PDA

View Full Version : Falling letters screensaver for DOS



profdc9
January 30th, 2014, 06:17 PM
I was having some fun and I created a falling letters screensaver for DOS. I have attached the source and the compiled COM files. There is one for CGA and one for MGA. Take a look at the screenshot and see what you think.

Dan



Instructions from README are below:


This is a "falling letters" screensaver for DOS I wrote for kicks. It is based on DSCRNSAV
by David Markovitch and Peter Summers who wrote it over 20 years ago. It is compiled using
Borland C++ 3.1.

It comes in two flavors:

fallscr.com: works on CGA,EGA,VGA and uses an auxillary part of video memory for
the animation as the CRTC of the CGA card supports page flipping. Works on MGA
but does not restore the screen properly.

mfallscr.com: works on MGA, CGA,EGA, and VGA, but takes more resident space. Saves
the screen contents to a temporary memory buffer to try to approximate a true
screensaver, but will clobber any changes to the display made while the screensaver is active.

The monochrome version is especially appealing on a real IBM PC green monochrome screen, where
the actual persistence of the phosphors produces the falling letters effect.

The code is broken out so that to modify it to produce other types of text screen savers,
one should just have to modify scrnsav.c.

Have fun with it!

Dan


/*

Falling letters screen saver

Copyright (C) 2014 by Daniel Marks

This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.

Daniel L. Marks profdc9@gmail.com

*/


The original DSCRNSAV text follows:


DSCRNSAV v1.2

DSCRNSAV was originally written by David Markovitch, who I've never met
or even corresponded with. My contribution has merely been to improve
an already very useful program.

DSCRNSAV is the smallest screen saver I've ever come across. It works
by reprograming the video hardware to move the screen image around, thus
not requiring any storage space for the screen. It works in all video
mode on all the machines I've come across, including CGA, Herc, EGA and
VGA screens. I've had one report of a machine on which it wouldn't
work, and several of programs with seem to deactivate it.

DSCRNSAV could probably be improved further. I leaves 256 bytes of PSP
still resident, and doesn't release its environment. I may look at
fixing this some other time. For smallest resident size, load it before
you start defining environment string (including path and prompt).

Version 1.1 recoded the installation software so that DSCRNSAV could
find and control the resident copy when it was loaded high, and took
the installation messages out of the resident section of code, reducing
the TSR size by about 200 bytes.

Version 1.2 allows selectable delays, taking a single command line
parameter which specifies the delay. A parameter of zero disables the
screen saver.

Peter Summers, U5533129@ucsvc.unimelb.edu.au

commodorejohn
January 30th, 2014, 07:16 PM
Sweet :D I'll have to try this on the 5150 I picked up today...

SomeGuy
January 30th, 2014, 08:41 PM
Very, very, cool! But keep in mind that displaying anything at all can still cause screen burn in over time. And with text modes, burn in occurs as a distracting 80*24 arrangement of darks spots.

Tr3vor
January 31st, 2014, 11:43 AM
Sadly I don't have a monochrome screen to try this out on, but I did run it on my 486 and it looks really cool.

barythrin
January 31st, 2014, 01:07 PM
When I was first learning C and writing a screen saver, realizing I was doing mostly the opposite of a screen saver by keeping the screen pixels on; I just cleared the screen once and a while. I used to enjoy "bugs" (sometimes called bugjoke) though which was a nicer one. I eventually just wrote a pong style bouncing happy face (ascii 00 or 01) to wipe the screen.

edit: That's cool, I didn't understand or catch the matrix like part, just thought it was the old prank/virus code for letters on your dos screen start falling.. which I did think was pretty funny.

bruenor
October 20th, 2016, 01:35 AM
Ah..it's not working in dosbox:) what a shame...

romanon
October 21st, 2016, 01:43 AM
works fine in my dosbox. Great work btw. I would like to run matrix screen immediately after running program, it would be better.

33939