History of computing

Until about the middle of the 20th century, the word computer generally meant a person who computes. The earliest reference to the term, in 1631, comes from the French word with the same meaning, derived from the Latin word computare meaning "to count, to sum up." The word is formed from two roots: com- meaning "with", and +putare meaning "to reckon" (originally "to prune.") According to the first definition given by the Oxford English Dictionary, a computer is: "One who computes; a calculator, reckoner; spec. a person employed to make calculations in an observatory, in surveying, etc."

Early devices

Long before the arrival of mechanical computing, ancient civilizations devised various methods to calculate and keep track of numbers.

• Salamis Tablet: A very early counting device, the Salamis Tablet, was used by the Babylonians to track numbers in their society.

• Abacus: The abacus, a mechanical aid to performing arithmetic, dates back many centuries and is still in use in various forms.

Mechanical computing

• Da Vinci: On 13 February 1967, the "Codex Madrid", written by Leonardo Da Vinci, was discovered in the National Library of Spain in Madrid by Dr. Roberto Guatelli. Inside the Codex Madrid was a drawing for an elaborate mechanical computational device. Guatelli noticed that a similar construct appeared in Da Vinci's "Codex Atlanticus". A prototype of this machine was created in 1968, and was observed that it exhibited traits that of a ratio machine. One revolution of the first shaft(10^1) invoked ten revolutions of the second(10^2), repeating until the last shaft which rotated at a rate of ten to the power of 13. Whether this was a true computational device was under some debate. Previously been displayed at IBM, the exhibit was removed due to a nonconsensus, and is presumed to be in one of IBM's storage facilities.

• Pascaline: An early mechanical computational device is the Pascaline, created by Blaise Pascal circa 1642. The Pascaline performed simple addition and subtraction. The concept of the pascaline came about from the carrying of places by gear rotation. Functionally, the machine worked by increasing values on a single cog, which ranged from values 0 to 9. Upon the next rotation, a series of cogs would rotate the next gear over one iteration to read 1 while the first cog would reset back to 0.

• Difference Engine and Analytical Engine: It would take Charles Babbage, born on December 26, 1791 and inducted as a Fellow of the Royal Society to develop the first real successful automatic calculating machine. In 1821, Babbage developed the Difference Engine No. 1, which was a functional machine designed to compile mathematical tables based on polynomial caculation.. The difference engine's physical algorithm was based on a mathematical technique known as the Method of Differences, which Babbage contributed work on. Unfortunately only a fragment of the machine would ever come to fruitition due to various financial disputes and accusations of fund mismanagement from the British Government. More importantly, the machine was never fully developed due to Babbage's realization of a more improved machine called the Analytical Engine. Functionally, the Analytical Engine was capable of various algorithmic operations that were broken down into basic algebraic operations. Two cards would be used to program the system: the first would detail what operations were required to be performed, and the second would contain the values to be operated on. In this sense, the Analytical Machine was much like a computer, having an input(the algorithm as described on a card), a processor(the machine), an output(the result), and memory(using a storage method--the cards themselves). Like the pascaline, both the Difference and Analytical Engines relied on series of cogs and gears to compute values.

• Punched card input:Herman Hollerith was born on February 29, 1860 in New York. In 1875 Hollerith attended the City College of New York, he graduated from the Columbia School of Mines in 1879 with an engineering degree. After graduating, Hollerith took up work with the United States Census Bureau, and was appointed Chief Special Agent. Hollerith's contribution to computing was inspired by his work at the USCB, especially from Dr. John Shaw Billings who suggested that there should be a way to process the large amount of census data by some mechcanical means. In 1884, Hollerith worked to develop a way to tabulate census information through the use of punch cards. Eventually, he recognized that cards could be used as storage medium for census data. His experiments lead to a process by where a pin would go through a hole in the card to complete an electrical circuit. His system by which cards could be read and tabulated on a mechanical counter through a circuit completion was called the Hollerith Electric Tabulating System. By 1890, the machines were improved so that a simple keyboard could be used to tabulate data instead of entry by hand.

Electrical computing

Boolean algebra, a mathematical system known for centuries, was destined to become the basis for describing digital logic circuits used to build electronic computers. Use of "switching algebra", as boolean algebra came to be known by computer designers, to describe logic circuits was a major conceptual breakthrough first documented by Claude Shannon (1916-2001) in his 1938 MIT master's thesis. Shannon's thesis created quite a stir in the world of electronics at the time of its appearance, though Shannon is better known for the seminal contributions he made later towards the burgeoning field of information theory.

The development of an almost totally-autonomous system came about on August 7, 1944, when the IBM Automated Sequence Controlled Calculator(ASCC) was shipped and assembled that year to Harvard University, thereby earning its more popular name, the Harvard Mk I. It was widely accepted that the Harvard Mark I was the first electromechanical automatic digital calculator, until it was discovered that German engineer Konrad Zuse had developed the Z3 in 1941. Unfortunately this fact was discovered shortly after the end of World War II. All photographs of the system were destroyed by allied raids throughout the war. Consequently, later in life, Zuse would rebuild all of his machines; the Z1, originally created between 1936 and 1938; the Z2, created sometime between 1936 and 1939; and the Z3, contructed from 1939 to 1941. German patent applications provide evidence of Zuse's development of a mechanical memory device in 1936, used in the Z1. The most significant advancements from Zuse's constructions' were the implementation of the binary numeral system and other advanced design concepts.

Having survived the war, Zuse built another computer in Switzerland, and later was the first designer to propose pipelining the computations of a computer processor. In 1949, Zuse formed Zuse KG, where he worked until 1966.

Meanwhile, in America, the idea for the Harvard Mark I automatic digital calcuator was conceived by Howard H. Aiken, then a graduate student from Harvard University with a Ph. D. in theoretical physics. The Mark I had a total of 78 adding machines linked together containing 765,000 parts; 3,300 electrical relays; over 500 miles of wire and more than 175,000 connections. The machine accepted input via punched cards, paper tape or through manually set switches to indicate the values to be processed. The output was generated by an electric typewriter or punched into additional cards. Multiple operations were programmed into the machine with perforated tape. Physically the machine performed calculations through a series of small gears, electro-mechanical counter wheels, and switches. The successor to the Mark I, the Mark II, would still used relays, but also featured an electrical memory and a system of 'constant' values that were referenced during run-time.

Between 1937 and 1942, Dr. John V. Atanasoff and graduate student Clifford Berry, of Iowa State University, worked on a prototype electronic computer that introduced key design ideas. Some of these ideas may have been communicated to John Mauchly, who assisted in the development of the ENIAC. Mauchly and J. Presper Eckert of the University of Pennsylvania proposed the ENIAC (Electrical Numerical Integrator And Computer) to the U.S. Army Ordnance Department's Ballistics Research Laboratory in 1943, and then served as its main designers until construction was finished in 1946. It was a military project justified by a need to compute ballistic trajectories, and was one of the earliest general-purpose, programmable electronic computers.

ENIAC performed its computations using the decimal numeral system, instead of the binary numeral system used by most subsequent digital computers, although the ENIAC was not yet able to store its own program in memory. It had to be programmed by setting switches on function tables and by changing the wiring and considerable human effort was required to reprogram it.

Throughout the war, the British and Americans developed computers under secret military programs. The Colossus project produced a series of about ten electronic computers used by British codebreakers to read encrypted German messages during World War II. The first Colossus prototype was initially completed by engineer Tommy Flowers in 1943 at the Post Office Research Station, Dollis Hill, with input from mathematician Max Newman and a few others. It used the binary numeral system for calculations, utilizing vacuum tubes and very fast optical punch tape readers. By 1944, the project moved to Bletchley Park and lasted until the end of the war. Shortly after, in 1946, Winston Churchill gave official orders to have the machines destroyed.

The designers of ENIAC jointly formed the Eckert-Mauchly Computer Corporation in 1946, which was bought by Remington Rand in 1950. In 1951, this company delivered the first U. S. commercial computer, called the UNIVAC, to the United States Census Bureau. It was a stored-program computer, like its non-commercial sister the EDVAC. Competing fiercely with IBM, the company eventually built 46 of the earliest commercial computer systems.

Postwar computing

The EDVAC ((Electronic Discrete Variable Automatic Computer) was a successor to ENIAC, intended to resolve some design difficulties. It was the first internally stored program computer to be built, a major improvement over the ENIAC. The U.S. Army Ballistics Research Laboratory funded the development of EDVAC, and it was built at the Aberdeen Proving Ground by the University of Pennsylvania, including ENIAC designers Eckert & Mauchly. They were joined on the EDVAC design by John von Neumann and some others.

The EDVAC realized the stored-program concept first published in von Neumann's 1945 report First Draft of a Report on the EDVAC.

Although its design predates the UNIVAC, the EDVAC did not become fully operational until 1952.

Famous people in history of computing

For now, see this list of people who made conceptual breakthroughs in computer science.

Famous concepts in history of computing

For now, see this list of seminal concepts in computer science.