Gidubba/readme.md

Gidubba
========

Gidubba (Sumerian for 'stylus') is a simple line editor for the
Thingamajig computer architecture. Its git repository can be found at
https://ahti.space/git/crazyettin/Gidubba and that of Thingamajig at
https://ahti.space/git/crazyettin/Thingamajig.

System requirements
-------------------

Gidubba requires a terminal with local echo at address FFFF, and
optionally a line printer at address FFFE and a punched tape reader and
punch or a casette drive at FFFD. If your setup differs from this you
have to modify the code yourself.

Usage
-----

The commands are individual letters that can be followed by one or two
arguments separated by a comma, all case-insensitive. The first argument
is a line number between 0 and FFFF and the second a range of lines
between 0 and FF. To append lines, insert them to any line number after
the text or to the shortcut hash (#); in other commands line numbers or
parts of a range after the text are ignored. Instead of a predetermined
range a prompt to insert the next line appears automatically after the
previous one has been committed.

Commands with a single argument:
  * I: Insert lines

Commands with two arguments:
  * D: Delete lines
  * L: List lines

Commands with no arguments:
  * P: Print
  * R: Read from the tape reader or casette drive
  * W: Write to the tape punch or casette drive

A delete (^?) discards the preceding character if any and outputs an
underscore to the terminal. An escape (^[) discards the current command
or line and gives a prompt for retyping it. An end-of-file (^Z) discards
the current command and halts the computer or discards the current line
and returns to the command prompt.