EXOS 2.1 Video Driver Specification

8. Quick Reference Summary

8.1 EXOS Calls

Open/Create Channel

Treated identically.
Supports multiple channels.
Device name "VIDEO:".
Filename and unit number ignored.
EXOS variables MODE_VID, COLR_VID, X_SIZ_VID, Y_SIZ_VID must be set before open.

Close/Destroy Channel

Treated identically.

Read Character/Block

Returns cursor character or pixel colour.
Can be used to read cursor/beam position.

Write Character/Block

Displays printing characters.
Many control codes and escape sequences interpreted to provide special features.

Read Status

Always returns C = 0.

Set Status

Not supported.

Special Function

@@DISP = 1 - display page on screen
@@SIZE = 2 - return mode & size of page
@@ADDR = 3 - return video RAM address
@@FONT = 4 - reset character font

8.2 EXOS Variables

These must be set up before a channel is opened:

MODE_VID - video mode
COLR_VID - colour mode
X_SIZ_VID - characters/line (1..42)
Y_SIZ_VID - lines in page


ST_FLAG - zero to display status line
BORD_VID - overall screen border color
BIAS_VID - bias colour for palette colours 8 to 15
SPRITE - external color priority.

David Bouman. (dsbouma@cs.vu.nl)