Olivier "Baudsurfer" Poudade, Red Sector Inc., 2015. Boot-sector.
BootChess is a chess program that fits in a PC boot sector. Olivier “Baudsurfer” Poudade of the demo group Red Sector Inc. released it in January 2015, with help from Peter “QKumba” Ferrie.
Its release notes call it the smallest computer implementation of chess on any platform, beating the 1024 bytes of 1K ZX Chess, a record that had stood for 33 years. The smallest version is 487 bytes. The bootable version shown here uses all 512 bytes and can promote pawns to queens.
The computer plays white and always opens with e2e4. You play black by typing a move as four characters: the square a piece starts on, then the square it moves to. The board is drawn as text, with white pieces in capitals and black pieces in lower case. The source code was published under the WTFPL.