Science Museum visit, 2005

Difference Engine (640 x 427)

To my delight, the first thing I saw when I entered the exhibition was a real, full-size, operational Difference Engine. Of course, they had to put the thing inside a glass case, or people like me would've been all over it. I'd wanted to see this ever since taking a History of Computing class at university. Not a Babbage original — he never completed his — but a replica built by the museum according to Babbage's plans, and with the bugs fixed.

Difference Engine closeup (640 x 427)

The inconvenience of flash glare didn't put me off taking far too many photos.

Another Difference Engine closeup (640 x 427)

Precisely-machined brass components.

Difference Engine, end-on (427 x 640)

Whoa, careful with those reflections.

Difference Engine, low shot (640 x 427)

I had to lie on the floor to take this one; I like shots from odd angles. Loads of reflection on the glass, but not a bad picture.

Difference Engine under construction (640 x 427)

A second replica being constructed by the museum.

Partial prototype of the Analytical Engine (640 x 427)

Babbage abandoned the Difference Engine in order to concentrate on the more ambition Analytical Engine, his plan for a mechanical, general-purpose programmable computer. It was never completed, although partial prototypes like this one were built.

Analytical Engine punched cards (427 x 640)

Examples of the punched cards on which Analytical Engine programs would have been entered.

Ferranti Pegasus (640 x 427)

Flash forward to the 1950s, when valve computers were the state of the art. The Science Museum has a Ferranti Pegasus computer, probably the last surviving operational valve computer. These beasts were among the first commercial computers, sold to businesses and operable by office staff. They cost around £45,000, which even today is a lot, but back then would've bought 40 houses.

DEC PDP-8 (427 x 640)

The first minicomputer. Not very "mini" by modern standards, but back in 1965, it was a revolution in compact computers. It operated on bytes of 12 bits in length, having been built before the 8-bit byte became standardized. It had 4096 bytes of memory, was clocked at 1MHz, and consumed 780W of power.

Core memory (640 x 427)

A lattice of tiny ceramic rings storing data magnetically, used in computers such as the PDP-8. Core memory's legacy lives on in computing terms such as "core dump".

Sinclair Executive calculator (427 x 640)

The first pocket calculator. Gotta love Sinclair kit from any era.