Write a program to find the Smallest Common Divisor of a given number.

smallest_divisor.c

#include <stdio.h>

int main() {
    int n, i;

    printf("Enter a number: ");
    scanf("%d", &n);

    if(n <= 1) {
        printf("Smallest divisor is not defined for %d\n", n);
    } else {
        for(i = 2; i <= n; i++) {
            if(n % i == 0) {
                printf("Smallest divisor of %d is %d\n", n, i);
                break;   // stop at the first divisor found
            }
        }
    }

    return 0;
}

✅ Step-by-Step Explanation

🔹 1. Input a number

• User enters a number (example: n = 28)
• scanf() reads the integer input

🔹 2. Check for valid input

if(n <= 1) {
    printf("Smallest divisor is not defined for %d\n", n);
}

• Numbers ≤ 1 don't have proper divisors
• Program handles this edge case immediately

🔹 3. Find smallest divisor

for(i = 2; i <= n; i++) {
    if(n % i == 0) {
        printf("Smallest divisor of %d is %d\n", n, i);
        break;
    }
}

• Loop starts from 2 (first possible proper divisor)
• Modulo operator % checks divisibility
• break exits loop after first divisor found

🖨️ Example Runs

Composite Number Example:

Enter a number: 28
Smallest divisor of 28 is 2

Prime Number Example:

Enter a number: 37
Smallest divisor of 37 is 37

(37 is prime, so its smallest divisor is itself)

📌 Key Concepts Covered

For Loop

Iterates from 2 to n to check possible divisors

Modulo Operator %

Tests if n is divisible by current number (n % i == 0)

Break Statement

Exits loop immediately after finding first divisor

Edge Case Handling

Special handling for numbers ≤ 1

Prime Number Logic

If no divisors found before n, the number is prime