Channel programming wasn’t really at the time.   Maybe the guys at PASC didn’t know, but it was available.

Never saw anything written in PL/I there.    Now the other 370 mainframe stuff that wasn’t in assembler was written in PL/S which was sort of PL/I but not really.   They used it for TSO (suitable for kicking dead whales down the beach) and MVT (multiprocessing with a variable number of turds, part of the virtual toilet access protocol).

Of course, the RS/6000 AIX was completely different and somewhat weird.    I might buy it being written in PL/S.   I spent a lot of time over the years either pursuing security vulnerabilities or patching up ones that I had found.     IBM loaned us an RS/6000 and didn’t give me the root password.    This took me a while to figure out.    I found however that if you turned the key on the front to the service (wrench) position, it would boot up in a canned “diagostic” program.    I poked at this a while until I realized that the help program just spawned more and I could shell escape out to a root shell.

From: TUHS [mailto:tuhs-bounces@minnie.tuhs.org] On Behalf Of Dan Cross
Sent: Monday, March 6, 2017 11:21 AM
To: ron minnich
Cc: TUHS main list
Subject: Re: [TUHS] Source code abundance?

On Mon, Mar 6, 2017 at 10:57 AM, ron minnich <rminnich@gmail.com> wrote:

Yes, the AIX code looks nothing like SYS V. It's been 20+ years since I did a lot of work in AIX, and most of my work was in networking, external pagers, and NFS, and even there you could see it was different (although much of the NFS was clearly the Sun reference code, one giveaway being the Sun copyrights in it :-) I always thought it was an interesting code base -- they seemed to get preemptability right from the start, for example. As it was explained to me, IBM did a full implementation from manuals of both the kernel and the commands. 

There were lots of little weirdnesses in the commands. mkdir -p, for example, would give you an error if the directory existed -- they got the creation of the tree right, but the error wrong. There were tons of these little gotchas in the commands and it's one thing that made NTP and Condor, for just two examples, a real chore on AIX.

I visited the now-closed IBM Palo Alto center in 1991, and they told me an interesting AIX story. Seems to that point, on the mainframes, AIX had run under VM. The native port was either starting or soon to start, and there was some question about channel programming -- mainly, if the people who really knew how it worked were still at IBM, or even still alive. I guess they worked it out, however ;-)

I once heard that some version of AIX was actually implemented in PL/I. I strongly doubted that, and no one's mentioned it so I assume that's apocryphal? It would be so distinctive that I can't imagine someone NOT mentioning it if it were the case.

        - Dan C.