Fortran: difference between f and F extension

Question

I\'m a bloody beginner in Fortran.

I wonder: what is the difference between the .f and .F extensions of Fortran files. I know that muc

Answer 1

In gfortran, free-form (no special meaning for cols 7, 72) is set by the compiler switch -ffree-form and has nothing to do with .f or .F file suffixes. The difference between .f and .F is that the latter goes through a pre-processor, the most common use of which is allowing C-like #define statements. For example:

#define MAXN 100
program example
integer N(MAXN)
end

will compile if it is .F but not if it is .f