Call by Value and Call by Reference in C Programming - A Complete Tutorial for Beginners in 2023

Article by: Manish Methani

Last Updated: November 3, 2021 at 2:04pm IST
3 min 11 sec read

1. Call by Value Call by value is a method of passing arguments to a function by copying the values of the arguments into the function's parameters. The function then works with the copied values, leaving the original values unchanged. Here's an example of a function that uses call by value:

#include <stdio.ht>

void changeValue(int x) {
    x = 10;
    printf("The value of x inside the function is %d", x);
}

int main() {
    int x = 5;
    printf("The value of x before the function call is %d", x);
    changeValue(x);
    printf("The value of x after the function call is %d", x);
    return 0;
}

Output:

The value of x before the function call is 5
The value of x inside the function is 10
The value of x after the function call is 5

In this example, the changeValue() function takes an argument x and sets its value to 10. However, since we're using call by value, the original value of x in the main() function remains unchanged.

   2. Call by Reference Call by reference is a method of passing arguments to a function by passing their memory addresses instead of their values. The function then works with the original values, and any changes made to the parameters affect the original variables. Here's an example of a function that uses call by reference:

#include <stdio.ht>

void changeValue(int *x) {
    *x = 10;
    printf("The value of x inside the function is %d", *x);
}

int main() {
    int x = 5;
    printf("The value of x before the function call is %d", x);
    changeValue(&x);
    printf("The value of x after the function call is %d", x);
    return 0;
}

Output:

The value of x before the function call is 5
The value of x inside the function is 10
The value of x after the function call is 10

In this example, the changeValue() function takes a pointer to an integer x and sets its value to 10 by dereferencing the pointer. Since we're using call by reference, the changes made to x inside the function also affect the original value of x in the main() function.

Conclusion: In summary, call by value and call by reference are two methods of passing arguments to a function in C programming. Call by value copies the values of the arguments into the function's parameters, while call by reference passes the memory addresses of the arguments instead. Understanding the difference between these two methods is crucial when working with functions in C programming.