/* example that demonstrates the use of functions */
#include <stdio.h>
#include <string.h>

float P,M; /*Global variables declared here */

int world (int z)
{
  int n; /* a local variable only exists within the function */
  printf("\nHello World\n");
  n = 66;
  return (n);
}

void swap (int *x, int *y)
{
  int *temp;
  temp = *x;
  *x = *y;
  *y = temp;
}

void strfunc(char s[80])
{
  printf("In strfunc s = %s\n",s);
  strcpy(s,"Its feet were white and grey\n");
}

int main (void)
{
  int z,w;
  printf("\nCalling function\n");
  w = world(z);
  z = 3; w = 9;
  swap(&z,&w);
  printf("Z = %i, W = %i\n",z,w);
  /*functions in c call by value i.e. z cannot be changed by the 
  function. However, global variables can be changed and a function
  can also change the values to which pointers point */ 
  printf("\nReturned from functions\n");
  char s1[80] = "Mary had a little lamb\n";
  strfunc(s1);
  strfunc(s1);
}