Loops

Syntax

for (int i = 0; i < 5; i++) {
    printf("%d\n", i);
}

int i = 0;
while (i < 5) {
    printf("%d\n", i);
    i++;
}

int i = 0;
do {
    printf("%d\n", i);
    i++;
} while (i < 5);

Example

for (int i = 1; i <= 3; i++) {
    printf("Count: %d\n", i);
}

Expected output

Count: 1
Count: 2
Count: 3

A do...while always runs its body at least once, checking the condition only afterward — useful for a menu loop that must show at least one prompt.

Common mistakes

• Forgetting to update the loop variable, causing an infinite loop.
• Off-by-one errors when looping over an array — i <= length reads one element past the end, which C will not stop you from doing (see Arrays, next).

Practice

Print the numbers 1 through 5 using a for loop.

for (int i = 1; i <= 5; i++) {
    printf("%d\n", i);
}