CORAL 66 Language Support for Visual Studio Code

Language Server Protocol (LSP) implementation for CORAL 66 (Computer On-line Real-time Applications Language), the UK Ministry of Defence standard real-time programming language.

About CORAL 66

CORAL 66 was developed in 1964-1966 at the Royal Radar Establishment (RRE), Malvern, UK. The language became the inter-service standard for British military programming and was widely adopted in the control and automation industry.

CORAL 66 has been used in:

• Tornado aircraft flight control systems
• Royal Navy submarine and surface vessel systems
• British Army battlefield systems
• Industrial control and automation
• Nuclear power station monitoring

The language is based on ALGOL 60 with features from JOVIAL and FORTRAN, designed specifically for real-time computing and embedded systems.

Features

• Syntax highlighting for CORAL 66 constructs
• Code completion for keywords, variables, procedures, arrays
• Hover information with type details
• Go to definition for symbols
• Find references across the document
• Document outline showing programme structure
• Support for all CORAL 66 constructs:
  • Number declarations (INTEGER, FLOATING, FIXED)
  • ARRAY declarations with dimensions
  • TABLE definitions with elements
  • PROCEDURE/RECURSIVE declarations
  • SWITCH jump tables
  • OVERLAY storage mapping

Installation

1. Install the extension from the VS Code Marketplace
2. Ensure Python 3.8+ is installed and available in PATH
3. Open any .cor, .crl, or .coral file

File Extensions

Language Overview

CORAL 66 uses an ALGOL-like syntax with uppercase keywords:

COMMENT This is a comment;

BEGIN
    INTEGER count, total := 0;
    FLOATING temperature;
    FIXED(16, 8) velocity;

    FLOATING ARRAY readings[0:99];

    TABLE sensors[4, 100][
        id INTEGER 0;
        value FIXED(16, 8) 1
    ];

    SWITCH action := start, process, finish;

    INTEGER PROCEDURE square(VALUE INTEGER: x);
    BEGIN
        ANSWER x * x
    END;

    RECURSIVE PROCEDURE factorial(VALUE INTEGER: n);
    BEGIN
        IF n <= 1 THEN ANSWER 1
        ELSE ANSWER n * factorial(n - 1)
    END;

start:
    count := 0;
    FOR count := 1 STEP 1 UNTIL 100 DO
        total := total + readings[count];

process:
    temperature := FLOATING(total) / 100.0;
    IF temperature > 50.0 THEN GOTO finish;
    GOTO start;

finish:
    COMMENT Done;
END

Key Syntax Elements

• Comments: COMMENT text;
• Assignment: :=
• Statement terminator: ; (semicolon)
• Blocks: BEGIN ... END
• Type specifiers:
  • INTEGER - Integer values
  • FLOATING - Floating-point values
  • FIXED(totalbits, fractionbits) - Fixed-point with scaling
  • UNSIGNED(totalbits) - Unsigned values
• Word-logic operators: AND, OR, DIFFER, UNION, MASK
• Parameter modes: VALUE, LOCATION
• Communicators: COMMON, LIBRARY, EXTERNAL, ABSOLUTE

Documentation Sources

This extension was developed using official UK Government documentation:

1. Official Definition of CORAL 66 (HMSO 1970, reprinted 1974)

   • Crown Copyright, ISBN 0 11 470221 7
   • Her Majesty's Stationery Office

2. XGC CORAL 66 Language Reference Manual

   • XGC Software, based on the HMSO definition

3. British Standard BS 5905

   • Specification for Computer Programming Language CORAL 66

Configuration

Requirements

• Visual Studio Code 1.75.0 or later
• Python 3.8 or later

Known Limitations

• The parser handles core CORAL 66 constructs but may not cover all implementation-specific extensions
• CODE statements (embedded assembly) are recognised but not parsed
• Some advanced overlay patterns may not be fully supported

Licence

Copyright 2025 Zane Hambly

Licensed under the Apache Licence, Version 2.0. See LICENSE for details.

Contributing

Contributions are welcome! Please open an issue or pull request on GitHub.

Acknowledgements

• Royal Radar Establishment (RRE), Malvern
• UK Ministry of Defence
• Her Majesty's Stationery Office (HMSO)
• XGC Software for maintaining online documentation
• Edinburgh Computer History project