lassie% cat hello.c
/* File: hello.c

   Hello world revisited.
*/
#include <stdio.h>

main() {
#include "print.c"   
}
lassie% 

lassie% cat print.c
printf("Hello World\n") ;
lassie% 

lassie% cc201 hello.c

lassie% a.out
Hello World
lassie%