sectorlisp is a 512-byte implementation of LISP that's able to bootstrap John McCarthy's meta-circular evaluator on bare metal.
https://justine.lol/sectorlisp2/
SectorLISP now supports garbage collection. This is the first time that a high-level garbage collected programming language has been optimized to fit inside the 512-byte boot sector of a floppy disk. Since we only needed 436 bytes, that means LISP has now outdistanced FORTH and BASIC to be the tiniest programming language in the world.
SectorLISP consists of 223 lines of assembly. It provides a LISP system that's powerful enough to let you write your own LISP interpreter in just 40 lines of LISP. It's compatible with all PC models dating back to 1981 which have at least 64kb of RAM. This isn't a toy because SectorLISP can run the proof assistant that was included in LISP 1.5. We achieved the small file size thanks to 20/20 hindsight and an unbiased approach of maximum austerity. The goal of this project has been to have fun building a kit that optimizes for file size at the expense of everything else, which means SectorLISP has more in common with a game like Universal Paperclips than a talking paperclip like Clippy.