MicroDOS

MicroDOS is a modern C++ UEFI-native DOS-compatible micro-OS foundation inspired by the uploaded MS-DOS 1.25 source tree.

It is not a direct binary port of MS-DOS. MS-DOS 1.x depends on 16-bit real mode, BIOS interrupts, segment registers, IVT, PSP layout, FCB APIs, and direct .COM/.EXE loading assumptions that do not exist in UEFI x86_64.

The correct design is a compatibility rewrite:

UEFI Platform Layer
    -> DOS Kernel Services
        -> FAT / File Abstraction
            -> Command Shell
                -> Optional 8086 .COM Emulator

Current stage

Implemented foundation:

• EDK2 package: MicroDOSPkg.
• UEFI application module: MicroDOSApp.inf.
• UefiMain bridge to the C++ MicroDOS entry point.
• Minimal UEFI type/protocol declarations.
• Console abstraction over UEFI text output/input.
• UEFI LoadedImageProtocol + SimpleFileSystemProtocol binding.
• Interactive command shell.
• Implemented commands: HELP, CLS, ECHO, VER, MEM, EXIT, REM, DIR, TYPE.
• Recognized from COMMAND.ASM: COPY, DEL/ERASE, REN/RENAME, PAUSE, DATE, TIME.
• DOS service boundary stubs.
• FAT BPB parser foundation.
• Source analysis docs for the uploaded MS-DOS 1.25 archive.

Build with EDK2

Windows:

.\scripts\build-edk2-windows.ps1 -Edk2Root C:\src\edk2 -Target DEBUG -ToolChain VS2022

Linux:

./scripts/build-edk2-linux.sh ~/src/edk2 DEBUG GCC5

Expected output:

dist/esp/EFI/BOOT/BOOTX64.EFI

See docs/build-edk2.md for full setup and QEMU/VirtualBox boot notes.

Source-guided compatibility target

From COMMAND.ASM, the DOS 1.x internal command set is:

DIR, RENAME, REN, ERASE, DEL, TYPE, REM, COPY, PAUSE, DATE, TIME

From MSDOS.ASM, the filesystem compatibility target is FAT12-style 8.3 directory handling with 32-byte directory entries and packed 12-bit FAT chains.