EQU statements to assign a number to my register
symbols.
As a purely pragmatic rule, I decided that if I just couldn't shuffle the
numbers to match the symbols, the routine must be too large and so needed
"subroutinising". This actually never happened that I can recall.
This technique did yield one very well remembered situation. I found myself
with an LR instruction as follows:
LR RREC,RBUF
While coding up the register EQU statements, I found that I had finished
working with RBUF at precisely the point I started working with RREC - which
is very sensible when a reasonable guess is made as to what sort of routine
was being written - *and* RBUF and RREC happened to have been assigned the
same register number.
The "problem" was resolved by placing an asterisk in column 1!
Chris Mason
[1] "JCL passing parms to ASM module?", 17 Aug.
[2] Being British, I don't always insert "smileys" or "grins" where list
conventions would normally require them.
----- Original Message -----
From: "J R" <[EMAIL PROTECTED]>
Newsgroups: bit.listserv.ibm-main
To: <[email protected]>
Sent: Thursday, August 23, 2007 9:34 PM
Subject: Re: Calling a AMODE 31 program from AMODE 64
(Selectively quoted above)
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