C Program to Check Whether a Number can be Express as Sum of Two Prime Numbers - Source Code, Output & Execution Flow

C Program to Check Whether a Number can be Express as Sum of Two Prime Numbers

This C program checks whether a number can be written as the sum of two prime numbers.

#include <stdio.h>
int isPrime(int n) {
    int i;
    if (n <= 1) return 0;
    for (i = 2; i * i <= n; i++) if (n % i == 0) return 0;
    return 1;
}
int main() {
    int n, i, found = 0;
    printf("Enter a number: ");
    scanf("%d", &n);
    for (i = 2; i <= n / 2; i++) {
        if (isPrime(i) && isPrime(n - i)) {
            printf("%d = %d + %d
", n, i, n - i);
            found = 1;
        }
    }
    if (!found) printf("%d cannot be expressed as sum of two primes.
", n);
    return 0;
}

Enter a number: 34
34 = 3 + 31
34 = 5 + 29
34 = 11 + 23
34 = 17 + 17

Practice This Program

In this program, the input is read first when required, the core logic is applied step by step, and the final result is displayed using printf(). Follow the execution flow beside the code to understand how each statement contributes to the output.