Terminates program execution.  Statement format:

     STOP [disp]

     disp  Is a character constant or a string of up to
           six digits.  (Fortran 95/90 and FORTRAN 77 limit
           digits to five.)

  If you specify the optional argument "disp", the STOP statement
  displays the contents of "disp" at your terminal, terminates
  program execution, and returns control to the operating system.

  If you do not specify a value for "disp", no message is displayed.