Early Computing (1600’s)

In the 1600’s a mechanical, analogue computing device called the slide ruler was invented. Slide rulers were continually improved and were eventually able to calculate logarithms, trigonometric functions, squares, cubes and their roots, and some other complicated functions.

In addition to the slide ruler the term was often used to mean a person who performed mathematical calculations such as:

• Compiling mathematical tables

• Calculating the movements of celestial bodies for astronomers or astrologers

• Working out trajectories (flight paths) of missiles for the army

Charles Babbage (1822, 1830)

In 1822, Charles Babbage designed The Difference Engine, it was a mechanical calculator that could solve polynomial functions. The difference was not considered a computer as it was not a general-purpose machine.

Short after 1830, Babbage started designing The Difference Engines Successor, The Analytical Engine. The Analytical Engine was designed to carry out general purpose computations on data stored on punch cards. However, due to a lack of funding the Analytical Engine was never built.

Ada LoveLace

Even though The Analytical Engine was never built, Ada Lovelace (1815 – 1852) realised that the Analytical Engine could be used for more than just simple calculations. She believed it could be programmed to do general purpose computing.

Ada Lovelace wrote programs for the Analytical Engine; she also created the first algorithm to be carried out by a machine.

Alan Turing and The Turing Machine (1936)

In 1936, Alan Turing described a mathematical model of computation, which he called an a-machine (automatic machine) which later became known as a Turing Machine. A Turing Machine can perform any computation that a real computer can.

Turing machines are important as they provide a relatively simple way to model general and powerful computational concepts and programs.

Note: The Turing Machine was a logical computational construct but not a real computer.

Electromechanical Computers (1940’s, 1941)

In the 1940’s, Electromechanical computers, using electrical switches to move mechanical parts, were developed.

The electromechanical Z3, developed in Germany in 1941, was the first digital, programmable computer to be built. The Z3 used Binary numbers, this reduced complexity compared to Babbage’s machines which used decimal numbers.

Vacuum Tubes (1940’s onwards)

Vacuum tubes are electrical devices that control the flow of electricity. They look like lightbulbs and are of a similar size; or often bigger.

The development of vacuum tubes led to the rapid growth of electronic devices from the 1940’s onwards including radio, television, and computers based on vacuum tube technology

Impact of World War II and Bletchley Park (1939 – 1945)

The second world war saw an increase in government spending on computer and related devices. Code breaking became a critical challenge facing the British government and their allies. A top-secret operation was set up by the allies at a country mansion called Bletchley Park.

Alan Turing was a key figure at Bletchley Park. Along with others he used electromechanical devices known as bombes to crack Nazi codes created by Enigma machines.

The intelligence collected from Bletchley Park shortened the year by up to two years according to many historians

Both Enigma machines and Bombes were not considered general purpose computers as they were designed to do only one thing, nonetheless they advanced many of the technologies required to jump-start the era of modern computing, much of which has taken place since WWII

Additionally, the first digital, programmable computer was Colossus, which was installed at Bletchley Park. However, Colossus was used specifically for code breaking and was therefore not considered to be general purpose.

ENIAC (1946)

In 1946, the first electronic, digital, programmable, general-purpose computer was invented it was named ENIAC. An Irish woman named Kathleen McNulty was one of the first programmers of ENIAC

Many of the first computers ended in “AC” as prior to the electronic computer age, people were referred to as computers if they did calculations, so computer names ended in “AC” or automatic computer.

With time, the word computer came to mean the machine, not a person. These machines, all-electronic and based on vacuum tubes, became known as the first generation of computers.