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Computer is a device that processes information with astonishing speed and accuracy. Computers process information by helping to create it and by displaying it, storing it, reorganizing it, calculating with it, and communicating it to other computers. Computers can process numbers, words, still pictures, moving pictures, and sounds. The most powerful computers can perform tens of billions of calculations per second. The computer has changed the way we work, learn, communicate, and play. Virtually every kind of organization throughout the world conducts business with computers. Students, teachers, and research scientists use the computer as a learning tool. Millions of individuals and organizations communicate with one another over a network of computers called the Internet. Computer games entertain people of all ages.

Almost all computers are electronic digital computers. They are electronic in their use of electric current (a flow of electric charge) to carry information. They are digital in that they process information as units of electric charge representing numbers. The word digital means having to do with numbers.

To enable a computer to process information that is not numerical-such as words, pictures, or sounds-the computer or some other device must first digitize that information. A device digitizes information by translating it into charges that represent numbers. After the computer processes the digitized information by working with the charges, the computer or a device connected to the computer translates its results back into their original form.

Thus, an artist might use a machine called a scanner to digitize a photograph. The artist would next process the resulting electric charges in a computer to change the photograph-perhaps to add a border. The artist would then use a printer connected to the computer to produce a copy of the altered photo.

Digital computers are one of two general kinds of computers. The other kinds are calculating devices called analog computers. An analog computer represents amounts with physical quantities, such as distances along a scale, rather than with numbers.

The technology of computer hardware (the physical parts of com­puter systems) has ad­vanced tremendously since 1946, when the first electronic digital compu­ter was built. That ma­chine filled a huge room. Today, a single microprocessor, a device the size of a fingernail, can do the same work as that pioneering machine.

The technology of software (programs, or sets of computer instructions and information) is also advancing rapidly. Early users of computers wrote their own software. Today, most users buy programs created by companies that specialize in writing software. Hundreds of thousands of different programs are available for businesses and individuals.

Because of advances in hardware and software, the price of computing has dropped sharply. As a result, the number of computers in operation has risen rapidly ever since the first commercial digital computers were manufactured in the 1950's.

More than 10,000 computers were in operation worldwide by 1961. Ten years later, the number exceeded 100,000. By 1990, about 100 million computers were running. By the mid-1990's, the number bad reached about 200 million. This process is going on.

Exercises

I. Which statement best expresses the main idea of the text?

1. Instructions and data must be given to the computer to act on.

2. Almost all computers are electronic digital computers.

3. Computers have greatly changed our life.

4. Computers have changed the way in which many kinds of jobs are done.

1. Computers are widely used all over the world.

2. Computers operate at a very high speed.

3. Input and output devices refer to peripherals.

4. Computer networks have been created in order to enable people to communicate.

5. A digital computer processes information given in the form of numbers.

6. Analog computers are mainly used in industry.

7. Computers are devices notable for their fast evolution.

8. Scientists focus their attention on computer technologies.

9. There are special companies writing software.

10. Software companies provide two kinds of programs: systems software and applications software.
TEXT 2. INPUT DEVICES

Input devices send information and instructions to the computer. Some input devices are hand-operated, but others work automatically once they are turned on. There are five main kinds of hand-operated units: (1) a keyboard, (2) a mouse, (3) a trackball. (4) a light pen, and (5) a touch screen. There are three principal types of automatic units: (1) a modem, (2) a scanner, and (3) a microphone. In addition, all storage devices can function as input devices.

A keyboard is the main input device. Modern computer keyboards are different from typewriter keyboards. For example, along the top of the keyboard of a desktop PC is a row of function keys, which are designated F1, F2, F3, and so on. Function keys perform special tasks, such as removing a passage of text from one part of a document and inserting it in another. Elsewhere on the keyboard are keys that control the movement of an electronic marker called the insertion point that appears on the monitor screen. The insertion point indicates where the next character typed will appear.

Special keys with such names as command, control, and option give other keys extra functions. For example, with some software, pressing the command and p keys at the same time instructs the computer to prepare to print a document. A user can also reprogram the keyboard to change the function of certain keys, or even make¹ them produce letters from a different alphabet.

The keyboard itself is an electronic device. When the user types a character, electronic circuits in the keyboard translate the character into bit charges. The charges travel through wire to a buffer, a temporary storage location in the computer. As soon as the charges appear in the buffer, the microprocessor moves them to RAM. At the same time, the microprocessor instructs the monitor to put the character on the screen.

A mouse is a palm-sized device that the computer operator moves about ona flat surface. The mouse has two functions: (1) to move the insertion point, and (2) to give commands to the computer. Computer users commonly operate the mouse on a smooth plastic rectangle called a mouse pad. Built into the bottom of the mouse is a ball that rotates when the user moves the mouse. On the upper surface are one or more buttons. An optic mouse can do without a pad as it has no ball on the bottom. When the mouse is moved on the pad, an electronic code representing le movement of the ball travels by cable to the computer box. The microprocessor uses this code to move the electronic marker called the pointer in the same way as the mouse was moved.

To move the insertion point, the operator moves the mouse to position the pointer in the new location. The' operator then presses a mouse button and releases it, an action known as clicking the mouse.

To give a command, the user moves the mouse so that the pointer travels to a tiny picture called an icon. Each icon represents a command. The user then clicks the mouse.

The user can also use the mouse to drag (change the location of) an icon. The user moves the pointer to the icon, then presses a mouse button. Holding the button down, the user moves the mouse. The pointer and icon move together to the new location. The user then releases the button, removing the icon from the control of the mouse. Other uses of the mouse include dragging and changing the size of windows (rectangular frames that appear on the screen). The system of icons, pointer, and mouse is known as a graphical user interface (GUI).

A trackball is commonly used instead of a mouse on laptop and notebook computers. The main part of this device is a ball built into the keyboard. The ball has the same function as the ball built into the bottom of a mouse. Turning the ball by hand moves the pointer.

A light pen enables a computer user to write words or draw pictures directly into a computer. The user touches the point of the pen on the screen of a special pad, then makes writing or drawing motions. Electronic devices in the pen and under the surface of the pad interact to translate the motions into computer code. The microprocessor then uses the code to put an image corresponding to the motions on the screen. Some artists and designers use an electronic pen and pad to produce illustrations.

Words produced in this manner are processed as pictures of words, rather than as individually encoded letters. These words therefore cannot be edited like words entered via a word-processing program. However, a computer equippedwith handwriting-recognition software² can translate hand-printed characters into editable code. The code, in turn, produces characters that look as if they were typed. Pen-based computers use such software. These portable machines are used to record data in situations where typing would be difficult. For example, people who deliver packages by track use them.

A touch screen can produce the same results as an electronic pen and pad. A touch screen produces electric current underneath whatever areas of the screen are pressed. A microprocessor uses the current to produce an image. Notes:

1. A light pen and a touch screen are the most advanced types of input devices.

2. A great variety of input devices is available nowadays.

3. A keyboard is the main input device.

1. All input devices operate automatically once they are turned on.

2. The only function of the keyboard keys is to control the movement of an electronic marker.

3. A keyboard is a reprogrammable device.

4. The keyboard is mechanical hand-operated device.

5. When the user types a character he sends it straight to the screen.

6. If you want to give a command by means of a mouse you should put the pointer on some icon.

7. An icon has a fixed location on the screen.

8. A mouse is a multifunctional device.

9. CD-ROMs can distribute multimedia programs.