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C++ Program to Print Prime numbers in a Given Range

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In this C++ programming example, we will write a C++ Program to display Prime Numbers between two intervals. Let us start by understanding what is a prime number.

Prime Number:

A Prime Number is a number that is only divisible by 1 and itself. Example: 2, 3, 5, 7, 11, 13, 17, etc. These numbers are only divisible by 1 and the number itself.

Note:
0 and 1 is not a prime number and 2 is the only even and smallest prime number.

To understand the following program, you should have a basic idea about the following topics in C++ programming.

C++ Program to Print Prime Numbers

The program takes the user input for the starting number ( lower range) and the end number (upper range). Then prints all the prime numbers that fall within that range.

Also notice in the program that 0 and 1 are specifically checked to make sure that those two are not printed even if the lower range entered by the user is 0.

Print Prime Numbers in a Given Range in C++.

#include <iostream>
using namespace std;

int main()
{
  int lrRange, upRange, i, flag;

  cout << "Enter the lower range: ";
  cin >> lrRange;
  cout << "Enter the upper range: ";
  cin >> upRange;

  cout << "\nList of Prime numbers between " << lrRange << " & " << upRange << ": " << endl;

  while (lrRange < upRange)
  {
    flag = 0;

    // checking for 0 and 1
    if (lrRange == 0 || lrRange == 1)
    {
      flag = 1;
    }
    else
    {
      for (i = 2; i <= lrRange / 2; ++i)
      {
        if (lrRange % i == 0)
        {
          flag = 1;
          break;
        }
      }
    }

    if (flag == 0)
      cout << lrRange << " ";

    ++lrRange;
  }

  return 0;
}

Output:

Enter the lower range: 0
Enter the upper range: 30

List of Prime numbers between 0 & 30:
2 3 5 7 11 13 17 19 23 29

You can also print the prime numbers between 0 to any range or 100 using the same logic as above. You may go through the following program for more.

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