LGP-21 DevKit

VS Code language extension for the LGP-21 drum-memory computer (1963). Provides a full language server for .lgp21 assembly source files.

Features

Tokens are coloured by category: instructions, directives, labels, addresses, strings, comments, and numeric literals.

Real-time error detection for:

Hover over any token for inline documentation:

Instructions — description and operand format from the 1963 LGP-21 Programming Manual
Directives — .ORG and .DATA usage notes
Addresses — ttSS address decoding (track and sector) when used as an instruction or .ORG operand
String escapes — {uc}, {lc}, {cs}, {cr}, {bs}, {tab} typewriter control codes

Go to Definition — jump to a label's definition
Find All References — list every use of a label
Rename Symbol — safely rename a label and all its references across the file

Open the Outline panel to see all labels in the file as a navigable symbol tree.

Element	Syntax
File extension	`.lgp21`
Comment	`# text`
Label	`label:` (inline labels supported)
Load address	`.ORG ttSS`
Data	`.DATA value, value, …` (where values are string or numeric literals)
Address format	`ttSS` — `tt` = track (00–63), `SS` = sector (00–63)

Escape	Meaning
`{uc}`	Shift to upper case
`{lc}`	Shift to lower case
`{cs}`	Clear screen / carriage return to column 1
`{cr}`	Carriage return
`{bs}`	Backspace
`{tab}`	Tab

VS Code 1.120 or later.