Section 3.4 Repetition: A Simple for-Loop

Suppose you wanted to print the same line of text five times. Here is one way to do so:

But imagine how many times you’d have to type the same line if you wanted to print it 100 times! Or imagine wanting to make a change to all of those lines, for example wanting two exclamation marks at the end of each output line. Here is a more elegant solution: a so-called loop:

Try it out right now by hitting that “Run” button!

C actually supports multiple types of loops. This one is called a for-loop; we’ll learn about the other types of loops later. We will also soon learn more about the use of the rather mysterious-looking “i” and the line “int i;”. For now, just think of i as something that can hold different values. In this particular example, i takes on values between 1 and 5, and for each value of i between 1 and 5 this loop prints out Hello, World!. That is, Hello, World! is printed exactly 5-times.

You can place multiple statements into your loops:

#include <stdio.h>

int main(void) {
    int i; 
    
    for (i = 1; i<=3; i++) {
        printf("Hello, World! ");
        printf("Today is Saturday.\n");
    }
    
    return(0);
}