Introduced by Hewlett-Packard in 1974, the HP-65 calculator was the first handheld programmable calculator, with a built-in magnetic card reader/writer. In an article in the the Hewlett-Packard Journal in May 1974 it introduced the HP-65 as "This new computing device is a combination of electronic calculator and general-purpose small computer. It offers the convenience and easy operation of a calculator, but its programmability makes it versatile enough to fit the needs of a wide variety of disciplines, including science, engineering, finance, statistics, mathematics, navigation, medicine, surveying, and many others."

The HP-65's program memory had storage for up to 100 steps. Programs could be chained for those longer than 100 steps. Programs could be recorded on blank magnetic cards, or pre-programmed cards could also be purchased. In 1975 HP advertised that there were 15 'Application Pacs' available to purchase on top of the 'Standard Pac' which came with the calculator. There was also a HP-65 Users' Library, which contained programs contributed by HP-65 users, which contained over 4000 programs. The calculator had 51 built-in mathematical functions and data-manipulation operations, a four-register operational stack, nine addressable data registers, and five user-definable keys.

Like all Hewlett-Packard calculators of the era, and most since, the HP-65 used reverse Polish notation (RPN). The HP-65 had a 10+2 digit LED display. It was powered by three AA batteries, or AC power supply.

The HP-65 cost $795. In February 1975 it was on sale for £442.80 (including VAT) in the UK.

In 1975 the HP-65 was taken into space for use on the Apollo-Soyuz Test Project flight. The Apollo astronauts used the calculator to calculate critical course-correction manoeuvres. The programs, which had almost 1000 steps, were written by NASA scientists before the mission, and they were then recorded onto the magnetic cards so they could be run automatically when needed. The HP-65 also served as a backup for Apollo's on-board computer.

Our calculator was kindly donated by Francis Hookham.

Manufacturer: Hewlett-Packard
Date: 1975

This exhibit has a reference ID of CH31306. Please quote this reference ID in any communication with the Centre for Computing History.

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