ATASCII - WikiHQ

frame|The entire visible ATASCII character set, both normal and inverse glyphs, upscaled to 2x to better show details

The ATASCII character set, from ATARI Standard Code for Information Interchange, alternatively ATARI ASCII, is a character encoding used in the Atari 8-bit computers. ATASCII is based on ASCII, but is not fully compatible with it. It was first used in the Atari 400 and 800 in 1979 and was kept in all subsequent models until the line was discontinued in 1992. The Atari ST family of computers use the different Atari ST character set.

Like most other variants of ASCII, ATASCII has its own distinct characters (arrows, blocks, box-drawing characters, playing card suits, etc.) in place of the C0 control codes in ASCII (characters 0–31), as well as replacing a few other ASCII code points.

Implementation

Atari 8-bit systems have three distinct sets of codes: interchange codes (ATASCII), internal codes (also called screen codes), and keyboard codes. Later XL and XE models required the user to update a register in RAM (e.g., via a POKE command in BASIC). The Atari 65XE Najm, which was distributed in the Middle East, has an Arabic character encoding as its default encoding and displays text right-to-left, while the international character set was replaced by the standard ATASCII encoding. Hebrew versions of the Atari 600XL and 800XL were distributed in Israel, which had a Hebrew character set in place of the international character set. The Hebrew character set had Hebrew letters instead of lowercase Latin letters, but preserved the uppercase Latin letters. When typing in Hebrew mode, typing Latin letters advances the cursor to the right, while typing Hebrew letters advances the cursor to the left.

Character set

Default graphic characters

The following table shows the default ATASCII character set. Control characters with a graphic representation are displayed using that representation. Each character is shown with a Unicode equivalent.

The box-drawing characters are arranged relative to their corresponding letter keys on the Atari keyboard, appearing 64 code points earlier than the corresponding uppercase letter. For example, ┌, ┬, and ┐ are the graphics characters found on the top left Q, W, and E keys, and appear 64 code points before those uppercase letters in ATASCII.

International character set

The following table shows the lower half of ATASCII international character set. The upper half are inverse video variants of the lower half, in exactly the same way as the standard ATASCII character set.

Control characters

ATASCII has 16 control characters, defined in four separate ranges (0x1B to 0x1F, 0x7D to 0x7F, 0x8B to 0x8F, and 0xFD to 0xFF).

ATASCII animations

The control codes in ATASCII are transmissible to other computers such as BBSs, 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 their heyday.

Because cursor control operations are represented with a single character (as opposed to multi-byte 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.

References

External links

ATASCII concise graphical overview (4.2KB GIF image)
Typography in 8 bits: System fonts