EXOS 2.1 Video Driver Specification

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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

Miscelaneous:

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.