Exercise:
Write a C++ program to check if the number is a prime number or not.
Click Here to View the Solution:
#include <iostream>
using namespace std;
int main()
{
int num, Prime = 1;
// bool Prime = true
cout << "Enter a positive integer: ";
cin >> num;
// since 0 and 1 are not prime numbers
if (num = 0 || num == 1)
{
Prime = 0;
}
else
{
for (int i = 2; i <= num / 2; ++i)
{
if (num % i == 0)
{
Prime = 0;
break;
}
}
}
if (Prime)
cout << "it is a prime number";
else
cout << " is not a prime number";
return 0;
}
Click Here to View the Output:
Enter a positive integer: 23 it is a prime number
Click Here to View the Explanation:
- Some variables are declared in this program.
num
andPrime
. The value ofPrime
is declared as 1. - The user is requested to enter a number.
- The value of
Prime
can be changed to zero using anif statement
and an OR operator. - It checks if the entered numbers are 0 or 1, the
Prime
value is changed to zero, the compiler jumps to the last step and prints out that the entered numberis a prime number
. - If
Prime
remains 1, thefor
loop is iterated. It checks ifi
perfectly dividesnum
leaving 0 as remainder. - A range is given to enter the for loop, listing that it can only be entered if value of
i
is lesser thannum/2
and/or equal to 2. - With every iteration, the value of
i
is increased by 1 through increment operators. - If the number is divided by
i
at any iteration, thePrime
is reduced to zero and the for loop is exited. - The output is printed accordingly.