After several hours I have figured this out, but because the % statement is confusing to me I was wondering if someone wolud not mind explaining to me my for statement in the following program?

using System;

/*This program is designed to identify the prime numbers from 1 to 100.  Then total their sum and find the average of the prime numbers from 1 to 100.*/ 

public class PrimeNumbers
{
    /* Main method entry point*/
    public static void Main()
    {
        /*declare variables*/
        int num = 2,
            totalPrimeNum = 0,
            x;
        double countPrimeNum = 0,
               avg;

        /*while loop, which determines when num <= 100 (or 2 <= 100).*/

        while (num <= 100)
        {
            bool isPrime = true;
            /*test num to see if it is prime*/
            for (x = 2; x < num; ++x)
            {
                if ((num % x) == 0)
                {
                    isPrime = false;
                    break;
                }
            }
            if(isPrime)
            {
                /* List the prime number, once the program determines a number is prime*/
                Console.WriteLine (num);
                countPrimeNum = countPrimeNum + num;
                ++totalPrimeNum;
            }
            //Add 1 to the number and then go to the begining of the loop and test to see wether to re-enter the loop or to go to the next step*/
            ++num;
        }
        avg = countPrimeNum / totalPrimeNum;
        Console.WriteLine ("The average of the prime numbers between 2 to 100 is: {0}", avg);
    }

}

Edited 3 Years Ago by mike_2000_17: Fixed formatting

The % operator, or modulo operator returns the remainder when you divide the numbers.
Ex. 5%2 = 1
4 % 2 = 0

In your code the statement if ((num % x) == 0) checks to see if num is divisible. If it is, the number is obviously not prime.

Still confused. In the for statement for (x = 2; x < num; ++x)
what I am I saying??

And then for the modulus if I understand you correctly? The prime number is false, when the number does not evenly divide into the number below it?? example
33/32 = 1.03125 Therefore since it doesn't divide evenly it has a modulus of 1. Is that correct???

the for construct can be looked at like a while construct. Maybe this will help you understand it
x=2;
num = 100;
while ( x < num )
{
// do something with x
x = x + 1;
}

Hope that helps.
The modulus returns the remainder of the division. 33/32 = 1.03125 (remainder is .03125)

Thanks,
For the help guys. I think I have a much better understanding.

the for construct can be looked at like a while construct. Maybe this will help you understand it
x=2;
num = 100;
while ( x < num )
{
// do something with x
x = x + 1;
}

Hope that helps.
The modulus returns the remainder of the division. 33/32 = 1.03125 (remainder is .03125)

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