Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!uunet!mcsun!hp4nl!alchemy!evermeer
From: evermeer@cs.ruu.nl (Erik Vermeer)
Newsgroups: comp.graphics
Subject: Memory-addresses for real-time animation on IBM-PC
Keywords: Memory-addresses, IBM-PC, Basic
Message-ID: <1991May06.111036.511@cs.ruu.nl>
Date: 6 May 91 11:10:36 GMT
Organization: Utrecht University, Dept. of Computer Science
Lines: 36

Hello folks,

I'm writing a program about graphical real-time animation on an IBM-XT
(e.g. a rotating cube). My strategy is to draw a picture on an hidden,
virtual screen and when the drawing is finished to place the virtual 
screen onto the actual screen. 
After that the drawing is rotated a bit, and the drawing starts again 
(on the hidden screen).

I know it is easy to do when you use an EGA or VGA graphics card. The
only problem is, my computer has a CGA graphics card.

I wrote a machine-code routine for the copying of the virtual screen
onto the actual screen (it is a simple block move in memory).

The only problem is, I don't know the memory addresses of the pointers
(I assume there are several) to the start of the actual screen (the
screen is placed at hex B8000). I need to know them, because I want to
redirect the making of the drawing to the virtual screen.

My intention was to write the program is BASIC. When I succeed, I will
think of writing the same program in a more structured language.

I use Microsoft GW-Basic and Borland Turbo-Basic. I think the addresses
needed are different for GW-Basic and Turbo-Basic.


Can anybody help me with my problem !!

Erik Vermeer
University of Utrecht, the Netherlands.

e-mail: evermeer@cs.ruu.nl


Sorry for my poor English !!!!