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CONTENTSCONTENTSCONTENTSCONTENTS

OPERATE A COMPUTER 3

Types of Computer Hardware 3

What Different Types of Computer Hardware are there and How to Use Them 3

The Central Processing Unit (CPU) 3

Input Devices 4 Mouse 4 Light Pen 4 Keyboard 4 Touch Screen Display 5 Graphics Tablet 5 Voice Recognition 5 Microphone 5 Mouse 6 Joystick 6 Optical Scanner 6 Modem 6

Output Devices 7 Monitors 7 Printers 7 Sound 8

Memory Storage 8 Disc Drives 9 Random Access Memory or RAM 10

Connections 10 Bus 10 Data Transfer 11 Microprocessor 11 Printed Circuit Board 11 Expansion Slot 11

Connecting up a Computer 11

Tools and Functions 13

What the Tools and Functions of Software Can Do 13

Computer Uses 13

How it Works 13

Computer Program or Software 13 Different types of Software 14 Application 14 Word Processor 14 Spreadsheet Program 15 Network Applications 15 Shareware 15 Software Suites 15 The Operating System 16 Multi-tasking 16

Health and Safety Issues 18

The Health and Safety Issues in Using IT 18

Regulations and Obligations for Employers 18 Health and Safety at Work Act 1974 18 Health & Safety (Display Screen Equipment) Regulations 1992 18 Management of Health & Safety at Work Regulations 1992 20 Provision and Use of Work Equipment Regulations 1992 20 Workplace (Health, Safety and Welfare) Regulations 1992 21 Ergonomics 21

The Risks 22

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Musculoskeletal problems 22 Eye strain 23

Action and Prevention 24 Avoiding Musculoskeletal problems 24 Avoiding Eyestrain Problems 25 General working environment 25

Compatibility 26

Why and how to make sure that hardware and software are compatible 26

Hardware Issues 26

Software Issues 26 Forward compatibility 27 Backward compatibility 27

How to Avoid Compatibility Issues 27 Cross Platform Connectivity 27 Choosing Software and Hardware 27 File Format Compatibility 28

Setting Standards 28

The Problem with Vista 28

The Windows Compatible Hardware and Software Web site 28

Data Transmission Speeds 30

Why and How Data Transmission Speeds Vary 30

Modems 30 Analogue Modem 31 Integrated Digital Services Network (ISDN) 31 Asymmetrical Digital Subscriber Line (ADSL) 31

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OPERATE A COMPUTER

Types of Computer Hardware

What Different Types of Computer Hardware are there and How to Use Them Modern digital computers are all conceptually similar, regardless of size. Nevertheless, they can be divided into several categories on the basis of cost and performance: the personal computer or microcomputer, a relatively low-cost machine, usually of desk-top size (though “laptops” are small enough to fit in a briefcase, and “palmtops” can fit into a pocket); the workstation, a microcomputer with enhanced graphics and communications capabilities that make it especially useful for office work; the minicomputer, generally too expensive for personal use, with capabilities suited to a business, school, or laboratory; and the mainframe computer, a large, expensive machine with the capability of serving the needs of major business enterprises, government departments, scientific research establishments, or the like (the largest and fastest of these are called supercomputers). A digital computer is not a single machine: rather, it is a system composed of five distinct elements: (1) a central processing unit; (2) input devices; (3) output devices; (4) memory storage devices; and (5) a communications network, called a bus, which links all the elements of the system and connects the system to the external world. The hardware are the parts of computer itself including the Central Processing Unit (CPU) and related microchips and micro-circuitry, keyboards, monitors, case and drives (floppy, hard, CD, DVD, optical, tape, etc...). Other extra parts called peripheral components or devices include mouse, printers, modems, scanners, digital cameras and cards (sound, colour, and video) etc... Hardware, then, in computer science is the physical components of a computer system, including any peripheral equipment such as printers, modems, and mice. Together they are often referred to as a personal computer or PC. The Central Processing Unit (CPU) The CPU may be a single chip or a series of chips that perform arithmetic and logical calculations and that time and control the operations of the other elements of the system. Miniaturization and integration techniques made possible the development of the microprocessor, a CPU chip that incorporates additional circuitry and memory. The result is smaller computers and reduced support circuitry. Microprocessors are used in personal computers. Most CPU chips and microprocessors are composed of four functional sections: (1) an arithmetic/logic unit; (2) registers; (3) a control section; and (4) an internal bus. The arithmetic/logic unit gives the chip its calculating ability and permits arithmetical and logical operations. The registers are temporary storage areas that hold data, keep track of instructions, and hold the location and results of these operations. The control section has three principal duties. It times and regulates the operations of the entire computer system; its instruction decoder reads the patterns of data in a designated register and translates the pattern into an activity, such as adding or comparing; and its interrupt unit indicates the order in which individual operations use the CPU, and regulates the amount of CPU time that each operation may consume. The last segment of a CPU chip or microprocessor is its internal bus, a network of communication lines that connects the internal elements of the processor and also leads to external connectors that link the processor to the other elements of the computer system. The three types of CPU buses are: (1) a control bus consisting of a line that senses input signals and another line that generates control signals from within the CPU; (2) the address bus, a one-way line from the processor that handles the location of data in memory addresses; and (3) the data bus, a two-way transfer line that both reads data from memory and writes new data into memory. Though the term relates to a specific chip or the processor a CPU's performance is determined by the rest of the computer's circuitry and chips. Currently the Pentium chip or processor, made by Intel, is the most common CPU though there are many other companies that produce processors for personal computers. Examples are the CPU made by Motorola and AMD. With faster processors the clock speed becomes more important. Compared to some of the first computers which operated at below 30 megahertz (MHz) the Pentium chips began at 75 MHz in the late 1990's. Speeds now exceed 3000+ MHz or 3 gigahertz (GHz) and different chip manufacturers use different measuring standards. It depends on the circuit board that the chip is housed in, or the motherboard, as to whether you are able to upgrade to a faster chip. The motherboard contains the circuitry and connections that allow the various components to communicate with each other.

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Input Devices These devices enable a computer user to enter data, commands, and programs into the CPU. The most common input device is the keyboard. Information typed at the typewriter-like keyboard is translated by the computer into recognizable patterns. Other input devices include the mouse, which translates physical motion into motion on a computer video display screen; the joystick, which performs the same function, and is favoured for computer games; the trackball, which replaces the mouse on laptops; scanners, which “read” words or symbols on a printed page and translate them into electronic patterns that the computer can manipulate and store; light pens, which can be used to “write” directly on the monitor screen; graphics tablets which use a pen and a pen for inputting; and voice recognition systems, which take spoken words and translate them into digital signals for the computer. Strictly speaking the latter may be considered software but would use a microphone (the hardware) for inputting speech - hence its inclusion here. Mouse Most modern computers today are run using a mouse controlled pointer. Generally if the mouse has two buttons the left one is used to select objects and text and the right one is used to access menus. If the mouse has one button (Mac for instance) it controls all the activity and a mouse with a third button can be used by specific software programs. One type of mouse has a round ball under the bottom of the mouse that rolls and turns two wheels which control the direction of the pointer on the screen. Another type of mouse uses an optical system to track the movement of the mouse. Note: It is important to clean the mouse periodically, particularly if it becomes sluggish. A ball type mouse has a small circular panel that can be opened, allowing you to remove the ball. Lint can be removed carefully with a tooth pick or tweezers and the ball can be washed with mild detergent. A build up will accumulate on the small wheels in the mouse. Use a small instrument or finger nail to scrape it off taking care not to scratch the wheels. Track balls can be cleaned much like a mouse and touch-pad can be wiped with a clean, damp cloth. An optical mouse can accumulate material from the surface that it is in contact with which can be removed with a finger nail or small instrument. Light Pen Light Pen, a pointing device in which the user holds a wand, which is attached to the computer, up to the screen and selects items or chooses commands on the screen (the equivalent of a mouse click) either by pressing a clip on the side of the light pen or by pressing the light pen against the surface of the screen. The wand contains light sensors and sends a signal to the computer whenever it records a light, as during close contact with the screen when the non-black pixels beneath the wand's tip are refreshed by the display's electron beam. The computer's screen is not all lit at once—the electron beam that lights pixels on the screen traces across the screen row by row, all in the space of 1/50 of a second. By noting exactly when the light pen detected the electron beam passing its tip, the computer can determine the light pen's location on the screen. The light pen doesn't require a special screen or screen coating, as does a touch screen, but its disadvantage is that holding the pen up for an extended length of time is tiring to the user. Keyboard The keyboard is used to type information into the computer or input information. The most common English-language key pattern for typewriters and keyboards is called QWERTY, after the layout of the first six letters in the top row of its keys (from left to right). In the late 1860s, American inventor and printer Christopher Sholes invented the modern form of the typewriter. Sholes created the QWERTY keyboard layout by separating commonly used letters so that typists would type slower and not jam their mechanical typewriters. Subsequent generations of typists have learned to type using QWERTY keyboards, prompting manufacturers to maintain this key orientation on typewriters. Computer keyboards copied the QWERTY key layout and have followed the precedent set by typewriter manufacturers of keeping this convention. Modern keyboards connect with the computer CPU by cable or by infrared transmitter. When a key on the keyboard is pressed, a numeric code is sent to the keyboard’s driver software and to the computer’s operating system software. The driver translates this data into a specialized command that the computer’s CPU and application programs understand. In this way, users may enter text, commands, numbers, or other data. The term character is generally reserved for letters, numbers, and punctuation, but may also include control codes, graphical symbols, mathematical symbols, and graphic images. The standard keyboard has 101 keys. Notebooks have embedded keys accessible by special keys or by pressing key combinations (CTRL or Command and P for example). Ergonomically designed keyboards are designed to make typing easier.

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Some of the keys have a special use. There are referred to as command keys. The 3 most common are the Control or CTRL, Alternate or Alt and the Shift keys though there can be more (the Windows key for example or the Command key). Each key on a standard keyboard has one or two characters. Press the key to get the lower character and hold Shift to get the upper. Touch Screen Display Touch-screen displays, which are video displays with a special touch-sensitive surface, are also becoming popular with personal electronic devices - examples include the Apple iPhone and Nintendo DS video game system. Touch-screen displays are also becoming common in everyday use. Examples include ticket kiosks in airports and automated teller machines (ATM). Graphics Tablet A graphics tablet is an input device used by artists which allows one to draw a picture onto a computer screen without having to utilize a mouse or keyboard. A graphics tablet consists of a flat tablet and some sort of drawing device, usually either a pen or stylus. A graphics tablet may also be referred to as a drawing tablet or drawing pad. While the graphics tablet is most suited for artists and those who want the natural feel of a pen-like object to manipulate the cursor on their screen, non-artists may find them useful as well. The smooth flow of a graphics tablet can be refreshing for those who find the mouse to be a jerky input device, and repetitive stress injuries such as carpal tunnel syndrome are less likely when using a graphics tablet. The stylus included with a graphics tablet is also an important consideration for the consumer. A stylus may be either attached to the tablet by a cord or tether-free. Corded tablets do not require batteries, but many people find the cord severely limiting to their range of motion. A good stylus will also have function buttons on the side, so that you can perform common actions, such as switching a tool in a drawing program from paint to erase, without having to use the mouse or keyboard. Voice Recognition Voice recognition or speech recognition in this case, is a computer technology that utilizes audio input for entering data rather than a keyboard. Speaking into a microphone, for example, produces the same result as typing words manually with a keyboard. Simply stated, voice recognition software is designed with an internal database of recognizable words or phrases. The program matches the audio signature of speech with corresponding entries in the database. Though turning speech into text might sound easy, it is an extremely difficult task. The problem lies in the virtually infinite array of individual speech patterns and accents, compounded by the natural human tendency to run words together. Various models of voice recognition software are used for an array of applications, from personal dictation to commercial automated call routing, from aiding the disabled to sports and news event subtitling. Each model behaves differently and has its own capabilities and boundaries. Voice recognition programs that require the user to "train" the software to recognize their particular stylized patterns of speech are called speaker dependent systems. Individuals commonly use these types of programs at home or at the office. Email, memos, letters, data and text can be input by speaking into a microphone. Microphone This is a device used to transform sound energy into electrical energy. Microphones are important in many kinds of communications systems and in instruments that measure sound and noise. The American inventor Alexander Graham Bell built the first microphone in 1876 when he constructed his telephone transmitter. The simplest type of modern microphone is the carbon microphone, used in telephones. This microphone consists of a metallic cup filled with carbon granules; a movable metallic diaphragm mounted in contact with the granules covers the open end of the cup. Wires attached to the cup and diaphragm are connected to an electrical circuit so that a current flows through the carbon granules. Sound waves vibrate the diaphragm, varying the pressure on the carbon granules. The electrical resistance of the carbon granules changes with the varying pressure, causing the current in the circuit to change according to the vibrations of the diaphragm. The varying current may either actuate a nearby telephone receiver or may be amplified and transmitted to a distant receiver. If the current variation is suitably amplified, it may also be used to modulate a radio transmitter. Another common type, the crystal microphone, utilizes piezoelectric crystals, in which a voltage develops between two faces of the crystal when pressure is applied to the crystal. In this microphone sound waves vibrate a diaphragm, which in turn varies the pressure on a piezoelectric crystal. This generates a small voltage, which is then amplified.

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Examples of dynamic microphones include ribbon microphones and moving-coil microphones. In ribbon microphones, a thin metallic ribbon is attached to the diaphragm and placed in a magnetic field. When sound waves strike the diaphragm and vibrate the ribbon, a small voltage is generated in the ribbon by electromagnetic induction. A moving-coil microphone operates on essentially the same principle but has a coil of light wire, instead of a ribbon, attached to the diaphragm. Some modern microphones, designed to pick up sound from one direction only, combine both ribbon and coil elements. Mouse This is a common pointing device used with personal computers that have a graphical user interface (GUI). A user typically operates a mouse with one hand in order to move a cursor over images or text on a computer screen. Clicking buttons on the mouse activates, opens, or moves icons or other graphical objects on the screen when they are displayed under the floating cursor. Another type of pointing device called a joystick is typically used for interacting with computer games. A mouse is commonly attached to a personal computer by a cord that connects to a universal serial bus (USB) port. The rectangular USB interface allows the mouse to report its position at a very high rate. Other types of interfaces include a PS/2 port, which uses a smaller, round connector and reports the mouse’s position at a lower rate. The PS/2 port is a dedicated mouse port built into the motherboard of the computer. The basic features of a mouse are a casing with a flat bottom, designed to be gripped by one hand; one or more buttons on the top; a multidirectional detection device on the bottom; and a cable connecting the mouse to the computer. By moving the mouse on a surface (such as a desk), the user typically controls an on-screen cursor. A mouse is a relative pointing device because there are no defined limits to the mouse’s movement and because its placement on a surface does not map directly to a specific screen location. To select items or choose commands on the screen, the user presses one of the mouse's buttons, producing a “mouse click.” Most computer mice now have a small vertical wheel between two buttons to allow easy scrolling up and down a screen. Left-handed people can also reprogram a mouse to switch functions assigned to the right and left buttons Joystick In computer science, a popular pointing device, used mostly for playing computer games but used for other tasks as well. A joystick usually has a square or rectangular plastic base to which is attached a vertical stem. Control buttons are located on the base and sometimes on top of the stem. The stem can be moved omni-directionally to control the movement of an object on the screen. The buttons activate various software features, generally producing on-screen events. A joystick is usually a relative pointing device, moving an object on the screen when the stem is moved from the centre and stopping the movement when the stem is released. In industrial control applications, the joystick can also be an absolute pointing device, with each position of the stem mapped to a specific on-screen location. Optical Scanner An optical scanner is a computer input device that uses light-sensing equipment to scan paper or another medium, translating the pattern of light and dark (or colour) into a digital signal that can be manipulated by either optical character recognition software or graphics software. A frequently encountered type of scanner is “flatbed,” meaning that the scanning device moves across or reads across a stationary document. On a flatbed scanner such as the common office copier, such objects are placed face down on a flat piece of glass and scanned by a mechanism that passes under them. Another type of flatbed scanner uses a scanning element placed in a stationary housing above the document. Other scanners work by pulling in sheets of paper, which are scanned as they pass over a stationary scanning mechanism, as in the common office fax machine. Some specialized scanners work with a standard video camera, translating the video signal into a digital signal for processing by computer software. A very popular type of scanner is the hand-held scanner, so called because the user holds the scanner in his or her hand and moves it over the document to be scanned. Hand-held scanners have the advantage of relatively low cost; however, they are somewhat limited by their inability to scan areas more than a few inches wide. Modem A modem, which stands for modulator-demodulator, is a device that connects a computer to a telephone line or cable television network and allows information to be transmitted to or received from another computer. Each computer that sends or receives information must be connected to a modem. The digital signal sent from one computer is converted by the modem into an analogue signal, which is then transmitted by telephone lines or television cables to the receiving modem, which converts the signal back into a digital signal that the receiving computer can understand.

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Modems are measured by the speed that the information is transferred. The measuring tool is called the baud rate. Originally modems worked at speeds below 2400 baud but today analog speeds of 56,000 are common. Cable, wireless or digital subscriber lines (DSL) modems can transfer information much faster with rates of 300,000 baud and up. Modems also use Error Correction which corrects for transmission errors by constantly checking whether the information was received properly or not and Compression which allows for faster data transfer rates. Information is transferred in packets. Each packet is checked for errors and is re-sent if there is an error. Anyone who has used the Internet has noticed that at times the information travels at different speeds. Depending on the amount of information that is being transferred the information will arrive at it's destination at different times. The amount of information that can travel through a line is limited. This limit is called bandwidth. A network interface card (NIC) allows the computer to access a local area network (LAN) through either a specialized cable similar to a telephone line or through a wireless (Wi-Fi) connection. The vast majority of LANs connect through the Ethernet standard, which was introduced in 1983. Output Devices Output hardware consists of internal and external devices that transfer information from the computer’s CPU to the computer user. Graphics adapters, which are either an add-on card (called a video card) or connected directly to the computer’s motherboard, transmit information generated by the computer to an external display. Displays commonly take one of two forms: a video screen with a cathode-ray tube (CRT) or a video screen with a liquid crystal display (LCD). A CRT-based screen, or monitor, looks similar to a television set. Information from the CPU is displayed using a beam of electrons that scans a phosphorescent surface that emits light and creates images. An LCD-based screen displays visual information on a flatter and smaller screen than a CRT-based video monitor. Laptop computers use LCD screens for their displays but generally speaking CRT screens are now antiquated and one would be hard pushed to find one nowadays. Monitors This is a device connected to a computer that displays information on a screen. Modern computer monitors can display a wide variety of information, including text, icons (pictures representing commands), photographs, computer rendered graphics, video, and animation. A TFT LCD monitor is a type of flat-panel display that works as either a computer monitor or as a television. TFT LCD is short for thin film transistor liquid crystal display. Most of the time, manufacturers shorten the term for such displays to LCD, dropping the TFT from the name. TFT simply refers to the type of LCD monitor, and TFT is easily the most popular type of LCD. The thin film transistor in a TFT LCD monitor consists of a thin film of a semiconductor material applied over a glass substrate. Each pixel in a TFT LCD monitor has its own transistor along with the liquid crystal material. The liquid crystal material exhibits properties of both a liquid, because of its ability to change quickly, and a crystal, because of its ability to remain in an arranged position. The transistor applies a voltage to the pixel, determining the colour and intensity of the pixel. A pixel is short for picture element, and the tiny pixels blend together to create the image on a display. The amount of detail, or resolution, that a monitor can display depends on the size of the screen, the dot pitch, and on the type of display adapter used. The display adapter is a circuit board that receives formatted information from the computer and then draws an image on the monitor, displaying the information to the user. Display adapters follow various standards governing the amount of resolution they can obtain. Most colour monitors are compatible with Video Graphics Array (VGA) standards, which are 640 by 480 pixels (640 pixels on each of 480 rows), or about 300,000 pixels. VGA yields 16 colours, but most modern monitors display far more colours and are considered high resolution in comparison. Super VGA (SVGA) monitors have 1024 by 768 pixels (about 800,000) and are capable of displaying more than 60,000 different colours. Some SVGA monitors can display more than 16 million different colours. Printers A printer is a computer peripheral that puts text or a computer-generated image on paper or on another medium, such as a transparency. Printers can be categorized in any of several ways. The most common distinction is impact versus non-impact. Impact printers physically strike the paper and are exemplified by pin dot-matrix printers and daisy-wheel printers; non-impact printers include every other type of print mechanism, including laser and ink jet. A Laser Printer is an electrophotographic printer that is based on the technology used by photocopiers. A focused laser beam and a rotating mirror are used to draw an image of the desired page on a photosensitive drum. This

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image is converted on the drum into an electrostatic charge, which attracts and holds toner. A piece of electrostatically charged paper is rolled against the drum, which pulls the toner away from the drum and onto the paper. Heat is then applied to fuse the toner to the paper. Finally, the electrical charge is removed from the drum and the excess toner is collected. By omitting this final step and repeating only the toner-application and paper-handling steps, the printer can make multiple copies. Ink-jet printers, at the most basic level place small drops of ink onto the paper. The ink is transferred to the paper by way of nozzles. These nozzles then spray the ink directly onto the paper. A dot-matrix printer is any printer that produces characters made up of dots using a wire-pin print head. The quality of output from a dot-matrix printer depends largely on the number of dots in the matrix, which might be low enough to show individual dots or might be high enough to approach the look of fully formed characters. Dot-matrix printers are often categorized by the number of pins in the print head - typically 9, 18, or 24. Sound Computers can also output audio via a specialized chip on the motherboard or an add-on card called a sound card. Users can attach speakers or headphones to an output port to hear the audio produced by the computer. Many modern sound cards allow users to create music and record digital audio, as well. The sound card is a printed circuit board, or card, that can translate digital information into sound and back; also called a sound board or sound adapter. Sound cards plug into a slot on the motherboard (the main circuit board of a computer) and are usually connected to a pair of speakers (see Sound Recording and Reproduction). To play sounds, the sound card receives digital information from a stored file and turns it into an electrical signal it sends to the speakers, which produce the sound. If the sound card is attached to a microphone, the sound card can take the incoming sound and convert it into digital information by sampling, or taking tiny sections of, the sound many times each second. Each sample is given a number that represents the loudness and tone of the sample and the order in which it occurs in the entire sound. Memory Storage Memory can be very confusing but is usually one of the easiest pieces of hardware to add to your computer. It is common to confuse chip memory with disc storage. An example of the difference between memory and storage would be the difference between a table where the actual work is done (memory) and a filing cabinet where the finished product is stored (disc). To add a bit more confusion, the computer's hard disc can be used as temporary memory when the program needs more than the chips can provide. Storage hardware provides permanent storage of information and programs for retrieval by the computer. The two main types of storage devices are disc drives and memory. There are several types of disc drives: hard, floppy, magneto-optical, magnetic tape, and compact. Hard disc drives store information in magnetic particles embedded in a disc. Usually a permanent part of the computer, hard disc drives can store large amounts of information and retrieve that information very quickly. Floppy disc drives also store information in magnetic particles embedded in removable discs that may be floppy or rigid. Floppy discs store less information than a hard disc drive and retrieve the information at a much slower rate. While most computers still include a floppy disc drive, the technology has been gradually phased out in favour of newer technologies. Magneto-optical disc drives store information on removable discs that are sensitive to both laser light and magnetic fields. They can store up to 9.1 gigabytes (GB) of data, but they have slightly slower retrieval speeds as opposed to hard drives. They are much more rugged than floppy discs, making them ideal for data backups. However, the introduction of newer media that is both less expensive and able to store more data has made magneto-optical drives obsolete. Magnetic tape drives use magnetic tape similar to the tape used in VCR cassettes. Tape drives have a very slow read/write time, but have a very high capacity; in fact, their capacity is second only to hard disc drives. Tape drives are mainly used to back up data. Compact disc drives store information on pits burned into the surface of a disc of reflective material. CD-ROMs can store up to 737 megabytes (MB) of data. A Compact Disc-Recordable (CD-R) or Compact Disc-ReWritable (CD-RW) drive can record data onto a specialized disc, but only the CD-RW standard allows users to change the data stored on the disc. A digital versatile disc (DVD) looks and works like a CD-ROM but can store up to 17.1 GB of data on a single disc. Like CD-ROMs, there are specialized versions of DVDs, such as DVD-Recordable (DVD-R) and DVD-ReWritable (DVD-RW), that can have data written onto them by the user. More recently Sony Electronics developed DVD technology called Blu-ray. It has much higher storage capacities than standard DVD media.

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Disc Drives These are devices that read or write data, or both, on a disc medium. The terms “disc” and “disk” are interchangeable with latter being the popular term in America. I will use the former. The disc medium may be either magnetic, as with floppy discs or hard discs; optical, as with CD-ROM (compact disc-read only memory) discs; or a combination of the two, as with magneto-optical discs. Nearly all computers come equipped with drives for these types of discs, and the drives are usually inside the computer, but may also be connected as external, or peripheral, devices. The main components of a disc drive are the motor, which rotates the disc; the read-write mechanism; and the logic board, which receives commands from the operating system to place or retrieve information on the disc. To read or write information to a disc, drives use various methods. Floppy and hard drives use a small magnetic head to magnetize portions of the disc surface, CD-ROM and magneto-optical drives use a combination of magnetic and optical techniques to store and retrieve information. Floppy and hard disc drives store information on magnetic discs. The disc itself is a thin, flexible piece of plastic with tiny magnetic particles imbedded in its surface. To write data to the disc, the read-write head creates a small magnetic field that aligns the magnetic poles of the particles on the surface of the disc directly beneath the head. Particles aligned in one direction represent a 0 while particles aligned in the opposite direction represent a 1. To read data from a disc, the drive head scans the surface of the disc. The magnetic fields of the particles in the disc induce an alternating electric current in the read-write head, which is then translated into the series of 1s and 0s that the computer understands. Unlike hard or floppy discs, most CD-ROM drives are unable to write data to the CD. Data is initially written to CD-ROM discs by burning microscopic pits into the disc's reflective surface with a laser. To read the information contained on the disc, the drive shines a low-power laser beam onto the surface. When the laser light hits flat spots on the reflective surface of the CD, it bounces back to a photo detector, which records the impulse as a 0. When the laser light hits pits in the surface, it does not reflect light back to the photo detector, and this absence of light corresponds to a 1. Most CD-ROM drives are only capable of reading data and cannot write data to the CD. Hard discs have one or more inflexible platters coated with material that allows the magnetic recording of computer data. Hard discs provide faster access to data than floppy discs and are capable of storing much more information. Because platters are rigid, they can be stacked so that one hard-disc drive can access more than one platter. Most hard discs have from two to eight platters. Floppy Discs are round, flat piece of Mylar coated with ferric oxide, a rust like substance containing tiny particles capable of holding a magnetic field, and encased in a protective plastic cover, the disc jacket. Data is stored on a floppy disc by the disc drive’s read/write head, which alters the magnetic orientation of the particles. Orientation in one direction represents binary 1; orientation in the other, binary 0. Typically, a floppy disc is 5.25 inches in diameter, with a large hole in the centre that fits around the spindle in the disc drive. Depending on its capacity, such a disc can hold from a few hundred thousand to over 1 million bytes of data. A 3.5-inch disc encased in rigid plastic is usually called a microfloppy disc but can also be called a floppy disc. Floppy discs have been superseded by other data storage devices such as recordable compact discs (CDs) and digital versatile discs (DVDs), and solid-state memory sticks and flash drives. A CD-ROM, in computer science, is an acronym for compact disc read-only memory, a rigid plastic disc that stores a large amount of data through the use of laser optics technology. Because they store data optically, CD-ROMs have a much higher memory capacity than computer discs that store data magnetically. However, CD-ROM drives, the devices used to access information on CD-ROMs, can only read information from the disc, not write to it. The underside of the plastic CD-ROM disc is coated with a very thin layer of aluminum that reflects light. Data is written to the CD-ROM by burning microscopic pits into the reflective surface of the disc with a powerful laser. The data is in digital form, with pits representing a value of 1 and flat spots, called land, representing a value of 0. Once data is written to a CD-ROM, it cannot be erased or changed, and this is the reason it is termed read-only memory. Data is read from a CD-ROM with a low power laser contained in the drive that bounces light—usually infrared—off of the reflective surface of the disc and back to a photodetector. The pits in the reflective layer of the disc scatter light, while the land portions of the disc reflect the laser light efficiently to the photodetector. The photodetector then converts these light and dark spots to electrical impulses corresponding to 1s and 0s. Electronics and software interpret this data and accurately access the information contained on the CD-ROM. CD-ROMs can store large amounts of data and so are popular for storing databases and multimedia material. The most common format of CD-ROM holds approximately 630 megabytes. By comparison, a regular floppy disc holds approximately 1.44 megabytes.

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CD-ROMs and Audio CDs are almost exactly alike in structure and data format. The difference between the two lies in the device used to read the data—either a CD-ROM player or a compact disc (CD) player. CD-ROM players are used almost exclusively as computer components or peripherals. They may be either internal (indicating they fit into a computer’s housing) or external (indicating they have their own housing and are connected to the computer via an external port). A DVD or Digital Versatile Disc, is an optical storage device in the form of a flat plastic platter that has the same diameter as a compact disc (CD). Originally called a digital video disc, the digital versatile disc is able to hold many times the digital information that can be stored on a CD. In addition, one side of a DVD can have two (dual) superimposed, readable layers, nearly doubling the data capacity. If a DVD is two-sided, the amount of stored data can be doubled again. DVDs have been widely adopted for recordings of motion pictures and other video material sold for home viewing, as well as for distributing copies of computer software, and interactive video and computer game software. Other types of material available in digital form on DVDs include multimedia encyclopaedias, high-fidelity audio, and collections of photographs. High-definition DVDs have much higher storage capacity, permitting high-definition video and a wider variety of interactive features. Recordable DVDs can store many types of information and media in digital form, transferred using a personal computer or different types of DVD recorders. Random Access Memory or RAM Random Access Memory or RAM, is the memory that the computer uses to temporarily store the information as it is being processed. The more information being processed the more RAM the computer needs. RAM memory chips come in many different sizes and speeds and can usually be expanded. Older computers came with 512 Kb of memory which could be expanded to a maximum of 640 Kb. In most modern computers the memory can be expanded by adding or replacing the memory chips depending on the processor you have and the type of memory your computer uses. Memory chips range in size from 1 Mb to 4 Gb. As computer technology changes the type of memory changes as well making old memory chips obsolete. Typically, programs are transferred from storage on a disc drive to RAM. RAM is also known as volatile memory because the information within the computer chips is lost when power to the computer is turned off. Read-only memory (ROM) contains critical information and software that must be permanently available for computer operation, such as the operating system that directs the computer's actions from start up to shut down. ROM is called non-volatile memory because the memory chips do not lose their information when power to the computer is turned off. A more recent development is solid-state RAM. Unlike standard RAM, solid state RAM can contain information even if there is no power supply. Flash drives are removable storage devices that utilize solid-state RAM to store information for long periods of time. Solid-state drives (SSD) have also been introduced as a potential replacement for hard disc drives. SSDs have faster access speeds than hard discs and have no moving parts. However, they are quite expensive and do not have the ability to store as much data as a hard disc. Solid-state RAM technology is also used in memory cards for digital media devices, such as digital cameras and media players. Some devices serve more than one purpose. For example, floppy discs may also be used as input devices if they contain information to be used and processed by the computer user. In addition, they can be used as output devices if the user wants to store the results of computations on them. Connections To function, hardware requires physical connections that allow components to communicate and interact. A bus provides a common interconnected system composed of a group of wires or circuitry that coordinates and moves information between the internal parts of a computer. A computer bus consists of two channels, one that the CPU uses to locate data, called the address bus, and another to send the data to that address, called the data bus. A bus is characterized by two features: how much information it can manipulate at one time, called the bus width, and how quickly it can transfer these data. In today’s computers, a series of buses work together to communicate between the various internal and external devices. Bus The bus enables the components in a computer, such as the CPU and the memory circuits, to communicate as program instructions are being carried out. The bus is usually a flat cable with numerous parallel wires. Each wire can carry one bit, so the bus can transmit many bits along the cable at the same time. For example, a 16-bit bus, with 16 parallel wires, allows the simultaneous transmission of 16 bits (2 bytes) of information from one component to another. Early computer designs utilized a single or very few buses. Modern designs typically use many buses; some of them specialized to carry particular forms of data, such as graphics.

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A Bus then, is a set of wires used for data transfer among the components of a computer system. A bus is essentially a shared highway that connects different parts of the system - including the central processing unit (CPU), disk-drive controller, memory, and input/output ports - and enables them to transfer information. Usually controlled by a microprocessor, the bus is, in computers such as the Apple Macintosh and IBM and compatible models, specialized for carrying different types of information. One group of wires (actually, traces on a printed circuit board), for example, carries data; another carries the addresses (locations) where specific information can be found; yet another carries control signals to ensure that the different parts of the system use their shared highway without conflict. Buses are characterized by the number of bits they can transfer at a single time. A computer with an 8-bit data bus, for example, transfers 8 bits of data at a time, and one with a 16-bit data bus transfers 16 bits at a time. Because the bus is integral to internal data transfer and yet computer users often need to add extra components to the system, most microcomputer buses allow for expansion through one or more expansion slots (connectors for add-on circuit boards). Such boards, when they are added, make an electrical connection to the bus and effectively become part of the system. Data Transfer Data Transfer, in computer science, the movement of information from one location to another, either within a computer (as from a disk drive to random access memory) or between a computer and an external device (as between two computers or a file server and a computer on a network). The speed of transfer is called the data rate, or data transfer rate, and is usually measured in bits per second, or bps. The raw data rate (the maximum transfer speed) is usually considerably higher than the actual rate at which meaningful data is transferred because of idle time, error-checking procedures, and other overhead. Also, data transfers from different sources to different destinations often compete with each other if they use the same data path - for example, on a network, or on a bus in a computer system. Microprocessor A Microprocessor is an electronic circuit that functions as the central processing unit (CPU) of a computer, providing computational control. Microprocessors are also used in other advanced electronic systems, such as computer printers, automobiles, and jet airliners. The microprocessor is one type of ultra-large-scale integrated circuit. Integrated circuits, also known as microchips or chips, are complex electronic circuits consisting of extremely tiny components formed on a single, thin, flat piece of material known as a semiconductor. Modern microprocessors incorporate transistors (which act as electronic amplifiers, oscillators, or, most commonly, switches), in addition to other components such as resistors, diodes, capacitors, and wires, all packed into an area about the size of a postage stamp. A crystal oscillator in the computer provides a clock signal to coordinate all activities of the microprocessor. The clock speed of the most advanced microprocessors allows billions of computer instructions to be executed every second. Printed Circuit Board A Printed Circuit Board, sometimes abbreviated PCB, is a flat board made of non-conducting material, such as plastic or fibreglass, on which chips and other electronic components are mounted, usually in predrilled holes designed to hold them. The components on a printed circuit board - or, more specifically, the holes that hold them - are connected electrically by predefined conductive metal pathways that are printed on the surface of the board. The metal leads protruding from the electronic components are soldered to the conductive metal pathways to form a connection. A printed circuit board should be held by the edges and protected from dirt and static electricity to avoid damage. Expansion Slot This is a socket inside a computer console, designed to hold expansion boards and connect them to the system bus (data pathway). The number of sockets, or slots, determines the amount of expansion allowed. Most personal computers have from three to eight expansion slots. Expansion slots provide a means of adding new or enhanced features or more memory to the system. Connecting up a Computer The connections on the back of a computer unit are, most often than not, colour coded to make it simple to see what fits into where. Even if the connections are not colour coded, there is usually only one place that a device will plug into. There are different connections that will be used to connect different peripheral devices to the base or tower unit of a computer, as follows:

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1. Serial - this is a port on the base unit that can be used to connect modems, mouse devices and PDA’s. 2. Parallel - this port on the system can be used to connect printers. 3. PS/2 - this port on the system can be used to connect keyboard, joysticks and mouse devices. 4. USB - this port on the system can be used to connect mouse devices, keyboards, printers, digital cameras,

music players, scanners, satellite navigation devices, older CD/DVD drives and older external hard drives. 5. Firewire - FireWire is one of the fastest peripheral standards ever developed, which makes it great for use with

multimedia peripherals such as digital video cameras and other high-speed devices like the latest hard disk drives, CD/DVD drives and printers.

There are usually two steps to connecting a piece of hardware to a computer. The first step is to physically attach the hardware to the computer by plugging it into the respective socket or port on the rear of the base unit. The second step is installing the driver, a small piece of software which enables the computer to recognise the hardware and work properly with it. Usually, when one purchases some hardware there will be a CD in the box that contains the driver. The exception to this is hardware that is connected to the USB port of the computer. Any device connected to the USB port is instantly recognised by the operating system and installed automatically. Microsoft operating systems from Windows 2000 and beyond has a list of drivers and finds the appropriate one when hardware is connected. It is not necessary, then, to use the driver on the CD that comes with the hardware. This ability to plug the piece of hardware into the computer and the Windows operating system install it automatically is known as ‘plug and play’.

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Tools and Functions

What the Tools and Functions of Software Can Do A computer is a machine that performs tasks, such as calculations or electronic communication, under the control of a set of instructions called a program, or computer software. Programs usually reside within the computer and are retrieved and processed by the computer’s electronics. The program results are stored or routed to output devices, such as video display monitors or printers. Computers perform a wide variety of activities reliably, accurately, and quickly. What most people think of as a computer can actually be divided into two parts. The first part, computer hardware, does all of the physical work computers are known for. The second part, computer software, tells the hardware what to do and how to do it. If you were to think of a computer as a living being, then the hardware would be the body that does things like seeing with eyes, lifting objects, and filling the lungs with air; the software would be the intelligence, interpreting the images that come through the eyes, telling the arms how to lift objects, and forcing the body to fill the lungs with air. Computer hardware, being part of a machine, can only understand two basic concepts: on and off. The on and off concept is called binary. Computer software was developed in order to make binary into a useful way to tell the computer hardware what to do. Computer software translates concepts and directions that people can understand into something that can actually be done on the computer hardware. Computer Uses People use computers in many ways. In business, computers track inventories with bar codes and scanners, check the credit status of customers, and transfer funds electronically. In homes, tiny computers embedded in the electronic circuitry of most appliances control the indoor temperature, operate home security systems, tell the time, and turn DVD recorders on and off. Computers in automobiles regulate the flow of fuel, thereby increasing gas mileage, and are used in anti-theft systems. Computers also entertain, creating digitized sound on stereo systems or computer-animated features from a digitally encoded laser disc. Computer programs, or applications, exist to aid every level of education, from programs that teach simple addition or sentence construction to programs that teach advanced calculus. Educators use computers to track grades and communicate with students; with computer-controlled projection units, they can add graphics, sound, and animation to their. Computers are used extensively in scientific research to solve mathematical problems, investigate complicated data, or model systems that are too costly or impractical to build, such as testing the air flow around the next generation of aircraft. The military employs computers in sophisticated communications to encode and unscramble messages, and to keep track of personnel and supplies. How it Works The physical computer and its components are known as hardware, (as described above). Computer hardware includes the memory that stores data and program instructions; the central processing unit (CPU) that carries out program instructions; the input devices, such as a keyboard or mouse, that allow the user to communicate with the computer; the output devices, such as printers and video display monitors, that enable the computer to present information to the user; and buses (hardware lines or wires) that connect these and other computer components. The programs that run the computer are called software. Software generally is designed to perform a particular type of task - for example, to control the arm of a robot to weld a car’s body, to write a letter, to display and modify a photograph, or to direct the general operation of the computer. Computer Program or Software A Computer Program is a set of instructions that directs a computer to perform some processing function or combination of functions. For the instructions to be carried out, a computer must execute a program, that is, the computer reads the program, and then follows the steps encoded in the program in a precise order until completion. A program can be executed many different times, with each execution yielding a potentially different result depending upon the options and data that the user gives the computer. Programs fall into two major classes: application programs and operating systems. An application program is one that carries out some function directly for a user, such as word processing or game-playing. An operating system is a program that manages the computer and the various resources and devices connected to it, such as RAM (random access memory), hard drives, monitors, keyboards, printers, and modems, so that they may be used by other programs. Examples of operating systems are DOS, Windows Vista, Mac Leopard, Ubuntu and UNIX. Software or computer programs are instructions that cause the hardware - the machines - to do the work. Software as a whole can be divided into a number of categories based on the types of work done by programs. The two primary software categories are operating systems (system software), which control the workings of the computer,

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and application software, which addresses the multitude of tasks for which people use computers. System software thus handles such essential, but often invisible, chores as maintaining disk files and managing the screen, whereas application software performs word processing, database management, and the like. Two additional categories that are neither system nor application software, although they contain elements of both, are network software, which enables groups of computers to communicate, and language software, which provides programmers with the tools they need to write programs. In addition to these task-based categories, several types of software are described based on their method of distribution. These include the so-called canned programs or packaged software developed and sold primarily through retail outlets, (proprietary software); freeware and public-domain software, which is made available without cost by its developer, and; shareware, which is similar to freeware but usually carries a small fee for those who like the program. Different types of Software Computer software falls into two primary categories: system software and application software. System software represents programs that allow the hardware to run properly. Application software represents programs that allow users to do something besides simply run the hardware. A few different types of computer software include: • Computer Games: a form of entertainment software that has many genres. Some of these genres include

MMOs (Massive Multiplayer Online games), first-person shooters, action games, roleplaying games, and adventure games.

• Driver Software: programs that allow a computer to interact with additional hardware devices such as printers,

scanners, and video cards. • Educational Software: programs and games that teach the user or provide drills to help memorize facts.

Educational software is diverse, and can teach anything from computer-related activities like typing to higher education subjects like chemistry.

• Media Players and Media Development Software: software designed to play and/or edit digital media files

such as music and videos. • Productivity Software: an older term that refers to any programs that would allow the user to be more

productive in a business sense. Word processors, database management utilities, and presentation software all fall into this category.

• Operating Systems: software that coordinates system resources and allows other programs to run. A few

examples are Windows Vista, Mac OS X, and Linux. Application An Application is a computer program designed to help people perform a certain type of work. An application thus differs from an operating system (which runs a computer), a utility (which performs maintenance or general-purpose chores), and a language (with which computer programs are created). Depending on the work for which it was designed, an application can manipulate text, numbers, graphics, or a combination of these elements. Some application packages offer considerable computing power by focusing on a single task, such as word processing; others, called integrated software, offer somewhat less power but include several applications, such as a word processor, spreadsheet programs or network applications, for example. Word Processor A Word Processor is an application program for manipulating text-based documents; the electronic equivalent of paper, pen, typewriter, eraser, and most likely, dictionary and thesaurus. Word processors run the gamut from simple through complex, but all ease the tasks associated with editing documents (deleting, inserting, rewording, and so on). Depending on the program and the equipment in use, word processors can display documents either in text mode, using highlighting, underlining, or colour to represent italics, boldfacing, and other such formatting, or in graphics mode, wherein formatting and, sometimes, a variety of fonts appear on the screen as they will on the printed page. All word processors offer at least limited facilities for document formatting, such as font changes, page layout, paragraph indention, and the like. Some word processors can also check spelling, find synonyms, incorporate graphics created with another program, correctly align mathematical formulas, create and print form letters, perform calculations, display documents in multiple on-screen windows, and enable users to record macros that simplify difficult or repetitive operations.

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The term word processor has also been used to refer to computers introduced in the 1980s that were designed solely for word processing. Word processing computers were able to perform multiple editorial functions, such as editing text, inserting new text, deleting text, and performing search and replace functions within the text. Spreadsheet Program A Spreadsheet Program is an application program commonly used for budgets, forecasting, and other finance-related tasks. In a spreadsheet program, data and formulas to calculate those data are entered into ledger like forms (spreadsheets or worksheets) for analysis, tracking, planning, or “what-if” evaluations of the impacts of real or proposed changes on an economic strategy. Spreadsheet programs use rows and columns of cells; each cell can hold text or numeric data or a formula that uses values in other cells to calculate a desired result. To ease computation, these programs include built-in functions that perform standard calculations. Depending on the program, a single spreadsheet can contain anywhere from thousands to millions of cells. Some spreadsheet programs can also link one spreadsheet to another that contains related information, and can update data in linked spreadsheets automatically. Spreadsheet programs may also include macro facilities, and some can be used for creating and sorting databases. For printed output, spreadsheet programs usually provide graphing capabilities and a variety of formatting options for both printed pages and text, numeric values, and captions and legends in graphs. Network Applications A Network is a system used to link two or more computers. Network users are able to share files, printers, and other resources; send electronic messages; and run programs on other computers. A network has three layers of components: application software, network software, and network hardware. Application software consists of computer programs that interface with network users and permit the sharing of information, such as files, graphics, and video, and resources, such as printers and disks. One type of application software is called client-server. Client computers send requests for information or requests to use resources to other computers, called servers, which control data and applications. Another type of application software is called peer-to-peer. In a peer-to-peer network, computers send messages and requests directly to one another without a server intermediary. Network software consists of computer programs that establish protocols, or rules, for computers to talk to one another. These protocols are carried out by sending and receiving formatted instructions of data called packets. Protocols make logical connections between network applications, direct the movement of packets through the physical network, and minimize the possibility of collisions between packets sent at the same time. Network hardware is made up of the physical components that connect computers. Two important components are the transmission media that carry the computer's signals, typically on wires or fibre-optic cables, and the network adapter, which accesses the physical media that link computers, receives packets from network software, and transmits instructions and requests to other computers. Transmitted information is in the form of binary digits, or bits (1s and 0s), which the computer's electronic circuitry can process. Freeware These are computer programs given away free of charge. Freeware is often made available on bulletin boards, user groups, and freeware sites and all over the internet if you know where to look. An independent program developer might offer a product as freeware either for personal satisfaction or to assess its reception among interested users. Freeware developers often retain all rights to their software; users are not necessarily free to copy or distribute it further. Shareware Shareware is copyrighted computer software that is distributed free of charge but is usually accompanied by a request for a small payment from satisfied users to cover costs and registration for documentation and program updates. Software Suites Software suites are groups of related programs that interact nearly seamlessly with each other to make certain tasks easier among different programs. The popularity of software suites has only increased in recent years as people have turned more to computing for tasks that used to done without the aid of newer technology. However, as with most types of software, the true value of the programs is in their usage. Not everyone will need a software suite. The main benefit of software suites is in the integration of some data sets between the programs. While most software will be able to cut and paste different sets of data fairly easily, software suites take it a step further. Often, the data will retain any other information, such as formatting and any other embedded information. While it may not be guaranteed to carry over, it will in most cases. This may be harder to accomplish, if not impossible, among completely non-related programs.

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The other benefit of software suites is the cost savings that often come with purchasing the programs in a bundle. To purchase each program individually would likely cost much more. Depending on which suite is used, the programs included can be anywhere from two programs to more than five. The most common suites are business software suites and Internet security software suites. While they each perform different functions, they tend to work to accomplish a greater goal. Business suites may need reports, which can be written in a word processor, but may also need a slide show, which a presentation program can produce. Internet security software usually focuses on one particular task, such as defending against viruses. Spyware and adware protection, along with a firewall, may call for an entirely different program or set of programs. The most common and recognizable software suite is the Microsoft Office™ line of products. This will include Microsoft Word™, Microsoft Excel™, Microsoft Outlook™, and Microsoft PowerPoint™ in the most basic form, which is for home and student use. Other versions, such as Microsoft Office Small Business™, and Microsoft Office Pro™, will include additional programs. It should be noted that while purchasing the software titles bundled in a suite is a much more cost effective method than purchasing them individually, they may not all be needed. Instead of buying something you may not need, carefully consider what you will need and whether purchase one or two titles individually may make more sense economically. In most cases, all titles in a software suite are usually available separately. The Operating System The operating system has three major functions: It coordinates and manipulates computer hardware, such as computer memory, printers, disks, keyboard, mouse, and monitor; it organizes files on a variety of storage media, such as floppy disk, hard drive, compact disc, digital video disc, and tape; and it manages hardware errors and the loss of data. When a computer is turned on it searches for instructions in its memory. These instructions tell the computer how to start up. Usually, one of the first sets of these instructions is a special program called the operating system, which is the software that makes the computer work. It prompts the user (or other machines) for input and commands, reports the results of these commands and other operations, stores and manages data, and controls the sequence of the software and hardware actions. When the user requests that a program run, the operating system loads the program in the computer’s memory and runs the program. Popular operating systems, such as Microsoft Windows and the Macintosh system (Mac OS), have graphical user interfaces (GUIs - that use tiny pictures, or icons, to represent various files and commands. To access these files or commands, the user clicks the mouse on the icon or presses a combination of keys on the keyboard. Some operating systems allow the user to carry out these tasks via voice, touch, or other input methods. Operating systems control different computer processes, such as running a spreadsheet program or accessing information from the computer's memory. One important process is interpreting commands, enabling the user to communicate with the computer. Some command interpreters are text oriented, requiring commands to be typed in or to be selected via function keys on a keyboard. Other command interpreters use graphics and let the user communicate by pointing and clicking on an icon, an on-screen picture that represents a specific command. Beginners generally find graphically oriented interpreters easier to use, but many experienced computer users prefer text-oriented command interpreters. Operating systems are either single-tasking or multitasking. The more primitive single-tasking operating systems can run only one process at a time. For instance, when the computer is printing a document, it cannot start another process or respond to new commands until the printing is completed. All modern operating systems are multitasking and can run several processes simultaneously. In most computers, however, there is only one central processing unit (CPU; the computational and control unit of the computer), so a multitasking OS creates the illusion of several processes running simultaneously on the CPU. The most common mechanism used to create this illusion is time-slice multitasking, whereby each process is run individually for a fixed period of time. If the process is not completed within the allotted time, it is suspended and another process is run. This exchanging of processes is called context switching. The OS performs the “bookkeeping” that preserves a suspended process. It also has a mechanism, called a scheduler, which determines which process will be run next. The scheduler runs short processes quickly to minimize perceptible delay. The processes appear to run simultaneously because the user's sense of time is much slower than the processing speed of the computer. Operating systems can use a technique known as virtual memory to run processes that require more main memory than is actually available. To implement this technique, space on the hard drive is used to mimic the extra memory needed. Accessing the hard drive is more time-consuming than accessing main memory, however, so performance of the computer slows. Multi-tasking

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Multi-tasking, in computer science, is a mode of operation offered by an operating system in which a computer works on more than one task at a time. There are several types of multitasking. Context switching is a very simple type of multitasking in which two or more applications are loaded at the same time but only the foreground application is given processing time; to activate a background task, the user must bring the window or screen containing that application to the front. In cooperative multitasking, exemplified by the Macintosh operating system, background tasks are given processing time during idle times in the foreground task (such as when the application waits for a keystroke), and only if the application allows it. In time-slice multi-tasking each task is given the microprocessor's attention for a fraction of a second. To maintain order, tasks are either assigned priority levels or processed in sequential order. Because the user's sense of time is much slower than the processing speed of the computer, time-slice multitasking operations seem to be simultaneous. Current Operating Systems Operating systems commonly found on personal computers include UNIX, Macintosh OS, and Windows. UNIX, developed in 1969 at AT&T Bell Laboratories, is a popular operating system among academic computer users. Its popularity is due in large part to the growth of the interconnected computer network known as the Internet. Software for the Internet was initially designed for computers that ran UNIX. Variations of UNIX include SunOS (distributed by SUN Microsystems, Inc.), Xenix (distributed by Microsoft Corporation), and Linux (available for download free of charge and distributed commercially by companies such as Red Hat, Inc.). UNIX and its clones support multitasking and multiple users. Its file system provides a simple means of organizing disk files and lets users control access to their files. The commands in UNIX are not readily apparent, however, and mastering the system is difficult. Consequently, although UNIX is popular for professionals, it is not the operating system of choice for the general public. Instead, windowing systems with graphical interfaces, such as Windows and the Macintosh OS, which make computer technology more accessible, are widely used in personal computers (PCs). However, graphical systems generally have the disadvantage of requiring more hardware - such as faster CPUs, more memory, and higher-quality monitors than do command-oriented operating systems.

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Health and Safety Issues

The Health and Safety Issues in Using IT There are several health issues that are related to using computers but many of these can be avoided by the correct layout of the computer area and by following good practices when using the. Furthermore both employers and employees must be aware of the regulations surrounding computer health and safety. Posture, lighting, furniture, work organization, and other work conditions and habits cay affect the way you feel and how well you work. By adjusting your work environment and personal practices, you may be able to minimize fatigue and discomfort, and reduce the risk of resulting strains that some scientists believe can lead to injury. Whenever you use a computer, you make choices that can affect your comfort and potentially your safety. This is true whether you use a desktop keyboard and monitor in an office, laptop computer, wireless keyboard on your lap, or handheld at the airport. In every case, you choose your working posture and your body’s position relative to your computer, phone, reference books, and papers. You may also have some control over lighting and other factors. Many factors in our work environment determine whether we work efficiently and in a manner that promotes good health and safety. Some studies have suggested that long periods of typing, improper workstation set up and incorrect work habits could lead to injury. The warning signs of these disorders can occur in the hands, wrists, arms, shoulders, neck, back and the eyes. These may include aching, pain, tightness, stiffness and blurred vision. Symptoms may be felt during typing, while using the mouse, or even when no work with the hands is being performed. If you experience these symptoms or any other kind of recurring discomfort then you should consult your doctor and, if possible, your company's health and safety department. The earlier a problem is properly diagnosed and treated, the less chance there is that it will end up as a disabling condition. The number of computers in the workplace has increased rapidly over the last few years and it is now quite normal for most staff to be exposed to computer usage. The Health and Safety at Work Act 1974 lays down legal standards for computer equipment and requires employers to take steps to minimise risks for all workers. Workers have received substantial damages for injuries caused through use of computers where the employer could have foreseen the risk but did nothing about it. Regulations and Obligations for Employers Health and Safety at Work Act 1974 The prime objective of the Health and Safety at Work Act 1974 is to set out the general duties of employers to ensure the health and safety and welfare of themselves and others who may be affected in any way by what they do or fail to do. The duties are qualified in the Act by the principle of “so far as is reasonably practicable”. The Act applies to all work activities and premises and everyone at work has responsibilities under it including the self-employed and employees. Individuals are responsible for: • Taking reasonable care of their own health and safety and that of others who may be affected by what they do

or do not do. • Co-operating with their employers on health and safety. • Correctly using work items provided by their employer, including personal protective equipment (PPE), in

accordance with training and instructions. • Not interfering with or misusing anything provided for their health safety or welfare. The main regulations covering the use of computer equipment include: Health & Safety (Display Screen Equipment) Regulations 1992 The 1992 Health and Safety (Display Screen Equipment) Regulations offer a legal framework to control many of the risks identified above, and the general risk assessments required by other legislation should address any outstanding issues. Musculoskeletal problems These can be split between upper limb disorders and back problems.

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Back problems associated with DSE work most frequently arise because of a combination of poor work practices and inadequate (or incorrectly adjusted) seating.Upper limb disorders can result from poor posture and/or equipment set-up, incorrect work organisation, work overload, poorly designed software requiring too much use of a mouse etc. The first key control for all musculoskeletal risks is training: all staff working with DSE should be trained to understand: The importance of proper ergonomic set-up; How to achieve a proper ergonomic set-up including how adjustment mechanisms for items such as chairs operate correctly; The importance of following arrangements for breaks/changes of activity; What to do to report difficulties with equipment or early stage symptoms of pain; The key aspects of the DSE regulations, including such things as arrangements for eyesight testing; Training should be repeated after a suitable interval, to ensure that staff retain the information and skills. Once proper training systems are in place, the next key control measure is workstation analysis - or risk assessment. Each workstation must be assessed to identify risk factors and to plan actions to reduce those risks to the lowest possible level. Risk assessments should be undertaken on a one to one basis, and should take into account what the person uses the VDU for, how often, for how long, etc. They should be recorded and kept updated. The assessment should identify whether the user is comfortable and able to work without risk to their health. It is preferable for all workstations to receive a follow-up visit from an assessor. Workstation checks should be repeated if any changes occur and regularly reassessed to ensure that information is up to date. Where a workstation may be used by more than one person, a separate analysis is required for each worker who uses the workstation. In such 'hot desking' situations, particular attention needs to be paid to any equipment provided for the needs of an individual member of staff - for example, how does someone who has a non-standard chair ensure that they have access to it, regardless of which workstation they may be using? Work routine and breaks The other key part of controlling musculoskeletal risks is work routine and organisation. The DSE Regulations place a legal duty on employers to ensure that workers' daily work is organised so as to break up long periods of VDU work. This is best done by ensuring that there is a mix of VDU and non-VDU work, but the regulations realise that this is not always possible and in such circumstances it requires physical breaks from screen-based work. There is a lot of guidance about how and when such breaks should be taken: the key issues are that employees should have some discretion over when to take a break, that more frequent shorter breaks are preferable to longer, less frequent ones and that breaks/changes of activity, whether part of other duties or a formal break, should allow the worker to leave the workstation, to stand up, move around and change posture and should avoid duties that utilise the same sort of postures and muscle groups as used for VDU work. Care is needed to ensure that breaks are not too short to allow adequate recovery time - which can occur when employers rely on what are termed 'micro-breaks': very short breaks from using a keyboard which can occur as part of daily work routine, but which don't allow for posture change or movement away from the workstation. Eyes and eyesight Although medical evidence does not support any idea that VDU usage can damage eyesight, there are several issues that can result in visual fatigue or other eye and eyesight problems. For example: If lighting condition are inadequate, including causing glare and/or reflected images in the screen; Prolonged screen use, without adequate breaks; Dry eyes, where humidity levels are low. This can be a particular problem for wearers of contact lenses; The visually demanding nature of intense screen work can also highlight problems arising from uncorrected vision defects that might otherwise pass unnoticed. To guard against this, the DSE regulations prescribe that every user of DSE equipment should be entitled to an eye/eyesight test BEFORE they start DSE work and at regular intervals thereafter. The cost of the eye test should be borne by the employer. 'Regular' is not defined in the regulations and most employers rely on the optician's recommended re-test interval. Additional tests before a scheduled retest can be obtained, at the employer's expense, if visual difficulties occur that can reasonably be considered to be caused by the DSE work. Where an eyesight test reveals the need for 'special corrective appliances' to correct vision defects for DSE usage, the employer is liable for the cost of a basic corrective appliance.

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Lighting and DSE It is vital that lighting is correct to avoid glare, reflections and over- or under-lit working environments. Failure to do so can cause headaches and visual fatigue. It can also be a source of musculoskeletal problems, if workers have to adopt incorrect postures to see round screen reflections. The Schedule of Minimum Standards for workstations, part of the DSE regulations, has detailed requirements on provision of adequate lighting, prevention of glare, reflections and provision of blinds or other means of screening workstations from daylight/sunlight from windows. These Regulations on DSE, place a duty on employers to ensure the protection of health and safety of employees and also the self-employed who habitually use DSE for the purposes of an employers undertaking as a significant part of their work. In this context a self-employed person is described as an operator and an employee as a user. Employers must decide which of their employees are DSE users and also whether they make use of other users or operators. In the regulations and with few exceptions, DSE means any alphanumeric or graphic display screen regardless of the display process involved. What comprises a workstation is also defined whether it be situated on the employers premises, at a persons home or another employers premises. Employers are also directed to ensure that they comply with general duties place upon them by other overlapping Acts and Regulations. The Regulations require employers to minimise the risks in DSE work by ensuring that workplaces are well designed. They have to analyse workstations, and ensure that they meet minimum requirements by reducing the risks. This includes: looking at the whole workstation including equipment, furniture and the work environment; the job being done; and any special needs of individual staff. Employees should be encouraged to participate in the risk assessments. Other compliances are:

a) Planning the work to provide breaks or a change of activity (excludes self-employed). b) Arrange eye tests if requested and provide special spectacles if needed (excludes self-employed). c) Provide health and safety training and information. d) Employees should make full use of the equipment provided and adjust it to get the best from it and

avoid potential health problems. Training should cover such matters. If DSE users think that they have problems connected to their work they should talk in the first instance to their supervisor, manager or safety representative. If this doesn’t help, then users and employers should get assistance from the relevant authorities.

Management of Health & Safety at Work Regulations 1992 These regulations explain many of the duties which were implied in the HASAWA Act 1974 and provide a framework within which employers can manage the health and safety aspects of their undertaking. Overall, they have the effect of requiring employers and the self�employed to assess the risks at work (Regulation 3) and to devise and implement appropriate control measures (Regulation 4). The duties of employees are also set out in greater detail (Regulation 14). The regulations include such matters as; health and safety arrangements, health surveillance, health and safety assistance, information for employees, capabilities and training, protection of young persons, risk assessment for new and expectant mothers. Other of these regulations is related to the consequential amendment and revocation of certain other different regulations where they affect one another.

Provision and Use of Work Equipment Regulations 1992 The Provision and Use of Work Equipment Regulations (PUWER) are made under the Health and Safety at Work Act 1974. The primary objective is to ensure that work equipment should not result in health and safety risks regardless of its age, condition or origin. PUWER applies to the provision and use of all working equipment including mobile and lifting equipment. It applies to all workplaces and work situations where the HSW Act applies and extends outside GB to certain offshore activities in British territorial waters and on the UK Continental Shelf. The Regulations cover anyone with responsibility directly or indirectly for work equipment and its use. This includes; employers, employees, the self employed, those who hire work equipment and other specified duty holders. Main aspects covered by the regulations are:

a) Suitability, maintenance, inspection specific risks, training, information and instructions. b) Conformity with EC requirements, dangerous parts of machinery and protection against specified

hazards. c) High or very low temperatures, starting and stopping controls and emergency stops.

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d) General controls, isolation, stability, lighting, maintenance operations, markings. e) Warnings, regulations specific to mobile work equipment, miscellaneous items.

Workplace (Health, Safety and Welfare) Regulations 1992 These regulations apply to all workplaces except domestic premises (private dwellings) and other exclusions as per Regulation 3. They expand on the duties of employers imposed under Section 2 of the Health and Safety at Work Act 1974. The regulations are intended to protect the health and safety of everyone in the workplace, including disabled persons and to ensure that adequate welfare facilities are provided for people at work. Employers have a duty to ensure that workplaces under their control comply with these regulations. Tenant employers are similarly responsible. Landlords and owners of premises are also responsible for matters within their control. Tenants should cooperate with one another and with the landlord. A risk assessment would show that the workplace may need reorganisation to satisfy requirements. Facilities should be readily accessible but can be located in neighbouring workplaces if required. Main aspects covered by the regulations include:

a) Maintenance of the workplace, equipment, devices and systems. b) Ventilation, temperature in indoor premises and lighting, windows etc. c) Cleanliness and waste materials, sanitary conveniences and washing facilities. d) Room dimensions, space, workstations and seating. e) Facilities for rest, eating, changing clothes and their storage. f) Provision of drinking water. g) Condition of floors and traffic routes, walkways, escalators, doors, gates, h) Organisation of traffic routes and pedestrian walkways. i) Protection against falls and falling objects.

Health and safety regulations which related specifically to the use of visual display units (VDUs) and computers in the workplace came into effect in January 1993 to implement an EU directive. The regulations apply to staff that habitually use VDUs as part of their day to day job, i.e. any display screen or monitor, usually forming part of a computer, that displays text, numbers and graphics. Employers must: • Analyse work stations and assess and reduce risks. This includes the equipment, furniture, the work

environment; the job being done and any special needs required by staff. • Provide adjustable chairs and suitable lighting. • Plan work so there are breaks or changes of activity away from the computer. The breaks are not required to

be a specific length of time but the general advice is to provide more frequent, shorter ones as opposed to less, longer ones. Ideally, the operator should be allowed a certain amount of discretion as to when to take breaks away from the screen.

• On request, provide eye tests or spectacles if special ones are required. Employees can ask their employer to

pay for eye tests and there is also a requirement to test at regular intervals. • Provide health, safety and training information specific to the safe use of working with VDUs and computers. In order to provide the satisfactory equipment for their employees, employers use ergonomics to assist the equipment design process. It is the science concerned with designing safe and comfortable machines for humans. This includes furniture design and the design of parts of the computer like keyboards. Ergonomics Ergonomics is about 'fit': the fit between people, the things they do, the objects they use and the environments they work, travel and play in. If good fit is achieved, the stresses on people are reduced. They are more comfortable, they can do things more quickly and easily, and they make fewer mistakes. So when one talks about 'fit', it doesn't just mean physical fit, as ergonomics is concerned with psychological and other aspects too. That is why ergonomics is often called 'Human Factors'. Many scientists believe that working intensely, or for a long time in uncomfortable positions on a Visual Display Unit, (VDU), has consequences for your health, safety and comfort. Posture, lighting, furniture and other work conditions and habits may affect the way you feel and how well you work. By adjusting your work environment and

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practices you may be able to reduce the risk of the resulting injuries and strains that some scientists believe can lead to injury. It is important for both employers and employees alike to note that regulations exist, in law, that are about the usage of Visual Display Equipment, i.e. The Health and Safety (Display Screen Equipment) Regulations 1992. Improving health and safety practice should be taken seriously, although it need not take much time or expense. Measures employers should take include: • Understanding the law - making sure that someone in an organisation, company, etc. has a health and safety

brief covering all areas, not just computers. • Being aware of the health risks - the government officially recognises some of the risks although there are

some grey areas that an organisation, company, etc, needs to make up its own mind about. • Assessing the risks - a company needs to use procedures set out in the law - they need to be systematic and

get help if they need it. A health and safety audit can done by a competent organisation if necessary. • Taking steps to minimise the risks - this may only involve taking simple measures. • Training all users to recognise the risks - if people aren't aware of the dangers they can't take adequate

precautions to protect their health. • Taking users views seriously - if users feel there is something wrong there often is. The Risks With the increase in computer use, a number of health and safety concerns related to vision and body aches and pains have arisen. Many problems with computer use are temporary and can be resolved by adopting simple corrective action. Most problems related to computer use are completely preventable. However it is important to seek prompt medical attention if you do experience symptoms including: • continual or recurring discomfort • aches and pains • throbbing • tingling • numbness • burning sensation • stiffness It is important to seek help even if symptoms occur when you are not working at your computer. Laptop computers can present particular problems due to small screens, keyboards and inbuilt pointing devices (e.g. a small portable mouse or touchpad). Prolonged use of laptops should be avoided. If using a laptop as a main computer (i.e. use as a normal desktop computer in addition to use as a portable), it is advisable to use the laptop with a docking station. This allows an ordinary mouse, keyboard and monitor to be used with the laptop. The main risks associated with using computers include: 1. Musculoskeletal problems. 2. Eye strain and a greater awareness of existing eye problems. 3. Rashes and other skin complaints have also been reported, although it is thought these are caused by the dry

atmosphere and static electricity associated with display units rather then by the display units themselves. There are potential risks from radiation though this is a contentious area.

Musculoskeletal problems These can range from general aches and pains to more serious problems and include: • Upper limb disorders such as repetitive strain injury (RSI) tenosynovitis and carpal tunnel syndrome - by far the

most important as it can quickly lead to permanent incapacity. • Back and neck pain and discomfort. • Tension stress headaches and related ailments. There has been much debate over recent years regarding health risks associated with VDU's. The most widely reported risk is RSI type injuries from over-use of the keyboard and mouse. Repetitive Strain Injury (RSI) is the name given to a group of injuries affecting the muscles, tendons and nerves primarily of the neck and upper limbs. It is an umbrella term and is also known as Work Related Upper Limb Disorder (WRULD).

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Muscolo-skeletal disorders are commonly reported by VDU users. These include backache, stiff neck and shoulders and cramps in the fingers and hands. Other symptoms of RSI - type conditions include tingling sensations, sharp pains in the arms and hands and loss of power or grip. These conditions appear slowly over a period of time, rather than occuring overnight. The problem here is that people don't notice that their discomfort is increasing until it becomes really problematic. The main cause of these conditions is undertaking repetitive tasks for prolonged periods without taking any breaks or changes in activity. Static posture, insufficient recovery time, and stress is often a contributing factor to injury. The muscles and tendons become overloaded and over a period of time they will be damaged. RSI is preventable and treatable. It is vital not to ignore the early warning signs. Back pain and neck pain can be caused by sitting for prolonged periods putting increased stress on the neck, arms, back and legs as well as the back muscles and discs. Sitting in a slouched manner can cause the spinal ligaments and muscles to become overstretched. Poor ergonomics can cause damage to your body. The spine, particularly the lower back and neck, are the most commonly injured areas leading to recurrent pain. If you have a slumped posture you are more likely to have pain and discomfort. Is your spine flexible enough to allow you to sit with good posture? Are your postural muscles strong enough and do they have the endurance to help you to sit correctly throughout the day? Having a muscle imbalance will cause poor posture. Poor posture has also been linked with poorer health. A forward slumped posture is also associated with restricted breathing. These types of problem can be caused by:

• Maintaining an unnatural or unhealthy posture while using the computer. • Inadequate lower back support. • Sitting in the same position for an extended period of time. • An ergonomically poor workstation set up.

Eye strain Computer users can experience a number of symptoms related to vision including: • Visual fatigue • Blurred or double vision • Burning and watering eyes • Headaches and frequent changes in prescription glasses People who use VDU's regularly often complain of tired eyes, including deterioration in focus, dryness in the eyes and general discomfort. Other symptoms include headaches and loss of concentration. This is caused by people staring at a fixed distance for prolonged periods. Their eye muscles become stiff and tired. With the rising number of people using computers at work and at home there has also been an increase in the number of people complaining of eye strain. Although scientific research has not proved a link between using computers and permanent eye damage using VDUs for a long period of time can cause some minor eye problems. Computer vision syndrome is a common eye condition amongst VDU users. Symptoms can range from tired eyes to blurred vision. If you do experience any of the following symptoms you could have computer vision syndrome. If you find it difficult to focus on distant objects after using a computer, you have headaches, eyestrain or dry eyes you need to take extra care when using a VDU to avoid getting computer vision syndrome. It is also best to visit your optician for an eye test to rule out anything more serious. Computer work hasn't been proven to cause permanent eye damage, but the temporary discomfort that may occur can reduce productivity, cause lost work time and reduce job satisfaction. Eye problems are usually the result of visual fatigue or glare from bright windows or strong light sources, light reflecting off the display screen or poor display screen contrast. These symptoms can be relieved by:

• Using screen filters as they can remove a high percentage of the harmful rays emitted from a computer screen.

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• Using screens that do not flicker, suing modern flat TFT monitors and setting the correct resolution in the settings.

• Taking regular breaks - do not work for more than one hour without a break. • Lighting must be suitable and blinds fitted to windows to reduce glare.

Action and Prevention Quite simply, prevention is better than the cure and there are several relatively straightforward precautions that can be taken by computer users to avoid problems. Avoiding Musculoskeletal problems General precautions to avoid musculoskeletal problems include: 1. Taking regular breaks from working at your computer - a few minutes at least once an hour. 2. Alternating work tasks. 3. Regular stretching to relax your body. 4. Using equipment such as footrests, wrist rests and document holders if you need to. 5. Keeping your mouse and keyboard at the same level. 6. Avoiding gripping your mouse too tightly - hold the mouse lightly and click gently. 7. Familiarise yourself with keyboard shortcuts for applications you regularly use (to avoid overusing the mouse). It is also important to have your workstation set up correctly. Your workstation includes monitor, keyboard, mouse, seating, desk, and where appropriate, footrest (to enable you to put your feet flat if they would otherwise not reach the floor), wrist rest, and document holder. Monitors should:

• Swivel, tilt and elevate - if not use an adjustable stand, books or blocks adjust the height. • Be positioned so the top line of the monitor is no higher than your eyes or no lower than 20° below t he

horizon of your eyes or field of vision. • Be at the same level and beside the document holder if you use one. • Be between 18 to 24 inches away from your face.

Keyboards should:

• Be detachable and adjustable (with legs to adjust angle). • Allow your forearms to be parallel to the floor without raising your elbows. • Allow your wrists to be in line with your forearms so your wrists do not need to be flexed up or down. • Include enough space to rest your wrists or should include a padded detachable wrist rest (or you can use

a separate gel wrist rest which should be at least 50 mm deep). • Be placed directly in front of the monitor and at the same height as the mouse, track ball or touch pad.

Chairs should:

• Support the back - and have a vertically adjustable independent back rest that returns to its original position and has tilt adjustment to support the lower back.

• Allow chair height to be adjusted from a sitting position. • Be adjusted so the back crease of the knee is slightly higher than the pan of the chair (use a suitable

footrest where necessary). • Be supported by a five prong caster base. • Have removable and adjustable armrests. • Have a contoured seat with breathable fabric and rounded edges to distribute the weight and should be

adjustable to allow the seat pan to tilt forward or back. Tables and desks should:

• Provide sufficient leg room and preferably be height adjustable. • Have enough room to support the computer equipment and space for documents. • Be at least 900 mm deep. • Have rounded corners and edges.

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Avoiding Eyestrain Problems Precautions for avoiding eyestrain may include the following:

• Exercising the eyes by periodically focusing on objects at varying distances. • Blinking regularly. • Keeping the air around you moist - for example using plants, open pans of water or a humidifier (spider

plants are said to be particularly good for this and removing chemical vapours from the air). • Adjusting the screen height / seating so that when sitting comfortably your eyes are in line with the top of

the monitor screen. • Adjusting the brightness control on your monitor for comfort. • Adjusting the contrast on your monitor to make the characters distinct from the background. • Adjusting the refresh rate of your monitor to stop it flickering. • Positioning monitors to avoid glare (e.g. not directly in front of windows). • Keeping your monitor the screen clean. • Keeping the screen and document holder (if you use one) at the same distance from your eyes. • Servicing, repairing or replacing monitors that flicker or have inadequate clarity. • Regular eye testing - do this at least once every 2 years and more frequently if necessary - especially if you

are experiencing eye problems related to using display equipment. Indicate the distance from your eyes to the monitor to your optician and talk to them regarding special lenses or the use of bifocals.

General working environment Don't forget that rules for all electrical appliances apply in a computer room. This means:

• There should be no trailing wires. • Food and drink should not be placed near a machine. • Electrical sockets must not be overloaded. • There must be adequate space around the machine. • Heating and ventilation must be suitable. • Lighting must be suitable with no glare or reflections. • Benches must be strong enough to support the computers.

Summary Computers are an essential tool in the work of most organisations. Although problems can occur through their use, with the proper equipment, ergonomic workstation design, proper techniques and working practices, the risk of problems can be greatly reduced. The law places certain responsibilities firmly with the employer; however, as individuals there are practical measures we all can and should take to avoid harming our health. It is a good idea to promote a health and safety culture within a workplace and to make sure that everyone recognises that they have a responsibility for health and safety within it.

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Compatibility

Why and how to make sure that hardware and software are compatible By design, computers are made to run a wide variety of applications, created by almost as wide a variety of software publishers. Sometimes these different programs simply aren't compatible with each other and you will find your word processing program may not want to play nicely with your illustration program. Or worse yet, maybe the application you just installed on your computer conflicts with your computer's operating system and causes it to malfunction. Understanding compatibility issues with software will help the computer user to avoid these problems or to troubleshoot them if they do arise. In terms of computer science, Compatibility is the degree to which a computer, an attached device, a data file, or a program can either work with or understand the same commands, formats, or language as another. A common concern of computer users, compatibility is the issue at the heart of all industry attempts to establish standards that will enable both hardware and software to work harmoniously and share information, regardless of the manufacturer. Hardware Issues The backbone of your computer is the ‘motherboard’. Everything else that is installed on your motherboard needs to be compatible with it. If you are buying new components for your computer it is always best to check that it is compatible with the motherboard before you purchase it. In terms of computers and associated hardware; compatibility has two meanings: the extent to which two machines can work in harmony and the extent to which a piece of hardware conforms to an accepted standard. In the first case, compatibility (or the lack thereof) between two machines indicates whether, and to what degree, the computers can communicate, share data, or run the same programs. For example, an Apple Macintosh and a PC are generally incompatible because they cannot communicate freely or share data without the aid of hardware and/or software that functions as an intermediary or a converter. In the standards arena, computers and other hardware are often advertised as being compatible with certain other, widely accepted, models, for example, computers are called IBM-compatible and modems are called Hayes-compatible. In this sense, compatibility means that the hardware ideally operates in all respects like the standard on which it is based. True compatibility means that any operational differences are invisible to people and programs alike. When installing new hardware you usually have to install a ‘driver’ for the hardware – the driver aids the hardware to run on your computer. If the driver has not been ‘digitally signed’ by Microsoft, you will get a message telling you that it has not been approved by them. This doesn’t always mean that you can not install it, just that its not been updated on the list. However, it is worth checking with either the manufacturer or with Microsoft if you can safely install it. You can do this by e-mailing them. Software Issues In terms of software; compatibility again refers to harmony, but on a task-oriented level between and among computers and computer programs. Computers deemed software-compatible are those that can run programs originally designed for other makes or models; for example, if the same program disk could be used on an Apple Macintosh and a PC, the machines would be software-compatible. Software compatibility also refers to the extent to which programs can work together and share data. Programs whose designers take pains to ensure that they can work with earlier versions are said to be downwardly compatible; those whose designers intentionally leave them open-ended to work with foreseeable upgrades are said to be upwardly compatible. In another area, totally different programs, such as a word processor and a drawing program are compatible with one another if each can incorporate images or files created using the other. All types of software compatibility become increasingly important as computer communications, networks, and program-to-program file transfers become near-essential aspects of microcomputer operation. PCs using Windows as their operating system can be vulnerable to a wide variety of software incompatibilities. For one, the sheer number of operating system versions can cause problems. A program written for Windows XP may not work properly on a computer that is using Windows Vista or any of the other versions of the operating system. Another problem facing PC users is the fact that the PC is licensed to be designed and manufactured by a number of different companies. One computer manufacturer may use a different piece of hardware than another, so installing a particular software application may be fine on one machine but could give you compatibility issues with the other computer because of different drivers installed. A good I.T. department should check with the manufacturer to make sure they have the needed software, hardware, and operating system to run an application before purchasing.

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When many applications are installed on a PC, a DLL (Dynamic Link Library), or small collection of programs, is also installed on your computer. These DLLs are created to conserve RAM usage while running your program but at times a DLL installed from one program may conflict with a DLL from another program and could cause problems with a computer. A manufacturer cannot build a single computer that will fit everyone's needs. Examples of that could be a person who wants to work in 3D, and needs a graphics card that supports high end computer aided design programs or has a much higher capacity of useable RAM. A sound engineer might want a better sound card to work on audio files. Each and every option can lead to compatibility issues. Lower end computers often use generic and less components that are suitable for a computer system, but often lack in qualities that people find important. Knowing what is compatible on a computer in both hardware and software goes a long way towards enhancing a computer experience. Compatibility in the computer world means two things - forward and backward compatibility. Forward compatibility This is nothing more than a program's ability to accept input from a newer version of itself. It does this by ignoring unknown tags and references that the newer version will have. This ability is important when you consider the high price one may pay for some software applications or hardware. If it were not forward capable, then ones chosen software would be useless, and I would then need to buy the newest version to access the latest features. Backward compatibility This is a bit different, because the software has relationship with the other, instead of an attribute. In other words, a new component or software program is backward compatible if it provides all of the functionality of the old component. Backward compatibility can only exist if the new component has a direct historical ancestral relationship with the old component. How to Avoid Compatibility Issues Cross Platform Connectivity Remember to think about compatibility when working on a network, because it determines how well different computers are able to interact. Two computers are compatible if they are able to communicate with each other. A computers platform refers to the framework of the computer, including operating system and other software and hardware. When two computers are cross-platform, it means that they aren’t set up in exactly the same way. This could mean that they don’t have the same operating system or exactly the same set of hardware and software. An application, a device, or a file format is called cross-platform if it can be accessed by computers that have different platforms. One way to help solve cross-platform issues is to choose software that is cross-platform and install it on networked computers. If you want to connect computers of different operating systems on the same network (cross-platform connectivity), you should ensure that there is a compatible network operating system. This serves to help networked computers with different operating systems connect properly. Choosing Software and Hardware Before installing hardware and software, always check they are compatible with the operating system. Most major manufacturers tend to produce their software/hardware for the most current operating systems that are available, for example many now produce for Windows Vista, but they also allow for previous operating systems, but not always all. So it’s best to check first to avoid problems altogether. As I have said, not all software works with all computers so a computer user should be sure to acquaint oneself with the specifications of a system before he or she goes out to make the purchase. A use should make sure he or she knows the operating system (e.g. Windows Vista) used on the computer as well as the type and speed of the processor and the space available on the hard drive. The minimum requirements are almost always on the packaging and on the documentation inside the packaging. By knowing this before making a purchase, a user can save the headache of having to return software or hardware that can't be used on their system. I also recommend a computer user should investigate the compatibility of the software programs and peripherals (i.e., printers, scanners, external drives) that he or she relies upon on prior to installing any new operating system on their computers. Most software vendors list compatibility issues with new operating system releases on their Web sites. A vendor whose products have compatibility problems with a new operating system may release updates, fixes, or patches to their programs shortly after the release of the upgraded operating system. I suggest that a computer user should monitor the Web sites of those vendors whose products they use to find out when their updates become available.

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File Format Compatibility File types also need to be compatible. A file type describes the program a file was created in or the way it was saved. Not all file types can be opened in every program. When saving a file you must consider what programs you want to open it in later. One way you can solve file type compatibility issues between computers is to make sure all computers have the same program (so they will all be able to open the file in the program it was saved in). You can also save your documents with compatible file types so more than one type of program can access them. Setting Standards The setting of standards in the area of computers is essential to enable the fluent development, growth and manipulation of new technologies. Standards are usually set by companies working together to develop, establish, endorse and promote those standards. Sometimes alliances are forged between companies that trade with each other for components. For example, Microsoft and Intel have teamed up to make sure that the chips that Intel produce and the operating designs that Microsoft design work smoothly together. More often, though, companies that are in competition with each other will agree on compatibility to build adequate support for new technology. There are many standards in computer hardware, e.g. the VGA video display standard for monitors, the standard for serial buses that transport data from one hardware component to another and the standard for microprocessors that drive the computer. Standards in software include the Microsoft Windows operating system, the MPEG standard for compressing video data, the PostScript page language for printing, and Adobe Acrobat for making documents portable. All hardware and software that is used in a computer must be compatible. If an item of hardware is not compatible with another piece of hardware then it is known as a ‘conflict’. When this occurs it may result in one or none of them working properly. It is important that the I.T. department in ones place of work checks the compatibility of new systems before any hardware or software upgrades and installations take place. In order that a computer can communicate with other computers, both inside and outside ones place of work, there must be compatible standards. There has to be standardised hardware and software formats and, in order to e-mail someone, there must be standard internet protocols. For example, all modems must adhere to the standards set by the International Telecommunications Union, to be compatible regardless of which company has made them. The Problem with Vista One of the current biggest issues with compatibility has come about with the release of Windows Vista. People with older computers found that Vista just would not work, because the hardware supporting their computer was not capable of running the strongly graphical new operating system. On release, there was an extremely long list of components and software that failed to install or crashed the system upon access. A long list can be found at www.iexbeta.com/wiki/index.php/Windows_Vista_Software_Compatibility_List. Although Microsoft has recently released a service pack which should address a lot of these issues, it is still a new operating system. Microsoft is notorious for releasing operating systems with a lot of bugs just to get it on the market on launch date. A lot of software developers had to redo programs to allow it to run on Vista. Notable issues were with antivirus software, media players, some Bluetooth systems, network systems and a lot of graphics programs. Vista has been out long enough now so that a lot of things have been fixed. Microsoft quickly released Vista patch KB929427, which makes good some of the more challenging application incompatibilities. Research shows that the biggest issue is drivers. Manufacturers were not releasing drivers quickly enough to afford compatibility to this new operating system, and a lot of people were finding that video cards and chipsets would just not work with the new system. A great deal of problems may come from peripherals such as printers and scanners. Because people don't go out and buy a new one each time they upgrade, it can be an issue with an older computer being upgraded to Win Vista. Myself, I would recommend that a computer user does their research to make sure that their hardware and software is compatible before deciding to run out and buy the latest Microsoft operating systems. The Windows Compatible Hardware and Software Web site

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The Windows Compatible Hardware and Software Web site is an informational service that helps you determine which programs and hardware work best with your computer. When you visit the Windows Compatible Hardware and Software Web site, you can preview hardware and software before you buy it. New software and hardware compatibility status information is added to the Web site regularly, so that you can always get the most recent information to protect your computer and keep it running smoothly When you visit the Web site, you can search or browse by manufacturer or product to determine which hardware or software is compatible or incompatible with Windows XP. You can check the site to determine if you need an update. In many cases, Microsoft, Independent Software Vendors (ISV) or Independent Hardware Vendors (IHV) have tested a product and rated its compatibility. Or, the product's compatibility status is determined through practical use. Microsoft encourages ISV and IHV representatives to submit information about how their product functions with Windows XP. Problems may arise if a computer user is using older software or bespoke software created especially for the company he or she works for. This is particularly salient for the company I work for, the NHS. They have many database systems created for them by Universities, I.T. specialists and consultants. This type of software would need extensive testing before being introduced to mainstream operations.

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Data Transmission Speeds

Why and How Data Transmission Speeds Vary In computer science data transfer is the movement of information from one location to another, either within a computer (as from a disk drive to random access memory) or between a computer and an external device (as between two computers or a file server and a computer on a network). The speed of transfer is called the data rate, or data transfer rate, and is usually measured in bits per second, or bps. The raw data rate (the maximum transfer speed) is usually considerably higher than the actual rate at which meaningful data is transferred because of idle time, error-checking procedures, and other overheads. Also, data transfers from different sources to different destinations often compete with each other if they use the same data path, for example, on a network, or on a bus in a computer system. Data transfer is measured in bytes, the unit most computers use to represent a character such as a letter, number, or typographic symbol (such as k, 6, or !). Even characters you do not see, such as blank spaces and characters that make up HTML tags (<title>) are stored in a computer as bytes. To make it easier to talk about large numbers of bytes, we use variations of the word byte. 1,000 bytes (B) = 1 kilobyte (KB) 1,000 kilobytes (KB) = 1 megabyte (MB) 1,000 megabytes (MB) = 1 gigabyte (GB) In a world where programs and files are becoming ever-larger, the highest data transfer rate is most desirable. However, as technology moves quickly to advance the data transfer rate of many components, consumers are often faced with systems that incorporate varying specifications. There are two types of signals are used for data transmission: digital and analogue. A digital signal is a stream of 0's and 1's. So this type is particularly appropriate for computers to use. An analogue signal uses variations (modulations) in a signal to convey information. It is particularly useful for wave data like sound waves. Analogue signals are what your normal phone line and sound speakers use. As I am only concerned about computers for this research I will only focus my findings on digital data transmission. Saving a file to a floppy disc can take up to 10 times longer than saving to a hard drive. Saving files to a network drive can also be slightly slower than saving to the hard drive because your computer has to communicate with the server. Moving files to a CD is a slightly different process. The speed at which files will ‘burn’ to a CD depends on the speed of the CD drive you have. Speeds can also vary depending on the type of connection an external device is using to connect to your computer. For example, saving to a device connected via the parallel port on your computer is slower than saving to a device connected to the USB port on your computer. The speed of sending data from one computer to another depends on the method by which you are communicating with the other computer. If you use the Internet to send and receive e-mails and to search the Web, it may help to understand the way in which the information travels. The Internet is an International Network of linked computers. Data is sent from your computer in digital packets. These packets are routed from one computer to another until they reach the destination computer. These packets don’t necessarily travel along the same route - they may go different ways but they join together again at their destination. If I use a dial-up connection, I am using an analogue telephone line to send and receive data. Because the data from my computer is digital and the telephone line can only transmit an analogue signal I will need a modem. Modems A Modem is a device that enables computers, facsimile machines, and other equipment to communicate with each other across telephone lines or over cable television network cables. In the strictest sense, a modem is a device that converts between analogue signals, such as sound waves, and digital signals, which are used by computers. However, the term has also come to include devices that permit the transmission of entirely digital signals. Modems transmit data at different speeds, measured by the number of bits of data they send per second (bps). A 28.8 Kbps modem sends data at 28,800 bits per second. A 56 Kbps modem is twice as fast, sending and receiving data at a rate of 56,000 bits per second.

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There are different types of Modem, the analogue, the ISDN, and ADSL. Analogue Modem An analogue modem converts the digital signals of the sending computer to analogue signals that can be transmitted through telephone lines. When the signal reaches its destination, another modem reconstructs the original digital signal, which is processed by the receiving computer. A standard analogue modem has a maximum speed of 33.6 Kbps. The word modem is an acronym formed from the two basic functions of an analogue modem: modulation and demodulation. T o convert a digital signal to an analogue one, the modem generates a carrier wave and modulates, or adjusts, it according to the digital signal. The kind of modulation used depends on the application and the speed of operation for which the modem is designed. For example, many high-speed modems use a combination of amplitude modulation, in which the amplitude of the carrier wave is changed to encode the digital information, and phase modulation, in which the phase of the carrier wave is changed to encode the digital information. The process of receiving the analogue signal and converting it back to a digital signal is called demodulation. Integrated Digital Services Network (ISDN) Instead of converting between analogue telephone lines and digital applications, Integrated Services Digital Network (ISDN) carries digital signals throughout the transmission process. Because an ISDN modem does not convert between digital and analogue signals, it does not perform the modulation and demodulation functions from which modems derived their name. An ISDN modem simply processes the digital signal between the computer and the ISDN lines. ISDN transmission lines are ordinary two-wire telephone lines that carry digital signals on three separate channels. The telephone company uses one channel for tracking and control purposes; the remaining two channels can be used to transmit voice, data, or both. Digital data bypasses the analogue voice network, enabling it to travel much faster. ISDN has a maximum speed of 128 Kbps. Asymmetrical Digital Subscriber Line (ADSL) Like ISDN, Asymmetrical Digital Subscriber Line (ADSL) permits the transmission of digital data over ordinary telephone lines. It is called asymmetrical because it transmits data in one direction (from the network) faster than it does in the other direction (to the network). ADSL carries signals to the network at speeds of up to 640 Kbps, and it can deliver data from the network at speeds of up to 8.1 million bits per second (Mbps). An ADSL modem splits an ordinary telephone line into three separate data channels, each with different capacities and speeds. The lowest-capacity channel transmits analogue voice data; a second, medium-capacity channel transmits data to the network; and the highest-capacity channel transmits data from the network. A number of other forms of DSL are also available, depending on the speed of data transmission and the distance of the customer from the central office. These include High-Data-Rate Digital Subscriber Line (HDSL), Very-High-Data Rate Digital Subscriber Line (VDSL), and Symmetric Digital Subscriber Line (SDSL). So then, the transmission speed of data travelling along an analogue telephone line is relatively slow. How fast data can be transmitted is called bandwidth. Bandwidth is the amount of information that can be sent through a connection between two computers in a given amount of time. Computers may be connected by telephone wires, by coaxial cable, by fibre-optic cable, or through radio waves or microwaves. A connection that can transmit more data in a shorter period of time is said to have more bandwidth than another, slower connection. There are many other ways that computers can communicate and a popular technology is broadband. Broadband can convert the analogue line into a digital one and the bandwidth is broader so data can travel faster through the connection. Virgin media now advertises broadband speeds of up to 50Mbps using fibre optic cable - this is about the fastest it gets but availability depends on where you live. My Talk Talk connection can barely handle 2.5Mbps. Below is a table of some of the different ways to connect computers together and their speeds. Technology being used Downstream (Receive) Upstream (Send) 56K modem (dial-up) 56 Kbps 56 Kbps 1-channel ISDN line 64 Kbps 64 Kbps 2-channel ISDN line 56 Kbps 56 Kbps Bluetooth (wireless radio signal) 721 Kbps 721 Kbps ASDL (broadband) slow 500 Kbps 400 Kbps ASDL (broadband) fast 2.5 Mbps 640 Kbps T1 leased line 1.554 Mbps 1.554 Mbps

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Below is a table showing the time it would take to fill various storage media, using the different connections available: Capacity 56K modem ADSL (broadband) slow ADSL (broadband) slow 1 MB hard drive 3 minutes 2.2 seconds 1.3 seconds Floppy disc 4 minutes 3.1 seconds 1.8 seconds 600 MB CD 30 hours 21 minutes 13 minutes 1 GB hard drive 50 hours 36 minutes 21 minutes