command64

An MS-DOS style operating system for the Commodore 64.

Overview

command64 provides a familiar command-line interface and DOS-compatible API for the C64. It leverages the RAM Expansion Unit (REU) to provide up to 16MB of virtual memory and a robust handle-based file system.

Features

• MS-DOS Shell: Commands like DIR, TYPE, CLS, and VER.
• Environment Variables: Persistent configuration (SET, PATH) stored in the REU.
• Service Bus API: Stable INT 21h-style entry point for external programs (JSR $1000).
• Virtual Memory: 4KB page-based allocation in the REU (up to 16MB).
• Handle-based I/O: Modern file management system mapping handles to C64 channels.
• Multi-Device Support: Seamlessly switch between C64 devices 8-11.
• External Utilities: Support for external applications (e.g., DEBUG, LABEL, CONWAY, PACMAN).
• App Manager: Resident registry of loaded programs (APPS/PS, FREE) with memory-safe pre-flight validation and dynamic auto-slotting on LOAD.
• Binary Relocator: Load relocatable binaries at arbitrary memory addresses.

Getting Started

Requirements

• Commodore 64 (or VICE emulator)
• RAM Expansion Unit (REU) - 512KB or larger recommended.
• Java Runtime Environment (for KickAssembler)
• CMake (version 3.20 or newer)
• GNU Make (optional wrapper)

Building

The project is built using CMake. A Makefile wrapper is also provided at the root for convenience.

1. Configure CMake:

   cmake -B build

2. Build the OS and all utilities:

   cmake --build build
   # OR using the Makefile wrapper:
   make all

3. Build the OS disk image only:

   cmake --build build --target image_d64
   # OR using the Makefile wrapper:
   make image

Running

1. Load the compiled command64.prg into your C64 or emulator.
2. Run with SYS 4608 (or simply RUN if loaded via BASIC).
3. To load external utilities, ensure they are present on the same disk as the OS.

Internal Commands

Command	Description
CLS	Clear the screen.
DIR	List files on the current disk.
TYPE	Display the contents of a file (e.g., TYPE README.TXT).
COPY	Copy a file to another location.
DEL	Delete a file from disk.
REN	Rename a file on disk.
DRIVE	Switch active device (8, 9, 10, 11). Aliases: DEVICE, DEV.
SET	Display or set environment variables.
PATH	Display or set the executable search path.
LOAD	Load a program by name, optionally at an address; auto-picks a free memory region if omitted.
RUN	Execute a program by name or address; with no argument, runs the program already loaded at the base of user program space. Alias: GO.
APPS	List currently loaded/registered programs (name, address, size). Alias: PS.
FREE	Deregister a named program, or all loaded programs if no name is given.
VOL	Display the disk name/ID.
VER	Show OS version and build information.
HELP	Display available commands.
EXIT	Return to BASIC.

For Users

See the User Manual for a comprehensive guide to using command64. Details on external utilities like DEBUG can be found in the Applications Guide.

For Developers

See the following documents in the docs/ directory:

• API Reference
• Programmer's Reference
• VMM Specification
• PETSCII API