Conditionals (if-else & switch)

🔵 C Programming Lesson 4 Beginner

Conditionals execute specific code pathways depending on whether boolean parameters resolve to true or false. In C, any non-zero value represents true, and zero represents false.

1 True and False in C (Truthy vs Falsy)

C historically does not have a native primitive boolean type (though `<stdbool.h>` was added in C99). Instead, C evaluates conditions numerically:

False: Represented by the integer value `0`.
True: Represented by **any non-zero value** (both positive and negative numbers like `1`, `5`, `-12`).

2 Logical Structures and Switch Fall-through

The conditional statements use `if`, `else if`, and `else` keywords. In switch-case blocks, omitting a `break` statement causes execution to "fall through" and execute subsequent case blocks without validation. Let's test this behavior:

C — If statements and Switches ▶ Run Code

#include <stdio.h>

int main() {
    int age = 17;
    int hasPermit = 1; // 1 is true in C

    if (age >= 18) {
        printf("Eligible for driving license.\n");
    } else if (age >= 16 && hasPermit) {
        printf("Eligible to drive with supervision.\n");
    } else {
        printf("Not eligible to drive.\n");
    }

    // Switch case with break checks
    char grade = 'B';
    switch(grade) {
        case 'A':
            printf("Excellent work!\n");
            break;
        case 'B':
            printf("Good progress!\n");
            // No break! Fall-through will execute next case too!
        case 'C':
            printf("Passed!\n");
            break;
        default:
            printf("Try again!\n");
    }

    return 0;
}

3 Code Challenge

Challenge: Write a nested conditional checking if a year is a leap year. A year is a leap year if it is divisible by 4, except for years divisible by 100 unless they are also divisible by 400. Print the leap year status for `2026` and `2024`.