## I/O Device Names

Each physical input/output device supported by the system must have a unique name. The actual names used are defined when the system is set up and cannot be changed while the system is running. The device names used for the computer are:

TERM | Video display/keyboard
P | Printer port
D0 | Disk drive unit zero
D1 | Disk drive unit one
PIPE | Pipes

Device names may only be used as the first name of a pathlist, and must be preceded by a slash “/” character to indicate that the name is that of an I/O device. If the device is not a disk or similar device the device name is the only name allowed. This is true for devices such as terminals, printers, etc. Some examples of of pathlists that refer to I/O devices are:

/TERM
/P
/D1

I/O device names are actually the names of the “device descriptor modules” kept by OS-9 in an internal data structure called the “module directory” (See the OS-9 System Programmer's Manual for more information about device driver and descriptor modules). This directory is automatically set up during OS-9's system start up sequence, and updated as modules are added or deleted while the system is running.