Understanding the Differences Between Subroutine and Function in C

In C programming, both subroutines and functions are essential for encapsulating reusable code. However, they differ significantly in terms of terminology and usage. Understanding these differences is crucial for writing efficient and clean code. In this article, we will explore the distinctions between subroutines and functions in the C programming language.

Definitions

A function in C is a block of code that executes a specific task and returns a value. Functions are defined with a return type, a name, and parameters if necessary. They can be called from anywhere within the program after they are declared. On the other hand, a subroutine is a more general term that can refer to any callable routine, but often in C, it is used interchangeably with 'function' to describe a routine that does not return a value.

Key Differences

Return Value

Function: Functions typically return a value of a specific type such as int, float, etc. Subroutine: Subroutines, often referred to as void functions in C, do not return a value. They are used for performing actions that do not require a return value.

Usage

Function: Functions are used when a specific value is needed as a result of the operation performed. For example, a function might calculate the sum of two integers and return the result. Subroutine: Subroutines are used for performing actions that do not require a return value but might change global variables or print output. For instance, a subroutine might print a message to the console.

Terminology

Function: The term is more commonly used in C programming to refer to any callable block of code. Functions in C are designed to return a value, and they may or may not return a void. Subroutine: This term is more generic and can refer to any callable routine, including functions. In the context of C, it is often used to refer to functions that do not return a value.

Example

Below is a simple example to illustrate the difference between a function and a subroutine in C:

#include stdio.h



// Function that returns an integer
int add(int a, int b) {
    return a   b;
}

// Subroutine that prints a message
void printMessage() {
    printf(Hello, World!);
}

int main() {
    // Call the function
    int sum  add(5, 3);

    printf(The sum is: %d
, sum);



    // Call the subroutine
    printMessage();



    return 0;

}

In this example, the add function takes two integers as parameters, performs a task (adding them), and returns the result. The printMessage subroutine simply prints a message to the console, which does not require a return value. Note that the printMessage function is defined with a void return type, indicating that it does not return any value.

Summary

In summary, while both functions and subroutines are used to structure code in C, the key difference lies in whether they return a value. Functions return values, while subroutines (or void functions) perform actions without returning a value. Understanding these distinctions can help you write more efficient and modular C code.