milliForth is being touted as the smallest real programming language ever created, fitting into just 422 bytes. It is a modified version of the hello world program used by sectorFORTH and is designed to fit within a 512-byte boot sector. This makes it smaller than sectorLISP, a 436-byte implementation of LISP, by 14 bytes. milliForth is intentionally similar to sectorFORTH, with just a handful of words. The code is available on GitHub, along with tools for running and testing it. While it may lack some features and error handling, the sheer compactness of milliForth is impressive. Overall, it is a remarkable achievement in minimal programming language implementation.
https://github.com/fuzzballcat/milliForth