Module : VIDEO.ASM - Direct Video Access Routines for TASM Version 1
Author : Dave Bennett
Version : 1.0
Date : 11/9/88
CIS PPN : 74635,1671

Description:
------------

This is a module of FAST direct video routines for TASM. At this time they
are released to the public domain. Much thanks to Brian Foley for
FASTWR.PAS (Turbo Pascal V3 Inline Assember Screen Routines) which gave much
insight on screen positioning and snow suppresion (horiz retrace waiting)

These routines are dying to have someone write an accompaning windowing
module... (hint hint)

Please contact me a tell me what you think via EPlex, IBMNET, Borland
forums etc... I am very interested in your opinions, bug reports, etc..

--Dave

Files in the distributed archive
--------------------------------

Name Ext Size Description
---- --- ----- -----------
VIDDEMO ASM 20487 Demonstration program
VIDEO ASM 26416 Video routines
VIDEO DOC 6792 This file
VIDDEMO EXE 2662 Compiled video demo (Not bad for 2.5K!)
VIDEO INC 2366 Global Declareations & equates for VIDEO.ASM
VIDDEMO MAK 165 Turbo Make file for VIDDEMO.EXE

Features:
---------

- Video mode detection
- Monochrome/CGA/EGA support
- Snow suppression
- Direct character & string writing
- Screen saving & restoring
- Area fills (character, attribute, and both)
- Cursor on & off control
- All commands w/ or w/o attribute changes


Global Data:
------------

BaseOfScreen Word value set by GetVideoMode proc. This is
set to B800h / B000h depending video mode.

SnowCheck Byte value set by GetVideoMode. Set to 1 if
adapter is CGA (Not EGA) by default. Mono and
EGA cards will set this to 0 by default.

VideoMode Video mode set by GetVideoMode. This holds the
video mode at the time of the last GetVideoMode
call (Set by BIOS INT 10 func 0Fh).


Global Procedures:
------------------

Note: No routines preserve the flags register!

See VIDDEMO.ASM for examples of all routines, all references to this module
and VIDEO.INC have been highlighted with a ($) so that you may better
scan VIDDEMO.ASM for examples of how to apply these routines. --Dave


EGAInstalled
------------
This procedure checks to see if the current adapter card is an
EGA.

Output
AL = 1 if EGA Adapter is found / 0 if not

Modified
AX


GetVideoMode
------------
This procedure checks the video mode and sets the BaseOfScreen
accordingly. It also sets SnowCheck to 1 if adapter is a CGA.

Output
BaseOfScreen
VideoMode
SnowCheck

Uses
EGAInstalled


DWriteCH
--------
Writes a character to the screen using direct memory access.

*** IMPORTANT -- CALL GetVideoMode Before using this routine!

Input
AH Row on screen 1-25
AL Column on screen 1-80
BH Video Attribute
BL Character
CX Number of times

Output
Screen memory (B000:0000 or 8000 CGA/MONO


DWriteCHNA
----------
Writes a character to the screen using direct memory access.
This procedure does not disturb current attr setting.

*** IMPORTANT -- CALL GetVideoMode Before using this routine!

Input
AH Row on screen 1-25
AL Column on screen 1-80
BL Character
CX Number of times

Output
Screen memory (B000:0000 or 8000 CGA/MONO


DWriteStr
---------
This procedure writes a null delimited string to the screen using
direct memory access.

*** IMPORTANT -- CALL GetVideoMode Before using this routine!

Input
DS:SI Null terminated string to print
AH Row on screen 1-25
AL Column on screen 1-80
BH Video Attribute

Output
Screen memory (B000:0000 or 8000 CGA/MONO

Modifies
SI - Returns 1 byte past null of displayed string


DWriteStrNA
-----------
This procedure writes a null delimited string to the screen using
direct memory access, attribute is not changed.

*** IMPORTANT -- CALL GetVideoMode Before using this routine!

Input
DS:SI Null terminated string to print
AH Row on screen 1-25
AL Column on screen 1-80

Output
Screen memory (B000:0000 or 8000 CGA/MONO)

Modifies
SI - Returns 1 byte past null of displayed string


DFillCH
-------
This procedure fills an area of the screen with the specified
character and attribute.

*** IMPORTANT -- CALL GetVideoMode Before using this routine!

Input
AH = Top Row
AL = Left Column
BH = Number of rows
BL = Number of columns
DH = Attribute
DL = Character


DFillCHNA
---------
This procedure fills an area of the screen with the specified
character. Attribute remains the same.

*** IMPORTANT -- CALL GetVideoMode Before using this routine!

Input
AH = Top Row
AL = Left Column
BH = Number of rows
BL = Number of columns
DL = Character


DFillAttr
---------
This procedure fills an area of the screen with the specified
attribute. Character remains the same.

*** IMPORTANT -- CALL GetVideoMode Before using this routine!

Input
AH = Top Row
AL = Left Column
BH = Number of rows
BL = Number of columns
DH = Attribute


StoreToMem
----------
This procedure moves an image from the screen to the designated
memory area.

*** IMPORTANT -- CALL GetVideoMode Before using this routine!

Input
AH = Top Row
AL = Left Column
BH = Number of rows
BL = Number of columns
ES:DI = Memory Destination

Modifies
DI


StoreToScr
----------
This procedure moves an image from memory to the designated
screen location.

*** IMPORTANT -- CALL GetVideoMode Before using this routine!

Input
AH = Top Row
AL = Left Column
BH = Number of rows
BL = Number of columns
DS:SI = Memory Area of image

Modifies
SI


CursorOff
---------
This procedure simply turns the Cursor off


CursorOn
--------
This procedure simply turns the Cursor on


Disclaimer
----------

The current status of these routines is public domain. Author makes no
claims to the usefullness of these routines and cannot be held responsible
for any situation resulting from the use of these routines.

- David Bennett