C void Function Tutorial

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In this section, we will learn what the void function is and how to use it in C.

Note: we’re assuming you’re already familiar with the functions in C.

What is void in C?

The void keyword in C is used as the return data type of a function when, in fact, the target function does not return a value.

Basically, the `void` keyword is a sign to the execution engine and developers that the target function won’t return a value and so the function shouldn’t be used in places where a value is excepted (for example as the argument of another function, or as the assignment to a variable, etc.).

Void Function in C: Syntax

This is how we create a void function.

void functionName();

As you can see, we use the `void` keyword right where the data-type of a function is used to declare that the function won’t return a value.

Example: declaring void function in C

#include <stdio.h>

void printSum(int, int);

int main() {

    printSum(100, 200);
    return 0;
}

void printSum(int val1, int val2){
    int res = val1 + val2; 
    printf("The result is: %d\n",res);
}

Output:

The result is: 300

In this example, the `printSum()` function’s return type is set to void, which means the function does not return a value when we call it.

Note: when a function does not return a value (its data type is set to void), you should not use the `return` statement in that function anymore. If you do so, you’ll get a compile time error instead.

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