[thom]

You can buy the annotated source code for Oscar Toledo G’s Nanochess here:

http://www.amazon.com/Toledo-Nanochess-commented-source-code...

It was certainly a humbling experience for me.

[mysterydip]

There's also these two books: boot sector games http://www.lulu.com/shop/oscar-toledo-gutierrez/programming-...

more boot sector games (includes this OS): http://www.lulu.com/shop/oscar-toledo-gutierrez/more-boot-se...

[acqq]

also:

C:

Nanochess online: https://nanochess.org/chess3.html

Micro-Max: https://home.hccnet.nl/h.g.muller/max-src2.html

assembly:

Atomchess Game

The world's smallest chess program in x86 machine code, only 326 bytes!

https://nanochess.org/chess6.html

[acqq]

And another:

https://smmax.sourceforge.net/

Written in C:

"The current "shrinking level" of this version is around 670 bytes." ...

"Later on this version has been extended to allow playing with full FIDE rules, meaning including the management of en-passant, castling and under promotion. This new version is around 750 characters (35 lines of codes when pretty printed)."

+

full FIDE version assembly 583 bytes .COM

+

ZX81 1K version