Limitations can be a burden for developers, but a lot of times it result to be a challenge and make the best of them. Now, tell me, how long it would take to write down all the chess rules, and teach a computer to play them. Well, just check this examples...
The written Chess
1951 Alan Turing developed the first program capable of playing a full game of chess. The problem is that the computer to run that program did not yet exist. Anyway, in 1952 without a computer powerful enough Turing played a game in which he simulated the computer. Every movement take 30 minutes, and at the end it lost against Turing's colleague Alick Glennie.
The 8K Chess
SARGON was a chess game written by Dan and Kathleen 'Kathe' Spracklen in a Z80-based computer called Wavemate Jupiter III using assembly language through TDL Macro Assembler. It won the first computer chess tournament held strictly for microcomputers. Theres even a book on the game.
The 5K Chess
The 2K Chess
Toledo Nanochess is the game created by Oscar Toledo. It has only 1257 characters (without spaces and comments) and considered the smallest and best one ever. It has 6 levels of analysis and time control. Its followed by the 2000 characters game created by H.G. Muller called Micromax.
The 1k Chess
Finally arrives this amazing creation, a 1K chess game written for the Sinclair ZX81 by David Horn and it weights less than 1K. The Sinclair-81 had 1k of capacity, so the actual program actually weights 672 Bytes. And it had an AI, so the program not only let you play, but also verify your movements and make their own. He published the source code and a detailed explanation of how it was done in the February 1983 issue of `Your Computer' magazine. The software didn't do the tricky things like castling, queening en passant, but I think is enough to be surprised.