Good day,,my problem is:
use recursion to write a program that returns the factorial of any number greater than 0. (Factorial is number*number-1*number-2...*1)
Hope you can help!thankS:]

Hi, Isheen.

The factorial of an integer (non-negative) is defined as the product of every positive integer less than or equal to the integer.  The symbol for a factorial is the exclamation point (!).  So, the factorial of A (represented as A!) would be the product of every integer from 1 to A.  5!, for example, is:

  1 * 2 * 3 * 4 * 5 = 120

The algorithm for this is really quite simple and makes for an easy recursive function:

  int factorial(int num)
      if (num == 1)
         return num;
         return factorial(num - 1) * num;

You can see here how the function calls itself, decrementing num by one.  In this manner, there is a change in the input value and a defined end point (num == 1).  Once the end point is reached, the return values cascade back until the initial caller of the recursive function is reached.

If you have any further questions, or if I have raised any new questions for you, please do not hesitate to ask.  I'm here to help. :)


All Answers

Answers by Expert:

Ask Experts


Joseph Moore


I've been programming in one form or another since my brother taught me BASIC when I was 6. I've been programing professionally since I was 20, first web development with HTML, JS, DHTML, CSS, etc., then I became a video game developer, writing code in C, C++, C#, SQL, assembly, and various scripting languages. I've even written my own scripting languages, custom designed for the games I was making. I also dabble in Java, PHP, and Perl. I've worked on pretty much every aspect of game development, including graphics, audio, gameplay, tool, UI, input, animation, and physics.


I've been writing C++ code for 12 years, both on my own in my spare time and professionally.


Bachelor of Science in Game Design and Development, Full Sail University, Winter Park, FL

Awards and Honors
Salutatorian and Advanced Achiever Awards at Full Sail; Independent Games Festival Student Showcase winner, 2004; Featured article on Gamasutra about an experimental game developed in 2004

©2017 About.com. All rights reserved.

[an error occurred while processing this directive]