FIND PRIME NUMBER IN C++

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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


  1. #include<iostream.h>
  2. #include<conio.h>
  3.         void main()
  4.         {
  5.          //clrscr();
  6.          int number,count=0;
  7. cout<<"ENTER NUMBER TO CHECK IT IS PRIME OR NOT ";
  8.           cin>>number;
  9.            for(int a=1;a<=number;a++)
  10.                {
  11.                 if(number%a==0)
  12.                    {
  13.                   count++;
  14.                    }
  15.                }
  16.        if(count==2)
  17.          {
  18.           cout<<" PRIME NUMBER \n";
  19.          }
  20.        else
  21.          {
  22.           cout<<" NOT A PRIME NUMBER \n";
  23.          }
  24.        //getch();
  25.        }



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. 
Prime number program image view
C++ program to find prime numbers 
Sample Output:

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Recommended: For fast learning change the logic and do experiment with codes.
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