A recursive algorithm is in essence an algorithm which calls itself over and over again, eventually terminating when a end condition is met.
In 'C', this example of of recursive factorial function (algorithm):
int Factorial(n) { if (n == 1)
return(n)
else
return(n*factorial(n-1));
}
If you examine this short code block, you can see how it functions. For example, if the Italic textfunctionItalic text Bold textfactorialBold text with n=3, it runs like this:
1)Bold textFactorialBold text(3) function called
2)Italic textElseItalic text branch is taken
3)Return value of Bold textFactorialBold text, this time with argument of n=2
4)In new function call, else branch is chosen again
5)Return value of Bold textFactorialBold text with arg n=1
6)New functional call of Bold textFactorialBold text terminates on Italic textifItalic text statement, and returns value of 1
7)Next function return yields 2 * 1
8)Last function return yields 3 * 2 * 1, and terminates with a value of 6.
The computer running this sequence uses what is known as a Bold textstackBold text to hold these function calls with their associated values until each is resolved in reverse order. These wait in line to be resolved one at a time.
Bold textFactorial(1) Factorial(2) Factorial(3)Bold text
Recursive algorithms are used for many purposes. They can be used to clear an overload of a holograms interactive matrix, or used to retrieve missing data from a log. (ENT: "Affliction"; VOY: "Nothing Human", "Warhead", "Renaissance Man")
Most Cardassian access codes are based on a recursive encryption algorithm. (DS9: "In Purgatory's Shadow")