Use pointer as function parameter : Function Parameter « Function « C Tutorial

1. C Tutorial
2. Function
3. Function Parameter

#include <stdio.h>

int change(int* pnumber);              /* Function prototype              */

int main(void)
{
  int number = 10;
  int *pnumber = &number;
  int result = 0;        

  result = change(pnumber);
  printf("\nIn main, result = %d\tnumber = %d", result, number);
  return 0;
}

int change(int *pnumber)
{
  *pnumber *= 2;
  printf("\nIn function change, *pnumber = %d\n", *pnumber );

  return *pnumber;
}

In function change, *pnumber = 20
     
     In main, result = 20    number = 20