FORTRAN subroutine for rotation of three-dimensional line figures (1970) [pdf]
ntrs.nasa.gov
ntrs.nasa.gov
Start at 6000 and go up in increments of 10 or 100 and to use 6999 for the last label in a routine.
so when you wanted to exist a subroutine or function you would use GOTO 6999.
And we also used it at BT where Fortran 77 was used in one of the Billing systems.
It might be a more UK thing