ATASCII


ATASCII

The ATASCII character set, from "ATARI Standard Code for Information Interchange", alternatively "ATARI ASCII", is the variation on ASCII used in the Atari 8-bit family of home computers. The first of this family were the Atari 400 and 800, released in 1979, and later models were released throughout the 1980s. The last Atari 8-bit computer, and therefore the last computer to use the ATASCII character set, was the XEGS (short for "XL Extended Gaming System,") which was released in 1989.

Like most other non-standard ASCIIs, ATASCII has its own special block graphics symbols (arrows, blocks, circles, line segments, playing card suits, etc.) corresponding to the control character locations of the standard ASCII table (characters 0–31), plus a few other character locations.

Unlike many alternate implementations of ASCII, ATASCII had a character set of only 128 characters. If the high-order bit was set on a character (i.e., if the byte value of the character was between 128 and 255) then the character was generally rendered in inverse video (also called "reverse video" by some), using the bitwise negation of the character. The two exceptions to this rule were that an "escape" character (ATASCII 27) with its high order bit set became an "EOL" or "End Of Line" character (ATASCII 155), and that a "clear screen" character (ATASCII 125) with its high order bit set became a "bell" or "buzzer" character (ATASCII 253).

The most notable difference between standard ASCII and ATASCII is the use of control characters. In standard ASCII, a character with its three high order bits cleared (i.e., with a byte value under 32) is construed as a command, leading to the movement of a cursor, screen clearing, an end of line, and similar features. ATASCII uses the codes from ATASCII 0 through ATASCII 31 exclusively for low-level graphics, using other codes for cursor commands.

This caused problems during modem communication between Ataris and other computers, since cursor commands (and even carriage returns and line feeds) coming from the non-Atari computer would be rendered as garbage on the Atari and vice-versa. Terminal programs would need to translate between ATASCII and standard ASCII. Some Atari-based BBS's, however, exploited this difference by first asking a user to hit their "Return" key. If the received code was ASCII 13, then standard ASCII would be used. If the BBS received ATASCII 155, however, it would switch into ATASCII mode, allowing full use of the ATASCII graphic set. Some Atari BBS's would also block certain features (or even block access completely) for non-Atari users.

"See also": PETSCII, Spectrum Character Set

ATASCII Animations

Because of the inclusion of various graphical shapes in the character set, combined with the fact that certain characters represented cursor movements, clear screens, insert and delete operations, and were interpreted as such by Atari communication software, crude animations were possible.

These animations, also known as 'break movies', often took the form of short cartoons and were a popular feature of Atari BBSs.

Because cursor control operations were represented with a single character (as opposed to multi-byte 'escape' sequences that were common in other schemes, like ANSI or VT100),creation of these animations were easy too. They could be created with a short BASIC program that captured keyboard commands, echoed them to the screen and saved them to a disk file. Since such a simple program doesn't have editing features, ATASCII movies frequently had errors that were quickly corrected by repositioning the cursor and printing over the mistake.

Current Atari BBS's where you can see ATASCII in action:

The Boot Factorytelnet://bfbbs.no-ip.comor: telnet://bfbbs.dtdns.net

Inside The 8-bit - (2 lines)telnet://TCPIPExpress.dyndns.org:8888 or 8889

MouseNet BBStelnet://atari-bbs.kicks-ass.net

Closer to Home BBStelnet://cth.dtdns.net(There is a "Break Movie" directory on this BBS)

Many Atari 8-bit users currently log in over telnet using a program called "Bobterm" to view the ATASCII graphics. If you are on a Win 95/NT computer, a terminal simulator called "ATS 2.0" can help you view these graphics as well. This can be found at:http://www.atarimax.com/atariterm/downloads/ats.exe

External links

* [http://www.infos.cz/raster/atari/chars/atascii.htm ATASCII concise graphical overview] (4.2KB GIF image)
* [http://www.faqs.org/faqs/atari-8-bit/faq/section-49.html ATASCII <&ndash;> IBM ASCII tables] (mostly plain ASCII text)


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