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A simple, indirect-threaded Forth, written in C; for target compiling; runs on Linux, BSD, OSX, and Cygwin

[muforth.dev/](https://muforth.dev/ "https://muforth.dev/")

### License

[View license](/nimblemachines/muforth/blob/master/LICENSE)

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stars](/nimblemachines/muforth/stargazers) [34
forks](/nimblemachines/muforth/forks) [Branches](/nimblemachines/muforth/branches) [Tags](/nimblemachines/muforth/tags) [Activity](/nimblemachines/muforth/activity)

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# nimblemachines/muforth

master

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## Folders and files

| Name | | Name | Last commit message | Last commit date |
| --- | --- | --- | --- | --- |
| Latest commit   History[3,159 Commits](/nimblemachines/muforth/commits/master/)   3,159 Commits | | |
| [.vim](/nimblemachines/muforth/tree/master/.vim ".vim") | | [.vim](/nimblemachines/muforth/tree/master/.vim ".vim") |  |  |
| [doc](/nimblemachines/muforth/tree/master/doc "doc") | | [doc](/nimblemachines/muforth/tree/master/doc "doc") |  |  |
| [mu](/nimblemachines/muforth/tree/master/mu "mu") | | [mu](/nimblemachines/muforth/tree/master/mu "mu") |  |  |
| [scripts](/nimblemachines/muforth/tree/master/scripts "scripts") | | [scripts](/nimblemachines/muforth/tree/master/scripts "scripts") |  |  |
| [src](/nimblemachines/muforth/tree/master/src "src") | | [src](/nimblemachines/muforth/tree/master/src "src") |  |  |
| [talks](/nimblemachines/muforth/tree/master/talks "talks") | | [talks](/nimblemachines/muforth/tree/master/talks "talks") |  |  |
| [.gitattributes](/nimblemachines/muforth/blob/master/.gitattributes ".gitattributes") | | [.gitattributes](/nimblemachines/muforth/blob/master/.gitattributes ".gitattributes") |  |  |
| [BUILDING](/nimblemachines/muforth/blob/master/BUILDING "BUILDING") | | [BUILDING](/nimblemachines/muforth/blob/master/BUILDING "BUILDING") |  |  |
| [LICENSE](/nimblemachines/muforth/blob/master/LICENSE "LICENSE") | | [LICENSE](/nimblemachines/muforth/blob/master/LICENSE "LICENSE") |  |  |
| [README.md](/nimblemachines/muforth/blob/master/README.md "README.md") | | [README.md](/nimblemachines/muforth/blob/master/README.md "README.md") |  |  |
| View all files | | |

## Repository files navigation

* [README](#)
* [License](#)

# What is muforth?

muforth is a small, simple, fast, indirect-threaded code (ITC) Forth intended
for use as a cross-compiler for microcontrollers and other embedded devices.
It is written in C and its core is very portable. Because of its Forth nature,
it is naturally extensible, scriptable, and customizable.

muforth is very well-suited to interactive coding, debugging, and exploration,
and is a great tool for bringing up new hardware.

It has support – in varying degrees of completeness – for a number of
different architectures and chip families.

* [8051](/nimblemachines/muforth/blob/master/mu/target/8051)
* [ARMv6-m](/nimblemachines/muforth/blob/master/mu/target/ARM/v6-m) (aka Cortex-M0/M0+)
* [ARMv7-m](/nimblemachines/muforth/blob/master/mu/target/ARM/v7-m) (aka Cortex-M3/M4/M7)
* [AVR](/nimblemachines/muforth/blob/master/mu/target/AVR) (Atmel/Microchip)
* [HC08 and HCS08](/nimblemachines/muforth/blob/master/mu/target/S08) (Motorola/Freescale/NXP)
* [MSP430](/nimblemachines/muforth/blob/master/mu/target/MSP430) (TI)
* [PIC18](/nimblemachines/muforth/blob/master/mu/target/PIC18) (Microchip)
* [RISC-V](/nimblemachines/muforth/blob/master/mu/target/RISC-V) (initially, the SiFive FE310 and GigaDevice
  GD32VF103)

# Tethered vs self-hosted

Unlike a "self-hosted" Forth, where the target contains the dictionary, the
text interpreter, and all the tools necessary for assembling and compiling
code, muforth supports a *tethered* development model. muforth runs on the
*host* machine, compiling code and data that are later copied to the *target*
machine and executed there.

Because the dictionary and all the compilation tools reside on the *host*,
only the *compiled* code and data reside on the target. This makes it possible
to target *very* small devices that only have a few kilobytes of flash and a
few hundred bytes of RAM. In contrast, a self-hosted Forth often needs 16 KiB
(or more) of flash to be useful, and consumes RAM for the text interpreter and
compiler.

The host machine is also orders of magnitude faster than the target, so doing
the compilation on the host is essentially instantaneous.

# Why yet another Forth?

I initially wrote muforth because I wanted to try out some implementation
ideas. The core language primitives are written in C, but initially muforth
compiled Forth words via a simple native code compiler for the x86. I quickly
realized that simplicity and portability were more important than speed. The
current implementation is a straightforward indirect-threaded Forth - and it
is *quite* fast!

Its implementation is no longer the point. Its sole reason for existing is to
be a cross-compiler for *other* Forths, and their implementations are in no
way tied to muforth’s. In fact, muforth can be used to compile *any* sort of
code onto the target. I've used it very successfully as a smart assembler for
writing AVR and S08 code.

By keeping it small and simple, it is much more likely to be a useful tool
that people can customize.

It’s [BSD licensed](/nimblemachines/muforth/blob/master/LICENSE), so do what you want with it! I’d love to hear
about innovative or unusual uses of muforth.

# Starting points

[BUILDING](/nimblemachines/muforth/blob/master/BUILDING) will tell you how to build muforth. It’s very simple.

Look in [mu/target/](/nimblemachines/muforth/blob/master/mu/target) to find a target that interests you. There is
generally a `mu/target/<target-name>/build.mu4` that loads the cross-build
environment. Use it as an “index” to find the assembler, disassembler,
meta-compiler, kernel, and other key pieces of code.

# Documentation

Sadly, there isn’t a lot of documentation right now. A good place to start is
to read the source.

The code – both the C code that implements the Forth virtual machine and the
muforth code that does everything else – is carefully and in some cases
extensively (even obsessively!) commented. Right now your best source of
documentation is the code! Luckily for you, there isn’t that much of it, so
reading it is actually possible. That’s part of the point of muforth; I want
it to be a [convivial tool](https://www.nimblemachines.com/convivial-tool/).

The heart of the system is the Forth code that muforth reads when it first
starts: [mu/startup.mu4](/nimblemachines/muforth/blob/master/mu/startup.mu4). You’ll learn a lot by reading this!

[muforth.dev](https://muforth.dev/) will
eventually host the muforth documentation. At the moment, it is a collection
of [journals, essays, and “getting started” pages](https://muforth.dev/all-pages/).

# News

Follow [@muforth.dev](https://bsky.app/profile/muforth.dev) for updates about
the project and related things (eg, interesting development boards) that I'm
thinking about.

# Talks

In March 2008 I gave a [talk](https://vimeo.com/859408) about bootstrapping,
muforth, and [convivial tools](https://www.nimblemachines.com/convivial-tool/).

Warning: I wave my arms around a lot, and the audio and video quality isn’t
that great, but you might find it interesting, or at least amusing.

It’s also hard to see my slides. If you want to “follow along”,
[download my slides](https://raw.githubusercontent.com/nimblemachines/muforth/master/talks/2008-mar-30-PNCA),
and use `less` to view them – ideally in a text window that is at least 30
lines high – like so:

```
less -30 ~/muforth/talks/2008-mar-30-PNCA
```

[![March 2008 talk on Vimeo](https://user-images.githubusercontent.com/3320/214488827-47171f1b-5221-44d0-b9d9-7febcff83628.png)](https://vimeo.com/859408)

# Above all, enjoy!

## About

A simple, indirect-threaded Forth, written in C; for target compiling; runs on Linux, BSD, OSX, and Cygwin

[muforth.dev/](https://muforth.dev/ "https://muforth.dev/")

### Resources

[Readme](#readme-ov-file)

### License

[View license](#License-1-ov-file)

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