C program to print prime numbers between two numbers

Prime numbers are the numbers which have only two factors, 1 and the number itself. That means, they are not divisible by any number other than one and the number itself.

In this article, we’ll learn how to check whether a number is prime or not, with and without using function. But before that, we’ll write a program to print prime numbers from 1 to 200.

This C program prints prime numbers from 1 to 200. This algorithm can also be used to check whether a number is prime or not.

Program: C program to print prime numbers from 1 to 200

#include<stdio.h>
int main()
{
    int n,i,flag;
    for(n=1; n<=200; n++)   /*iterate over numbers from 1 to 200*/
    {
        flag=0;
        for(i=2;i<=(n/2);i++)
        {
           if((n%i)==0)         /* check prime or not*/
           {
            flag=1;
            break;
           }

        }
        if(flag==0)
            printf("%d ",n);
    }
    printf("\n");
    return 0;
}

Output: Prime numbers from 1 to 200

1 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 101 103 107 109 113 127 131 137 139 149 151 157 163 167 173 179 181 191 193 197 199

Now, we’ll write a program to check whether a number is prime or not using function. The same algorithm is used to serve this purpose.

Program: C program to check whether a number is prime or not using function

#include<stdio.h>
int checkPrime(int);
int main()
{
    int n,i,flag;
    printf("Enter a number: ");
    scanf("%d", &n);
    flag = checkPrime(n);
    if(flag == 1)
        printf("%d is not a prime number.", n);
    else
        printf("%d is a prime number.", n);
    printf("\n");
    return 0;
}
int checkPrime(int a){
    int i;
    for(i=2;i<=(a/2);i++)
    {
        if((a%i)==0)         /* check prime or not*/
            return 1;
    }
        return 0;
}

Output:

Sample output #1:

Enter a number: 4337
4337 is a prime number.

Sample output #2:

Enter a number: 4239
4239 is not a prime number.

Challenge: Write C program to check whether a number is prime or not in the comments.

In this article, we learnt to write program in C to check prime numbers and to print prime numbers between two numbers.

For more programming articles and code snippets, visit programming articles.

About ᴾᴿᴼᵍʳᵃᵐᵐᵉʳ

Linux and Python enthusiast, in love with open source since 2014, Writer at programming-articles.com, India.

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