Technical data

Fortran/C Interface

Fortran

C Fortran call to F, a function written

C in Fortran

EXTERNAL F

CHARACTER*10 F, G

G = F()

/* C call to SAM, a routine written in Fortran */

/* which returns a string. */

CHAR S[10];

. . .

f_(S, 10);

The function F, written in Fortran

C function F, written in Fortran

CHARACTER*10 FUNCTION F()

F = ‘0123456789’

RETURN

END

Array Handling

Fortran stores arrays in column-major order with the leftmost subscript

varying the fastest. C, however, stores arrays in the opposite arrangement

(row-major order), with the rightmost subscripts varying the fastest.

Here is how the layout of the Fortran array looks:

integer t (2,3)

t(1,1), t(2,1), t(1,2), t(2,2), t(1,3), t(2,3)

Here is how the layout of the C array looks:

int t [2] [3]

t[0][0], t[0][1], t[0][2], t[1][0], t[1][0], t[1][1],t[1][2]

Note that the default for the lower bound of an array in Fortran is 1, where

the default in C is 0.