Prime numbers

[dvdtomkins]

This is what I have to do in C++ but I'm stuck on how to go about it.


In this exercise write a program that detects if the integer inputed by the user is a prime number or a composite number. If you have not heard of these terms before then a prime number is a number that can only be divided by itself and one. A composite number is a number that has 2 or more factors. A factor is a number that will divide evenly into a number.

If the number inputed by the user is a prime number then the program will output something similar to this


Enter An Integer: 13
Your number 13 is a prime number


If the number is a composite number then the program's output will be something like this


Enter An Integer: 24
Your number 24 is a composite number.
It's factors are 2, 3, 4 ,6, 8, 12


If you can complete this exercise without any difficulties then you can proceed to the next lesson. If you found that you had any problems with this exercise then contact your instructor about the problems and attach any working code so that we can discuss where your solutions lay.

[Irfanerol]

I've written the program and it works very well.

You'll need a while and if loop. Moduler division will works!
I think you can solve the problem now, or if you want, I can send it here? I'm waiting your answer.

Thanks.

[WingedPanther]

dvdtomkins, we do not do people's homework here, but will help if you post your code so far or let us know what issue you're having getting started.

[Xav]

This looks like spam to me. I'm reporting.

EDIT:
Dunnit! Lihong, you're goin' down!

[soku11]

Here my code for this function:

bool IsPrime( unsigned int number )
{
  if( number<2 ) return false;
  if( number==2 ) return true;

  for( int i=2;i<=number/2;++i )
    if( number%i==0 ) return false;

  return true;
}

It returns true if the numer is a prime or false if it isnt.

[dvdtomkins]

I just wanted help getting started, anyway I found some help on another site and came up with this code:

#include <iostream>
using namespace std;


int main()
{
          int n; 
          int i;
          int c=0;
          cout<<"enter a number:";
          cin>>n;

        for(i=1;i<=n;i++) // below is the statements to test for a prime number
         {
           if(n%i==0)
           {
             c += 1;
           }
         }//end of for

       if(c==2)
         {
          cout<<n<<" is a prime number";
         }//end of if

       else
         {
          cout<<n<<" is a composite number it's factors are";    
         for(int k=1; k< n;k++)
            {
              if(n%k==0)
                {
                 cout<<","<<k;                  

                }//end of if


            }//end of for        
 
 

         }//end of else

  return 0;
}// end of mainA

[WingedPanther]

dvdtomkins:
your code seems a little inefficient. I would run through the loop once, building the factors into a string. If the string is empty, output "prime", otherwise output the factors with 1 and n added to the list. This would also make your loop shorter, as you could loop from 2 to n/2.

Also, please use code tags in the future.

[Xav]

Yes, you only need to check the numbers between 2 and half of n, as once you go above halfway, it's impossible to fit in a whole number?

@ Winged, is there a keyboard shortcut for code tags? I know Ctrl-B is bold, I is Italic, U is underlined... how about code?

[WingedPanther]

left-bracket + "CODE" + right-bracket. code goes here. left-bracket + "/CODE" + right-bracket.

[Xav]

Oh ha ha. Now seriously, is there a keyboard shortcut?