History of computing

The history of computing is so complex that entire museums are now devoted to it. The desire for computers existed for a long time before the invention of the first electronic computer. People had hankered after mechanical devices to help with mathematical calculations, inventing the abacus, the slide rule, and a host of mechanical adding machines. But the electronic computer's rapid evolution forever changed science and technology, the military, and the business world, making its invention a milestone for humanity on a par with the invention of the printing press.

ENIAC was a milestone in computing history.

Originally, the term "computer" referred to a person who performed numerical calculations, often with the aid of a mechanical calculating device or analog computer. Examples of these early devices, the ancestors of the computer, included the abacus and the Antikythera mechanism, an ancient Greek device for calculating the movements of planets which dates from about 87 BC. The end of the Middle Ages saw a reinvigoration of European mathematics and engineering, and Wilhelm Schickard's 1623 device was the first of a number of mechanical calculators constructed by European engineers.

In 1801, Joseph Marie Jacquard made an improvement to existing loom designs that used a series of punched paper cards as a program to weave intricate patterns. The resulting Jacquard loom is not considered a true computer but it was an important step in the development of modern digital computers.

Charles Babbage was the first to conceptualize and design a fully programmable computer as early as 1820, but due to a combination of the limits of the technology of the time, limited finance, and an inability to resist tinkering with his design, the device was never actually constructed in his lifetime. By the end of the 19th century a number of technologies that would later prove useful in computing had appeared, such as the punch card and the vacuum tube, and large-scale automated data processing using punch cards was performed by tabulating machines designed by Hermann Hollerith.

During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated special-purpose analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation (they became increasingly rare after the development of the programmable digital computer). A succession of steadily more powerful and flexible computing devices were constructed in the 1930s and 1940s, gradually adding the key features of modern computers.

The use of digital electronics was introduced by Claude Shannon in 1937 in his thesis A Symbolic Analysis of Relay and Switching Circuits. Here he introduced switches for implementing logic and aritmethic. He came up with the idea while studying the relay circuits of Vannevar Bush's Differential Analyzer. This point marked the beginning of binary digital circuit design and the use of logic gates. Precursors of this idea were Almon Strowger, who patented a device containing a logic gate switch circuit, Nikola Tesla who filed for patents of devices containing logic gate circuits in 1898 (see List of Tesla patents), and Lee De Forest's modification, in 1907, who replaced relays with vacuum tubes.

Defining one point along this road as "the first digital electronic computer" is exceedingly difficult. On 12 May, 1941 Konrad Zuse completed his electromechanical Z3, being the first working machine featuring automatic binary arithmetic and feasible programmability (therefore the first digital operational programmable computer, although not electronic); other notable achievements include the Atanasoff-Berry Computer (shown working around Summer 1941), a special-purpose machine that used valve-driven (vacuum tube) computation, binary numbers, and regenerative memory; the secret British Colossus computer (demonstrated in 1943), which had limited programmability but demonstrated that a device using thousands of valves could be both made reliable and reprogrammed electronically; the Harvard Mark I, a large-scale electromechanical computer with limited programmability (shown working around 1944); the decimal-based American ENIAC (1946) — which was the first general purpose electronic computer, but originally had an inflexible architecture that meant reprogramming it essentially required it to be rewired.

The team who developed ENIAC, recognizing its flaws, came up with a far more flexible and elegant design, which has become known as the Von Neumann architecture (or "stored program architecture"). This stored program architecture became the basis for virtually all modern computers. A number of projects to develop computers based on the stored program architecture commenced in the mid to late-1940s; the first of these were completed in Britain. The first to be up and running was the Small-Scale Experimental Machine, but the EDSAC was perhaps the first practical version that was developed.

Valve (tube) driven computer designs were in use throughout the 1950s, but were eventually replaced with transistor-based computers, which were smaller, faster, cheaper, and much more reliable, thus allowing them to be commercially produced, in the 1960s. By the 1970s, the adoption of integrated circuit technology had enabled computers to be produced at a low enough cost to allow individuals to own personal computers.

One of the most significant advances in computer design and business adoption of computer technology was IBM's introduction of the System/360 mainframe series in 1964. This family of computers allowed organizations to migrate to more powerful systems and add features as needed without a total rewrite of their software base that had been a problem with previous computer offerings from both IBM and other competitors. The design of the System/360 would influence computer designs for decades to come.