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 follow

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-x3dot9-1966-Fortran66.pdf http://www.fh-jena.de/~kleine/history/languages/ansi-x3dot9-... §8.4 p26 ‡ http://www.fortran.com/fortran/F77_std/rjcnf-15.html#sh-15.9.2 http://www.fortran.com/fortran/F77_std/rjcnf-15.html#sh-15.9...