16-bit SUBLEQ eForth

• Author: Richard James Howe
• Email: mailto:howe.r.j.89@gmail.com
• Repo: https://github.com/howerj/subleq
• License: The Unlicense / Public Domain

If you feel like supporting the project you can buy a book from Amazon, available here that describes how the project works and how to port a Forth to a new platform.

This project contains a working (self-hosting) Forth interpreter that runs on top of a SUBLEQ 16-bit machine. SUBLEQ machines belong to the class of One Instruction Set Computers, they only execute a single instruction but are still Turing Complete. The Forth system, specifically a variant of eForth, is provided as subleq.dec, passing this image to the tiny (~ 600 bytes) SUBLEQ C virtual machine allows you to run eForth on the machine. For a list of commands type "words" and hit enter, numbers are entered using Reverse Polish Notation, eg. "2 2 + . cr" prints "4", and new functions can be defined like so:

: hello cr ." Hello, World" ;

Be careful with the spaces, they matter, after typing that in, type "hello" and hit enter. A Forth tutorial will not be provided here. Many Forth words are defined including the bitwise words.

To build and run you will need a C compiler and Make, type "make run", failing that:

cc subleq.c -o subleq
./subleq subleq.dec

The system is self hosting, that is it can generate new eForth images using the current eForth image and the eForth source code. This is done like so:

./subleq subleq.dec < subleq.fth > new-image.dec

There is a website available that runs an interactive SUBLEQ interpreter in the browser in case you do not want to both compiling things, it is available at https://github.com/howerj/subleq-js. Or if you just want to try it out directly https://howerj.github.io/subleq.htm.

Happy hacking, and a shiny penny for anyone that manages to do something useful with this project!

Other SUBLEQ projects

• https://github.com/pbrochard/subleq-eForthOS
• https://github.com/howerj/subleq-python
• https://github.com/howerj/subleq-perl
• https://github.com/howerj/subleq-js
• https://github.com/howerj/subleq-forth
• https://github.com/howerj/subleq-vhdl

References

• https://en.wikipedia.org/wiki/Forth_(programming_language)
• https://github.com/howerj/bit-serial
• https://github.com/howerj/embed
• https://github.com/howerj/forth-cpu
• https://rosettacode.org/wiki/Subleq
• https://stackoverflow.com/questions/2982729
• https://stackoverflow.com/questions/34120161
• https://web.ece.ucsb.edu/~parhami/pubs_folder/parh88-ijeee-ultimate-risc.pdf
• https://esolangs.org/wiki/Subleq
• https://wikipedia.org/wiki/Threaded_code
• https://github.com/samawati/j1eforth
• https://www.bradrodriguez.com/papers/
• 8086 eForth 1.0 by Bill Muench and C. H. Ting, 1990
• https://www.bradrodriguez.com/papers/mtasking.html, For multitasking support
• https://forth-standard.org/standard/block, For the block word-set, which is partially implemented.
• https://github.com/howerj/subleq-js
• URISC, the original OISC, a SUBLEQ machine: Mavaddat, F.; Parhami, B. (October 1988). "URISC: The Ultimate Reduced Instruction Set Computer".
• https://en.wikipedia.org/wiki/Turing_tarpit, which SUBLEQ could be argued to be one.
• For other Single Instruction Set Computers: https://en.wikipedia.org/wiki/One-instruction_set_computer
• For the Forth-83 Standard: http://forth.sourceforge.net/standard/fst83/ http://forth.sourceforge.net/standard/fst83/FORTH-83.PRN
• DPANS84 FORTH standard: http://forth.sourceforge.net/std/dpans/