From: "glen herrmannsfeldt" <[email protected]>
Sent: Tuesday, 30 August 2011 8:39 PM
>(after Glen wrote)
The book "Computer Architecture: Concepts and Evolution" by
Blaauw and Brooks has many descriptions on how instructions got
to be the way they did.
The book covers a wide variety of machines, though S/360 is
a favorite example. (Blaauw was the main designer of S/360,
so it isn't so surprising.)
There is a small description of EDIT in section 5.1.3.
They trace back to "Store for Print" on the 702.
Then explain that EDIT
The instruction is ED, not EDIT; its companion is EDMK.
You want to argue with Blaauw on the name of an S/360 instruction?
The instruction is EDIT, the assembler nmemonic is ED.
Take a look at a manual. The instructions are ED and EDMK.
They are edit instructions.
is rarely used by COBOL or Fortran
for print conversions,
That's probably because the instruction was optional
on the small early models of S/360
and the software was written to use basic instructions.
Nevertheless, there's no reason for not using it,
because the small machines that didn't have those instructions
have long since passed to computer heaven.
For hand coded assembler, it isn't bad, but for high-level
languages it is easier to write a software loop than to
conform to the instruction.
No it isn't.
I already mentioned that XPL uses EDMK for all decimal output.
Much of S/360, as with VAX, was designed around assembler
programmers. Later it was found that compilers only generated
a small fraction of the instruction set on most machines.
That said, I understand that IBM 360 compilers didn't use TRT,
which IIRC was a standard instruction.
BTW, EDMK was used for all decimal output in the optimising
XPL compiler.
and that it is best that it should be left out of instruction sets.
A bad recommendation, because so much is done by ED and EDMK,
and with little effort and even less overhead compared with alternatives.
A reasonable cost/benefit analysis of the actual use, done some
years later.
No it isn't, because, for the reason given,
namely, that IBM software programmers didn't want to use the instruction.
I also mentioned that they didn't use TRT,
and I think that the reason for that was that
they didn't understand how to use it.
If you like asking questions like that, especially for a variety
of different machines, you should get the book.
I wouldn't bother, if that is the level of its advice.
If you don't believe Blaauw regarding S/360, then who do you believe?
Real experts.
