The Virtual Device Interface (VDI
) is a collection of drivers designed to provide applications with a device-independent method of accessing graphically based devices such as monitors, printers, and plotters. Applications which are written to use the VDI
rather than directly accessing hardware will be compatible with all currently available devices including those which have not yet been developed.
All Atari systems with TOS
in ROM include a VDI
screen driver adaptable to each display resolution the system can support. Soft-loaded screen drivers and drivers for other devices are loaded through a VDI
sub-system called the GDOS
system is disk-loaded as a TSR
utility at bootup. It loads device drivers based upon the contents of its configuration file(s).
Applications wishing to use the GDOS
extensions must verify its presence using the method described later in this chapter. If an application's output will be limited to the screen and no font other than the system font is needed, then the presence of GDOS
is not mandatory.
The following is a list of commonly used VDI currently in use: