positive integer N program assistance

[geko]

ok so i have to come up with something that will be prompt the user to input a positive integer N. the program should accomplish two tasks. For every natural number M that is less than or equal to N,
- Generate a list of all divisors of M, and
- Test to see if M is prime number.
Input: A positive integer (natural number) interactively.

[carlsum1986]

what help do u ned?

[geko]

Im kinda lost in knowing where i should start hahahha, im kinda of a novice programmer and am trying to teach this to myself

[EzwRko23]

Hint: Sieve of Eratosthenes.

[geko]

well this is what i have so far
but i dont know where to place the "cin>>" also im not sure why it wont run :(

#include <iostream>
using namespace std;

int isPrime(long num)
{
if (num < 2)
return 0;

if (num > 2 && (num % 2) == 0)
return 0;

for(int i = 2; i < num; i++ )
{
cout << " divisor: " << i << endl;
if ( (num % i) == 0)
{

return 0;
}
}


this is what the end program is sapose to look like
Input a positive integer : 8
Testing 1 ->
The divisors: 1
The number 1 is not a prime number.
Testing 2 ->
The divisors: 1 2
The number 2 is a prime number.
Testing 3 ->
The divisors: 1 3
The number 3 is a prime number.
Testing 4 ->
The divisors: 1 2 4
The number 4 is not a prime number.
Testing 5 ->
The divisors: 1 5
The number 5 is a prime number.
Testing 6 ->
The divisors: 1 2 3 6
The number 6 is not a prime number.
Testing 7 ->
The divisors: 1 7
The number 7 is a prime number.
Testing 8 ->
The divisors: 1 2 4 8
The number 8 is not a prime number.

[carlsum1986]

do you have a main function?
put the cin at the main function and pass the user inputs into the isprime function.

[Jauffre]

If you read what your assignment is it has the clues you need to make it work.

Lets break it down:

-->>prompt the user to input a positive integer N
//The number "has" to check to be positive for it to be valid

-->>For every natural number M that is less than or equal to N,
Generate a list of all divisors of M.
// So, create a for loop

-->>Test to see if M is prime number //Guesing you meant N :)
//use the loop to check if it's a prime number


So, A function to check if the number is valid, And a function to check if it's a prime number

http://www.anyexample.com/programming/cplusplus/cplusplus_function_for_prime_number_check_(primality_test).xml

that should help you on your way.