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UNII I 101



What is a computer?

When you read the following text, you will probably meet words and expressions that are new to you. First try to understand their meaning from the context - read the same passage a few times. When you have read the whole text, check new words in a dictionary. Most of the words in boldtypeface are explained in the Glossary at the end of this book.

[1] A computer is a machine with an intricate network of electronic 1

circuitsthat operate switchesor magnetize tiny metal cores.The switches, like the cores, are capable of being in one of two possible states, that is, on or off; magnetized or demagnetized. The machine is capable of storing and manipulating numbers, letters, and characters. 5 The basic idea of a computer is that we can make the machine do what we want by inputting signals that turn certain switches on and turn others off, or that magnetize or do not magnetize the cores.

[2] The basic job of computers is the processing of information. For this

reason, computers can be defined as deviceswhich accept information 10 in the form of instructions called a programand characters called data,perform mathematical and/or logical operations on the information, and then supply results of these operations. The program, or part of it, which tells the computers what to do and the data, which provide the information needed to solve the problem, are kept inside the computer 15 in a place called memory.

[3] Computers are thought to have many remarkable powers. However,
most computers, whether large or small have three basic capabilities.
First, computers have circuits for performing arithmetic operations,
such as: addition, subtraction, division, multiplication and 20

exponentiation. Second, computers have a means of communicating
with the user. After all, if we couldn't feed information in and get
results back, these machines wouldn't be of much use. However, certain
computers (commonly minicomputers and microcomputers) are used to
control directly things such as robots, aircraft navigation systems, 25

medical instruments, etc.

[4] Some of the most common methods of inputting information are to use punched cards, magnetic tape, disks,and terminals.The computer's input device(which might be a card reader,a tape driveor disk drive,


For outputting information, two common devices used are a printer which prints the new information on paper, or a CRT display screenwhich shows the results on a TV-like screen.

[5] Third, computers have circuits which can make decisions. The kinds of 35
decisions which computer circuits can make are not of the type: 'Who
would win a war between two countries?' or 'Who is the richest person
in the world?' Unfortunately, the computer can only decide three
things, namely: Is one number less than another? Are two numbers
equal? and, Is one number greater than another? 40

[6j A computer can solve a series of problems and make hundreds, even
thousands, of logical decisions without becoming tired or bored. It can
find the solution to a problem in a fraction of the time it takes a human
being to do the job. A computer can replace people in dull, routine
tasks, but it has no originality; it works according to the instructions 45

given to it and cannot exercise any value judgments. There are times
when a computer seems to operate like a mechanical 'brain', but its
achievements are limited by the minds of human beings. A computer
cannot do anything unless a person tells it what to do and gives it the
appropriate information; but because electric pulses can move at the 50


speed of light, a computer can carry out vast numbers of arithmetic-logical operations almost instantaneously. A person can do everything a computer can do, but in many cases that person would be dead long before the job was finished.


T F

I I I I 8. Computers can make any type of decision they are asked to.

I I I I 9. Computers can work endlessly without having to stop to rest unless there is a breakdown.


 




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