#include<stdio.h>
 
void zamiana(float *x, float *y)
{
   float tmp;
   tmp = *x;
   *x = *y;
   *y = tmp;
}
 
int main()
{
   float a=13;
   float b=42;

   printf("a=%f, b=%f\n", a, b);
   zamiana( &a, &b);
   printf("a=%f, b=%f\n", a, b);
 
}