Program to Find Prime Numbers in a Given Range in C

Finding Prime Numbers in a Range

A prime number is a natural number greater than 1 that has no divisors other than 1 and itself.

We will explore different methods to find all prime numbers within a given range using C programming.

Method 1: Using a for Loop

We iterate through the given range and check if each number is prime.

#include <stdio.h>

int isPrime(int num) {
    if (num < 2) return 0;
    for (int i = 2; i * i <= num; i++) {
        if (num % i == 0)
            return 0;
    }
    return 1;
}

int main() {
    int start, end;
    printf("Enter the range (start end): ");
    scanf("%d %d", &start, &end);
    
    printf("Prime numbers between %d and %d are: ", start, end);
    for (int i = start; i <= end; i++) {
        if (isPrime(i)) {
            printf("%d ", i);
        }
    }
    return 0;
}
            

Output:

Enter the range (start end): 10 20
Prime numbers between 10 and 20 are: 11 13 17 19