Handling User-Defined Types

Fortran 95/90 supports user-defined types (data structures similar to C structures). User-defined types can be passed in modules and common blocks just as other data types, but the other language must know the type's structure. For example:

Fortran Code:

     TYPE LOTTA_DATA
         SEQUENCE
         REAL A
         INTEGER B
         CHARACTER(30) INFO
         COMPLEX CX
         CHARACTER(80) MOREINFO
      END TYPE LOTTA_DATA
      TYPE (LOTTA_DATA) D1, D2
      COMMON /T_BLOCK/ D1, D2

In the Fortran code above, the SEQUENCE statement preserves the storage order of the derived-type definition.

C Code:

 /* C code accessing D1 and D2 */
 extern struct {
    struct {
       float a;
       int b;
       char info[30];
       struct {
          float real, imag;
          } cx;
       char moreinfo[80];
    } d1, d2;
} T_BLOCK;