On 30 Jun 2020 12:18:01 -0700, in bit.listserv.ibm-main (Message-ID:<cy4pr11mb1719018adc50b61e307153e3e4...@cy4pr11mb1719.namprd11.prod.outlook.com>) frank.swarbr...@outlook.com (Frank Swarbrick) wrote:

Some time ago I noticed that z/OS Language Environment has support for both "FORTRAN IV" and "VS FORTRAN" (FORTRAN 77 standard), even though the latest Fortran compiler hasn't been enhanced since 1993 (??). I've been learning modern Fortran (standards Fortran 90, 95, 03 and 08) using GNU Fortran and actually quite like it, but I can't imagine using anything prior to the 1990 standard. Anyway, I am curious if anyone uses Fortran on z/OS in their shop, and if so, why?

Is Pascal also still supported/used? I don't see any mention of it in LE documentation. Are there any other "legacy" MVS languages still in use (i.e., ones that haven't been updated in the last 30 years...)? I've seen mention of APL2 on MVS, and maybe even Smalltalk?

I'm going to answer what I take as the tone of your questions, rather than the specifics.

In a production environment, once a program has been written and debugged, when it has been working fine for years, you don't want to touch it, if at all possible. Unless it needs updating, you just keep running it, regardless of what language it was written in.

I someone wants to recompile a FORTRAN IV program with a modern compiler, that person is taking the responsibility for its future behavior, and that its behavior will match what it was before. That person is also taking responsibility for making sure that the source for the program is actually the source that was compiled decades ago, when there may be no one left from that programming team. And think of the hours to be lost in creating tests, running them, and going through all of the quality-control paperwork involved; and if it's only in order to recompile with a modern compiler, all that work and time is just to end with the same functionality you already had.

During the time of the 370s, I knew of a company which kept a 360 because it could do 1401 emulation in order to run a critical program. While I have no actual knowledge, I have little doubt that there are companies running old FORTRAN code, RPG, COBOL Report Writer, and pretty much anything else you can think of.

Downward compatibility means you can say, "If it ain't broke, don't fix it."
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