***THIS PAGE IS ALL ABOUT HARDWARE AND ITS GENERATIONS WHICH IS IMPORTANT FOR NOW TIME AND FOR NEW GENERATION***

Computing hardware is a platform for information processing (block diagram).

The history of computing hardware encompasses the hardware, its architecture, and its impact on software. The elements of computing hardware have undergone significant improvement over their history. This improvement has triggered worldwide use of the technology, performance has improved and the price has declined.^[1] Computers are accessible to ever-increasing sectors of the world's population.^[2] Computing hardware has become a platform for uses other than computation, such as automation, communication, control, entertainment, and education. Each field in turn has imposed its own requirements on the hardware, which has evolved in response to those requirements.^[3]

The von Neumann architecture unifies our current computing hardware implementations.^[4] Since digital computers rely on digital storage, and tend to be limited by the size and speed of memory, the history of computer data storage is tied to the development of computers. The major elements of computing hardware implement abstractions: input,^[5] output,^[6] memory,^[7] and processor. A processor is composed of control^[8] and datapath.^[9] In the von Neumann architecture, control of the datapath is stored in memory. This allowed control to become an automatic process; the datapath could be under software control, perhaps in response to events. Beginning with mechanical datapaths such as the abacus and astrolabe, the hardware first started using analogs for a computation, including water and even air as the analog quantities: analog computers have used lengths, pressures, voltages, and currents to represent the results of calculations.^[10] Eventually the voltages or currents were standardized, and then digitized. Digital computing elements have ranged from mechanical gears, to electromechanical relays, to vacuum tubes, to transistors, and to integrated circuits, all of which are currently implementing the von Neumann architecture.

Originally calculations were computed by humans, whose job title was computers.^[12] These human computers were typically engaged in the calculation of a mathematical expression, say for astronomical ephemerides, for artillery firing tables, or for nautical navigation. The calculations of this period were specialized and expensive, requiring years of training in mathematics.

Main article: calculator

Devices have been used to aid computation for thousands of years, using one-to-one correspondence with our fingers.^[13][14] The earliest counting device was probably a form of tally stick. Later record keeping aids throughout the Fertile Crescent included clay shapes, which represented counts of items, probably livestock or grains, sealed in containers.^[15]

The abacus was used for arithmetic tasks. The Roman abacus was used in Babylonia as early as 2400 BC. Since then, many other forms of reckoning boards or tables have been invented. In a medieval counting house, a checkered cloth would be placed on a table, and markers moved around on it according to certain rules, as an aid to calculating sums of money (this is the origin of "Exchequer" as a term for a nation's treasury).

A number of analog computers were constructed in ancient and medieval times to perform astronomical calculations. These include the Antikythera mechanism and the astrolabe from ancient Greece (c. 150–100 BC), which are generally regarded as the first mechanical analog computers.^[16] Other early versions of mechanical devices used to perform some type of calculations include the planisphere and other mechanical computing devices invented by Abū Rayhān al-Bīrūnī (c. AD 1000); the equatorium and universal latitude-independent astrolabe by Abū Ishāq Ibrāhīm al-Zarqālī (c. AD 1015); the astronomical analog computers of other medieval Muslim astronomers and engineers; and the astronomical clock tower of Su Song (c. AD 1090) during the Song Dynasty.

The "castle clock", an astronomical clock invented by Al-Jazari in 1206, is considered to be the earliest programmable analog computer.^[17] It displayed the zodiac, the solar and lunar orbits, a crescent moon-shaped pointer traveling across a gateway causing automatic doors to open every hour,^[18][19] and five robotic musicians who play music when struck by levers operated by a camshaft attached to a water wheel. The length of day and night could be re-programmed every day in order to account for the changing lengths of day and night throughout the year.

1801: punched card technology

Punched card system of a music machine, also referred to as Book music, a one-stop European medium for organs

As early as 1725 Basile Bouchon used a perforated paper loop in a loom to establish the pattern to be reproduced on cloth, and in 1726 his co-worker Jean-Baptiste Falcon improved on his design by using perforated paper cards attached to one another for efficiency in adapting and changing the program. The Bouchon-Falcon loom was semi-automatic and required manual feed of the program. In 1801, Joseph-Marie Jacquard developed a loom in which the pattern being woven was controlled by punched cards. The series of cards could be changed without changing the mechanical design of the loom. This was a landmark point in programmability.

In 1833, Charles Babbage moved on from developing his difference engine to developing a more complete design, the analytical engine, which would draw directly on Jacquard's punched cards for its programming.^[31] In 1835, Babbage described his analytical engine. It was the plan of a general-purpose programmable computer, employing punch cards for input and a steam engine for power. One crucial invention was to use gears for the function served by the beads of an abacus. In a real sense, computers all contain automatic abacuses (the datapath, arithmetic logic unit, or floating-point unit). His initial idea was to use punch-cards to control a machine that could calculate and print logarithmic tables with huge precision (a specific purpose machine). Babbage's idea soon developed into a general-purpose programmable computer, his analytical engine. While his design was sound and the plans were probably correct, or at least debuggable, the project was slowed by various problems. Babbage was a difficult man to work with and argued with anyone who didn't respect his ideas. All the parts for his machine had to be made by hand. Small errors in each item can sometimes sum up to large discrepancies in a machine with thousands of parts, which required these parts to be much better than the usual tolerances needed at the time. The project dissolved in disputes with the artisan who built parts and was ended with the depletion of government funding. Ada Lovelace, Lord Byron's daughter, translated and added notes to the "Sketch of the Analytical Engine" by Federico Luigi, Conte Menabrea

Advanced analog computers

Cambridge differential analyzer, 1938

Before World War II, mechanical and electrical analog computers were considered the "state of the art", and many thought they were the future of computing. Analog computers take advantage of the strong similarities between the mathematics of small-scale properties — the position and motion of wheels or the voltage and current of electronic components — and the mathematics of other physical phenomena,^[43] for example, ballistic trajectories, inertia, resonance, energy transfer, momentum, and so forth. They model physical phenomena with electrical voltages and currents^[44][45] as the analog quantities.

Centrally, these analog systems work by creating electrical analogs of other systems, allowing users to predict behavior of the systems of interest by observing the electrical analogs.^[46] The most useful of the analogies was the way the small-scale behavior could be represented with integral and differential equations, and could be thus used to solve those equations. An ingenious example of such a machine, using water as the analog quantity, was the water integrator built in 1928; an electrical example is the Mallock machine built in 1941. A planimeter is a device which does integrals, using distance as the analog quantity. Until the 1980s, HVAC systems used air both as the analog quantity and the controlling element. Unlike modern digital computers, analog computers are not very flexible, and need to be reconfigured (i.e., reprogrammed) manually to switch them from working on one problem to another. Analog computers had an advantage over early digital computers in that they could be used to solve complex problems using behavioral analogues while the earliest attempts at digital computers were quite limited.

A Smith Chart is a well-known nomogram.

Since computers were rare in this era, the solutions were often hard-coded into paper forms such as nomograms,^[47] which could then produce analog solutions to these problems, such as the distribution of pressures and temperatures in a heating system. Some of the most widely deployed analog computers included devices for aiming weapons, such as the Norden bombsight^[48] and the fire-control systems,^[49] such as Arthur Pollen's Argo system for naval vessels. Some stayed in use for decades after WWII; the Mark I Fire Control Computer was deployed by the United States Navy on a variety of ships from destroyers to battleships. Other analog computers included the Heathkit EC-1, and the hydraulic MONIAC Computer which modeled econometric flows.^[50]

The art of analog computing reached its zenith with the differential analyzer,^[51] invented in 1876 by James Thomson and built by H. W. Nieman and Vannevar Bush at MIT starting in 1927. Fewer than a dozen of these devices were ever built; the most powerful was constructed at the University of Pennsylvania's Moore School of Electrical Engineering, where the ENIAC was built. Digital electronic computers like the ENIAC spelled the end for most analog computing machines, but hybrid analog computers, controlled by digital electronics, remained in substantial use into the 1950s and 1960s, and later in some specialized applications. But like all digital devices, the decimal precision of a digital device is a limitation,^[52] as compared to an analog device, in which the accuracy is a limitation.^[53] As electronics progressed during the twentieth century, its problems of operation at low voltages while maintaining high signal-to-noise ratios^[54] were steadily addressed, as shown below, for a digital circuit is a specialized form of analog circuit, intended to operate at standardized settings (continuing in the same vein, logic gates can be realized as forms of digital circuits). But as digital computers have become faster and use larger memory (for example, RAM or internal storage), they have almost entirely displaced analog computers. Computer programming, or coding, has arisen as another human profession.

Punched tape programs would be much longer than the short fragment of yellow paper tape shown.

The era of modern computing began with a flurry of development before and during World War II, as electronic circuit elements^[55] replaced mechanical equivalents and digital calculations replaced analog calculations. Machines such as the Z3, the Atanasoff–Berry Computer, the Colossus computers, and the ENIAC were built by hand using circuits containing relays or valves (vacuum tubes), and often used punched cards or punched paper tape for input and as the main (non-volatile) storage medium.

In this era, a number of different machines were produced with steadily advancing capabilities. At the beginning of this period, nothing remotely resembling a modern computer existed, except in the long-lost plans of Charles Babbage and the mathematical ideas of Alan Turing. At the end of the era, devices like the Colossus computers and the EDSAC had been built, and are agreed to be electronic digital computers. Defining a single point in the series as the "first computer" misses many subtleties (see the table "Defining characteristics of some early digital computers of the 1940s" below).

Alan Turing's 1936 paper^[56] proved enormously influential in computing and computer science in two ways. Its main purpose was to prove that there were problems (namely the halting problem) that could not be solved by any sequential process. In doing so, Turing provided a definition of a universal computer which executes a program stored on tape. This construct came to be called a Turing machine; it replaces Kurt Gödel's more cumbersome universal language based on arithmetics. Except for the limitations imposed by their finite memory stores, modern computers are said to be Turing-complete, which is to say, they have algorithm execution capability equivalent to a universal Turing machine.

Further information: mainframe computer

Design of the von Neumann architecture (1947)

Even before the ENIAC was finished, Eckert and Mauchly recognized its limitations and started the design of a stored-program computer, EDVAC. John von Neumann was credited with a widely circulated report describing the EDVAC design in which both the programs and working data were stored in a single, unified store. This basic design, denoted the von Neumann architecture, would serve as the foundation for the worldwide development of ENIAC's successors.^[69] In this generation of equipment, temporary or working storage was provided by acoustic delay lines, which used the propagation time of sound through a medium such as liquid mercury (or through a wire) to briefly store data. As series of acoustic pulses is sent along a tube; after a time, as the pulse reached the end of the tube, the circuitry detected whether the pulse represented a 1 or 0 and caused the oscillator to re-send the pulse. Others used Williams tubes, which use the ability of a television picture tube to store and retrieve data. By 1954, magnetic core memory^[70] was rapidly displacing most other forms of temporary storage, and dominated the field through the mid-1970s.

Magnetic core memory. Each core is one bit.

EDVAC was the first stored-program computer designed; however it was not the first to run. Eckert and Mauchly left the project and its construction floundered. The first working von Neumann machine was the Manchester "Baby" or Small-Scale Experimental Machine, developed by Frederic C. Williams and Tom Kilburn at University of Manchester in 1948;^[71] it was followed in 1949 by the Manchester Mark 1 computer, a complete system, using Williams tube and magnetic drum memory, and introducing index registers.^[72] The other contender for the title "first digital stored program computer" had been EDSAC, designed and constructed at the University of Cambridge. Operational less than one year after the Manchester "Baby", it was also capable of tackling real problems. EDSAC was actually inspired by plans for EDVAC (Electronic Discrete Variable Automatic Computer), the successor to ENIAC; these plans were already in place by the time ENIAC was successfully operational. Unlike ENIAC, which used parallel processing, EDVAC used a single processing unit. This design was simpler and was the first to be implemented in each succeeding wave of miniaturization, and increased reliability. Some view Manchester Mark 1 / EDSAC / EDVAC as the "Eves" from which nearly all current computers derive their architecture. Manchester University's machine became the prototype for the Ferranti Mark I. The first Ferranti Mark I machine was delivered to the University in February, 1951 and at least nine others were sold between 1951 and 1957.

The first universal programmable computer in the Soviet Union was created by a team of scientists under direction of Sergei Alekseyevich Lebedev from Kiev Institute of Electrotechnology, Soviet Union (now Ukraine). The computer MESM (МЭСМ, Small Electronic Calculating Machine) became operational in 1950. It had about 6,000 vacuum tubes and consumed 25 kW of power. It could perform approximately 3,000 operations per second. Another early machine was CSIRAC, an Australian design that ran its first test program in 1949. CSIRAC is the oldest computer still in existence and the first to have been used to play digital music.^[73]

In October 1947, the directors of J. Lyons & Company, a British catering company famous for its teashops but with strong interests in new office management techniques, decided to take an active role in promoting the commercial development of computers. By 1951 the LEO I computer was operational and ran the world's first regular routine office computer job. On 17 November 1951, the J. Lyons company began weekly operation of a bakery valuations job on the LEO (Lyons Electronic Office). This was the first business application to go live on a stored program computer.

In June 1951, the UNIVAC I (Universal Automatic Computer) was delivered to the U.S. Census Bureau. Remington Rand eventually sold 46 machines at more than $1 million each. UNIVAC was the first 'mass produced' computer; all predecessors had been 'one-off' units. It used 5,200 vacuum tubes and consumed 125 kW of power. It used a mercury delay line capable of storing 1,000 words of 11 decimal digits plus sign (72-bit words) for memory. A key feature of the UNIVAC system was a newly invented type of metal magnetic tape, and a high-speed tape unit, for non-volatile storage. Magnetic media is still used in almost all computers.^[75]

In 1952, IBM publicly announced the IBM 701 Electronic Data Processing Machine, the first in its successful 700/7000 series and its first IBM mainframe computer. The IBM 704, introduced in 1954, used magnetic core memory, which became the standard for large machines. The first implemented high-level general purpose programming language, Fortran, was also being developed at IBM for the 704 during 1955 and 1956 and released in early 1957. (Konrad Zuse's 1945 design of the high-level language Plankalkül was not implemented at that time.) A volunteer user group was founded in 1955 to share their software and experiences with the IBM 701; this group, which exists to this day, was a progenitor of open source.

IBM 650 front panel wiring.

IBM introduced a smaller, more affordable computer in 1954 that proved very popular. The IBM 650 weighed over 900 kg, the attached power supply weighed around 1350 kg and both were held in separate cabinets of roughly 1.5 meters by 0.9 meters by 1.8 meters. It cost $500,000 or could be leased for $3,500 a month. Its drum memory was originally only 2000 ten-digit words, and required arcane programming for efficient computing. Memory limitations such as this were to dominate programming for decades afterward, until the evolution of hardware capabilities and a programming model that were more sympathetic to software development.

In 1955, Maurice Wilkes invented microprogramming,^[76] which allows the base instruction set to be defined or extended by built-in programs (now called firmware or microcode).^[77] It was widely used in the CPUs and floating-point units of mainframe and other computers, such as the IBM 360 series.^[78]

In 1956, IBM sold its first magnetic disk system, RAMAC (Random Access Method of Accounting and Control). It used 50 24-inch (610 mm) metal disks, with 100 tracks per side. It could store 5 megabytes of data and cost $10,000 per megabyte.^[79] (As of 2008, magnetic storage, in the form of hard disks, costs less than one 50th of a cent per megabyte).

Second generation: transistors

A bipolar junction transistor.

In the second half of the 1950s bipolar junction transistors (BJTs)^[80] replaced vacuum tubes. Their use gave rise to the "second generation" computers. Initially, it was believed that very few computers would ever be produced or used.^[81] This was due in part to their size, cost, and the skill required to operate or interpret their results. Transistors^[82] greatly reduced computers' size, initial cost and operating cost. The bipolar junction transistor^[83] was invented in 1947.^[84] If no electrical current flows through the base-emitter path of a bipolar transistor, the transistor's collector-emitter path blocks electrical current (and the transistor is said to "turn full off"). If sufficient current flows through the base-emitter path of a transistor, that transistor's collector-emitter path also passes current (and the transistor is said to "turn full on"). Current flow or current blockage represent binary 1 (true) or 0 (false), respectively.^[85] Compared to vacuum tubes, transistors have many advantages: they are less expensive to manufacture and are much faster, switching from the condition 1 to 0 in millionths or billionths of a second. Transistor volume is measured in cubic millimeters compared to vacuum tubes' cubic centimeters. Transistors' lower operating temperature increased their reliability, compared to vacuum tubes. Transistorized computers could contain tens of thousands of binary logic circuits in a relatively compact space.

Typically, second-generation computers^[86][87] were composed of large numbers of printed circuit boards such as the IBM Standard Modular System^[88] each carrying one to four logic gates or flip-flops. A second generation computer, the IBM 1401, captured about one third of the world market. IBM installed more than one hundred thousand 1401s between 1960 and 1964— This period saw the only Italian attempt: the ELEA by Olivetti, produced in 110 units.

This RAMAC DASD is being restored at the Computer History Museum.

Transistorized electronics improved not only the CPU (Central Processing Unit), but also the peripheral devices. The IBM 350 RAMAC was introduced in 1956 and was the world's first disk drive. The second generation disk data storage units were able to store tens of millions of letters and digits. Multiple Peripherals can be connected to the CPU, increasing the total memory capacity to hundreds of millions of characters. Next to the fixed disk storage units, connected to the CPU via high-speed data transmission, were removable disk data storage units. A removable disk stack can be easily exchanged with another stack in a few seconds. Even if the removable disks' capacity is smaller than fixed disks,' their interchangeability guarantees a nearly unlimited quantity of data close at hand. But magnetic tape provided archival capability for this data, at a lower cost than disk.

Post-1960: third generation and beyond

Intel 8742 eight-bit microcontroller IC.

The explosion in the use of computers began with 'Third Generation' computers. These relied on Jack St. Clair Kilby's^[90] and Robert Noyce's^[91] independent invention of the integrated circuit (or microchip), which later led to the invention of the microprocessor,^[92] by Ted Hoff, Federico Faggin, and Stanley Mazor at Intel.^[93] The integrated circuit in the image on the right, for example, an Intel 8742, is an 8-bit microcontroller that includes a CPU running at 12 MHz, 128 bytes of RAM, 2048 bytes of EPROM, and I/O in the same chip.

During the 1960s there was considerable overlap between second and third generation technologies.^[94] IBM implemented its IBM Solid Logic Technology modules in hybrid circuits for the IBM System/360 in 1964. As late as 1975, Sperry Univac continued the manufacture of second-generation machines such as the UNIVAC 494. The Burroughs large systems such as the B5000 were stack machines which allowed for simpler programming. These pushdown automatons were also implemented in minicomputers and microprocessors later, which influenced programming language design. Minicomputers served as low-cost computer centers for industry, business and universities.^[95] It became possible to simulate analog circuits with the simulation program with integrated circuit emphasis, or SPICE (1971) on minicomputers, one of the programs for electronic design automation (EDA). The microprocessor led to the development of the microcomputer, small, low-cost computers that could be owned by individuals and small businesses. Microcomputers, the first of which appeared in the 1970s, became ubiquitous in the 1980s and beyond. Steve Wozniak, co-founder of Apple Computer, is credited with developing the first mass-market home computers. However, his first computer, the Apple I, came out some time after the MOS Technology KIM-1 and Altair 8800, and the first Apple computer with graphic and sound capabilities came out well after the Commodore PET. Computing has evolved with microcomputer architectures, with features added from their larger brethren, now dominant in most market segments.

Systems as complicated as computers require very high reliability. ENIAC remained on, in continuous operation from 1947 to 1955, for eight years before being shut down. Although a vacuum tube might fail, it would be replaced without bringing down the system. By the simple strategy of never shutting down ENIAC, the failures were dramatically reduced. Hot-pluggable hard disks, like the hot-pluggable vacuum tubes of yesteryear, continue the tradition of repair during continuous operation. Semiconductor memories routinely have no errors when they operate, although operating systems like Unix have employed memory tests on start-up to detect failing hardware. Today, the requirement of reliable performance is made even more stringent when server farms are the delivery platform.^[96] Google has managed this by using fault-tolerant software to recover from hardware failures, and is even working on the concept of replacing entire server farms on-the-fly, during a service event.^[97]

In the twenty-first century, multi-core CPUs became commercially available. Content-addressable memory (CAM)^[98] has become inexpensive enough to be used in networking, although no computer system has yet implemented hardware CAMs for use in programming languages. Currently, CAMs (or associative arrays) in software are programming-language-specific. Semiconductor memory cell arrays are very regular structures, and manufacturers prove their processes on them; this allows price reductions on memory products. After semiconductor memories became commodities, computer software became less labor-intensive; programming codes became less arcane, more understandable.^[99] When the CMOS field effect transistor-based logic gates supplanted bipolar transistors, computer power consumption could decrease dramatically (A CMOS Field-effect transistor draws current during the 'transition' between logic states, unlike the higher current draw of a BJT). This has allowed computing to become a commodity which is now ubiquitous, embedded in many forms, from greeting cards and telephones to satellites. Computing hardware and its software have even become a metaphor for the operation of the universe.^[100]

An indication of the rapidity of development of this field can be inferred by the history of the seminal article.^[101] By the time that anyone had time to write anything down, it was obsolete. After 1945, others read John von Neumann's First Draft of a Report on the EDVAC, and immediately started implementing their own systems. To this day, the pace of development has continued, worldwide.

Source# wikipedia

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