Call by value and Call by Reference

Call by value

è      In this kind of function, pass the value directly to the called function through the calling function. The called function does process and returns the value back to the calling function.

è      In this method the value of each of actual argument in calling function is copied into corresponding formal arguments of the called function.

è      Any change  made to the arguments internally in the function are made only to the local copies of the arguments, It will not reflect to actual argument in calling function.

Ex,

#include < stdio.h>

void swap(int a, int b);

void main()

{

    int a, b;

    a = 5;

    b = 7;

    printf("From main: a = %d, b = %d\n", a, b);

    swap(a, b);

    printf("Back in main: ");

    printf("a = %d, b = %d\n", a, b);

}

void swap(int a, int b)

{

    int temp;

    temp = a;

    a = b;

    b = temp;

    printf(" \n Inside  function swap :");

    printf(" a = %d, b = %d", a, b);

}

       O/P

            From main: a = 5, b = 7

            Inside  function swap :a = 7, b = 5

            Back in main: a = 5, b = 7

Call By Reference

è      In call by reference , not need to pass value directly to the called function , Instead of that pass the address of the variable which hold the value. It can be got by passing the address to the function.

è      By this method  , change made to the parameters of  function will affect the variables which called the function.

#include < stdio.h>

void swap(int *a, int *b);

void main()

{

    int a, b;

    a = 5;

    b = 7;

    printf("From main: a = %d, b = %d\n", a, b);

    swap(&a,&b);

    printf("Back in main: ");

    printf("a = %d, b = %d\n", a, b);

}

void swap(int *a, int *b)

{

    int temp;

    temp = *a;

    *a = *b;

    *b = temp;

    printf(" Inside  function swap ");

    printf("a = %d, b = %d\n", *a, *b);

}

            O/P

            From main: a = 5, b = 7

            Inside  function swap :a = 7, b = 5

            Back in main: a = 7, b = 5

Posted By : Ruchita Pandya