Computer are electronic device that can receive a set of instructions, or program, and then carry out a program by performing calculations on numbered data or by compiling and correlating other forms of information. The old world of technology could not believe about the making of computers. Different types and sizes of computers find uses throughout our world in the handling of data including secret governmental files and making banking transactions to private household accounts. Computers have opened up a new world in manufacturing through the developments of automation, and they have made modern communication systems. They are great tools in almost everything you want to do research and applied technology, including constructing models of the universe to producing tomorrow's weather reports, and their use has in itself opened up new areas of development. Database services and computer networks make available a great variety of information sources. The same new designs also make possible ideas of privacy and of restricted information sources, but computer crime has become a very important risk that society must face if it would enjoy the benefits of modern technology. Two main types of computers are in use today, analog and digital, although the term computer is often used to mean only the digital type. Everything that a digital computer does is based on one operation the ability to determine if a switch, or gate is open or closed. That is, the computer can recognize only two states in any of its microscopic circuits on or off, high voltage or low voltage, or-in the case of numbers-0 or 1. The speed at which the computer performs this simple act, however, is what makes it a marvel of modern technology. Computer speeds are measured in megaHertz, or millions of cycles per second. A computer with a "clock speed" of 10 mHz-a fairly representative speed for a microcomputer-is capable of executing 10 million discrete operations each second. Business microcomputers can perform 15 to 40 million operations per second, and supercomputers used in research and defense applications attain speeds of billions of cycles per second. Digital computer speed and calculating power are further enhanced by the amount of data handled during each cycle. If a computer checks only one switch at a time, that switch can represent only two commands or numbers; thus ON would symbolize one operation or number, and OFF would symbolize another. By checking groups of switches linked as a unit, however, the computer increases the number of operations it can recognize at each cycle. The first adding machine, a precursor of the digital computer, was devised in 1642 by the French philosopher Blaise Pascal. This device employed a series of ten-toothed wheels, each tooth representing a digit from 0 to 9. The wheels were connected so that numbers could be added to each other by advancing the wheels by a correct number of teeth. In the 1670s the German philosopher and mathematician Gottfried Wilhelm von Leibniz improved on this machine by devising one that could also multiply. The French inventor Joseph Marie Jacquard , in designing an automatic loom, used thin, perforated wooden boards to control the weaving of complicated designs. Analog computers began to be built at the start of the 20th century. Early models calculated by means of rotating shafts and gears. Numerical approximations of equations too difficult to solve in any other way were evaluated with such machines. During both world wars, mechanical and, later, electrical analog computing systems were used as torpedo course predictors in submarines and as bombsight controllers in aircraft. Another system was designed to predict spring floods in the Mississippi River Basin. In the 1940s, Howard Aiken, a Harvard University mathematician, created what is usually considered the first digital computer. This machine was constructed from mechanical adding machine parts. The instruction sequence to be used to solve a problem was fed into the machine on a roll of punched paper tape, rather than being stored in the computer. In 1945, however, a computer with program storage was built, based on the concepts of the Hungarian-American mathematician John von Neumann. The instructions were stored within a so-called memory, freeing the computer from the speed limitations of the paper tape reader during execution and permitting problems to be solved without rewiring the computer. The rapidly advancing field of electronics led to construction of the first general-purpose all-electronic computer in 1946 at the University of Pennsylvania by the American engineer John Presper Eckert, Jr. and the American physicist John William Mauchly. (Another American physicist, John Vincent Atanasoff, later successfully claimed that certain basic techniques he had developed were used in this computer.) Called ENIAC, for Electronic Numerical Integrator And Computer, the device contained 18,000 vacuum tubes and had a speed of several hundred multiplications per minute. Its program was wired into the processor and had to be manually altered.
The use of the transistor in computers in the late 1950s marked the advent of smaller, faster, and more versatile logical elements than were possible with vacuum- tube machines. Because transistors use much less power and have a much longer life, this development alone was responsible for the improved machines called second-generation computers. Components became smaller, as did intercomponent spacings, and the system became much less expensive to build. Different types of peripheral devices-disk drives, printers, communications networks, and so on-handle and store data differently from the way the computer handles and stores it. Internal operating systems, usually stored in ROM memory, were developed primarily to coordinate and translate data flows from dissimilar sources, such as disk drives or co-processors (processing chips that perform simultaneous but different operations from the central unit). An operating system is a master control program, permanently stored in memory, that interprets user commands requesting various kinds of services, such as display, print, or copy a data file; list all files in a directory; or execute a particular program. A program is a sequence of instructions that tells the hardware of a computer what operations to perform on data. Programs can be built into the hardware itself, or they may exist independently in a form known as software. In some specialized, or "dedicated," computers the operating instructions are embedded in their circuitry; common examples are the microcomputers found in calculators, wristwatches, automobile engines, and microwave ovens. A general-purpose computer, on the other hand, contains some built-in programs (in ROM) or instructions, in a chip, but it depends on external programs to perform useful tasks. Once a computer has been programmed, it can do only as much or as little as the software controlling it at any given moment enables it to do. Software in widespread use includes a wide range of applications programs-instructions to the computer on how to perform various tasks.
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