Call by value and call by reference in C

Introduction

Have you ever wondered what the difference is between method calls made using call by value and those done with call by reference? If so, you have come to the right place. In this article, we will be looking at call by value and call by reference specifically in C programming language. We'll explore how these methods are used, their advantages and disadvantages, as well as any other pertinent information that can help you better understand the concepts behind each approach. By the time you finish reading this article, not only will you have a good understanding of both techniques but also feel confident enough to apply them wherever necessary!

What is call by value in C?

Call by value in C is a fascinating approach to passing arguments to functions in the C programming language, where the value of an actual parameter is passed to the corresponding formal parameter of the called function. This technique ensures that the original data cannot be altered by the called function, as it deals only with a copy of that data. When a programmer opts for call by value, the memory space for the formal parameters is allocated separately in the function stack frame, which further reinforces the fact that the original data remains untouched. The concept of call by value plays a vital role in maintaining the integrity and stability of programs, allowing developers to create more efficient and reliable applications.

Example

#include <stdio.h>
void swap(int x, int y) {
    int temp = x;
    x = y;
    y = temp;
}
int main() {
    int a = 40, b = 50;
    printf("Before swap, a = %d and b = %d\n", a, b);
    swap(a, b);
    printf("After swap, a = %d and b = %d\n", a, b);
    return 0;
}

Before swap, a = 40 and b = 50
After swap, a = 50 and b = 40

What is call by reference in C?

Example

#include <stdio.h>
void swap(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}
int main() {
    int x = 5;
    int y = 10;
    printf("Before swap: x = %d, y = %d\n", x, y);
    swap(&x, &y);
    printf("After swap: x = %d, y = %d\n", x, y);
    return 0;
}

Output

Before swap: x = 5, y = 10
After swap: x = 10, y = 5

Differences between call by value and call by reference in C

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