Reading. Read the text and try to guess the meaning of the words in bold. Check your variants in the dictionary.
The word “computer” has been part of the English language since 1646, but if you look in a dictionary printed before 1940, you might be surprised to find a computer defined as a person who performs calculations! Prior to 1940, machines designed to perform calculations were referred to as calculators and tabulators, not computers. The modern definition and use of the term “computer” emerged in the 1940s, when the first electronic computing devices were developed.
Most people can formulate a mental picture of a computer, but computers do so many things and come in such a variety of shapes and sizes that it might seem difficult to distill their common characteristics into an all-purpose definition. At its core, a computer is a device that accepts input, processes data, stores data, and produces output, all according to a series of stored instructions.
Computer input is whatever is typed, submitted, or transmitted to a computer system. Input can be supplied by a person, the environment, or another computer. Examples of the kinds of input that a computer can accept include words and symbols in a document, numbers for a calculation, pictures, temperatures from a thermostat, audio signals from a microphone, and instructions from a computer program. An input device, such as a keyboard or mouse, gathers input and transforms it into a series of electronic signals for the computer to store and manipulate.
In the context of computing data refers to the symbols that represent facts, objects, and ideas. Computers manipulate data in many ways, and this manipulation is called processing. The series of instructions that tell a computer how to carry out processing tasks is referred toas a computer program, or simply a “program”. These programs form the software that sets up a computer to do a specific task. Some of the ways that a computer can process data include performing calculations, sorting lists of words or numbers, modifying documents and pictures, keepingtrack of your score in a fact-action game, and drawing graphs. In a computer, most processing takes place in a component called the central processing unit (CPU), which is sometimes described as the computer’s “brain”.
A computer stores data so that it will be available for processing. Most computers have more than one place to put data, depending on how the data is being used. Memory is an area of a computer that temporarily holds data waiting to be processed, stored, or output. Storage is the area where data can be left on a permanent basis when it is not immediately needed for processing. Output is the result produced by a computer. Some examples of computer output include reports, documents, music, graphs, and pictures. An output device displays, prints, or transmits the results of processing.
Take a moment to think about the way you use a simple handheld calculator to balance your checkbook each month. You’re forced to do the calculations in stages. Although you can store data from one stage and use it in the next stage, you cannot store the sequence of formulas – the program – required to balance your checkbook. Every month, therefore, you have to perform a similar set of calculations. The process would be much simpler if your calculator remembered the sequence of calculations and just asked you for this month’s checkbook entries.
Early “computers” were really no more than calculating devices, designed to carry out a specific mathematical task. To use one of these devices for a different task, it was necessary to rewire its circuits. In a modern computer, the idea of a stored programmeans that a series of instructions for a computing task can be loaded into a computer’s memory. These instructions can easily be replaced by a different set of instructions when it is time for the computer to perform another task.
The stored program concept allows you to use your computer for one task, such as wordprocessing, and then easily switch to a different type of computing task, such as editing a photo or sending an e-mail message. It is the single most important characteristic that distinguishes a computer from other simpler and less versatile devices, such as calculators and pocket-sized electronic dictionaries.