Files of this type and auxiliary type contain Apple IIgs tool sets.
Files of type $BA contain Apple IIgs tool sets, designed to be called by the Tool Locator. The data fork is in OMF format; once it's been loaded by InitialLoad or InitialLoad2, the image in RAM starts with the tool set's function pointer table (FPT). The resource fork, if it exists, should be empty or in Apple IIgs Resource Manager format.
All RAM-based system tools are contained in the System folder of the boot volume, and are named by tool number (for example, tool #27 is named TOOL027). This convention is for system tools only.
User tools can reside in any directory (the directory with the application is a good choice) and may follow any naming conventions. User tool sets should also use file type $BA.
Please note that all system tool set numbers and names are reserved for Apple Computer, Inc. Third-party developers must not create tools using any system tool set numbers.
This and all of the other Apple II Technical Notes have been converted to HTML by Aaron Heiss as a public service to the Apple II community, with permission by Apple Computer, Inc. Any and all trademarks, registered and otherwise, are properties of their owners.