Topic       : TOS - The Operating System
Author      : 
Version     : tos.hyp (December 19, 2008)
Subject     : Programmieren/Atari
Nodes       : 3010
Index Size  : 93790
HCP-Version : 5
Compiled on : Atari
@charset    : atarist
@lang       : 
@default    : Title
@help       : 
@options    : +g -i -s +x +zz -t4
@width      : 70
View Ref-File7.1  About the VDI                                                 TOS

The VDI (Virtual Device Interface) is a part of GEM, and can be looked 
at in the first instance as a standardized graphics system. From the 
point of view of the programmer the VDI can be seen as a very 
comprehensive device-independent graphics library whose output format 
is portable across several platforms. The VDI can be divided into the 
following function groups:

   . Attribute functions
   . Output functions
   . Inquire functions
   . Input functions
   . Escape functions
   . Colour table functions
   . Control functions
   . Raster functions

Since the original VDI in Atari's TOS suffers from several weaknesses 
and, above all, is not particularly fast, many users have found NVDI 
to be the replacement for the normal VDI.

Some functions of the VDI require the GDOS extension that was meant to 
be part of the operating system originally, but had to be offloaded by 
Atari due to lack of memory space in the ROMs of the first STs. Hence 
it (or its later replacements such as FSM-GDOS, SpeedoGDOS, NVDI, ...) 
have to be loaded from (floppy or hard) disk.

With consistent use of the VDI routines every programmer can ensure 
that their programs will run cleanly on various computer variants and 
in almost all resolutions.

See Also: VDI fundamentals   Bindings of the VDI   AES