[kps]

I haven't heard of that, and it would be great if you could remember where you found it. It sounds to me like it might be an apocryphal corruption of the following:

Fortran passes arguments by reference. If the compiler uses a constant pool, and (lazily or efficiently, depending on your point of view) passes the constant pool location as an argument, a subroutine could inadvertently modify a constant.

FORTRAN 66 (the first ANSI standard) and FORTRAN 77 forbid passing a constant or expression as an argument that will be modified†‡, thereby blessing this implementation. (Fortran 90 and later are tl;dr.)

† http://www.fh-jena.de/~kleine/history/languages/ansi-x3dot9-... §8.4 p26

‡ http://www.fortran.com/fortran/F77_std/rjcnf-15.html#sh-15.9...

[bodyfour]

It's a war story from my father, so I have to admit that the details could be corrupted. He worked with a variety of machines in the 60s, so it was believable that one had a permissive enough FORTRAN to allow that. It's also possible that your explanation of it being reference-argument corruption.

I'm almost curious enough to fire up a PDP-8 emulator and see what 4K FORTRAN does. Almost. http://techtinkering.com/2009/07/14/running-4k-fortran-on-a-...