## The DEFS Directory

The directory `/d0/DEFS` is a directory that contains assembly language source code files which contain common system-wide symbolic definitions, and are normally included in assembly language programs by means of the OS-9 Assembler “use” directive. The presence and use of this directory is optional, but highly recommended for any system used for assembly language programs. The files commonly contained in this directory are:

OS9Defs | main system-wide definition file
RBFDefs | RBF file manager definition file
SCFDefs | SCF file manager definition file
Systype | System types definition file