Idun Shell

The file dos.app, with source in cbm/dos.app.s, is the Idun Shell, a command-line interface for the Idun cartridge that emulates the behavior of MS-DOS. It is the primary application that loads on startup if you just type the go command from BASIC, or if you specify it using go "dos".

Here is a summary of its key features and structure:

  • Core Functionality: It provides a classic command-line environment where users can enter commands at a prompt. It parses these commands, handles arguments, and executes them.

  • Startup Process:

    • It includes a resident Toolbox (sys/toolbox.asm), making a set of common routines available for other tools and applications that are launched from the shell.
    • It supports an autoexec.bat-like script (z:autoexec.bat) which runs automatically on startup to configure the environment.
    • It features a "fast reload" capability, caching parts of itself in ERAM to speed up subsequent launches.

  • Command Dispatcher:

    • The shell has a table of internal commands for common tasks (e.g., dir, cd, type, mem).
    • If a command is not found internally, it attempts to load and execute an external program from a disk or virtual drive.

  • Key Features:

    • I/O Redirection: Supports redirecting input and output using <, >, and >>, similar to DOS and Unix shells.
    • Wildcard Support: Allows the use of * in filenames for commands that operate on multiple files.
    • Batch File Execution: Can run scripts of shell commands using the exec command.
    • Drive Management: Includes mount to attach disk images and assign to map host directories to virtual drive letters.
    • System Interaction: Provides commands like mem to view memory usage and info to display information about system devices.
    • Host Integration: Features powerful commands like lua, nix, and linux that pass commands through a tty interface to be executed on the host system (the Raspberry Pi).
    • Macros: Implements a doskey-like macro system for creating command aliases.
    • Screen Saver: Includes a simple countdown timer that launches a blanker application after a period of inactivity.