What is Fortran in C?

Some programming languages support interoperability by enabling libraries written in another programming language to be used.

As such, Fortran-C interfaces exist to aid programmers in this regard. However, compatibility issues may arise, so it is essential for some of these interfaces to be agreeable in the following ways:

  • Function/subroutine

  • Datatypes

  • Arguments

  • Procedure

  • Libraries

Basic syntax

When FORTRAN calls C function

  • If the called C function returns a value, call it from Fortran as a function.
  • If the called C function does not return a value, call it a subroutine.

When C function calls FORTRAN subprogram

  • If the FORTRAN subprogram is a function, then call it a function from C to return a compatible data type.
  • If the called FORTRAN subprogram is a subroutine, call it as a function from C that returns a value of int (compatible to Fortran INTEGER*4) or void if otherwise.

Basic code

program test
implicit none
character*13 temp        //declaration of a variable
temp = "Hello World!"
write (*,*) temp         //print
end program test

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