Working printf, fopen, and a real filesystem on any CPU -- real, emulated, or yet to be designed. On day one, before any hardware exists.

Embedded bring-up has a chicken-and-egg problem. You can't debug your firmware until the serial port works. You can't test your filesystem until the flash driver works. The first six weeks of every new-hardware project go to fighting your way to a working printf.

Zero Board Computer (ZBC) eliminates the chicken-and-egg by giving any CPU file input/output, console, and clock services through a 32-byte memory-mapped device. The same firmware runs against your simulator, against a field-programmable gate array (FPGA) prototype, against the manufactured chip, and against a QEMU or a MAME virtual machine, because the contract is the same everywhere: read and write memory.

Why this matters, who it's for, and how it works: https://johnwbyrd.github.io/zbc/introduction.html

Five-minute slide intro: https://johnwbyrd.github.io/zbc/presentation-intro/

Full documentation and reference: https://johnwbyrd.github.io/zbc/

Wiki and community: https://www.zeroboardcomputer.com/

Sources are organized by language so new implementations can slot in as siblings without disturbing existing ones. The protocol primitives every implementation needs (RIFF codec, opcode table, header) live in shared/; each language tier owns its own client, host, and tests on top of that base.

• include/shared/ + src/shared/ -- protocol primitives (zbc_protocol.h, RIFF codec, opcode table); compiled into every host and client so the wire format can't drift.
• include/c/ + src/c/ -- C90 reference client and host libraries plus the ANSI/stdio backend and platform sandbox code.
• include/cpp/zbc/ + src/cpp/ -- C++17 host library (zbc::Device / zbc::Backend / zbc::Policy) intended for embedding in emulators.
• test/ -- c/ and cpp/ host tests, conformance/ for C-vs-C++ wire-protocol equivalence, target/ for cross-compiled on-emulator runs (i386 under QEMU, 6502 under MAME), common/ for the shared test harness.
• docs/ -- Sphinx site; docs/source/specification.rst is the canonical protocol spec, and docs/source/documentation-sources.rst records the governance boundary between this repo and the wiki at www.zeroboardcomputer.com.
• fuzz/ -- libFuzzer target and corpora for the RIFF parser.
• web/ -- MediaWiki content for www.zeroboardcomputer.com.

# Basic build + host tests
cmake -B build && cmake --build build && ctest --test-dir build

# With on-target tests (requires MAME + cross-compilers)
cmake -B build -DZBC_TARGET_TESTS=ON

# With seccomp sandbox (Linux)
cmake -B build -DZBC_USE_SECCOMP=ON

# With fuzzing (requires Clang)
cmake -B build-fuzz -DENABLE_FUZZING=ON

• CI matrix: Ubuntu, macOS, and Windows; gcc, clang, and MSVC.
• ASan + UBSan and seccomp-sandbox jobs gate every push.
• Continuous RIFF parser fuzzing via libFuzzer + ClusterFuzzLite.
• Zero heap allocation in the libraries, statically verified in test/CMakeLists.txt.

MIT