c64ux

Unix-inspired shell with RAM filesystem, built-in editor, disk bridging, REU persistence,
login support, and theming — for the Commodore 64 (6502 assembly)

C64UX is a Unix-inspired shell written entirely in 6502 assembly for the Commodore 64.
It combines a RAM-resident filesystem, a nano-style text editor, Commodore DOS integration, disk bridging, optional RAM Expansion Unit (REU) support, and now user authentication and theming to create a minimalist yet surprisingly capable retro system environment.

Current version: v0.7.3
Author: Anthony Scarola
Development: Designed and directed by Anthony Scarola; code developed with assistance from Claude Code (Anthropic)

C64UX provides a command-driven interface reminiscent of early Unix systems, running on real C64 hardware (including modern implementations such as the Ultimate 64) or emulators.
It requires no ROM patching, relies exclusively on standard KERNAL routines, and supports true disk access across multiple devices when drives are present.

This project is both a learning exercise and a functional retro shell that bridges in-memory workflows, interactive editing, disk storage, REU-backed persistence, and now system identity and personalization.

Downloads: The latest source and binary are in this repository. Older versioned releases are available on the Releases page.

Features

Interactive Unix-style shell
RAM-resident filesystem
Built-in nano-style multi-line text editor
File metadata (name, size, address, date, time)
User login with username and password (v0.7)
Persistent credentials stored on disk with password obfuscation (v0.7)
Auto-advancing clock based on the KERNAL jiffy timer
Accurate uptime tracking across midnight rollovers
Unix-like prompt with username
Integrated Commodore DOS command interface
RAM ↔ disk file bridging (SAVE / LOAD)
True SEQ file support for text files (v0.6.1)
Configurable default disk device (v0.6.1)
Optional RAM ↔ REU filesystem persistence (v0.6)
System color themes (v0.7)
Unix-style file operations (CP, MV, RM with wildcards)
RESET command to reclaim heap space on demand
Paged HELP display for full on-screen documentation
Structured boot sequence with system-style startup messages (v0.7)
Clean separation of subsystems (boot, console, filesystem, editor, auth, time, disk I/O, REU)

Commands

| Command | Description | |-----------|-------------| | HELP | Show available commands (paged output) | | LS | List RAM filesystem files | | STAT | Show detailed file metadata | | CAT | Display file contents | | WRITE | Create a new RAM-resident text file | | NANO | Edit or create a RAM file (multi-line editor) | | ECHO | Print text to the screen | | RM | Delete RAM files (supports prefix wildcards) | | CP | Copy a RAM file to a new RAM file | | MV | Rename a RAM file | | SAVE | Save a RAM file to disk (SEQ format) | | LOAD | Load a disk file into the RAM filesystem | | DRIVE | Show or set the default disk device (8–11) | | SAVEREU | Save the entire RAM filesystem to REU | | LOADREU | Restore the RAM filesystem from REU | | WIPEREU | Clear the REU-stored filesystem image | | PASSWD | Change the current user password | | THEME | View or change the system color theme | | MEM | Show free BASIC memory | | DATE | Show current session date | | TIME | Show current session time | | UPTIME | Show system uptime (DAYS HH:MM:SS) | | PWD | Show current working path (/HOME/<username>) | | RESET | Clear the RAM filesystem (with confirmation) | | UNAME | Show system and version information | | VERSION | Show version/build info (alias: VER) | | WHOAMI | Show current username | | CLEAR | Clear screen (alias: CLS) | | DOS | Send Commodore DOS command to the active drive | | EXIT | Return to BASIC |

Boot Sequence & Login (v0.7)

C64UX now features a structured, system-style boot process followed by user authentication.

Boot Sequence

Displays staged [ OK ] initialization messages:
- STARTING C64UX KERNEL V0.7
- MEMORY CHECK: 64K RAM SYSTEM
- INITIALIZING FILESYSTEM
- HEAP ALLOCATED AT $6000
- DETECTING HARDWARE
- REU: DETECTED or REU: NOT FOUND
- LOADING DEVICE DRIVERS
- MOUNTING /DEV/DISK (DEVICE 8)
Screen is cleared after boot for a clean banner display

Login System

On first run, the user is prompted to create a username and password, then enter the session date and time
Credentials are stored in a disk-based SEQ configuration file (CONFIG); the password is XOR-obfuscated before being written to disk to prevent casual plaintext inspection
On subsequent runs, credentials are automatically loaded and the user is prompted for the session date and time
User must authenticate before entering the shell
Three failed login attempts return control to BASIC

Themes (v0.7)

C64UX supports simple system-wide color themes.

THEME Command

THEME
THEME <name>

Available themes:

NORMAL
DARK
GREEN

Themes control:

Border color
Background color
Text color

Themes are reset to NORMAL on each program launch and applied after the banner to avoid PETSCII color conflicts.

Nano-Style Editor (v0.4+)

C64UX includes a built-in nano-style text editor for RAM files.

NANO Command

NANO <filename>

Opens an existing RAM file for editing, or creates it if it does not exist
Displays existing file contents before editing
Accepts multi-line text input
Editing ends when the user enters a single . on its own line
Lines are stored using CR ($0D) separators
Changes are saved back into the RAM filesystem

RAM ↔ Disk Bridging (v0.5+)

C64UX supports direct bridging between the RAM filesystem and disk storage using SEQ files.

SAVE

SAVE <filename>
SAVE <device>:<filename>

Writes a RAM file to disk as a SEQ file
Uses streamed KERNAL I/O
Honors the currently selected default drive
Optional per-command device override

LOAD

LOAD <filename>
LOAD <device>:<filename>

Loads a SEQ file from disk into the RAM filesystem
Creates or updates a RAM directory entry
Streams file data directly into the RAM heap

Default Drive Selection (v0.6.1)

DRIVE Command

DRIVE
DRIVE <8–11>

Displays the current default drive
Sets a new default drive for SAVE, LOAD, DOS, and directory operations

REU Filesystem Persistence (v0.6)

C64UX includes optional RAM Expansion Unit (REU) support, allowing the entire RAM filesystem to be preserved across program exits or restarts without disk I/O.

REU Commands

SAVEREU
LOADREU
WIPEREU

The directory table and heap are copied via DMA and restored exactly as saved.
Systems without an REU continue to function normally.

Filesystem Design (RAM)

Directory size: fixed (DIR_MAX = 8 entries)
Filename length: 8 characters (space-padded)
Storage: contiguous heap in RAM starting at $6000
Directory entry (30 bytes each) includes:
- Name (8 bytes)
- Start address (2 bytes)
- Length (2 bytes)
- Creation date — 10 bytes (YYYY-MM-DD)
- Creation time — 8 bytes (HH:MM:SS)

RAM filesystem data is volatile by default but can be preserved using REU support or saved to disk individually via SAVE.

Development Notes

C64UX is designed and directed by A. Scarola. The 6502 assembly code was developed with the assistance of Claude Code (Anthropic AI). All architecture decisions, feature design, subsystem structure, version planning, and testing were performed by the author. The project has been iteratively developed across 7 releases.

This project is released under the MIT license. The author asserts copyright based on the creative and architectural contributions described above. The legal landscape around AI-assisted software authorship is evolving; if you have concerns, treat this project as you would any open-source release — use it, fork it, and build on it freely.

Build

Assemble using ACME:

acme -f cbm -o c64ux.prg c64ux.asm

C64ux

Install / Use

README