On Mon, 09 Apr 2018 17:47:07 +0100, "James Wilkinson Sword"
wrote:

On Mon, 09 Apr 2018 17:31:19 +0100, wrote:

On Mon, 9 Apr 2018 10:19:51 -0600, rbowman wrote:

On 04/09/2018 04:57 AM, wrote:
No pocket protector but everyone had a green card.
"Octal"? IBM didn't use octal on anything I ever saw. It was BCD or
Hex.

It's been a long time but I remembered 360 opcodes using 3 bit
designations for the registers and operations.

Nobody referred to them as being octal. The various fields were of
different lengths. Typically you were actually filling them bit by
bit. If you were writing LOICS they were largely invisible to you
anyway, you were guided by the assembler but if you wrote PIOCS you
were actually writing the CCWs and had far more control. If you knew
how STIXIT worked, you could even write your own PSW and insert it,
allowing you to change the problem state bit and other scary things.
I wrote the only program I ever saw that actually used that big red
"interrupt" button on a 360 console.
I was the most dangerous kind of programmer. I came at that stuff from
the hardware side. ;-)
"Supervisor and I/O macros" was my favorite book.

You are specifically told not to touch the buttons:
https://en.wikipedia.org/wiki/IBM_Sy...rofile.agr.jpg

Nobody ever told me that. In fact I spent a lot of time in various
schools finding out what they all did. I agree typical users had no
use for most of them and when the machine was running, most had no
effect anyway. Lots of people, even a lot of programmers, were
surprised when I made the interrupt button do something.
They would have even been scared if they knew what I was doing with
it.
After showing the STIXIT trick to a few students at the college, one
did take the machine away from them using a program running in
background. He left the machine in "system state" and assumed it would
switch back. Nope. The next student who tried to execute a privileged
instruction, succeeded and crashed the system. Fortunately no real
damage was done.