Conditions (if / else) in C — Revision Notes

Definition

Syntax

if (condition) {
    // code
} else if (condition2) {
    // code
} else {
    // code
}

Example

#include <stdio.h>

int main() {
    int marks = 72;
    if (marks >= 90) {
        printf("Grade: A\n");
    } else if (marks >= 60) {
        printf("Grade: B\n");
    } else {
        printf("Grade: C\n");
    }
    return 0;
}

Output

Important Points

• Only the first matching branch executes — the rest are skipped automatically.
• Curly braces {} can be omitted for a single statement, but it's safer to always use them.
• switch is a clean alternative when checking one variable against many exact values.
• Don't forget break; inside each switch case, or execution will "fall through" into the next case.

Common Mistakes

• Putting a semicolon right after if (condition); — this creates an empty if-body bug.
• Forgetting break; in a switch statement.
• Using = instead of == inside a condition.

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