Answer 1

#include <iostream>
#include <math.h>

class Prime
{
int i=2;
int flag=0;
int x=2;
int count=0;
public:
void calcPrime(int no)
{
while(x<=no)
{ while(i<=floor(sqrt(x)))
/*
Fastest method I know
this comes from
sieve of Eratosthenes
method of finding prime numbers
*/
{
if(x%i==0)
{ flag=1; break;}
i++;
}
if(flag==0)
{
std::cout<<x<<"\n";
count++;
}
x++;
i=2;
flag=0;
}
}
int getcount()
{
return count;
}
};

int main()
{

int no;
Prime prime;
std::cout<<"Enter number\n";
std::cin>>no;
std::cout<<"Prime Numbers till "<<no<<" are\n";

prime.calcPrime(no);

std::cout<<"So "<<prime.getcount()<<" Primes till "<<no;
std::cout<<"\n !!!!!Please Like it!!!!!";
return 0;
}