### Program to print prime numbers between 1 to n

/**

* C program to print all prime numbers between 1 to n

*/

#include <stdio.h>

int main()

{

int i, j, n, isPrime; //isPrime is used as flag variable

/* Reads upper limit to print prime */

printf(“Find prime numbers between 1 to : “);

scanf(“%d”, &n);

printf(“nAll prime numbers between 1 to %d are:n”, n);

/* Finds all Prime numbers between 1 to n */

for(i=2; i<=n; i++)

{

/* Assume that the current number is Prime */

isPrime = 1;

/* Check if the current number i is prime or not */

for(j=2; j<=i/2; j++)

{

/*

* If i is divisible by any number other than 1 and self

* then it is not prime number

*/

if(i%j==0)

{

isPrime = 0;

break;

}

}

/* If the number is prime then print */

if(isPrime==1)

{

printf(“%d is Prime numbern”, i);

}

}

return 0;

}

**Note:**For checking whether a number is Prime or not we just need to check that the number should not be divisible by any number between 2 to n-1. Apart from that you can also check between 2 to n/2. Since any number more than (n/2)+1 cannot be exactly divided by n except self n.

Output

Find prime numbers between 1 to : 100

All prime numbers between 1 to 100 are:

2 is Prime number

3 is Prime number

5 is Prime number

7 is Prime number

11 is Prime number

13 is Prime number

17 is Prime number

19 is Prime number

23 is Prime number

29 is Prime number

31 is Prime number