Computer

• 1. Introduction

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  In a 1613 book called The Yong Mans Gleanings, the English writer Richard Brathwait wrote of "the truest computer of Times, and the best Arithmetician that euer breathed." He was not describing a machine. According to the Oxford English Dictionary, this is the first known use of the word computer, and it meant a person. For more than three centuries, a computer was someone who carried out calculations by hand. The word would not acquire its modern meaning until the middle of the 20th century. So how did a job title for human calculators become the name for a device that powers the Internet and links billions of users? How did machines that numbered only a few in the 1930s become so ubiquitous that they hide inside key fobs, microwave ovens, and remote controls? The answer runs through clay spheres buried in the Fertile Crescent, a writing doll built by a Swiss watchmaker, code-breakers at Bletchley Park, and a single chip the size of a coin.

• 2. Before Electricity

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  Calculi, small clay spheres and cones, were sealed inside hollow unbaked clay containers across the Fertile Crescent to represent counts of items, likely livestock or grains. These were among the earliest record-keeping aids, predating any machine by thousands of years. The Roman abacus was developed from devices used in Babylonia as early as 2400 BCE, and in a medieval European counting house a checkered cloth was laid on a table so markers could be moved according to rules to sum money. The Antikythera mechanism, believed by Derek J. de Solla Price to be the earliest known mechanical analog computer, was designed to calculate astronomical positions. Divers found it in 1901 in a wreck off the Greek island of Antikythera, between Kythera and Crete, and it has been dated to approximately 100 BCE. Devices of comparable complexity would not reappear until the fourteenth century, a gap of well over a thousand years. Abū Rayhān al-Bīrūnī invented the planisphere, a star chart, in the early 11th century, and around 1000 AD he built a mechanical geared lunisolar calendar astrolabe with a gear train. Abi Bakr of Isfahan, in Persia, made an astrolabe with a mechanical calendar computer and gear-wheels in 1235. Each of these instruments solved problems in spherical astronomy through physical models rather than written instructions. William Oughtred, an English clergyman, invented the slide rule around 1620 to 1630, shortly after the concept of the logarithm was published. This hand-operated analog computer handled multiplication and division, and later versions added scales for squares, cube roots, logarithms, and trigonometry. A version still survives in modern use: the E6B circular slide rule, used for time and distance calculations on light aircraft.

• 3. The Father Of The Computer

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  Charles Babbage, an English mechanical engineer and polymath, is considered the "father of the computer." He announced his difference engine in 1822, in a paper to the Royal Astronomical Society titled "Note on the application of machinery to the computation of astronomical and mathematical tables." By 1833 he realized a far more general design was possible, which he called the analytical engine. Punched cards were to feed both programs and data into Babbage's machine, the same method used to direct mechanical looms such as the Jacquard loom. For output it would have a printer, a curve plotter, and a bell, and it could even punch numbers onto cards to be read later. The engine would include an arithmetic logic unit, conditional branching and loops, and integrated memory, making it the first design for a general-purpose machine describable in modern terms as Turing-complete. All the parts for the machine had to be made by hand, a major problem for a device with thousands of components. The project was dissolved when the British Government ceased funding, and Babbage's drive to keep building ever more sophisticated designs outpaced what anyone could follow. His son, Henry Babbage, completed a simplified version of the analytical engine's computing unit, the mill, in 1888, and gave a successful demonstration of it computing tables in 1906.

• 4. From Relays To Vacuum Tubes

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  Claude Shannon's master's thesis of 1937 laid the foundations of digital computing through a single insight: Boolean algebra could analyze and synthesize switching circuits. That concept underlies all electronic digital computers. Around the same time, the United States Navy had developed the Torpedo Data Computer by 1938, an electromechanical analog machine for submarines that used trigonometry to fire at a moving target. Konrad Zuse, a German engineer, built the Z2 in Berlin in 1939, one of the earliest electromechanical relay computers. In 1941 he followed it with the Z3, the world's first working electromechanical programmable, fully automatic digital computer. The Z3 used 2000 relays and a 22-bit word length, ran at a clock frequency of about 5 to 10 Hz, and took its program from punched film while storing data in 64 words of memory. Zuse chose a binary system over decimal, which made his machines easier to build and potentially more reliable. Tommy Flowers, working at the Post Office Research Station in London, spent eleven months from early February 1943 building the first Colossus, commissioned by Max Newman to crack the German Lorenz SZ 40/42 machine. Colossus reached Bletchley Park on the 18th of January 1944 and attacked its first message on the 5th of February. It was the world's first electronic digital programmable computer, though it was not Turing-complete. Colossus Mark I held 1,500 thermionic valves, while Mark II ran on 2,400 valves and was five times faster. The ENIAC was the first electronic programmable computer built in the United States, and unlike Colossus it was Turing-complete. Built under John Mauchly and J. Presper Eckert at the University of Pennsylvania from 1943 to full operation at the end of 1945, it weighed 30 tons, drew 200 kilowatts, and contained over 18,000 vacuum tubes. It could add or subtract 5000 times a second, a thousand times faster than any other machine. Its six programmers, all women, were known collectively as the "ENIAC girls."

• 5. The Idea Of The Universal Machine

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  Alan Turing proposed the principle of the modern computer in his 1936 paper, On Computable Numbers. He described a simple device he called a "Universal Computing machine," now known as a universal Turing machine, and proved it could compute anything computable by executing instructions stored on tape. Von Neumann acknowledged that the central concept of the modern computer was due to this paper. Early computing machines had fixed programs, so changing a machine's function meant re-wiring and re-structuring it. The stored-program idea changed that by keeping a set of instructions in memory alongside the data. Turing joined the National Physical Laboratory in 1945 and wrote "Proposed Electronic Calculator," the first specification for such a device. That same year John von Neumann circulated his First Draft of a Report on the EDVAC. The Manchester Baby ran its first program on the 21st of June 1948, becoming the world's first stored-program computer. Frederic C. Williams, Tom Kilburn, and Geoff Tootill built it at the University of Manchester as a testbed for the Williams tube, the first random-access digital storage device. A 1998 retrospective called it "small and primitive," yet it held every element essential to a modern electronic computer. The Manchester Mark 1 grew out of the Baby and became the prototype for the Ferranti Mark 1, the world's first commercially available general-purpose computer, delivered to the University of Manchester in February 1951. Meanwhile the British catering company J. Lyons & Company decided in October 1947 to promote commercial computing, and its LEO I computer, modelled on the Cambridge EDSAC, ran the world's first routine office computer job in April 1951.

• 6. The Shrinking Switch

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  Julius Edgar Lilienfeld proposed the concept of a field-effect transistor in 1925, decades before one could be built. John Bardeen and Walter Brattain, working under William Shockley at Bell Labs, built the first working transistor, the point-contact transistor, in 1947, followed by Shockley's bipolar junction transistor in 1948. From 1955 onward transistors replaced vacuum tubes, giving rise to the second generation of computers, which were smaller, used less power, and ran far more reliably. A team led by Tom Kilburn at the University of Manchester had a transistorized machine, the first in the world, operational by 1953. It still relied on valves to generate its 125 kHz clock waveforms, so the title of first fully transistorized computer goes instead to the Harwell CADET of 1955, built at the Atomic Energy Research Establishment at Harwell. The metal-oxide-silicon field-effect transistor, or MOSFET, was invented at Bell Labs between 1955 and 1960. It was the first truly compact transistor that could be miniaturized and mass-produced, with high scalability, lower power consumption, and higher density than bipolar junction transistors. It also enabled MOS semiconductor memory, which replaced earlier magnetic-core memory, and it became the fundamental building block of digital electronics. Geoffrey W.A. Dummer, a radar scientist at the Royal Radar Establishment, gave the first public description of an integrated circuit on the 7th of May 1952 in Washington, D.C. The first working integrated circuits came from Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor. Kilby demonstrated his first working example on the 12th of September 1958, but his was a hybrid circuit with external wires. Noyce produced the first true monolithic chip, made of silicon and fabricated using the planar process developed by his colleague Jean Hoerni in early 1959.

• 7. From Microprocessor To Coin-Sized Computer

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  Federico Faggin developed the first silicon-gate MOS integrated circuit with self-aligned gates at Fairchild Semiconductor in 1968, building on the self-aligned gate transistor created by Robert Kerwin, Donald Klein, and John Sarace at Bell Labs in 1967. That technology made the microprocessor possible. The first single-chip microprocessor was the Intel 4004, designed by Faggin along with Ted Hoff, Masatoshi Shima, and Stanley Mazor at Intel. By the early 1970s, MOS technology could integrate more than 10,000 transistors on a single chip. Moore's law noted that transistor counts doubled every two years, and that pace drove the Digital Revolution of the late 20th and early 21st centuries. The microprocessor heralded an explosion in the commercial and personal use of computers, leading to the microcomputer revolution of the 1970s. The 50 lb IBM 5100 was an early mobile computer, heavy and run from mains power. Later portables such as the Osborne 1 and the Compaq Portable were lighter but still needed plugging in, until the first laptops, such as the Grid Compass, added batteries. By the early 2000s the same miniaturization let manufacturers fold computing into cellular phones, and smartphones and tablets recently became the dominant computing device on the market. System on a Chip designs are complete computers the size of a coin. The Snapdragon 865 is hundreds of thousands of times more powerful than ENIAC, integrates billions of transistors, and consumes only a few watts of power. ENIAC ran in 1945; the gap between it and a coin-sized chip is the measure of how far this story has travelled.

• 8. Anatomy Of A Machine

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  A general-purpose computer has four main components: the arithmetic logic unit, the control unit, the memory, and the input and output devices. Inside them sit thousands to trillions of tiny electrical circuits, each switchable on or off. Each circuit represents one bit, on for a "1" and off for a "0," and the circuits are arranged into logic gates so that some can control the state of others. The control unit reads and decodes program instructions, turning them into signals that activate the rest of the machine. A key component in every CPU is the program counter, a special register that tracks where the next instruction will be read from. Adding 100 to the program counter sends the machine 100 locations further down the program; instructions that change it are called "jumps," and they make loops and conditional execution possible. Memory works as a list of numbered cells, each storing a single number, so a computer can be told to "put the number 123 into the cell numbered 1357." In almost all modern computers each cell holds a byte of eight bits, representing 256 different values, and modern computers hold billions or even trillions of bytes. RAM can be read and written anytime, while ROM is preloaded and unchangeable, typically holding the start-up instructions such as a PC's BIOS. Grace Hopper, an American computer scientist and developer of the first compiler, is credited with first using the term "bugs" in computing, after a dead moth was found shorting a relay in the Harvard Mark II computer in September 1947. Bugs are nearly always the result of programmer error, since the machine only executes the instructions it is given. To add every number from 1 to 1,000 by hand would take thousands of button presses, yet a few lines of MIPS assembly let a modern PC finish it in a fraction of a second.