ATASCII
Encyclopedia
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 computer
s. 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), and a few other character locations.
ATASCII has a character set of only 128 characters. If the high-order bit is set on a character (i.e., if the byte value of the character is between 128 and 255) the character is generally rendered in the reverse video (also called "inverse video") of its counterpart between 0 and 127, using a bitwise negation of the character's glyph. This is done by the ANTIC
chip. The two exceptions to this rule are that an "escape" character (ATASCII and ASCII 27) with its high order bit set becomes an "EOL" or "End Of Line" character (ATASCII 155; ASCII 13), and a "clear screen" character (ATASCII 125) with its high order bit set becomes a "bell" or "buzzer" character (ATASCII 253; ASCII 7). No Atari printers actually have a bell, but the computer will sound if it is written to the screen device.
The ATASCII control characters have associated graphic symbols that can be displayed by preceding them by the "escape" character (ATASCII 27). For example, a right arrow can be displayed on a screen or printer by preceding it with the escape character followed by the "cursor right" character itself (ATASCII 31).
The text cursor was simply implemented by inverting the character at the cursor position (by XOR with $80). It did not flash.
Some Atari-based BBS
s exploited this difference by asking the client to hit the "Return" key. If it got 13 (ASCII CR), then standard ASCII would be used. If it got 155 (ATASCII CR) it would switch to ATASCII, allowing full use of the ATASCII graphic set. Some Atari BBSs would also block features (or even block access completely) for non-Atari users.
Because cursor control operations are represented with a single character (as opposed to multi-byte 'escape' sequences that were common in other schemes, like ANSI
or VT100
), it is quite easy to make these animations. They can be created by a short BASIC program that captures keyboard commands, echoes them to the screen and saves them to a file. The Atari also allowed commands to be typed and captured as part of its operating system. Of course this required care to get it right, but after a few attempts it normally became quite easy. The simple capture programs didn't have editing features, so ATASCII movies frequently had errors that were corrected by repositioning the cursor and printing over the mistake (a computer version of correction fluid
).
>
(right ¼ block)
(upper ¼ block)
Note the asymmetry in the selection of graphics characters: There are lower triangles but no upper triangles, a left half block but no right half block, and a lower half block but no upper half block. These missing characters could be displayed by using inverse video.
Characters 1B-1F and 7D-7F had a dual use as graphics characters and control characters.
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:
ASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
used in the Atari 8-bit family
Atari 8-bit family
The Atari 8-bit family is a series of 8-bit home computers manufactured from 1979 to 1992. All are based on the MOS Technology 6502 CPU and were the first home computers designed with custom coprocessor chips...
of home computer
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...
s. 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
Playing card
A playing card is a piece of specially prepared heavy paper, thin cardboard, plastic-coated paper, cotton-paper blend, or thin plastic, marked with distinguishing motifs and used as one of a set for playing card games...
suits, etc.) corresponding to the control character locations of the standard ASCII table (characters 0–31), and a few other character locations.
Control characters
The most notable difference between standard ASCII and ATASCII is the use of control characters. In standard ASCII, a character in the range 0 to 31 is construed as a command, which might move the cursor, clear the screen, end a line, and so on. Some of these work just as well on printers as on screen (to advance the paper, overtype, and so on).ATASCII has a character set of only 128 characters. If the high-order bit is set on a character (i.e., if the byte value of the character is between 128 and 255) the character is generally rendered in the reverse video (also called "inverse video") of its counterpart between 0 and 127, using a bitwise negation of the character's glyph. This is done by the ANTIC
ANTIC
Alphanumeric Television Interface Controller is an early video system chip used in the Atari 8-bit family of microcomputers as well as the Atari 5200 in the 1980s. The chip was patented by Atari, Inc. in 1981...
chip. The two exceptions to this rule are that an "escape" character (ATASCII and ASCII 27) with its high order bit set becomes an "EOL" or "End Of Line" character (ATASCII 155; ASCII 13), and a "clear screen" character (ATASCII 125) with its high order bit set becomes a "bell" or "buzzer" character (ATASCII 253; ASCII 7). No Atari printers actually have a bell, but the computer will sound if it is written to the screen device.
The ATASCII control characters have associated graphic symbols that can be displayed by preceding them by the "escape" character (ATASCII 27). For example, a right arrow can be displayed on a screen or printer by preceding it with the escape character followed by the "cursor right" character itself (ATASCII 31).
The text cursor was simply implemented by inverting the character at the cursor position (by XOR with $80). It did not flash.
Interoperation
The differences between character representation causes problems during modem communication between Ataris and other computers. Cursor movement commands (and even carriage returns and line feeds) from computers not using ATASCII will be nonsense on an Atari, and vice-versa. Terminal programs need to translate between ATASCII and standard ASCII.Some Atari-based BBS
Bulletin board system
A Bulletin Board System, or BBS, is a computer system running software that allows users to connect and log in to the system using a terminal program. Once logged in, a user can perform functions such as uploading and downloading software and data, reading news and bulletins, and exchanging...
s exploited this difference by asking the client to hit the "Return" key. If it got 13 (ASCII CR), then standard ASCII would be used. If it got 155 (ATASCII CR) it would switch to ATASCII, allowing full use of the ATASCII graphic set. Some Atari BBSs would also block features (or even block access completely) for non-Atari users.
ATASCII animations
The control codes in ATASCII are transmissible to other computers such as BBS's, and crude animations are possible. These animations, also known as "break movies", often take the form of short cartoons, and were a popular feature of Atari BBSs in its heyday.Because cursor control operations are represented with a single character (as opposed to multi-byte 'escape' sequences that were common in other schemes, like ANSI
ANSI art
ANSI art is a computer art form that was widely used at one time on BBSes. It is similar to ASCII art, but constructed from a larger set of 256 letters, numbers, and symbols — all codes found in IBM code page 437, often referred to as extended ASCII and used in MS-DOS and Unix environments...
or VT100
VT100
The VT100 is a video terminal that was made by Digital Equipment Corporation . Its detailed attributes became the de facto standard for terminal emulators.-History:...
), it is quite easy to make these animations. They can be created by a short BASIC program that captures keyboard commands, echoes them to the screen and saves them to a file. The Atari also allowed commands to be typed and captured as part of its operating system. Of course this required care to get it right, but after a few attempts it normally became quite easy. The simple capture programs didn't have editing features, so ATASCII movies frequently had errors that were corrected by repositioning the cursor and printing over the mistake (a computer version of correction fluid
Correction fluid
A correction fluid is an opaque, white fluid applied to paper to mask errors in text. Once dried, it can be written over. It is typically packaged in small bottles, and the lid has an attached brush which dips into the bottle...
).
Graphic characters
Note the asymmetry in the selection of graphics characters: There are lower triangles but no upper triangles, a left half block but no right half block, and a lower half block but no upper half block. These missing characters could be displayed by using inverse video.
Characters 1B-1F and 7D-7F had a dual use as graphics characters and control characters.
Control characters
| ATASCII | Function | Keystroke |
|---|---|---|
| 27 | Escape key | ESC |
| 28 | Cursor Up | |
| 29 | Cursor Down | |
| 30 | Cursor Left | |
| 31 | Cursor Right | |
| 125 | Clear Screen | |
| 126 | Delete | |
| 127 | Tab Tab key Tab key on a keyboard is used to advance the cursor to the next tab stop.- Origin :The word tab derives from the word tabulate, which means "to arrange data in a tabular, or table, form"... |
TAB |
| 155 | End of line Newline In computing, a newline, also known as a line break or end-of-line marker, is a special character or sequence of characters signifying the end of a line of text. The name comes from the fact that the next character after the newline will appear on a new line—that is, on the next line below the... |
RETURN |
| 156 | Delete Line | |
| 157 | Insert Line | |
| 158 | CTRL+TAB | |
| 159 | SHIFT+TAB | |
| 253 | Buzzer Bell character A bell code is a device control code originally sent to ring a small electromechanical bell on tickers and other teleprinters and teletypewriters to alert operators at the other end of the line, often of an incoming message... |
CTRL+2 |
| 254 | Delete Character | |
| 255 | Insert Character |
External links
- ATASCII concise graphical overview (4.2KB GIF image)
- ATASCII <–> IBM ASCII tables (mostly plain ASCII text)
- ATASCII Character Sets
ATASCII in action
- The Boot Factory telnet://bfbbs.no-ip.com or: telnet://bfbbs.dtdns.net
- Inside The 8-bit - (2 lines) telnet://TCPIPExpress.dyndns.org:8888 or 8889
- MouseNet BBS telnet://atari-bbs.kicks-ass.net
- Closer to Home BBS telnet://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