Prime Numbers

C++ Program to FIND PRIME NUMBER

By: bscsprogramming.tk

What is a PRIME NUMBER?

" A Natural number greater than 1 which has only two divisor 1 and itself is called prime number ".
For Example:
5 is prime, because it has only two divisors 1 and itself.

C++ Program To Find Prime Numbers

#include<iostream.h>
using namespace std;
        main()
        {
         
         int number,count=0;
cout<<"ENTER NUMBER TO CHECK IT IS PRIME OR NOT ";
          cin>>number;
           for(int a=1;a<=number;a++)
               {
                if(number%a==0)
                   {
                  count++;
                   }
               }
       if(count==2)
         {
          cout<<" PRIME NUMBER \n";
         }
       else
         {
          cout<<" NOT A PRIME NUMBER \n";
         }
       
       }

UNDERSTANDING PRIME NUMBERS PROGRAM LOGIC

•      To make logic first think about PRIME NUMBER definition that a number which divides by 1 and itself.
•    So we have make a condition like that in which user will enter a number and our program will check it by dividing it from 1 up to itself.
•    To check that how much times it has divided to numbers from 1 to itself we take a variable and increment it each times when a number is divided.
•    In C++ CODING we take a FOR LOOP which will start from 1 up to number that has entered to check whether it is PRIME NUMBER or not with in FOR LOOP we set an IF condition and placed counter (count++) variable in its body so whenever a number from 1 to number which has entered to check divides than IF condition becomes true and counter variable will be incremented.
•    When FOR LOOP is completed we check from IF condition that if counter variables value is equal to 2 than number is PRIME else NUMBER IS NOT PRIME.
•    Because if number divided two times by 1 and itself counter variable will incremented two times if more than two times counter variable will have value greater than 2.