Editor’s note: This is a guest blog by Peter Zawistowski, who wanted us to know that this is a 70-year-old computer that is programmable and digital.
The National Museum of Computing, located at Bletchley Park, celebrated the 70th anniversary of Colossus, the first partially programmable electronic computer. Colossus went into service on February 1944, used for code breaking and the deciphering of Lorenz-encrypted communications used between Hitler and his generals.
It was designed by a single British telephone engineer, Tommy Flowers. So incredible are the statics of Colossus Mark 1. Its size, 7 feet high by 17 feet by 11 feet. It contained 1,500 vacuum tubes. The next version, known as Colossus Mark 2, had 2,500 tubes of which 501 were thyraton switches. The Mark 2 also contained nearly 4.5 miles of wiring, roughly 10,000 plus resistors, and so many other components. It weighed about 11,000 pounds and used 8 kW of power.
The Mark 1 began operation on February 5, 1944. The Mark 2 unit replaced it in June of 1944, just in time for D-Day invasion. One of the early deciphered messages allowed the Allies to know that Hitler had swallowed the bait for a false landing at Calais on D-Day, giving the Allies a decisive advantage. This Mark 2 version was easier to program and was five times faster than the Mark 1. By the end of the war, nine Colossus Mark 2 units had been built. The original Mark 1 was converted into a Mark 2, making ten Mark 2 units delivered and operating.
The American built ENIAC received the credit of being the first programmable digital computer. The National Security Agency had released some Freedom of Information Act (FOIA) information in the late 1970s that had shown that Colossus had beaten ENIAC by two years. Note that Colossus was a partially programmable computer. It was not a general purpose machine, but was designed for a specific cryptanalytic task. ENIAC was the first fully programmable digital electronic computer.
The Colossus computers, hardware, and documentation were classified from the inception and remained so long after the war ended. Winston Churchill specifically ordered the destruction of most of the Colossus machines into “pieces no larger than a man's hand.” Tommy Flowers, the designer of Colossus, was instructed to burn all the records, which he did. Some components were used for training purposes. In 1960, the remaining two Colossus machines were disassembled and stored. The need for these machines disappeared in the early 1960s as digital transmission and all-digital encryption became widespread.
Using eight photographs of Colossus and a few diagrams kept hidden or stored by engineers, the project of rebuilding a fully functioning Colossus began. Tony Sale, along with engineers who originally worked on the project, along with many volunteer technicians and engineers labored for years on the project. November 15, 2007, the rebuilt and fully functioning Colossus Mark 2 was unveiled to the public at the National Museum of Computing at Bletchley Park. A new and extended Colossus Gallery opened on March 6, 2012. The new gallery allows visitors to the museum to walk around the huge machine.