In addition to being defined in binary modules, Tool Palette components also are described in ATC catalog files that are stored in a location known to AutoCAD. ATC files contain XML content that provides information for labels, graphics files, implementation modules, tool and tool palette configuration, and tool properties data. AutoCAD consults the ATC files when the tool palette is initially launched, and displays all tool palettes and tools whose definitions it resolves successfully.
Client applications usually read and write ATC file content by using the Tool Palette API's tool catalog classes.