As I point out now and then, Colossus was not a computer. It was a key-tester, like a Bitcoin miner. Here's the block diagram of Colossus.[1]

Before there were general-purpose stored program digital computers, there were many special-purpose computing devices. They checked some, but not all, of those boxes.

- IBM had electronic arithmetic in test before WWII, but that went on hold during the war. Mechanical arithmetic worked fine, although slowly, and by 1939, Columbia University and IBM had something that looked vaguely like a programmable computer, built from IBM tabulator parts.

- The G.P.O. (the UK's post office and telephony provider) had been fooling around with electronic switching since 1934. That's where Tommy Flowers, who designed the electronics of Colossus, came from.[2] He had a tough life. After the war, he wanted to get into computers, but couldn't get funding because he couldn't talk about what he'd done for security reasons.

- Memory was the big problem. Colossus just had some registers, built from tubes. And plugboards, the ROM technology of the 1930s and 1940s. Useful memory devices were all post-war. Needed storage to get to stored program computers.

[1] https://www.researchgate.net/figure/Logical-architecture-of-...

[2] https://en.wikipedia.org/wiki/Tommy_Flowers

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gerdesj 8 days ago | parent [-]

"Colossus was not a computer. It was a key-tester,"

The original definition of computer was basically a person wot computes (analyzes data and performs arithmetic and so on). That would have mostly involved pencil and paper, fag packets and napkins. IT co-opted the term for their devices, many years later.

What is your issue with Colossus performing automated computations/analysis given some inputs of some sort and hence being described as a computer?

One of the earliest modern day IT related truisms is "garbage in/garbage out" - that dates back to at least getting the clipper out on the cards. Can that notion be applied to Colossus or rather is Colossus the sort of device that gi/go might refer to?

What exactly is a computer?

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Spooky23 8 days ago | parent [-]

I think the gp was confused with other devices. Colossus was indeed a computer by most definitions. I think the poster winced it up with the Bombe or other systems - not surprising because colossus wasn’t really known for many years. (It was secret into the 1970s iirc)

Other devices would calculate but not store instructions. The common ones you see are the fire directors on naval ships, which were analog “computers”, but single purpose.

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Animats 7 days ago | parent [-]

By "computer" I mean what we call a computer today - a stored program general purpose electronic digital computer.

There were many early machines which checked some, but not all, of those boxes. IBM's electronic multiplier. The Harvard Mark I. The SSEC. Colossus. Reservisor. Western Electric Plan 55-A. General Railway Signal's NX. The Bell Labs Complex Calculator. The Automatic Odds option for racetrack totalizators. The Mathatron. All of those machines did something that resembled computation.

The late 1940s, 1950s, and 1960s were full of strange special-purpose electronic digital hardware that didn't quite make it to a computer, because the parts count to get to a general purpose machine was too high.

Then came microprocessors, and it became cheaper to use general purpose microprocessors in dedicated applications. Now all those weird machines are forgotten.

Here's a brochure from Teleregister, which built custom special purpose systems for railroads, the military, airlines, stock exchanges, and such, from before WWII into the 1960s. There's no computer in those things, but a lot of electronics.

	▲	adrian_b 7 days ago \| parent [-]
		The Harvard Mark I and its successors, and especially the IBM SSEC were "stored program general purpose computers". Mark I was an electro-mechanical computer, while SSEC was hybrid, including both electro-mechanical parts and parts with vacuum tubes. For a few years, IBM's SSEC was the world's most powerful "supercomputer", and it has solved a great number of diverse problems. SSEC had some advanced features that have been introduced in fully electronic computers only about a decade later, e.g. pipelined instruction execution (to compensate for its slow circuits). What you mean is that none of your examples was a von Neumann computer, i.e. where there is a common memory for program storage and data storage, enabling the computer to create or modify programs by itself. Obviously the common memory was an essential element for the evolution of electronic computers, enabling many features that were impossible when the programs were stored separately, on a ROM such as punched tape. However, saying just "stored program" also covers the case when the program is stored in a separate ROM, as it may still be the case for a microcontroller, though nowadays most of them store the program in an alterable flash memory.