primeBTWnos.cpp

// C++ program to find the prime numbers between a given interval
#include <iostream>
using namespace std;
int main()
{
	int a, b, i, j, flag;
	// Ask user to enter lower value of interval
	cout << "Enter lower bound of the interval: ";
	cin >> a;
	// Ask user to enter upper value of interval
	cout << "Enter upper bound of the interval: ";
	cin >> b;
	cout << "Prime numbers between " << a << " and " << b	<< " are: ";
	// Traverse each number in the interval with the help of for loop
	for (i = a; i <= b; i++) {
		// Skip 0 and 1 as they are neither prime nor composite
		if (i == 1 || i == 0)
			continue;
		// flag variable to tell if i is prime or not
		flag = 1;
		for (j = 2; j <= i / 2; ++j) {
			if (i % j == 0) {
				flag = 0;
				break;
			}
		}
		// flag = 1 means i is prime and flag = 0 means i is not prime
		if (flag == 1)
			cout << i << " ";
  }
	return 0;
}