Awesome Open Source
Awesome Open Source

( Subset of Forth94 )

This is a self-hosted implementation of Forth, which can regenerate itself from Forth source code. The bootstrapping process uses a metacompiler written in Lisp to target a small inner interpreter and a handful of code words written in C. A new metacompiler written in Forth generates an x86 executable using using assembly language code words.

There are also ARM, RISC-V, Motorola 68000, PDP-11, and asm.js targets. There is a cross compiler for 6502, 8051, AVR, Cortex-M, MSP430, PDP-8, PIC, and STM8.

( Continuous integration )

The code is continuously built and tested in Linux, MacOS X, and Windows using several cloud-based continuous integration services. This is documented in

( Further reading )

INSTALL \ How to build.
doc \ Classic (and recent) texts not related to this project.
lib/README \ Information about libraries.
targets/ \ Information about current and possibly future targets.

( Implementation guide )

The Forth kernel contains everything needed to read and compile the rest of the system from source code, and not much else. It's composed of two parts: a target-specific file nucleus.fth containing all primitive CODE words, and a target-independent kernel.fth. These two are compiled by the metacompiler.

The C target nucleus used for bootstrapping has only twelve proper primitives. There is also the COLD word which compiles to main(), and four I/O words.

When the kernel starts, it jumps to the word called WARM. This is responsible for loading the rest of the system and entering the text interpreter. The first file loaded by WARM is core.fth, which implements the CORE wordset. Because the kernel only has a bare minimum of words, the start of core.fth looks a little strange.

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forth (46
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asmjs (17