An object doesn't have to show all of its inner workings on its outer surface. Programmers can hide the guts of an object from the interface, allowing an object to work without fear of interference from other parts of the program. Not all data has to be on the surface, either. Internal variables can be hidden and the object made a 'black box,' receiving input and giving output without having to show what happened in between.

This file created with Hypertype 2.2 by Simon St.Laurent