TEXT II. COMPUTER SYSTEMS
(1) Computer can be divided into three main types, depending on their size and power. (2) Mainframe computers are the largest and most powerful. They can handle large amounts of information very quickly and can be used by many people at the same time. They usually fill a whole room and are sometimes referred to as mainframes or computer installations. They are found in large institutions like universities and government departments.(3) Minicomputers, commonly known as minis, are smaller and less powerful than mainframes. They are about the size of an office desk and are usually found in banks and offices. They are becoming less popular as microcomputers improve. (4) Microcomputers, commonly known as micros, are the smallest and least powerful. They are about the size of a typewriter. They can handle smaller amounts of information at a time and are slower than the other two types. They are ideal for use as home computers and are also used in education and business. More powerful microcomputers are gradually being produced; therefore they are becoming the most commonly used type of computers. (5) A computer can do very little until it is given some information. This is known as the input and usually consists of program and some data. (6) A program is a set of instructions, written in a special computer language, telling the computer what operations and processes have to be carried out and in what order they should be done. Data, however, is the particular information that has to be processed by the computer, e.g. numbers, names, measurements. Data brought out of the computer is known as the output. EXAMPLE: A computer calculating 34 – 4 = 7 uses the following program and data: PROGRAM Add two numbers then display the result. INPUT DATA 3, 4 OUTPUT DATA 7 (7) When a program is run, i. E. Put into operation, the computer executes the program step by step to process the data. The same program can be used with different sets of data. (8) Information in the form of programs and data is called software, but the pieces of equipment making up the computer system are known as hardware. (9) The most important item of hardware is the CPU (Central Processing Unit). This is the electronic unit at the center of the computer system. It contains the processor and the main memory. (10) The processor is the brain of the computer. It does all the processing and controls all the other devices in the computer system. (11) The main memory is the part of the computer where programs and data being used by the processor can be stored. However it only stores information while the computer is switched on and it has a limited capacity.(12) All the other devices in the computer system, which can be connected to the CPU, are known as peripherals. These include input devices, output devices and storage devices. (13) An input device is a peripheral, which enables information to be fed into the computer. The most commonly used input device is a keyboard, similar to a typewriter keyboard. (14) An output device is a peripheral, which enables information to be brought out of the computer, usually to display the processed data. The most commonly used output device is a specially adapted television known as a monitor or VDU (Visual Display Unit). Another common output device is a printer. This prints the output of the CPU onto paper. (15) A storage device is a peripheral used for the permanent storage of information. It has a much greater capacity than the main memory and commonly uses magnetic tape or magnetic disks as the storage medium. (16) These are the main pieces of hardware of any computer system whether a small “ micro” or a large mainframe system.
TEXT III. TO YOUR HEALTH
(1) Can all this computing be good for you? Are there any unhealthy side effects? The computer seems harmless enough. How bad can it be, sitting in a padded chair in a climate-controlled office? (2) Health questions have been raised by the people who sit all day in front of the video display terminals (VDTs) of their computers. Are computer users getting bad radiation? What about eyestrain? And what about the age-old back problem, updated with new concerns about workers who hold their hands over a keyboard? What about repetitive-action injury also known as carpal tunnel syndrome? What about the risk of miscarriage? (3) Unions and legislators in many communities continue to push for laws limiting exposure to video screens. Many manufacturers now offer screens with built-in protection. (4) Meanwhile, there are a number of things workers can do to take care of themselves. A good place to begin is with an ergonomically designed workstation. Ergonomics is the study of human factors related to computers. A properly designed workstation takes a variety of factors into account, such as the distance from the eyes to the screen and the angle of the arms and wrists. (5) Experts recommend these steps as coping mechanisms:
- Turn the screen away from the window to reduce glare, and cover your screen with a glare deflector. Turn off overhead lights; illuminate your work area with a lamp.
- Put your monitor on a tilt-and-swivel base.
- Get a pneumatically adjustable chair. Position the seat back so your lower back is supported.
- Place the keyboard low enough to avoid arm and wrist fatigue. Do not bend your wrists when you type. Use an inexpensive, raised wrist rest. Do not rest your wrists on a sharp edge.
- Sit with your feet firmly on the floor.
- Exercise at your desk occasionally rotating your wrist, rolling your shoulders, and stretching. Better yet, get up and walk around at regular intervals.