Sort Images Uploaded Help

Hey guys, was wondering if you could help me solve this problem.  I'm trying to make it so that when a user uploads a file, it it's a .jpg it will go into a folder called /images/.  If the file is a GIF, then it goes into a folder called /GIF/.  And if a checkmark is checked then it will go into another folder called /test/.  I don't have a clue where to start since all the comments are in Spanish.  I saw that the default folder if already defined in the config.php file, but I'm not sure how to change it around to allow for sorting.  Thanks in advance.