I recall that I had some difficulties with the PoOp when I first had to
use it in the mid 1980s,
maybe with this numbering scheme of the operands, but must operations
involve only
two operands, some have three, and it is always clear from the context,
what happens.
BTW: we had a PoOp translated to German in those days which was not bad
- normally
I don't like translated IBM brochures, because they have bugs - the
English originals are
better IMHO.
But, when you once get accustomed to the logic of the PoOp, it's no
problem any more.
Kind regards
Bernd
Am 20.02.2013 06:23, schrieb John Ehrman:
Paul Gilmartin noted:
I would be careful not to create confusion by inviting undue attention
to the notion of "sequential position".
COMPARE AND SWAP
CS R1,R3,D2(B2) [RS-a]
If you wrote
CS 0,4,X
the assembler says operand 1 is 0, operand 2 is 4, and operand 3 is X,
while the PoP swaps the latter two.
Assembler programmers must deal with the confusion caused by multiple uses
of the word "operand". The PoP sense (and numbering) is different from the
assembler's sense. Sadly, the assembler's notation is just as old as that
of the PoP, and generations of assembler programmers have had to cope with
the differences..
