[Info-vax] OpenVMS async I/O, fast vs. slow

[Jake Hamby (Solid State Jake)]

On Sunday, November 5, 2023 at 10:02:14 AM UTC-8, bill wrote:
> On 11/5/2023 12:37 PM, John Dallman wrote: 
> > You'd also need relevant 
> > compilers, operating systems and hardware.
> Just like VMS has a student program IBM and UNISYS, the two biggest 
> mainframers left, offer programs for people to familiarize with their 
> world. There are also Open Source COBOL and Fortran systems available. 
> PL/i being the red headed step child. (As a side note, the recent 
> edition of the CACM has an article that claims IBM intended PL/I to 
> take over the computing world from the likes of COBOL, Fortran and 
> ALGOL. Funny considering that they kept it hidden in their corporate 
> bowels for so long.)

When I got interested in learning the state of z/OS last year, I looked at PL/I, among other mainframe tech. It has hundreds of keywords, like COBOL, but unlike COBOL you can give variables the same names as keywords, which seems like it'd cause a lot of trouble. The parser must have to be very good at recovery from syntax errors.

The original PL/I was developed in cooperation with the SHARE and GUIDE users groups. I've heard PL/I is still more popular in Europe, relative to COBOL, than elsewhere. It doesn't seem to have much to recommend it for business users, with all the focus being on new COBOL features.

The language that IBM *has* kept a confidential trade secret and which they write their z/OS compilers and large parts of their mainframe stack in is a PL/I derivative called PL/X.

PL/X is a descendent of PL/S, which has a brief Wikipedia entry: https://en.wikipedia.org/wiki/IBM_PL/S

Apparently if you're a really good customer, you can get access to PL/S, but I don't know if that includes PL/X. IBM is very protective of their IP and thwarting attempts to clone what they consider "their" tech, so having their flagship OS and compilers written in a language that you can't get a compiler for outside of IBM is likely a part of that thinking. So IBM engineers will talk about using PL/X but not exactly what's in it.

Regards,
Jake Hamby