Computer Fundamentals and Generations

What you need to know

• A computer is an electronic device that accepts data as input, processes it according to stored instructions, stores it, and gives out information as output. Say electronic device, not machine, and include all four stages, because the definition is marked phrase by phrase.
• Data are raw, unprocessed facts and figures such as a list of scores. Information is processed data that has meaning and is useful, such as the class average and the position of each student. Data goes in, information comes out.
• The characteristics of a computer are speed, measured in millions of operations per second; accuracy, since it does not make arithmetic mistakes of its own; storage, since it can keep and recall huge volumes of data; diligence, since it does not get tired or bored on the ten-thousandth repetition; versatility, since the same machine types a letter, keeps accounts and plays music; and automation, since it completes a job once started without further instruction.
• Garbage In Garbage Out is the rule that a computer's output can only be as good as the data fed into it. The computer does not know that a score of 450 out of 100 is wrong, so the error belongs to the user, not the machine.
• The counting aids that came before the computer are the abacus from China, Napier's bones invented by John Napier in 1617, the slide rule, the Pascaline adding machine built by Blaise Pascal in 1642, and the stepped reckoner of Gottfried Leibniz which could also multiply.
• Charles Babbage designed the Difference Engine and then the Analytical Engine in the 1830s, with an input section, a store, a mill for calculation and an output. Because the Analytical Engine already had the structure of a modern computer he is called the Father of the Computer, and Ada Lovelace, who wrote instructions for it, is regarded as the first programmer.
• Herman Hollerith built a punched card tabulating machine that processed the 1890 United States census, and his company grew into IBM. Punched cards remained the standard input medium until the 1960s.
• First generation, roughly 1940 to 1956, used thermionic valves or vacuum tubes. The machines filled whole rooms, generated enormous heat, consumed heavy power and were programmed in machine language using punched cards. Examples are ENIAC, EDVAC, EDSAC, UNIVAC I and the IBM 650.
• Second generation, roughly 1956 to 1963, used transistors, invented at Bell Laboratories in 1947. The machines became smaller, faster, cheaper and far more reliable, used magnetic core memory, and were programmed in assembly language and early high-level languages. Examples are the IBM 1401, IBM 7094 and Honeywell 400.
• Third generation, roughly 1964 to 1971, used integrated circuits, with many transistors on a single silicon chip. Keyboards and monitors replaced punched cards, operating systems allowed several programs to run at once, and high-level languages such as COBOL and FORTRAN came into general use. Examples are the IBM System/360 and the PDP-8.
• Fourth generation, from 1971 to the present, is built on the microprocessor, an entire processor on one chip, beginning with the Intel 4004 in 1971. It brought large and very large scale integration, the personal computer, the graphical user interface, the mouse and the networking that became the internet.
• Fifth generation covers present and emerging systems based on ultra large scale integration, parallel processing, natural language processing and artificial intelligence, including speech recognition, robotics, expert systems and quantum research. Learn the technology of each generation, because that is what the examiner tests, not the dates.
• By the type of signal handled, computers are analogue, which measure continuous physical quantities such as temperature, pressure and speed, like a mercury thermometer or a car speedometer; digital, which work with discrete values in binary and are what we normally mean by a computer; and hybrid, which combine both, like the monitoring equipment in an intensive care unit or a petrol station pump that measures flow and prints a bill.
• By size and capacity, computers are supercomputers, used for weather forecasting, oil exploration modelling and scientific simulation; mainframes, used by banks, telecoms and agencies such as NIMC to serve thousands of users at once; minicomputers or midrange servers; and microcomputers, which include desktops, laptops, notebooks, tablets, palmtops and smartphones. By purpose they are general purpose, able to run any program, or special purpose, built for one job such as an ATM, a traffic light controller or a digital wristwatch.