What are recursive functions?

We are aware about how functions are defined in C or C++ or Java or.Net.
In which ever case it is, in a programming language we start our process by defining a method or function.
We say Main method is the first method that gets called to start executing an application.
1) Function can expect parameters which is not mandatory.


2) When a function is called it is loaded then into memory with given parameters as well.
3) Function may or may not return a value

4) A function can call an another function or by itself.

5) Recursive function can be defined as a function calling by it self.

Memory structure:-
Let us consider a simple function as

If this is a recursive function (say it calls for it self 3 times) then

Example:-

I have created a .NET windows application for calculating the factorial of a given number.
If input is 5 then output should be 5*4*3*2*1
Code:

using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; namespace Sample { public partial class frmFactorial : Form { public frmFactorial() { InitializeComponent(); } private void btnFactorial_Click(object sender, EventArgs e) { try { //Checking given value is numeric or not if (!IsNumber(txtFact.Text)) throw new Exception("Enter numeric value for A"); //calling factorial function MessageBox.Show(Factorial(Convert.ToInt32(txtFact.Text)).ToString()); } catch (Exception exp) { MessageBox.Show(exp.Message); } } private int Factorial(int argVal) { //If input value is greater then one then once call once again //by multiplying input value with the return value of //factorial function by sending the value after deducting 1 //from the given input value if (argVal > 1) { argVal = argVal * Factorial(argVal - 1); } //returning the final value, which is calculated after multiplying //recursively return argVal; } private bool IsNumber(string argValue) { try { //checking if the given value is numeric Convert.ToInt32(argValue); return true; } catch { return false; } } } }

output:-