Difference Between Call By Value And Call By Reference

Call By Value:-

      call by value passes the copy of the variable to the function that process it

      Let’s take a look at a call by value example:
  
#include <stdio.h>

#include<conio.h>

void call_by_value(int x) 

{

       printf("Before adding 10 x = %d .\n", x);

       x=x+10;

       printf("After adding 10 x = %d.\n", x);

}

void main() 

{

  int a=10;

  clrscr();

  printf("a = %d before function call_by_val.\n",a);

  call_by_value(a); 

  printf("a = %d after function call_by_val.\n",a);

  getch();

}

Call By Reference:-

    call by reference passes the memory reference of the variable (pointer)
    to the function. 

Let’s take a look at a code example:

#include <stdio.h>

#include<conio.h>

void call_by_reference(int *y) 

{

      printf("Before adding 10 y = %d .\n", *y);

      (*y) += 10;

      printf("After adding 10 y = %d .\n", *y);

}

void main() 

{

      int b=10;

      clrscr();

      printf("b = %d before function call_by_ref.\n",b);

      call_by_reference(&b);

      printf("b = %d after function call_by_ref.\n",b);

}