## AST Objects

An AST ObjectObject is an entity which is used to store information and Objects come in various kinds, called classes, according to the sort of information they hold. Throughout this section, we will make use of a simple Object belonging to the “ZoomMapZoomMap” class to illustrate many of the basic concepts.

A ZoomMap is an Object that contains a recipe for converting coordinates between two hypothetical coordinate systems. It does this by multiplying all the coordinate values by a constant called the ZoomZoom factor. A ZoomMap is a very simple Object which exists mainly for use in examples. It allows us to illustrate the ways in which Objects are manipulated and to introduce the concept of a MappingMapping—a recipe for converting coordinates—which is fundamental to the way the AST library works.