lassie% /lib/cpp -C -P main2.c
/* File: main2.c

   This is a simple main program.
   It's main purpose is to include the header
   files header.h and header2.h to show how 
   #include and #ifndef work.
*/


/**** File: header.h 
   This is a  simple header file.
*/

int sum(int, int) ;
int global_variable = 1 ;

/**** End of file: header.h */

/**** File: header2.h 
   
   This is another simple header file.
   It includes the file header.h
   It contains one function prototype.
*/


/**** File: header.h 
   This is a  simple header file.
*/

int sum(int, int) ;
int global_variable = 1 ;

/**** End of file: header.h */

int diff(int, int) ;

/**** End of file: header2.h */

main() {
  int n ;

  n = sum(3, 4) ;
  n = diff(5,7) ;
}
lassie%