Loops in C — Revision Notes

Definition

Syntax

for (init; condition; update) { }
while (condition) { }
do { } while (condition);

Example

#include <stdio.h>

int main() {
    for (int i = 1; i <= 5; i++) {
        printf("%d ", i);
    }
    printf("\n");
    return 0;
}

Output

Important Points

• break exits a loop immediately; continue skips to the next iteration.
• Use for when the number of repetitions is known ahead of time.
• Use while when the loop should keep running until some condition changes.
• An incorrect loop condition can create an infinite loop — always double-check the update step.

Common Mistakes

• Forgetting to update the loop variable, causing an infinite loop.
• Off-by-one errors: using < instead of <= (or vice versa).
• Accidentally putting a semicolon right after the loop header: for(...);.

Interview Tip