The history of stored-program computers relates first to computer architecture, that is, the organization of the units to perform input and output, to store data and to operate as an integrated mechanism. Before the development of the general-purpose computer, most calculations were done by humans. Mechanical tools to help humans with digital calculations were then called "calculating machines"; by proprietary names, or even as they are now, calculators. It was those humans who used the machines who were then called computers. In the United States of America, the development of the computer was underpinned by massive government investment in the technology for military applications during the World War-II and then the Cold War. The latter superpower confrontation made it possible for local manufacturers to transform their machines into commercially viable products. It was the same story in Europe, where adoption of computers began largely through proactive steps taken by national governments to stimulate development and deployment of the technology. The invention of electronic amplifiers made calculating machines much faster than their mechanical or electro-mechanical predecessors. Vacuum tube (thermionic valve) amplifiers gave way to solid state transistors, and then rapidly to integrated circuits which continue to improve, placing millions of electrical switches (typically transistors) on a single elaborately manufactured piece of semi-conductor the size of a fingernail. By defeating the tyranny of numbers, integrated circuits made high-speed and low-cost digital computers a widespread commodity. There is an ongoing effort to make computer hardware faster, cheaper, and capable of storing more data. Computing hardware has become a platform for uses other than mere computation, such as process automation, electronic communications, equipment control, entertainment, education, etc. Each field in turn has imposed its own requirements on the hardware, which has evolved in response to those requirements, such as the role of the touch screen to create a more intuitive and natural user interface. As all 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. Earliest Hardware used: Devices have been used to aid computation for thousands of years in the history, mostly using one-to-one correspondence with our fingers. The abacus was early used for arithmetic tasks. What we now call the Roman abacus was used in Babylonia as early as 2400 BC. Several analog computers were constructed in ancient and medieval times to perform astronomical calculations. These include the Antikythera mechanism and the astrolabe from ancient Greece (150–100 BC), which is generally regarded as the earliest known mechanical analog computers. Hero of Alexandria (10–70 AD) made many complex mechanical devices including automata and a programmable cart. Other early versions of mechanical devices used to perform one or another type of calculations include the planisphere and other mechanical computing devices invented by Abu Rayhan Al-Biruni (AD 1000); the equatorium and universal latitude-independent astrolabe by Abu Ishaq Ibrahim Al-Zarqali (AD 1015); the astronomical analog computers of other medieval Muslim astronomers and engineers; and the astronomical clock tower of Su Song (AD 1090) during the Song Dynasty. Wilhelm Schickard, a German polymath, designed a calculating clock in 1623. A fire destroyed the machine during its construction in 1624 and Schickard abandoned the project. In 1642, while still a teenager, Blaise Pascal started some pioneering work on calculating machines and after three years of effort and 50 prototypes he invented the mechanical calculator. Gottfried Wilhelm von Leibniz invented the Stepped Reckoner and his famous cylinders around 1672 while adding direct multiplication and division to the Pascaline. Around 1820, Charles Xavier Thomas de Colmar created the first successful, mass-produced mechanical calculator, the Thomas Arithmometer that could add, subtract, multiply, and divide. In Japan, Ryoichi Yazu patented a mechanical calculator called the Yazu Arithmometer in 1903. It consisted of a single cylinder and 22 gears, and employed the mixed base-2 and base-5 number system familiar to users to the Japanese abacus Soroban. Carry and end of calculation were determined automatically. However, up to the 1940s, many subsequent designs (including Charles Babbage's machines of the 1822 and even ENIAC of 1945) were based on the decimal system; ENIAC's ring counters emulated the operation of the digit wheels of a mechanical adding machine. Desktop Calculator: By the 1920s Lewis Fry Richardson's interest in weather prediction led him to propose human computers and numerical analysis to model the weather; to this day, the most powerful computers on Earth are needed to adequately model its weather using the Navier–Stokes equations. Companies like Friden, Marchant Calculator and Monroe made desktop mechanical calculators from the 1930s that could add, subtract, multiply and divide. In 1948, the Curta was introduced. This was a small, portable, mechanical calculator that was about the size of a pepper grinder. Over time, during the 1950s and 1960s a variety of different brands of mechanical calculators appeared on the market. The first all-electronic desktop calculator was the British ANITA Mk.VII, which used a Nixie tube display and 177 sub-miniature thyratron tubes. In 1965, Wang Laboratories produced the LOCI-2, a 10-digit transistorized desktop calculator that used a Nixie tube display and could compute logarithms. Advanced analog computers: 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, for example, ballistic trajectories, inertia, resonance, energy transfer, momentum, and so forth. An ingenious example of such a machine, analog computers, using water as the analog quantity, was the water integrator built in 1928; an electrical example is the Mallock machine built in 1941. Some of the most widely deployed analog computers included devices for aiming weapons, such as the Norden bombsight, and fire-control systems, such as Arthur Pollen's Argo system for naval vessels. Some stayed in use for decades after World War II; 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. The art of mechanical analog computing reached its zenith with the differential analyzer, built by H. L. Hazen and Vannevar Bush at MIT starting in 1927. 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. ENIAC, 1946: Regarded as the first general purpose electronic computer, the Electronic Numerical Integrator and Computer (ENIAC) was initially commissioned for the use in World War II, but not completed until one year after the war had ended . Installed at the University of Pennsylvania, its 40 separate eight-foot-high racks and 18,000 tubes were intended to help calculate ballistic trajectories. SAGE, 1954: A gigantic computerized air defense systems, SAGE (Semi-Automatic Ground Environment) were designed to help the Air Force track radar data in real time. Equipped with technical advances such as modems and graphical displays, the machine weighed 300 tons and occupied one floor of a concrete blockhouse. NEAC 2203, 1960: Manufactured by the Nippon Electric Company (NEC), the drum-based machine was one of the earliest transistorized Japanese computers. It was used for business, scientific and engineering applications. IBM System/360, 1964: Part of a family of interchangeable computers, the IBM System/360 mainframe was the first to cover a complete range of applications, from small to large, from commercial to scientific. Users were able to enlarge or shrink their setup without having to make headache-inducing software upgrades as well. Higher-end System/360 models had roles in NASA's Apollo missions as well as air traffic control systems. CDC 6600, 1964: For a time the fastest machine in the world, Control Data Corporation's 6600 machine was designed by noted computer architect Seymour Cray. It retained its speed crown until 1969, when Cray designed his next supercomputer. DEC PDP-8, 1965: The first successful commercial minicomputer, the PDP-8, made by the Digital Equipment Corporation, sold more than 50,000 units upon its release, the most of any computer up to that time. Years before Apple and Gnu / Linux offered alternatives to the dominant IBM / Microsoft paradigms, DEC proposed its own vision, by encouraging users to educate themselves and take part in the evolution of the line. Interface Message Processor, 1969: Conceived at the height of the Cold War, when the U.S. government sought a way to keep its network of computers alive in case certain nodes were destroyed in a nuclear attack or other hostile act, the IMP featured the first generation of gateways, which are today known as routers. As such, IMP performed a critical task in the development of the ARPANET (Advanced Research Projects Agency Network), the world's first operational packet switching network, and the predecessor of the contemporary global Internet. Kenbak-1, 1971: Often considered the world's first "personal computer" the Kenbak was touted as an easy-to-use educational tool, but it failed to sell more than several dozen units. Lacking a microprocessor, it had only 256 bytes of computing power and its only output was a series of blinking lights. Cray-1, 1976: At the time of its release, the Cray-1, above, was the fastest computing machine at the world. Despite its price tag, between $5 and $10 million, it sold well. It is one of the many machines designed by Seymour Cray, a computer architect who devoted his life to the creation of so-called supercomputers, machines which prioritized processing capacity and speed of calculation. Apple-I, 1976: Initially conceived by Steve Wozniak (a.k.a. "Woz") as a build-it-yourself kit computer, Apple-I was initially rejected by his bosses at Hewlett-Packard. Undeterred, he offered it to Silicon Valley's Homebrew Computer Club and, together with his friend Steve Jobs, managed to sell 50 pre-built models to The Byte Shop in Mountain View, California. The suggested retail price: $666. Though sales were low, the machine paved the way for the smash success of the Apple-II. IBM Personal Computer, 1981: Featuring an independent keyboard, printer and monitor, the slick, complete-looking package that was the IBM PC helped push personal computing out of the hobbyist's garage and into the corporate and consumer mainstream. Its immense commercial success made it the hallmark of personal computing for many years and led other manufacturers to produce similar desktop models. Osborne 1 Portable Computer, 1981: The first commercial portable computer, the Osborne weighed 24 lbs. and cost less than $2,000. It gained popularity because of its low price and the extensive software library that came with it. Hewlett-Packard 150, 1983: Representing the first step in a technology widely available today, the HP 150 was the first commercially available computer with touch screen technology. The 9-inch computer screen was surrounded by infrared transmitters and receivers that detected the position of the user's finger. Deep Blue, 1997: Begun at IBM in the late 80's, the Deep Blue project was an attempt at using parallel processing to solve a difficult problem- namely, beating the best chess player in the world, Garry Kasparov. During a six-game match, which Kasparov ultimately lost, the confounded master attributed one move to "the hand of God." iPhone, 2007: The handy little device introduced by Apple CEO Steve Jobs in 2007 not only brings together internet access, a regular cell phone, camera and media player, it supports a wide variety of third party applications, or apps, that supply everything from recipes to maps of the night sky, and wraps it all in a sleek, glossy exterior. iPad, 2010: And now the tablet is finally here. It's called an iPad, and it's half an inch thick, weighs 1.5 pounds and features a 9.7 inch display. As Steve Jobs says in the presentation above, the device has a 10-hour battery life, so you'll be able to use all the 3rd-party apps, games, video and online newspapers you want. The Wi-Fi iPad begins at $499 while the 3G version begins at $629. Thanks a lot for reading this. 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