# C++ : Display Prime Numbers Between Intervals Using User-defined Function

Tutorial by:Manisha Dubey      Date: 2016-06-18 04:28:20

This program takes two positive integers from user and displays all prime numbers between these two intervals. To perform this task, user-defined function is created which will check whether a number is prime or not.

## Prime Numbers Between two Intervals by Making User-defined Function

``````
#include<iostream>
using namespace std;
int check_prime(int num);
int main(){
int n1,n2,i,flag;
cout << "Enter two numbers(intervals): ";
cin >> n1 >> n2;
cout << "Prime numbers between " << n1 << " and " << n2 << " are: " << endl;
for(i=n1+1;i<n2;++i)
{
flag=check_prime(i);
if(flag==0)
cout << i << endl;
}
return 0;
}
int check_prime(int num) /* User-defined function to check prime number*/
{
int j,flag=0;
for(j=2;j<=num/2;++j){
if(num%j==0){
flag=1;
break;
}
}
return flag;
}``````

Output

```Enter two numbers(intervals): 10 30
Prime numbers between 10 and 30 are: 11 13 17 19 23 29```

In this program, all numbers between two intervals is passed to function `int check_prime(int num)` using for loop. This function checks whether a number is prime or not. If the number is prime it returns 1, if not it return 0.

## C++

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