Is it good practice to always end a FORTRAN program with a STOP statement?

Question

As the title says, really.

Is there anything against not using stop, like this:

PROGRAM myprog
. 
. < do stuff >
.
END PROGRAM myprog

rather than using an explicit stop, as in this:

PROGRAM myprog
. 
. < do stuff >
.
STOP
END PROGRAM myprog

I see a lot of older fortran code that has a STOP before the END PROGRAM statment, but is it really needed there?

On our Cray machine, having a STOP stament at the end of the program writes the string "STOP" to STDERR, which is a bit annoying...

Answer 1

The code

stop
end program

is redundant as far as the program return value is concerned in modern Fortran. A stop with no integer or character stop-code should return a 0 exit code to the OS if exit codes are supported. If end program is encountered the behavior is the same, returning 0 to the OS.

The difference arises in program output. As you've noted, stop produces output. The standard (Fortran 2008 cl. 8.4) says

When an image is terminated by a STOP or ERROR STOP statement, its stop code, if any, is made available in a processor-dependent manner. If any exception (14) is signaling on that image, the processor shall issue a warning indicating which exceptions are signaling; this warning shall be on the unit identified by the named constant ERROR UNIT (13.8.2.8). It is recommended that the stop code is made available by formatted output to the same unit.

This recommends the stop-code be made available on standard error, which is where your STOP output is coming from. If you had given a stop-code to stop, it would have been output with STOP. Additionally, if there are floating point exceptions signalling, you will get additional output on standard error detailing that condition.

If you don't desire the additional output from stop and are not using it to return a non-zero error code to the OS, you can omit it from your program.

There is probably a historical reason for the stop,end ending of the main program, but my brief skimming of a FORTRAN66 manual did not enlighten me.