Fortran puzzle!

And the puzzle is not "why does anyone use Fortran", because that's unfair. Via James, from Rolf, is the excellent:

CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
       PROGRAM OBFUSCATE
        CONSTANT = 5.
          INVERSE = 1./CONSTANT
              photo1 = 5.*INVERSE + 5.
                  pH = CONSTANT + 3.
                  X = photo1 * pH
C         strange combination of pH and photolysis...
     GOTO      1
                  X = X + 17.
   1      CONTINUE
        IF (X .LT. 60.) THEN X = X + 7.
      PRINT *,'RESULT=',X
            STOP 
        END
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC

Hopefully the formatting comes out OK; consult the original if in doubt. The question, of course, is what does the code print, and more importantly exactly why? I'm off to the Lakes for a few days to get rained on, so unless you can work out the answer for yourselves, you'll have to wait till I come back.

Obviously, C would never do anything so odd.

Answer

And the answer, as EFS found, comes in three parts:

1. The easy one is that without IMPLICIT NONE, any variable starting with I (to N) is implicitly an integer, so INVERSE is 0, not 0.2.

2. The first amusing one is that any non-blank character in column 6 is a continuation marker. Comments are discarded, so we have:

      X = photo1 * pH
          OTO      1

and since spaces are also discarded, we actually have

      X = photo1 * pHOTO1

So (since case is also discarded) after that X is 25. To which we add 17, getting 42, of course.

3. Then, lastly, Fortran has a block IF, but also a single-line IF, and

      IF (X .LT. 60.) THEN X = X + 7

can't be a block IF (despite the formatting trying to make the end-of-code "END" look like it's closing), so it's actually

      IF (X .LT. 60.) THENX = X + 7

And so we end up with a variable called THENX with value 49, and X with value 42.