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-File7.2.4  GDOS drivers                                                TOS

A GDOS driver is essentially a normal program file without a startup 
code, which contains a dispatcher for the incoming VDI calls as a 
first routine. All drivers must be declared in the ASSIGN.SYS file 
that is evaluated by GDOS at the start.

The following list shows the most important drivers with their 
respective device numbers:

 Screen driver                   (01-10)
 Plotter driver                  (11-20)
 Printer driver                  (21-30)
 Metafile driver                 (31-40)
 Kamera driver                   (41-50)
 Tablet driver                   (51-60)
 Memory driver                   (61-70)
 Fax driver                      (81-90)
 Bit-Image driver                (91-100)
 Multimedia driver               (101-110)
 Sound driver                    (111-120)
 Load and draw Bit-Image driver  (121-130)

For implementing the dispatcher one should respect the following:

   . The address of the VDI parameter block is passed in register D1
   . The function itself is terminated with an RTS statement

A GDOS driver always operates in a raster-coordinate system; the 
conversion of values in the ptsin and ptsout fields is taken on by the 
GDOS. In addition one should bear in mind that not all functions reach 
the actual driver in exactly the same form as they were sent, since 
they are partially pre-processed by the GDOS.

See Also: GDOS   VDI fundamentals   Bindings of the VDI