/* a.c - defines an array */

int a[] = {1,2,3,4,5,6,7,8,9};


/* b.c - declare and use it. */

#define COUNT ((sizeof a)/(sizeof int))
extern int a[];  //size of array

.
.
.

int i;
for(i=0; i<COUNT; i++)
  printf("%d", a[i]);
.
.
.

int a[] = {1, 2, 3};
const int lengthofa = sizeof( a ) / sizeof( a[0] );

extern int a[];
// the extern (thanks Tim Post) declaration means the actual storage is in another
// module and fixed up at link time.  The const (thanks Jens Gustedt) prevents it
// from being modified at runtime (and thus rendering it incorrect).
extern const int lengthofa;

void somefunc() {
  int i;
  for ( i = 0; i < lengthofa; i++ )
    printf( "%dn", a[i] );
}

extern int a[9];

#ifndef A_DEF
#define A_DEF
int a[] = {1,2,3,4,5,6,7,8,9};
#endif