OpenPCW-OS

OpenPCW-OS is a small MIT-licensed operating environment for launching CP/M-compatible Amstrad PCW software. Its authored Z80 boot chain, resident kernel, terminal, disk services, keyboard services, interrupt ticker, shell, and application API run on the PCW hardware model implemented by emulators such as MAME and JOYCE and are designed for the corresponding physical machines.

Version 0.2.0 provides:

• a 180 KiB bootable PCW disk image;
• a resident command shell with physical A: disk replacement;
• a volatile M: work drive sized from installed expansion RAM;
• CP/M-compatible Page Zero, BIOS, BDOS, FCB, banked-memory, and error contracts;
• the documented Amstrad PCW extended-BIOS application interface;
• a 90-column terminal with PCW display controls and an MIT-licensed font;
• a resident DIR with drive prefix, five columns, space-separated extensions, and : column separators;
• deterministic artifacts and machine-checked layout boundaries.

Build

Requirements:

• Python 3.10 or newer;
• GNU Make;
• Pasmo available as pasmo.

Build and verify:

make dist
make check

make check verifies the recorded source and release files without rewriting them. make check-external additionally requires the native MAME and JOYCE integration probes to pass; see Testing for dependencies.

The release artifacts are written to dist/:

• OpenPCW-OS.dsk — complete bootable disk;
• OPENPCW.EMS — resident-kernel payload with the OPCWEMS1 container;
• OpenPCW-OS-font.bin — exact 128-glyph runtime font;
• OpenPCW-OS-integration.json — generated shell-ready integration point;
• LICENSES.txt — complete project and Microsoft copyright and permission notices;
• OpenPCW-OS.zip — the four runtime artifacts together with LICENSES.txt;
• SHA256SUMS — hashes of the ZIP and its five unpacked files.

Use OpenPCW-OS.zip for binary releases. Keep the applicable notices with files redistributed separately or embedded in another project.

make clean removes these generated artifacts. A subsequent make dist reconstructs them entirely from the versioned source and third-party font.

Use

Boot OpenPCW-OS.dsk as drive A:. At the A> prompt, replace the disk with a PCW program disk and enter the program's .COM name. The shell logs the new medium and executes the program at the conventional transient address.

Commands available after a disk exchange include drive selection (A: and M:), DIR, and direct .COM execution. Pressing the configured quit key in an individual program remains a property of that program.

Documentation

• Architecture
• Boot process
• Memory map
• BIOS and BDOS interfaces
• CP/M Plus compatibility scope
• Disk format
• Terminal
• Public ABI
• Implementation notes
• Design provenance
• References
• Third-party material
• Compatibility evidence
• Build and release
• Testing
• Symbol traceability
• Routine contract index

The source uses short identifiers such as REF-PCW-IO, DES-MEM-001, and VAL-BUILD-LAYOUT. docs/TRACEABILITY.yml resolves those identifiers to design records, public references, and validation commands. make check verifies that every material assembly routine is covered by a traceability rule.

The 24 MIT-licensed guest-side compatibility programs under tests/fixtures/ exercise public BDOS, BIOS, XBIOS, terminal, disk, filesystem, banked-memory, and warm-boot contracts. make check assembles all of them; emulator integrations execute the relevant binaries through the native guest implementation.

Integration

OpenPCW-OS is the canonical source of the guest operating environment. Emulator projects can pin a release and embed the generated DSK together with the published shell-ready metadata. The guest performs its own terminal, disk, filesystem, memory, and application services; an integration only needs to boot the helper disk, wait for the native prompt, exchange the content disk, and inject the selected command when automatic launch is desired. The EMS and font remain available separately for tools that consume those formats directly; integrations must carry the applicable notices from dist/LICENSES.txt.

Licence

Original OpenPCW-OS work is available under the MIT License in LICENSE. The display-font source in third_party/microsoft-msdos/ is distributed under Microsoft's MIT License preserved beside it. Exact origin and transformation records are in Third-party material.

OpenPCW-OS is an independent project, unaffiliated with the makers or owners of Amstrad PCW, CP/M, or MS-DOS. Those names identify hardware compatibility, software interfaces, or material attribution; they do not imply endorsement.