Step 3 of 7

void functions

Not every function computes a value. Some exist for what they do, like printing. Their return type is void, meaning "returns nothing":

#include <stdio.h>

void greet(int times) {
    for (int i = 0; i < times; i++) {
        printf("hi ");
    }
    printf("\n");
}

void banner(void) {
    printf("=== START ===\n");
}

int main(void) {
    banner();
    greet(3);
    greet(1);
    return 0;
}

=== START ===
hi hi hi 
hi 

Details

• A void function doesn't need a return statement; it ends when it reaches the closing brace. You can still write return; (with no value) to leave early.
• You can't use its result: int x = banner(); is a compile error, because there is no result.
• (void) in the parameter list means "takes no arguments". Call it with empty parentheses: banner(). Forgetting the parentheses (banner;) doesn't call it at all; the compiler warns expression result unused.

Why bother?

Even small helpers make code easier to read. print_bar(10) says what it does; a loop that prints ten = characters has to be read to be understood. And if you need the same output in five places, a function means one place to fix when it changes.

Your turn: write void print_bar(int n) that prints n = characters followed by a newline. print_bar(5) prints =====.

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