Category Archives: Computers

The Small Scale Experimental Machine, the Baby, was built in 1947 and 1948 to subject the Williams-Kilburn Tube to a searching test of its speed and reliability. It also demonstrated the feasibility and potential of a stored-program computer. It was quickly decided to press ahead to develop a realistic useable computer based on the same principles. As early as October 1948 a request was made from the government to Ferranti Ltd. to manufacture a commercial machine to Prof. Williams’ specification.

By the Autumn of 1949 the engineering team had produced a working computer with a larger store and more powerful instruction set, and with the addition of a hardware multiplier, address modification registers (“B-lines”), a two-level store comprising a set of Williams-Kilburn Tubes and a Magnetic Drum Store, and input/output from/to 5-hole paper-tape teleprinter. To improve reliability for the CRT store they were now using CRTs specially manufactured for them by GEC (with the particular assistance of Laurie Allard). With a programmable fast drum connected as well, this was the first working two-level store.

The BINAC was a bit serial binary computer designed by Eckert-Mauchly. It had a 512-word acoustic mercury delay line memory divided into 16 channels each holding 32 words of 31 bits with an additional 11-bit space between words to allow for circuit delays in switching. The clock rate was 4.25mh which yielded a word time of about 10 microseconds. The actual instruction execution rate was dominated by the access time for instructions and data and would have averaged about 3000-4000 instructions per second, unless minimum latency programming was employed. Each BINAC word held two instructions. Each instruction had a five bit operation code and a three octal digit address. All operands were 31-bit words. Arithmetic was two’s complement and there were single-bit arithmetic right and left shift instructions as well as addition, subtraction, multiplication and division. There were no logical instructions and no subroutine calls. Jump on negative was the only conditional instruction. The BINAC was the first dual processor computer, and was built for the U.S. Navy.

The University of Pennsylvania inaugurated the ENIAC (Electronic Numerical Integrator And Computer) on Feb 16th 1946. It is an electronic computer many times more complex than any previous. Eckert and Mauchly formulated the plans for the machine in 1943, and it runs its first trials in Nov 1945. It’s structure covers over 650 square feet, and had 300 neon lights. Built into a basement room, it had vacuum tubes that produced 150 kw of heat. This required the use of two twenty horsepower fans to help keep it cool! Everything about the machine is large, except the time it takes to compute. Performing 5,000 calculations per second, it’s a thousand times faster than the Harvard Mark I.

Developed and built by the U.S. Army for the Ballistics Research Laboratory, it was called Project PX and was commisioned on May 17th, 1943. It was built at the Moore School of Electrical Engineering at a cost of $500,000. It sported 17,468 vacuum tubes, 7,200 crystal diodes, 1,500 relays, 70,000 resistors, 10,000 capacitors and around 5 million hand-soldered joints. The ENIAC had to be rewired to run a new program. It operated continuously until October, 1955.

Howard Aiken and Grace Hopper designed the MARK series of computers at Harvard University. The MARK series began with the Mark I in 1944. Imagine a giant roomful of noisy, clicking metal parts, 55 feet long and 8 feet high. The 5-ton device contained almost 760,000 separate pieces. It was used by the US Navy for gunnery and ballistic calculations.

The computer, controlled by pre-punched paper tape, could carry out addition, subtraction, multiplication, division and reference to previous results. It had special subroutines for logarithms and trigonometric functions and used 23 decimal place numbers. Data was stored and counted mechanically using 3000 decimal storage wheels, 1400 rotary dial switches, and 500 miles of wire. Its electromagnetic relays classified the machine as a relay computer. All output was displayed on an electric typewriter. By today’s standards, the Mark II was slow, requiring 3-5 seconds for a multiplication operation.

Designed by Howard Aiken and IBM, the Harvard Mark I debuts to the public in a ceremony at Harvard University. It was powered by a five horsepower electric motor, weighed five tons, and measured two feet by fifty one feet. It was slower than other machines being developed at the time because it was not electronic.  The Mark I was originally known as the ASCC, and was described as sounding like a roomful of ladies knitting.  It captured the media and public attention, encased in glass and stainless steel. Intend for use as a general purpose calculating device, it winds up being used exclusively by the U.S. Navy for ballistics testing & calculation. It was later replaced by the Mark II.

 Considered the first electromechanical computers, they were created by Konrad Zuse in 1938. He began construction of the Z1 in 1936, setting out to make a computing machine with faster, more extensive calculating power than the existing desk calculators. Deciding on a binary system for greater calculating speed, he set the standard for it’s use in computing. The Z1 expressed the numbers using mechanical gates opened and closed by sliding plates. It was powered by electricity, and he intended to replace the gears and axles of desk calculators.

The Z1 read instructions from strips of film punched with binary, and functioned moderately but had trouble routing electrical signals from one location to another within itself. It’s significance was that it was the first freely programmable, binary based machine in the world. Zuse solved this problem in the Z2 by using an electromagnetic system that replaced the mechanical plates. He discovers this method is an excellent way to express binary numbers. Still not an impressive machine, it has potential and convinces the German Experimental Dynamics Institute to further fund Zuse’s projects. Later Zuse fled Germany with his machines, and the Z4 was born. It is the first working freely programmable, fully automatic machine. It was built with relays, and had a clock frequency of 5.33 Hz. The Harvard Mark I was considered the first until the discovery of the Z4 after the war.

In the last days of WWII the Z4 was transported under adventurous circumstances via truck and horse-drawn cart from Berlin to the Allgäu. Hidden in a stable, it remained undiscovered until 1949.

Conceived by John Atanasoff in 1937, the Atanasoff-Berry (or ABC) Computer was one of the first modern electronic digital computers. Designed to solve linear equations, it was tested in 1942. It formed the foundation of many modern computing concepts including binary arithmetic and electronic switching. Work was discontinued in the early 1940s due to Atanasoff moving on to working on assignments for the War Department during World War II.

Atanasoff created many of the key functions of the ABC during a nighttime drive in the winter of 1937. Such ideas as parallel processing and a separation of memory and computing functions was the outcome of this historic car ride. Over the following year mechanical and logic design was worked out and a grant was awarded to build a prototype. Together with graduate student Clifford Berry, Atanasoff built the machine in the basement of the Iowa State college physics building from 1939-1942.

The prototype was demonstrated in Oct.,1939. It weighed a whopping seven hundred pounds and was 800 square feet. With 1 mile of wire and 280 vacuum tubes, it was the size of an office desk. In comparison to other machines before and after, it was not programmable and was built for a particular purpose. The machine was not recognized for many years, causing the ENIAC to be considered the first modern computer in the U.S. until 1973 when a U.S. District Court ruled the ENIAC patent was submitted after the creation of the ABC.

Designed by the Department of Communications of the British Foreign Office, the Colossus was an entirely electronic deciphering machine. Driven by a need to break the codes being used by the Germans, who had their own electromechanical machine called Enigma creating them, they were built in secrecy and the first was completed in 1943.

By the end of the war there were 10 of them in operation, aiding the Allies in defeating Germany. Each Colossus contained hundreds of vacuum tubes and switches, and operated in binary. Reading incoming data off a punched tape, they had a single purpose, comparing Enigma codes with known codes and printing the results when a match was found. They were the first entirely electronic computing devices in the world.