Question

I have to work with eclipse in C. I wrote a simple program, but I have a problem with a printf command which doesn’t work properly. Any idea?
Here is the code :

#include <stdio.h>
void change(double *x, double *y)
{
 double help = *x;
  *x = *y;
 *y = help;
 return;
}

int main()
{
double x=0, y=0;

printf("please give a value to a  \n ");
scanf("%f",&x);
printf("please give a value to b  \n");
scanf("%f",&y);

printf("x=%.2f\t y=%.2f\n",x,y);
printf("will give \n");
change(&x,&y);
printf("x=%.2f\t y=%.2f\n",x,y);
return 0;
}

So the problem is that I dont’t get this first printf.

Answer 1

All your values are double for which you have to use %lf. Buut you are using %f which invokes undefined behaviour.

Change %f to %lf in your scanfs and prints.