With 26 letters in the English alphabet and comparable numbers in other
western and middle-eastern alphabets, the first power of 3 that lends itself to
representing a reasonable character set is 34 or 81. A 4-trit character allows encoding the Roman alphabet in
both upper and lower case, plus 10 digits and a modest (but insufficient) set
of control characters and punctuation marks. In this environment, a code
extension system comparable to that of Unicode invites a character code built
on 81-character blocks.
| Code | Meaning |
|---|
| ES | End of String, analogous to NULL
|
| EL | End of Line, analogous to LF or CR/LF
|
| ET | End of Text file
|
| LR | Left to Right rendering of following text
|
| OP | OverPrint following text on previous char
|
| RL | Right to Left rendering of following text
|
| SU | Shift Up (superscript) following by 1/3 baseline
|
| HT | Horizontal Tab in current rendering direction
|
| SD | Shift Down (subscript) following by 1/3 baseline
|
| SP | Space
|
