Thread: C++ prime number loop?

I am still very new to c++ and i am totally confused on loops so can anyone help me write a program to
"Write a program that finds and prints all prime numbers less than or equal to n, where n is a number input by the user."

This is the template were supposed to use

Code:

#include <iostream>

using namespace std;

// ======================
// main function
// ======================
int main()
{

// Variable declarations
int n, i, k;
int counter = 0;
bool isprime;

//Welcome user to the program



//Prompt user for an integer




// Outer loop, tests to see if k is prime for k=2 to n

{
// Assume k is prime


// Inner loop tests whether or not k is prime

{



}
// Check if flag isprime is still true


}

//Output total number of primes found


}

Our output is supposed to be
Program to compute prime numbers less than n.

Enter a positive integer n: 10

2 3 5 7
There are 4 primes less than 10.

[email protected]~/cs1500/lab3) a.out


Program to compute prime numbers less than n.

Enter a positive integer n: 50

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47
There are 15 primes less than 50.


Thanks sooooooo much

Well, Sieve of Eratosthenes - Wikipedia, the free encyclopedia would be a nice solution.

Do you know what a prime number is?

Do you know how to test any given number to see if it is prime or not?

Have you googled anything along the lines of "prime number algorithm" (like Xupicor has)?


Maybe start with

Code:

for ( i = 1 ; i < n ; i++ ) {
  cout << "Checking" << i << " for primality\n";
}