Designed by the legendary German engineer Konrad Zuse, the Z4 was a follow-up to its pioneering predecessor, the Z3 computer he built in 1941 (the world’s first programmable, automatic computing machine). The Z4 used about 4,000 watts of power and ran at approximately 40 Hz. It had 64 32-bit registers, the equivalent of 512 bytes of memory. One addition took 0.4 seconds.

Two generations of Colossus, the Mark 1 and Mark 2, were used by British codebreakers to decrypt coded German messages at the end of WW2. It processed 5,000 characters per second (it could process faster, but then the paper tapes holding the data would break). The existence of Colossus and other British codebreaking machines remained secret until the 1970s out of fear that widespread knowledge would encourage more efficient encryption algorithms.

When the ENIAC was announced in 1946 the press immediately started calling it a “Giant Brain”. ENIAC was the world’s first general-purpose electronic, digital computer and is probably the most famous of the ones included in this article. It weighed 27 tons. Among other things, ENIAC was used for calculations to create the hydrogen bomb. Programming the machine could take weeks, since after the program had been figured out on paper you first had to manipulate the various switches and cables that controlled the programming and then follow that with verification and debugging.

The Whirlwind was the first computer to use video displays for output. The first version had 512 bytes of main memory and could do 20,000 instructions per second, although a switch to a different kind of memory later doubled its performance and made it the fastest computer of its time.

An acronym for UNIVersal Automatic Computer, the UNIVAC I was the first US-produced commercial computer. It was designed by the inventors of the ENIAC. A total of 46 systems were built and delivered. It weighed 13 tons (29,000 pounds), ran at 2.25 MHz and could perform 1,905 instructions per second. The UNIVAC I cost up to $1.5 million per system.

Short for the Wolverhampton Instrument for Teaching Computing from Harwell, the WITCH was also known as The Harwell Dekatron Computer. It was slow (a multiplication took 5-10 seconds), but this was justified by its ability to run long periods of time unattended. It could therefore be left on its own with a large amount of input data. At one point it was left running over the Christmas and New Year holiday and was still working when the staff came back 10 days later.

Pingdom being Swedish in origin, we had to include this Swedish computer from 1953. BESK stands for Binär Elektronisk SekvensKalkylator, which is Swedish for Binary Electronic Sequence Calculator. The main memory was 512 40-bit words, the equivalent of 2,560 byte. An addition could be performed in 56 microseconds, and a multiplication in 350 microseconds. For a short time, it was the world’s fastest computer. Small aside, “besk” means “bitter” (as in taste) in Swedish, but besk is also an alcoholic beverage from the south of Sweden. The name was a pun sneaked in by the computer’s creator, who had previously had the computer name COGNAC rejected by officials.

The IBM 702 had been announced as early as 1953, but the first production model wasn’t installed until 1955. It was a commercial computer that could be leased from IBM. The system could have a maximum of 11,000 7-bit characters of main memory, i.e., roughly 10 kilobytes. It could do 3,950 additions or subtractions per second, but multiplication and division were significantly slower.

The IBM Naval Ordnance Research Calculator was arguably the first supercomputer and was the most powerful computer of its time. It could perform 15,000 operations per second, and the first version had 2,000 64-bit words of main memory, roughly the equivalent of 16 kilobytes.

This computer is most famous for being the first commercial computer delivered with a hard disk drive. The hard disk drive could store a total of just under 5 MB and consisted of 50 24-inch diameter disks. The 305 RAMAC was one of the largest computers IBM ever built. (If you find ancient hard drives fascinating, check out our post about the history of computer data storage.)

The Bendix G-15 weighed 450 kg (950 lb) and cost around $60,000. It had 2,160 29-bit words of memory, the equivalent of about 7.6 kilobyte. The G-15 has sometimes been called the first personal computer, although there are disagreements about this. More than 400 were made.

The British computer Ferranti Pegasus was designed and built to be cheap and reliable. It had 5,120 40-bit words of memory, the equivalent of 25 kilobyte, plus 56 words (280 byte) of fast memory. A Pegasus 2 from 1959 is still operational at the Science Museum in London. It is the world’s oldest working digital computer.

A successor to the Whirlwind, based largely on the design of the never-realized the AN/FSQ-7 was developed by IBM in collaboration with the US Air Force to be used with the SAGE air defense system. It is sometimes incorrectly referred to as the Whirlwind II. One computer took up 2,000 sqm of floor space (roughly half an acre) and weighed 275 tons. They are the largest computers ever built (52 of them were made). The AN/FSQ-7 could perform about 75,000 instructions per second.

A typical IBM 7090 system cost $2.9 million and was designed for large-scale scientific and technological applications. Among other things, it was used by NASA to control space flights. A 7090 system is featured in the movie Dr. Strangelove. In 1961, a later version, the 7094, became the first computer ever to sing (the song “Daisy Bell”). This was the inspiration for a scene in 2001: A Space Odyssey.

The Polish AKAT-1 was the world’s first transistor-based differential analyzer, designed specifically to solve systems of differential equations. It was never mass produced due to the country’s policies at that time.

Never massproduced, the Datasaab D2 was a concept computer build in Sweden. It weighed “only” 200 kg and could be placed on a desktop. It held the equivalent of 15 kilobyte of memory and could perform 100,000 additions per second. It was a prototype designed to test the feasibility of computerized navigation aid in aircraft. Datasaab was the computer division of the aircraft manufacturer Saab, which made fighter jets for Sweden.

The name BRLESC is an acronym for Ballistic Research Laboratories Electronic Scientific Computer. It was, as its name suggest, designed primarily for scientific and military tasks. It could do five million operations per second and had 4096 72-bit words of memory, the equivalent of 36 kilobyte.

The Honeywell 200 and its successors were introduced to compete with affordable commercial computers from IBM (specifically the IBM 1401). The native assembly language used to program the Honeywell computer was named Easycoder. Yes, at that time, assembly language was considered easy to code in. Honeywell ran an ad campaign over several years that they called the Liberator, using various very creative sculptures made from computer parts (one example available here).

The transistor-based UNIVAC 1108 supported up to three CPUs and up to 262,144 36-bit words of memory (more than 1 MB). The memory used integrated circuits (quite rare at the time) instead of the thin film core memory used in its predecessor, the 1107.