[aadilprabhakar]

To check if the number is prime or not.

/*
    To check if an integer is prime or not
*/

#include<iostream.h>
#include<conio.h>
void main()
{
     int num,i;

    clrscr();

    cout<< "Please enter the number ";
    cin >> num;
    i =2 ;


     while(1){
        if (num%i==0) {
         if(num == i){
             cout << "Prime Number";
            break;
         } else {
cout << "Not Prime";
break;
}
} else {
         i++;
}
}
}

[shabbir]

You don't need to loop till i but even i/2 or square root of i is also sufficient.

[back from retirement]

Yes....the actual is the square root of i. You can use the standard function sqrt(); for that purpose.

[skp819]

A simple program is here. to chech a number is prime or not.

void main()
{
    int a,b,i;
    cout<<"\n enter the no: ";
    cin>>a;
    for(i=2;i<=a;i++)
    {
        rem=a%i;
        if(rem==0)
        {
            cout<<"\nNo is not prime: ";    
        }
        else
        {
            cout<<"\nNo is  prime:";
        }
    }
}