The UK's largest public exhibition of slide rules has been unveiled at The National Museum of Computing at Bletchley Park.
The museum's latest exhibition celebrates the diversity of slide rules, which died out in the 1960s with the advent of electronic computers and calculators.
Curated by the UK Slide Rule Circle (UKSRC), the display of more than 40 British slide rules spans three centuries and shows the variety of shapes, sizes, materials, and purposes of this sophisticated calculating device.
The earliest exhibit is the wooden Gunter's Rule, first used in the mid 17th century by navigators and astronomers, and the most recent is a 1960s/70s Photographic Interpreters' slide rule made by Blundell Harling.
Colin Barnes, from UKSRC, said: "For 350 years the slide rule was the world's pre-eminent calculating device and its design needed remarkably little modification to maintain its dominance.
"They are marvellous pieces of engineering and craftsmanship and the display at The National Museum of Computing pays tribute to slide rule designers and users across the centuries."
The UKSRC and TNMOC have published a ten-page booklet, A Brief History and Types of Slide Rule, available for £5 (including p&p) at www.tnmoc.org.