Code below taken from [here](http://www.cplusplus.com/reference/clibrary/cstdlib/qsort/).

```
* qsort example */
#include <stdio.h>
#include <stdlib.h>

int values[] = { 40, 10, 100, 90, 20, 25 };

int compare (const void * a, const void * b)
{
  return ( *(int*)a - *(int*)b );
}

int main ()
{
  int n;
  qsort (values, 6, sizeof(int), compare);
  for (n=0; n<6; n++)
     printf ("%d ",values[n]);
  return 0;
}

```

We have a compare function with parameters in its signature but when we call it in qsort no arguments are passed. How are the values of `a` and `b` passed to the function? Thanks