Happy 40th Birthday HP-65

First pocket programmable calculator (Photo credit: Wikipedia)

Two years ago we celebrated the fortieth birthday of the HP-35, the first mass-produced, pocket-sized, scientific calculator.

Today marks the fortieth birthday of its younger sibling, the HP-65, released on 17 January 1974. This was the world's first programmable calculator.

The first programmable calculators were introduced in the mid-1960s by Mathatronics and Casio, but these machines were very heavy and expensive.

So the miniaturisation involved in the HP-65 was a breakthrough. Bill Hewlett is supposed to have insisted that the calculator should fit in his shirt pocket and this was partly achieved with the tapered body.

The HP-65 had a capacity of 100 instructions, and could store and retrieve programs with a built-in magnetic card reader. The magnetic program cards were fed in at the thick end of the calculator under the LED display.

Examples for programs provided with the calculator included algorithms for hundreds of applications, including the solutions of differential equations, stock price estimation and statistical functions.