Nested for loop to calculate prime number : For : Statement C# Examples

Nested for loop to calculate prime number

    
using  System;  
  
class  MainClass  {        
    public  static  void  Main()  {        
        int  num;  
        int  i;  
        int  factor;  
        bool  isprime;  
  
  
        for(num  =  2;  num  <  20;  num++)  {  
            isprime  =  true;    
            factor  =  0;  
  
            //  see  if  num  is  evenly  divisible  
            for(i=2;  i  <=  num/2;  i++)  {  
                if((num  %  i)  ==  0)  {  
                    //  num  is  evenly  divisible  --  not  prime  
                    isprime  =  false;  
                    factor  =  i;  
                }  
            }  
  
            if(isprime)  
                Console.WriteLine(num  +  "  is  prime.");  
            else  
                Console.WriteLine("Largest  factor  of  "  +  num  +  
                                                    "  is  "  +  factor);  
        }  
  
    }        
}
    
   
  
   

2 is prime.
3 is prime.
Largest factor of 4 is 2
5 is prime.
Largest factor of 6 is 3
7 is prime.
Largest factor of 8 is 4
Largest factor of 9 is 3
Largest factor of 10 is 5
11 is prime.
Largest factor of 12 is 6
13 is prime.
Largest factor of 14 is 7
Largest factor of 15 is 5
Largest factor of 16 is 8
17 is prime.
Largest factor of 18 is 9
19 is prime.

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