Text mode demos

Text Mode demos are real-time calculated computer animations which make use of the native text graphic mode(s) common on the IBM PC compatibles. The Text Mode Demo Scene is one of many different facets of the demoscene.

Text Mode as a medium offers several unique challenges for the creators of such a demo. Similar to the constraints of ASCII and ANSI art, the coder and artist both must take into consideration the limitations presented by text mode: a base "resolution" of 80×25 "blocks" and a mere 16 fixed colors by default.

Pseudographic resolution

By taking advantage of half blocks characters 220 (DCh) Unicode|▄ (bottom half) or 223 (DFh) Unicode|▀ (upper half) in the code page 437 (adapter's native) character set, one can effectively "double" the vertical resolution (from 80×25 to 80×50 in the default text mode).

Enhanced Graphics Adapter (EGA) and better adapters natively support text modes beyond 80×25 character cells: 80×43 (EGA), 80×50 (Video Graphics Array, VGA), 132×50 and 132×60 (VESA compatible Super VGA), etc., increasing the simulated "graphic" resolution available, doubled again through the half block characters.

Also, by tweaking the display's hardware, higher resolutions can be achieved. For example, a tweak mode can be set even in the original IBM Color Graphics Adapter (CGA) to give an extra, non-standard 160×100 "pixels", 16-color "graphic" mode.

Custom graphics and effects can also be achieved by customizing the character set (with the EGA and better adapters) on a per-pixel basis. Halving the available colors from 16 to 8, up to two customized character sets can be used simultaneously on screen with most Super VGA graphic cards, blurring the border between pure text modes and true graphic modes.

Expanding colors

In text mode, the blinking attribute effect is enabled by default, giving sixteen colors available for the foreground but only eight for the character cell background. By disabling the blinking effect, all 16 colors available can be used for both the background and the foreground of every character cell.

Creatively making use of the 3 shaded block characters 176 (B0h) Unicode|░ (25% halftone), 177 (B1h) Unicode|▒ (50% halftone) and 178 (B2h) Unicode|▓ (75% halftone) in the CP437 character set, one can achieve some interesting color combinations with the limited palette.

With the EGA and the VGA the color palette can be expanded from the original fixed 16-color CGA palette to 16 out of 64 colors (EGA palette) or 16 out of 262,144 colors (VGA palette), allowing smoother color transitions.

Text mode demoscene

The first evident IBM PC demo group to create text mode demos is said to be the Sorcerers. The ever-popular Finnish group Future Crew also began by creating some innovative creations which took advantage of text mode, with text intros such as "Yo!" and "Starport".

tAAt, a non-profit organization in Finland, organizes a semi-annual competitive event for authors of textmode demos called the Text Mode Demo Contest (TMDC).

ee also

*AAlib - Portable ascii art GFX library
*Code page 437
*List of palettes

External links

* [http://tmda.planet-d.net/ Text Mode Demo Archive]
* [http://taat.fi/tmdc/ Text Mode Demo Compo (TMDC)]
* [http://tomaes.32x.de/text/faq.php FAQ Page about Demos]
* [http://libcaca.zoy.org/ libcaca, the Colour AsCii Art library]
* [http://digitaltools.node3000.com/5minutes/jari_komppa_on_text_mode_demos_and_the_tmdc.php Interview with Jari Komppa] organizer of the TMDC, September 2007