# C++ program to display prime numbers between two intervals

In this example, you will learn about C++ program to display prime numbers between two intervals.

This program also checks for the higher number and performs swapping if the first number is greater than the second.

A number is called prime number if it is divisible by 1 and itself only.

For example: 1, 3, 5, …., 91, ….

## Example: C++ program to display prime numbers between two intervals

``````#include <iostream>
using namespace std;

int main ()
{
int num1, num2, i, j, temp, flag;

cout << "Enter two numbers(intervals): " << endl;
cin >> num1 >> num2;

//swapping numbers if first number is greater than second one
if (num1 > num2)
{
temp = num1;
num1 = num2;
num2 = temp;
}

cout << "\nPrime numbers between " << num1 << " and " << num2 << " are:" << endl;
// Displaying prime number between num1 and num2
for (i = num1 + 1; i < num2; ++i)
{
flag = 0; //flag is set to 0
for (j = 2; j <= i/2; ++j)
{
if (i % j == 0)
{
flag = 1;
break;
}
}
if (flag == 0) //if flag == 0, then display i
cout << i << "\t";
}
cout << "\n\n";
return 0;
}
``````

Output Explanation

This program will works if the first number is greater than the second one because `if` condition checks and performs swapping if necessary.

First `for` loop will continue till the first number equals the second.

`flag` will set to 1 if the number is perfectly divisible by other numbers than 1 and itself and `break` operation will occur.