The Colossus: A Historical View and A Consideration of the Influence on Modern Technology

Introduction

The Colossus was the name given to the machine which is widely considered as having been the world's first programmable electronic computer. It was designed in the early 1940's for use at Bletchley Park, the secret home of Britain's code-breaking activities during World War II and the birthplace of the UK Government Communications Headquarters. Colossus played a key part in the allied victory. Due to the top secret nature of the work at Bletchley Park, details of the work carried out at Bletchley Park were not released into the public domain until the 1970's. Subsequently, the historical significance of the Colossus has been realised to the extent that a replica of the machine has been rebuilt by some of the original engineers to demonstrate not only the colossal nature of the machine but also the enormous impact it had during the war and on advances in technology thereafter.

The Colossus At Work

Colossus Mk I was programmed by the use of plugboards and was installed on 8th December 1943 ready for use by the cryptanalysts at Bletchley Park. It was operated by the Women's Royal Naval Service (WRNS) staff stationed at Bletchley Park. Intercepted cipher text was punched onto five-bit channel paper tape and loaded into Colossus, which could read five thousand paper tape characters per second through it's optical tape reader. The operational machine speed was predicated on this tape reading speed. Colossus could process 100 Boolean calculations simultaneously across each of the five tape channels and a five character matrix – the five stream processing ability having been invented by Flowers. Colossus had no machine memory so consequently had to read the messages over and over again. It electronically recreated the patterns used on the originating cipher machine, and it was these patterns which could then be used to decipher the coded message. The machine itself was hard-wired and was programmed by means of switches within a large frame. It