In many ways Ritchie and Thompson can be seen as precursors of the personal computer programmers of the 80s - not driven by profit but by fun and enthusiasm for ideas.

Belle for Chess

There is a sideline to the career of Ken Thompson which has nothing to do with Unix, C or any of the types of program that he is usually associated with.

As a boy he enjoyed playing chess as well as electronics. What could be more natural then than to create a chess playing programs and machines.

In 1972 Thompson started work on Belle, a chess playing program that used traditional search techniques combined with a database of end games.

Ken Thompson and Joe Condon studying chess moves

Later (1976) he and Joe Condon developed a hardware prototype for a move generator for Belle, possibly the first dedicated chess playing hardware. This developed from a 200-move per second machine to 120,000 moves per second by 1980. This fast machine used 1700 chips and did all of the work necessary to play top class chess. Earlier versions had used a PDP 11 as a host but the 1980 version of Belle did everything and won three ACM computer chess championships (1980, 81 and 82).

It also made history in being the first program to be awarded the title of master (US). The Fredkin Foundation awarded Belle's creators with a prize of $5000 for the first software chess master.

Thompson even managed to get the rules of chess changed! The 50-move rule said that after 50 moves in which no pawn advanced and no piece was captured the game should be declared a stalemate. As the result of using his endgame database to analyse simple endings he managed to show that there were games that could be won if allowed to go on beyond the 50 moves. As a result the 50-move rule was changed - but then found to be unworkable and so changed back!

Lasting Legacy

Ritchie and Thompson can be considered as precursors of the personal computer programmers of the 80s - not driven by profit but by fun and enthusiasm for ideas.

In this video clip from the National Inventor's Hall of Fame, which explains how Unix is the forerunner of the modern day operating system, Ken Thompson states:

"Unix was built for me. I didn't build it as an operating system for other people, I built it to do games and do my stuff."

At the conclusion of the clip the narrator sums up:

Sometimes inventions come from an individual's pursuit to push the limits of existing technology for their own use. Often this pursuit ends up benefiting us all. 

Also appearing in the video is Brian Kernighan, co-author with Dennis Ritchie of the C language bible, "The C Programming Language" often simply referred to as "K&R".

 As well as having a book to promote it, C also had a song and here's a version that was posted to YouTube as a tribute to Dennis Ritchie shortly after his death in 2011: 

 Write in C is certainly a philosophy I endorse.

• Harry Fairhead is the author of Raspberry Pi IoT in C,  Micro:bit IoT in C and Fundamental C: Getting Closer to the Machine. He is currently working on  Applying C For The IoT With Linux which will; be published by  I/O Press as part of the I Programmer Library. 

Related Articles

Dennis Ritchie, co-creator of Unix and C, has died

Unix pioneers awarded Japan Prize

The Rise Of People Power - Computer languages in the 70's

Write in C - a tribute to Denis Ritchie

Brian Kernighan On C 

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