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## Friday, 27 March 2015

### program to count the number of prime numbers from 1 to limit

Program to count the number of prime numbers from 1 to limit

/*
* program to count the number of prime numbers from 1 to limit
*/
#include <stdio.h>
#include <conio.h>

int checkPrime(int val)
{ // tests if the given number is prime or not
int i;
if(val == 1 || val == 0)
return 0;
for(i=2; i<=val/2; ++i)
if((val%i) == 0)
return 0;
return 1;
}

int noOfPrimes(int lim)
{// this calls the function checkPrime to test if the number is prime
// if it is prime, 'count' is incremented.
int i, count = 0;
printf("\nlist of prime numbers from 2 to %d", lim);
for(i=2; i<=lim; ++i)
if(checkPrime(i))
{
++count;
printf("\n%d", i);
}
return count;
}

int main() /// the runtime complexity of this program is O(N^2)
{
int lim;
printf("enter the limit:");
scanf("%d", &lim);
printf("number of prime numbers from 2 to %d is %d", lim, noOfPrimes(lim));
return 0;
}