Charles Babage
born Dec. 26, 1791, London, Eng.
died Oct. 18, 1871, London
British mathematician and computer inventor.
Photograph:Charles Babbage, detail of an oil painting by Samuel Lawrence, 1845; in the National Portrait …
Educated at Cambridge University, he devoted himself from about 1812 to devising machines capable of calculating mathematical tables. His first small calculator could perform certain computations to eight decimals. In 1823 he obtained government support for the design of a projected machine with a 20-decimal capacity. In the 1830s he developed plans for the so-called Analytical Engine, capable of performing any arithmetical operation on the basis of instructions from punched cards, a memory unit in which to store numbers, sequential control, and most of the other basic elements of the present-day computer. The forerunner of the modern digital computer, the Analytical Engine was never completed. In 1991 British scientists built Difference Engine No. 2 (accurate to 31 digits) to Babbage's specifications. His other contributions included establishing the modern postal system in England, compiling the first reliable actuarial tables, and inventing the locomotive cowcatcher.
Computer
Programmable machine that can store, retrieve, and process data.
Today's computers have at least one CPU that performs most calculations and includes a main memory, a control unit, and an arithmetic logic unit. Increasingly, personal computers contain specialized graphic processors, with dedicated memory, for handling the computations needed to display complex graphics, such as for three-dimensional simulations and games. Auxiliary data storage is usually provided by an internal hard disk and may be supplemented by other media such as floppy disks or CD-ROMs. Peripheral equipment includes input devices (e.g., keyboard, mouse) and output devices (e.g., monitor, printer), as well as the circuitry and cabling that connect all the components. Generations of computers are characterized by their technology. First-generation digital computers, developed mostly in the U.S. after World War II, used vacuum tubes and were enormous. The second generation, introduced c. 1960, used transistors and were the first successful commercial computers. Third-generation computers (late 1960s and 1970s) were characterized by miniaturization of components and use of integrated circuits. The microprocessor chip, introduced in 1974, defines fourth-generation computers.
Personal computer
Microcomputer designed for use by one person at a time.
A typical PC assemblage comprises a CPU; internal memory consisting of RAM and ROM; data storage devices (including a hard disc, a floppy disc, or CD-ROM); and input/output devices (including a display screen, keyboard, mouse, and printer). The PC industry began in 1977 when Apple Computer, Inc. (now Apple Inc.), introduced the Apple II. Radio Shack and Commodore Business Machines also introduced PCs that year. IBM entered the PC market in 1981. The IBM PC, with increased memory capacity and backed by IBM's large sales organization, quickly became the industry standard. Apple's Macintosh (1984) was particularly useful for desktop publishing. Microsoft Corp. introduced MS Windows (1985), a graphical user interface that gave PCs many of the capabilities of the Macintosh, initially as an overlay of MS-DOS. Windows went on to replace MS-DOS as the dominant operating system for personal computers. Uses of PCs multiplied as the machines became more powerful and application software proliferated. Today, PCs are used for word processing, Internet access, and many other daily tasks.
Analog computer
Computer in which continuously variable physical quantities, such as electrical potential, fluid pressure, or mechanical motion, are used to represent (analogously) the quantities in the problem to be solved.
The analog system is set up according to initial conditions and then allowed to change freely. Answers to the problem are obtained by measuring the variables in the analog model. Analog computers are especially well suited to simulating dynamic systems; such simulations may be conducted in real time or at greatly accelerated rates, allowing experimentation by performing many runs with different variables. They have been widely used in simulating the operation of aircraft, nuclear power plants, and industrial chemical processes. See also digital computer.
Digital computer
Computer capable of solving problems by processing information expressed in discrete form.
By manipulating combinations of binary digits (see binary code), it can perform mathematical calculations, organize and analyze data, control industrial and other processes, and simulate dynamic systems such as global weather patterns. See also analog computer.
Micro computer
Small digital computers whose CPU is contained on a single integrated semiconductor chip.
As large-scale and then very large-scale integration (VLSI) have progressively increased the number of transistors that can be placed on one chip, the processing capacity of microcomputers has grown immensely. The personal computer is the most common example of a microcomputer, but high-performance microcomputer systems are widely used in business, in engineering, and in “smart” machines in manufacturing. See also integrated circuit, microprocessor.
source:Britannica Encyclopedia
