MACSOFT1,
I know from past experience that PL/1 is available as an OPM language. But, this was back in V3 days. I did about 3 months work using PL/1. It may be available as an ILE language but I don't know. On V5R1, I can create a new PLI source member. When I try to compile it, it tells me that it can't find the command CRTPLIPGM, so I'd have to buy and install the compiler.
The IBM website is very poor for PL/1. I found only 4 references to it. I couldn't find a reference text for PL/1.
Good luck.
Tom.