They were used throughout the 1930s, 40s and even the 1950s to perform all sorts of difficult computing tasks — to create artillery firing tables, for example, and to calculate soil erosion. However, the only original, complete Differential Analyser left in the world happens to be the one that helped Barnes Wallis design his famous bouncing bombs. They were the ones used in the Dam Busters attack on German hydro electric dams, in the Ruhr Valley, during World War II.
That machine was bought for £100 and came to New Zealand around 1950. Ironically, it was used to build the Benmore Hydro Dam and by the Department of Scientific and Industrial Research, to calculate rabbit populations. It then languished for years at Wellington Polytechnic before finding its way to the Museum of Transport and Technology in the 1970s, where it has been restored and is on display as a lead exhibit in the museum’s “Machines that Count” exhibition.
MOTAT’s Differential Analyser was built by J B Bratt at Cambridge University in 1935, largely from Meccano components. It is known as Meccano Differential Analyser No. 2.
Covering a base of three or four square metres, MOTAT’s machine is a complex arrangement of cogs, string and chains, used to drive a plotter (pictured). According to an article by William Irwin, in the New Zealand Federation of Meccano Modellers Magazine (which features other curious articles, such as "You, divorce and Meccano"), the machine qualifies as a true computer because it is programmable. The function, or calculations, produced can be changed by changing the arrangement of cogs and wheels and gears.
Speaking of the analogue family of calculators, Irwin wrote: “These devices usually perform one function only. When an analogue device can be ‘programmed’ in some way to perform different functions at different times, it can be called an analogue computer. The Differential Analyser is such a computer as it can be set up in different configurations, i.e. ‘programmed’, to suit a particular problem.”
MOTAT’s exhibition, sponsored by the ASB bank, is small but full of interest and surprises and, for people of a certain age, memories as well. Apart from four machines, the exhibit is largely made up from the private collection of Aucklander John Pratt, whose day job is business development manager for a local IT company. He has written a soon-to-be-published book of the same title as the exhibition.
Pratt was trying to write an essay about the Macintosh turning 20 when he became inspired, by errors he read during his research, to expand his project. He began collecting machines and planning the exhibition towards the end of 2001.
Computers on display range from machines such as the Analyser and census machines, the earliest punch-card digital computers, a grand IBM System 360 (also recently restored by volunteers), and more familiar PC-like devices.
“When New Zealand had two computers, that was one of them,” Pratt says of the System 360 on display. The machine is one of Pratt’s favourites, along with the Macintosh IIfx, which he describes as “blisteringly fast”.
One machine, which looks like a mainframe but has the heart of all modern PCs, is a 1973 Data General MicroNOVA. This computer and the company that made it originated with Edson deCastro bailing out of Digital Equipment to pursue his dream of building a 16-bit computer on a single board.
Data General was founded in 1968 and launched the first Nova in 1969. The large single board allowed for mass production, reduced wiring and improved reliability. The design, including a dedicated I/O bus, was highly influential, inspiring, in part, the Apple I and Xerox Alto. According to Wikipedia, 50,000 were sold to science labs and for other applications.
Pratt says Steve Wozniak, the Mac’s designer, was known to have posters of the DG Nova on his wall.
In addition to the machines, the MOTAT exhibit features highly educational panels, as well as write-ups about IT innovators through the years. Although it’s a small exhibit, one can easily spend an hour or more enjoying it. And the Differential Analyser makes it a must-see.
• A podcast interview with John Pratt is available here.
Former Bletchley Park code-breaker, Professor Donald Michie, 84, and his ex-wife, an eminent geneticist, were killed in a car crash last week.
UK technology site The Register reports that Michie was an artificial intelligence researcher who worked with mathematician Alan Turing at UK the code-breaking centre, Bletchley Park, during the World War II. Turing is considered one of the founders of modern computing and provided the definition of artificial intelligence.
Michie’s contributed to cracking a German teleprinter code, despite never having seen the machine that generated it. And it was at Bletchley Park that Michie became interested in machine intelligence. He studied medicine and worked in zoology after the war, but later returned to programming, establishing the University of Edinburgh’s Experimental Programming Unit and, later on, the Department of Machine Intelligence and Perception.