AcDb Classes

The ObjectARX classes with an AcDb prefix are components of the AutoCAD database. This database stores all the information for the graphical objects, called entities, that compose an AutoCAD drawing, as well as the non-graphical objects (for example, layers, linetypes, and text styles) that are also part of a drawing. You can query and manipulate existing instances of AutoCAD entities and objects with the AcDb classes and functions, and you can create new instances of database objects.

The AutoCAD database contains these major elements:

• A set of nine symbol tables that own uniquely named symbol table entry objects. These objects represent various commonly used AcDbDatabase objects and data members.
• A named object dictionary (of class AcDbDictionary), which provides the "table of contents" for an AutoCAD drawing. Initially, this table of contents contains the IDs of the four other dictionaries used by AutoCAD. Applications you develop are free to add other objects to the dictionary.
• A fixed set of about 200 header variables, whose values are set by AutoCAD.

For more information about the AcDb classes, see Database Primer, Database Operations, Database Objects, Entities, and Container Objects. For information on deriving new classes from AcDbObject and AcDbEntity, see Deriving from AcDbObject and Deriving from AcDbEntity.