📝Forth
An extremely small Stack-based programming language with few syntax rules. Often compared with Lisp because of its extensibility.
Forth is extremely extensible and could be implemented with only a couple of primitive operations. The rest of the words (Forth’s functions) could be implemented in Forth itself.
See also
Resources
quick interactive tutorial on Forth
a more technical tutorial
How to implement a Forth interpreter
JONESFORTH is a sometimes minimalistic implementation of Forth for x86
original publish rescued with Wayback Machine
WAForth—Forth running in WebAssembly