#include <stdio.h>
#include <stdlib.h>

int a,b;

//******************************************************************************

void troca1(c,d)
int c, d;
{
    int temp;
    
    temp = c;
    c = d;
    d = c;
    
    temp = a;
    a = b;
    b = temp;
    
    printf("\n1: %d %d %d %d",a,b,c,d);
}

//******************************************************************************

void troca2(int *c, int *d)
{
    int temp;
    
    temp = *c;
    *c = *d;
    *d = *c;
    
    temp = a;
    a = b;
    b = temp;
    
    printf("\n3: %d %d %d %d",a, b, *c, *d);
}

//******************************************************************************

int soma (int *c, int d)
{
    int total;
    total = *c + d;
    
    *c = 0;
    d = 0;
    
    return (total);    
}

//******************************************************************************

int main()
{
    int c,d;
    
    a=7;   b=a;  c=9;  d=21;
    
    troca1(c,d);
    printf("\n2: %d %d %d %d",a,b,c,d);
    
    a=5;   b=6;  c=7;  d=8;
        
    troca2(&c,&d);
    printf("\n4: %d %d %d %d",a,b,c,d);
    
    a=21;   b=1;  c=45;  d=99;
        
    a = soma(&c,d);
    printf("\n5: %d %d %d %d",a,b,c,d);
    
    getchar();
}