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Operating Systems

This page describes two minimalist operating systems: TINYROM, a ROM-based OS for the TINY board featuring a menu-driven interface without disk storage, and BCOS, a lightweight disk operating system for the MINI board providing basic file management and serial communication using familiar Linux-style commands.

TINYROM operating system (TINY board)

Overview

TINYROM is a minimalist ROM-based operating system and runtime environment for the TINY board. It is designed to be as small and simple as possible, offering a bare-metal interface that boots directly into a menu-driven selector for launching built-in programs, test routines, and games — all stored within a compact 32 KiB ROM image.

Unlike more complex operating systems that manage filesystems or dynamic storage (see below), TINYROM does not interface with disks or SD cards. Instead, it provides a tiny kernel consisting solely of low-level I/O routines for communicating with the 65C51 ACIA serial interface. These routines allow basic input and output over a serial terminal and form the foundation for user interaction and debugging.

Upon startup, TINYROM presents a static selection menu through the serial interface, enabling users to choose from a set of preloaded software — typically small utilities, diagnostics, or simple games.

ByteCradle Operating System (MINI board)

Overview

The MINI board runs on BCOS (ByteCradle Operating System), a minimalist, single-user disk operating system (SUDOS) purpose-built for the MINI. Designed with clarity, compactness, and practical utility in mind, BCOS offers essential functionality for persistent storage access and serial communication, without the complexity of multitasking or modern OS abstractions.

At its core, BCOS presents a simple, navigable view of the SD card’s contents, supporting basic file operations such as directory listing, file reading, writing, and — critically — the ability to load and execute binary programs directly from the SD card. This capability allows BCOS to serve as a lightweight but extensible platform for launching standalone applications with minimal runtime overhead.

In addition to its command-line shell, BCOS exposes a set of low-level I/O routines for working with the 65C51 ACIA serial interface. These include functions for reading characters, writing characters, and outputting entire strings over the serial port, enabling user programs to easily perform serial communication without reimplementing low-level logic.

Communication via the 65C51 ACIA serves both as the user console and as a fundamental I/O channel, making BCOS suitable for both interactive and automated tasks on constrained 8-bit hardware.

BCOS leverages common Linux-style commands for file and directory management, offering a familiar environment to users accustomed to Linux or UNIX systems. Below are examples of frequently used commands:

  • List directory contents (ls): To view the files and directories within the current directory, simply type: 

    ls

  • Change directory (cd): To navigate to another directory, use: 

    cd dirname
    For example, to move up one directory level: 
    cd ..

  • Executing programs: Executable files typically have a .COM extension. To run these files, type their base name (without the .COM extension). For instance, to execute a program named MYAPP.COM, simply type: 

    myapp

Note

While BCOS internally manages file names in uppercase, users may conveniently enter commands and file names in lowercase.