[{HVY-E}Jinxx]

Those types of programs are what we call "Brute Force" password crackers.
They operate by figuring the number of possible combinations (Permutations and Combinations) a password can have given the number of characters and weather or not the characters can repeat.

ie. You have a 5 character password that can contain any combination of letters (26) and numbers (0-9) for a total of 36 choices. Because there are 5 positions, your number of possible passwords are as follows:

Order of characters matters
Repeating Numbers/Letters allowed: 60,466,176 possible solutions.
(36 to 5th power)

if

Order of characters matters
Repeating Numbers/Letters not allowed: 45,239,040 possible solutions
n!
(n-r)!

http://www.mathsisfun.com/combinatorics/...lator.html

Hope this confuses you just a bit more.... 8)

S!