//---------------------------------------------------------------
// EXAMPLE EX15.C :  Demonstrate a FUNCTION call - IV.
//
// Passing POINTERS to access local variable and return multiple 
// values. 
//
// C.P. Diduch, Dec 1999.
//---------------------------------------------------------------
#define	KEY_PA	0x138	  // 82C55A port addresses for PA,
#define KEY_PB	0x13A	  // PB,
#define KEY_PC	0x13C	  // PC and the
#define KEY_CON	0x13E	  // Control Register.

#include <conio.h> 	  // conio.h contains prototypes for 
			  // inportb() and outportb(). 

// Function definitions or prototypes
void exchange(char *A, char *B); 
//---------------------------------------------------------------
void main()
{
char X, Y;

outportb(KEY_CON, 0x82);  // Initialize 82C55A PPI with ports 
			  // KEY_PC and KEY_PA as OP ports and 
			  // port PB as an IP port.
X = 5;
Y = 10;
exchange(&X, &Y);
outportb(KEY_PC, X);
outportb(KEY_PA, Y);
}
//---------------------------------------------------------------
void exchange(char *A, char *B) {
char tmp;
tmp = *A;
*A = *B;
*B = tmp;
}