C++ Program to find Prime Numbers between two numbers

What are Functions ?

Function is a block of statements that performs some operations. All C++ programs have at least one function – function called “main()”. This function is entry-point of your program.

A function declaration tells the compiler about a function’s name, return type, and parameters. A function definition provides the actual body of the function.

Defining a Function : :

The general form of a C++ function definition is as follows:

return_type Function_Name( list of parameters )
{
//function’s body
}

• return_type : suggests what the function will return. It can be void, int, char, some pointer or even a class object.
• Function_Name : is the name of the function, using the function name it is called.
• Parameters : are variables to hold values of arguments passed while function is called. A function may or may not contain parameter list.
• Function body : is he part where the code statements are written.

Below is the source code for C++ Program to find Prime Numbers between two numbers which is successfully compiled and run on Windows System to produce desired output as shown below :

SOURCE CODE : :

/* C++ Program to find Prime Numbers between two numbers */

#include <iostream>
using namespace std;

int checkPrimeNumber(int);

int main()
{
    int n1, n2;
    bool flag;

    cout << "\nEnter 1st positive integer :: ";
    cin >> n1;
    cout << "\nEnter 2nd positive integer :: ";
    cin >> n2;

    cout << "\nPrime numbers between [ " << n1 << " and " << n2 << " ] are :: ";

    for(int i = n1+1; i < n2; ++i)
    {
        // If i is a prime number, flag will be equal to 1
        flag = checkPrimeNumber(i);

        if(flag == true)
            cout << i << "  ";
    }
    return 0;
}

// user-defined function to check prime number
int checkPrimeNumber(int n)
{
    bool flag = true;

    for(int j = 2; j <= n/2; ++j)
    {
        if (n%j == 0)
        {
            flag = false;
            break;
        }
    }
    return flag;
}

OUTPUT : :

/* C++ Program to find Prime Numbers between two numbers */

Enter 1st positive integer :: 1

Enter 2nd positive integer :: 100

Prime numbers between [ 1 and 100 ] are :: 2  3  5  7  11  13  17  19  23  29  31  37 
41  43  47  53  59  61  67  71  73  79  83  89  97

Process returned 0

Above is the source code for C++ Program to find Prime Numbers between two numbers which is successfully compiled and run on Windows System.The Output of the program is shown above .