C Program to Print Prime Numbers From 1 to N

Prime numbers are positive integers greater than 1 that have no divisors other than 1 and themselves. In this article, we will learn to generate and display all prime numbers from 1 to N in C programming language.

Prime Numbers from 1 to 100

Algorithm

• Check every number from 1 to N whether it is prime by using isPrime() function.
• In isPrime() Function,
  • Iterate from 2 to n/2 and check if the number is divisible by any of the values other than itself.
  • If it is divisible by any number, it means the number is not prime, return false.
  • If it is not divisible by any number, it means the number is prime, return true.
• If isPrime() returns true, print the number.
• Else continue.

Program to Print Prime Numbers From 1 to N in C

C

// C program to print Prime numbers till N

#include <stdbool.h>
#include <stdio.h>

// This function is to check
// if a given number is prime
bool isPrime(int n)
{
    // since 0 and 1 is not prime
    // number return false.
    if (n == 1 || n == 0)
        return false;

    // Run a loop from 2 to n/2
    for (int i = 2; i <= n / 2; i++) {

        // if the number is divisible by i, then n is not a
        // prime number, otherwise n is prime number.
        if (n % i == 0)
            return false;
    }
    return true;
}

// Driver code
int main()
{
    int N = 50;

    // check for the every number from 1 to N
    for (int i = 1; i <= N; i++) {

        // check if i (current number) is prime
        if (isPrime(i)) {
            printf("%d ", i);
        }
    }
    return 0;
}

Output

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 

Complexity Analysis

• Time Complexity: O(N²)
• Space Complexity: O(1)

Refer to the complete article Program to print prime numbers from 1 to N for more methods to generate prime numbers.