Lab ManualComputer Hardware and Trouble Shooting Lab (Pr)

COT-314L T P- - 3

Practical exam: 40Sessional: 60

Experiment 1 (Motherboard)

I. To make the comparative study of various motherboards.(Intel 80386, Intel 80486, Pentium Processor, Pentium Pro, Pentium II, Celeron, Pentium III) [Refer Annexure 1]

Experiment 2 (Cables)

I. To study various cables used in computer communication. (Patch Cables , Ethernet Crossover Cables , USB cable , Unshielded Twisted Pair (UTP) Cable, Shielded Twisted Pair (STP) , Coaxial Cable , Fibre Optic Cable) [Refer Annexure 2]

Experiment 3 (Connections and Ports)

I. To study various connections and ports used in computer communication.PS/2 port and its specification,VGA Port and its specification, Serial port and its specification and applications, Parallel Ports and its specification,USB Port and its specification,RJ45 connector, Ethernet port, DVI Monitor port,Most DVI connector types,Modem RJ-11 port,DB-9 connector,DB-25 connector. [Refer Annexure 3]

Experiment 4 (Cards)

I. To study various cards used in a Computer System.(Ethernet Card, Sound Card, Video/Graphics Card, Network Interface card ,TV Tuner Card, Accelerator card) [Refer Annexure 4]

Experiment 5 (Drives)

I. To study rotational and loading mechanisms of the following drives:(Floppy disk drive, Hard disk, CD ROM,CD-R/RW,DVD-ROM, DVD recordable drives, DUAL LAYER DVD+/-RW) [Refer Annexure 5]

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Experiment 6 (Monitor and Circuitry)

I. To study monitor and its circuitry(CRT (Cathode Ray Tube),LCD (Liquid Crystal Display),LED (Light-Emitting Diodes),Plasma OLED ) [Refer Annexure 6]

Experiment 7 (To Study Printer Assembly)

I. Daisy Wheel Printer:

Daisy wheel printing uses interchangeable pre-formed type elements, each with typically 96 glyphs, to generate high-quality output.

The heart of the system is an interchangeable metal or plastic "daisy wheel" holding an entire character set as raised characters molded on each "petal". A servo motor rotates the daisy wheel to position the required character between the hammer and the ribbon. The solenoid-operated hammer then fires, driving the character type onto the ribbon and paper to print the character on the paper. The daisy wheel and hammer are mounted on a sliding carriage similar to that used by dot matrix printers.

Different typefaces and sizes can be used by replacing the daisy wheel. It is possible to use multiple fonts within a document: font changing is facilitated by printer device drivers which can position the carriage to the center of the platen and prompt the user to change the wheel before continuing printing. However, printing a document with frequent font changes and thus requiring frequent wheel changes was a tedious task.

II. Dot Matrix Printer:

Dot matrix printing or impact matrix printing is a type of computer printing which uses a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like the print mechanism on a typewriter.

Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which is driven forward by the power of a tiny electromagnet or solenoid, either directly or through small levers (pawls). Facing the ribbon and the paper is a small guide plate pierced with holes to serve as guides for the pins. This plate may be made of hard plastic or an artificial jewel such as sapphire or ruby. The portion of the

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printer containing the pins is called the print head.

The common serial dot matrix printers use a horizontally moving print head. The print head can be thought of featuring a single vertical column of seven or more pins approximately the height of a character box. In reality, the pins are arranged in up to four vertically or/and horizontally slightly displaced columns in order to increase the dot density and print speed through interleaving without causing the pins to jam.

III. Inkjet Printer:

Inkjet printing is a type of computer printing that creates a digital image by propelling droplets of ink onto paper, plastic, or other substrates. There are two main technologies in use in contemporary inkjet printers: continuous (CIJ) and Drop-on-demand (DOD).

In CIJ technology, a high-pressure pump directs liquid ink from a reservoir through a gunbody and a microscopic nozzle, creating a continuous stream of ink droplets via the Plateau-Rayleigh instability. A piezoelectric crystal creates an acoustic wave as it vibrates within the gunbody and causes the stream of liquid to break into droplets at regular intervals: 64,000 to 165,000 droplets per second may be achieved. The ink droplets are subjected to an electrostatic field created by a charging electrode as they form; the field varies according to the degree of drop deflection desired. This results in a controlled, variable electrostatic charge on each droplet. Charged droplets are separated by one or more uncharged "guard droplets" to minimize electrostatic repulsion between neighboring droplets.

The charged droplets pass through an electrostatic field and are directed (deflected) by electrostatic deflection plates to print on the receptor material (substrate), or allowed to continue on undeflected to a collection gutter for re-use. The more highly charged droplets are deflected to a greater degree.

In the thermal inkjet process, the print cartridges contain a series of tiny chambers, each containing a heater, all of which are constructed by photolithography. To eject a droplet from each

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chamber, a pulse of current is passed through the heating element causing a rapid vaporization of the ink in the chamber to form a bubble, which causes a large pressure increase, propelling a droplet of ink onto the paper (hence Canon's trade name of Bubble Jet). The ink's surface tension, as well as the condensation and thus contraction of the vapor bubble, pulls a further charge of ink into the chamber through a narrow channel attached to an ink reservoir. The inks used are usually water-based and use either pigments or dyes as the colorant. The inks used must have a volatile component to form the vapor bubble, otherwise droplet ejection cannot occur. As no special materials are required, the print head is generally cheaper to produce than in other inkjet technologies.

IV. LaserPrinter:

Laser printing is an electrostatic digital printing process that rapidly produces high quality text and graphics by passing a laser beam over a charged drum to define a differentially charged image. The drum then selectively collects charged toner and transfers the image to paper, which is then heated to permanently fix the image.

A laser beam, typically from an aluminum gallium arsenide semiconductor laser, projects an image of the page to be printed onto an electrically charged rotating drum coated with selenium[9] or, more common in modern printers, organic photoconductors. Photoconductivity allows charge to leak away from the areas exposed to light. Powdered ink (toner) particles are then electrostatically picked up by the drum's charged areas, which have not been exposed to the laser beam. The drum then prints the image onto paper by direct contact and heat, which fuses the ink to the paper.

There are typically seven steps involved in the process:

Raster image processing - The document to be printed is encoded in a page description language such as PostScript, Printer Command Language (PCL), or Open XML Paper Specification (OpenXPS). The raster image processor converts the page description into a bitmap in the raster memory.

Charging - In older printers, a corona wire positioned parallel to

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the drum, or in more recent printers, a primary charge roller, projects an electrostatic charge onto the photoreceptor (otherwise named the photo conductor unit), a revolving photosensitive drum or belt, which is capable of holding an electrostatic charge on its surface while it is in the dark.

Exposing - The laser is aimed at a rotating polygonal mirror, which directs the laser beam through a system of lenses and mirrors onto the photoreceptor. The cylinder continues to rotate during the sweep and the angle of sweep compensates for this motion. The stream of rasterized data held in memory turns the laser on and off to form the dots on the cylinder.

Developing - The surface with the latent image is exposed to toner, fine particles of dry plastic powder mixed with carbon black or coloring agents. The toner particles are given a negative charge, and are electrostatically attracted to the photoreceptor's latent image, the areas touched by the laser. Because like charges repel, the negatively charged toner will not touch the drum where the negative charge remains.

Transferring - The photoreceptor is pressed or rolled over paper, transferring the image. Higher-end machines use a positively charged transfer roller on the back side of the paper to pull the toner from the photoreceptor to the paper.

Fusing - The paper passes through rollers in the fuser assembly where heat of up to 200 °C (392 °F) and pressure bond the plastic powder to the paper.One roller is usually a hollow tube (heat roller) and the other is a rubber backing roller (pressure roller). A radiant heat lamp is suspended in the center of the hollow tube, and its infrared energy uniformly heats the roller from the inside. For proper bonding of the toner, the fuser roller must be uniformly hot.

Cleaning - When the print is complete, an electrically neutral soft plastic blade cleans any excess toner from the photoreceptor and deposits it into a waste reservoir, and a discharge lamp removes the remaining charge from the photoreceptor.

V. Bubble Jet Printer:

A bubble-jet printer is a type of ink-jet computer printer, which is one of the most

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common kinds of printers on the market. Each type of ink-jet printer transfers the ink to the paper in a different way. The main distinction is that most ink-jet printers use piezoelectric crystals to create the ink, while bubble-jet printers use heat to do so instead. They are so named because they emit a tiny bubble of heated ink, each of which creates a small drop of ink on printer paper.

Just one of many types of ink-jet machines, the bubble-jet printer uses a unique procedure to form the ink droplets that get transferred onto paper. During this process, heat is created by very small resistors. The newly developed heat is subsequently used to make the ink evaporate, which then shapes a bubble in the form of a droplet of ink. The droplet is then pushed out of the print head onto paper. Of course, this occurs countless times, with many drops of ink forming at the same time, until the image is complete.

The ink used in a bubble-jet printer is water-based, and is often touted as water-resistant. Additionally, the print head that comes with it is known for being quite inexpensive to replace. Another advantage of the bubble-jet printer is the fact that it is relatively quiet, so people can print either at home or in an office environment without disturbing others. Many people also claim that this a bubble-jet printer usually produces high-quality color images with high-resolution, which is why they may buy one just to print out pictures. In fact, some people connect their digital camera directly to their bubble-jet printer so that they can print without having to download and store the photographs on their computer first.

Experiment 8 (To Study parts of Keyboard)

I. Microprocessor and controller circuitry of a keyboard.

Computer keyboards include control circuitry to convert key presses into key codes (usually scancodes) that the computer's electronics can understand. The key switches are connected via the printed circuit board in an electrical X-Y matrix where a voltage is provided sequentially to the Y lines and, when a key is depressed, detected sequentially by scanning the X lines.

The first computer keyboards were for mainframe computer data terminals and used discrete electronic parts. The first keyboard microprocessor was introduced in 1972 by General Instruments, but keyboards have been using the single-chip 8048microcontroller variant since it became available in 1978. The keyboard switch matrix is wired to its inputs, it converts the keystrokes to key codes, and, for a detached keyboard, sends the codes down a serial cable (the keyboard cord) to the main processor on the computer motherboard. This serial keyboard cable communication is only bi-directional to the extent that the computer's electronics

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controls the illumination of the caps lock,num lock and scroll lock lights.

When pressing a keyboard key, the key contacts may "bounce" against each other for several milliseconds before they settle into firm contact. When released, they bounce some more until they revert to the uncontacted state. If the computer were watching for each pulse, it would see many keystrokes for what the user thought was just one. To resolve this problem, the processor in a keyboard (or computer) "debounces" the keystrokes, by aggregating them across time to produce one "confirmed" keystroke.

II. Membrane keyboard

There are two types of membrane-based keyboards, flat-panel membrane keyboards and full-travel membrane keyboards:

Flat-panel membrane keyboards are most often found on appliances like microwave ovens or photocopiers. A common design consists of three layers. The top layer (and the one the user touches) has the labels printed on its front and conductive stripes printed on the back. Under this it has a spacer layer, which holds the front and back layer apart so that they do not normally make electrical contact. The back layer has conductive stripes printed perpendicularly to those of the front layer. When placed together, the stripes form a grid. When the user pushes down at a particular position, their finger pushes the front layer down through the spacer layer to close a circuit at one of the intersections of the grid. This indicates to the computer or keyboard control processor that a particular button has been pressed.Generally, flat-panel membrane keyboards do not have much of a "feel", so many machines which use them issue a beep or flash a light when the key is pressed. They are often used in harsh environments where water- or leak-proofing is desirable. Although used in the early days of the personal computer (on the Sinclair ZX80, ZX81 and Atari 400), they have been supplanted by the more tactile dome and mechanical switch keyboards.

Full-travel membrane-based keyboards are the most common computer keyboards today. They have one-piece plastic keytop/switch plungers which press down on a membrane to actuate a contact in an electrical switch matrix.

III. Dome Switch keyboard

Dome-switch keyboards are a hybrid of flat-panel membrane and mechanical keyboards. They bring two circuit board traces together under a rubber or silicone keypad using either metal "dome" switches or polyurethane formed domes. The metal dome switches are formed pieces of stainless steel that, when compressed, give the

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user a crisp, positive tactile feedback. These metal types of dome switches are very common, are usually reliable to over 5 million cycles, and can be plated in either nickel, silver or gold. The rubber dome switches, most commonly referred to as polydomes, are formed polyurethane domes where the inside bubble is coated in graphite. While polydomes are typically cheaper than metal domes, they lack the crisp snap of the metal domes, and usually have a lower life specification. Polydomes are considered very quiet, but purists tend to find them "mushy" because the collapsing dome does not provide as much positive response as metal domes. For either metal or polydomes, when a key is pressed, it collapses the dome, which connects the two circuit traces and completes the connection to enter the character. The pattern on the PC board is often gold-plated.

Both are common switch technologies used in mass market keyboards today. This type of switch technology happens to be most commonly used in handheld controllers, mobile phones, automotive, consumer electronics and medical devices. Dome-switch keyboards are also called direct-switch keyboards.

IV. Mechanical Switch keyboard

Mechanical-switch keyboards use separate complete switches underneath every key. Each switch is composed of a base, a spring, and a stem. Depending on the shape of the stem, such keyboards have varying actuation and travel distance. Depending on the resistance of the spring, the key requires different amounts of pressure to actuate. Mechanical keyboards allow for the removal and replacement of keycaps.

Mechanical keyboards have proven popular amongst the PC gaming community and are gaining in popularity among typists.

The major mechanical switch producers are Cherry and Alps Electric. Companies such as Cooler Master, Corsair, Razer, and Thermaltake offer a variety of mechanical model keyboards targeted towards gamers.

Study of Capacitive keyboard - In this type of keyboard, pressing the key changes the capacitance of a pattern of capacitor pads. Unlike "dome switch" keyboards, the pattern consists of two D-shaped capacitor pads for each switch, printed on a printed circuit board (PCB) and covered by a thin, insulating film of soldermask which plays the role of a dielectric. The mechanism of capacitive switches is very simple, compared to mechanical ones. Its movable part is ended with a flat foam element (of dimensions near to a tablet of Aspirin) finished with aluminum foil below. The opposite side of the switch is a PCB with the capacitor pads.

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When a key is pressed, the foil tightly clings to the surface of the PCB, forming a daisy chain of two capacitors between contact pads and itself separated with thin soldermask, and thus "shorting" the contact pads with an easily detectable drop of capacitive reactance between them. Usually this permits a pulse or pulse train to be sensed. The keys do not need to be fully pressed to be fired on, which enables some typists to work faster.

V. Buckling Spring keyboard

Many typists prefer buckling spring keyboards. The buckling spring mechanism (expired U.S. Patent 4,118,611) atop the switch is responsible for the tactile and aural response of the keyboard. This mechanism controls a small hammer that strikes a capacitive or membrane switch.

In 1993, two years after spawning Lexmark, IBM transferred its keyboard operations to the daughter company. New Model M keyboards continued to be manufactured for IBM by Lexmark until 1996, when Unicomp purchased the keyboard technology.

Today, new buckling-spring keyboards are manufactured by Unicomp. Unicomp also repairs old IBM and Lexmark keyboards.

VI. Hall-effect Switch keyboard

Hall-effect keyboards use magnets and Hall-effect sensors instead of an actual switch. When a key is depressed, it moves a magnet, which is detected by the solid-state sensor. These keyboards are extremely reliable, and are able to accept millions of keystrokes before failing. They are used for ultra-high reliability applications, in locations like nuclear power plants or aircraft cockpits. They are also sometimes used in industrial environments. These keyboards can be easily made totally waterproof. They also resist large amounts of dust and contaminants. Because a magnet and sensor are required for each key, as well as custom control electronics, they are very expensive.

VII. Laser keyboard

A laser projection device approximately the size of a computer mouse projects the outline of keyboard keys onto a flat surface, such as a table or desk. This type of keyboard is portable enough to be easily used with PDAs and cellphones, and many models have retractable cords and wireless capabilities. However, sudden or accidental disruption of the laser will register unwanted keystrokes. Also, if the laser malfunctions, the whole unit becomes useless, unlike conventional keyboards which

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can be used even if a variety of parts (such as the keycaps) are removed. This type of keyboard can be frustrating to use since it is susceptible to errors, even in the course of normal typing, and its complete lack of tactile feedback makes it even less user-friendly than the lowest quality membrane keyboards.

VIII.

Roll-up keyboard

Some keyboards designed out of flexible materials that can roll up in a moderately tight bundle. Normally the external materials are either silicone or polyurethane. Though manufacturers may claim that keyboards are foldable, they cannot be folded without damaging the membrane that holds the circuitry. Typically they are completely sealed in rubber, making them watertight like membrane keyboards.Like membrane keyboards, they are reported to be very hard to get used to, as there is little tactile feedback, and silicone will tend to attract dirt, dust, and hair.

IX. Optical keyboard technology

Also known as photo-optical keyboard, light responsive keyboard, photo-electric keyboard, and optical key actuation detection technology. Optical keyboard technology was introduced in 1962 by Harley E. Kelchner for use in a typewriter machine with the purpose of reducing the noise generating by actuating the typewriter keys. An optical keyboard technology utilizes light-emitting devices and photo sensors to optically detect actuated keys. Most commonly the emitters and sensors are located at the perimeter, mounted on a small PCB.

The light is directed from side to side of the keyboard interior, and it can only be blocked by the actuated keys. Most optical keyboards require at least 2 beams (most commonly a vertical beam and a horizontal beam) to determine the actuated key. Some optical keyboards use a special key structure that blocks the light in a certain pattern, allowing only one beam per row of keys (most commonly a horizontal beam). The mechanism of the optical keyboard is very simple – a light beam is sent from the emitter to the receiving sensor, and the actuated key blocks, reflects, refracts or otherwise interacts with the beam, resulting in an identified key.

Some earlier optical keyboards were limited in their structure and required special casing to block external light, no multi-key functionality was supported and the design was very limited to a thick rectangular case.

The advantages of optical keyboard technology are that it offers a real waterproof keyboard, resilient to dust and liquids; and it uses about 20% PCB volume, compared

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with membrane or dome switch keyboards, significantly reducing electronic waste.

Experiment 9 (To Study parts of Mouse)

I. Mechanical mouse

A mechanical mouse is a computer mouse that contains a metal or rubber ball on its underside. When the ball is rolled in any direction, sensors inside the mouse detect this motion and move the on-screen mouse pointer in the same direction.

Bill English, builder of Engelbart's original mouse, created a ball mouse in 1972 while working for Xerox PARC. The ball mouse has two freely rotating rollers. They are located 90 degrees apart. One roller detects the forward–backward motion of the mouse and other the left–right motion. Opposite the two rollers is a third one (at 45 degrees) that is spring-loaded to push the ball against the other two rollers. Each roller is on the same shaft as an encoder wheel that has slotted edges; the slots interrupt infrared light beams to generate electrical pulses that represent wheel movement. Each wheel's disc, however, has a pair of light beams, located so that a given beam becomes interrupted, or again starts to pass light freely, when the other beam of the pair is about halfway between changes.

The mouse sends these signals to the computer system via the mouse cable, directly as logic signals in very old mice such as the Xerox mice, and via a data-formatting IC in modern mice. The driver software in the system converts the signals into motion of the mouse cursor along X and Y axes on the computer screen.

II. Trackball mouse

A trackball is a pointing device consisting of a ball held by a socket containing sensors to detect a rotation of the ball about two axes—like an upside-down mouse with an exposed protruding ball. The user rolls the ball with the thumb, fingers, or the palm of the hand to move a pointer.

Compared with a mouse, a trackball has no limits on effective travel; at times, a mouse can reach an edge of its working area while the operator still wishes to move the screen pointer farther. With a trackball, the operator just continues rolling, whereas a mouse would have to be lifted and re-positioned.

The trackball was invented as part of a post-World War II-era radar plotting system named Comprehensive Display System (CDS) by Ralph Benjamin when working for the British Royal Navy Scientific Service. Benjamin's project used analog computers

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to calculate the future position of target aircraft based on several initial input points provided by a user with a joystick. A more elegant input device named ball tracker system also called the roller ball was invented for this purpose in 1946. The device was patented in 1947, but only a prototype using a metal ball rolling on two rubber-coated wheels was ever built and the device was kept as a military secret.

The trackball was first built by Tom Cranston, Fred Longstaff and Kenyon Taylor as part of the Royal Canadian Navy's DATAR system in 1952. DATAR was similar in concept to Benjamin's display, but used a digital computer to calculate tracks, and sent the resulting data to other ships in a task force using pulse-code modulation radio signals. This trackball used a Canadian five-pin bowling ball.

DATAR's trackball used four disks to pick up motion, two each for the X and Y directions. Several rollers provided mechanical support. When the ball was rolled, the pickup discs spun and contacts on their outer rim made periodic contact with wires, producing pulses of output with each movement of the ball. By counting the pulses, the physical movement of the ball could be determined.

III. Optical mouse

An optical computer mouse uses a light source, typically a light-emitting diode, and a light detector, such as an array of photodiodes or an image sensor, to detect movement relative to a surface. It is an alternative to the mechanical mouse, which uses moving parts to perform the same function.

The technology underlying the modern optical computer mouse is known as digital image correlation, a technology pioneered by the defense industry for tracking military targets. Optical mice use image sensors to image naturally occurring texture in materials such as wood, cloth, mouse pads and Formica. These surfaces, when lit at a grazing angle by a light emitting diode, cast distinct shadows that resemble a hilly terrain lit at sunset. Images of these surfaces are captured in continuous succession and compared with each other to determine how far the mouse has moved.

Optical mice capture one thousand successive images or more per second. Depending on how fast the mouse is moving, each image will be offset from the previous one by a fraction of a pixel or as many as several pixels. Optical mice mathematically process these images using cross correlation to calculate how much each successive image is offset from the previous one.

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IV. Infrared mouse

The laser mouse uses an infrared laser instead of an LED to illuminate the surface beneath their sensor. As early as 1998, Sun Microsystems provided a laser mouse with their Sun SPARCstation servers and workstations. However, laser mice did not enter the mainstream market until 2004, when Paul Machin at Logitech, in partnership with Avago Technologies (formerly part of Agilent Technologies), introduced its MX 1000 laser mouse. This mouse uses a small infrared laser instead of an LED and has significantly increased the resolution of the image taken by the mouse. The laser illumination enables superior surface tracking compared to LED-illuminated optical mice.

Glass laser (or glaser) mice have the same capability of a laser mouse but can also be used on top of mirror or transparent glass with few problems. In 2008, Avago introduced laser navigation sensors whose emitter was integrated into the IC using VCSEL technology.

V. Stylus mouse

Pen computing refers to a computer user-interface using a pen (or stylus) and tablet, rather than devices such as a keyboard, joysticks or a mouse.

Pointing device - The tablet and stylus are used as pointing devices, such as to replace a mouse. While a mouse is a relative pointing device (one uses the mouse to "push the cursor around" on a screen), a tablet is an absolute pointing device (where one puts the stylus describes exactly where the cursor goes).

There are a number of human factors to be considered when actually substituting a stylus and tablet for a mouse. For example, it is much harder to target or tap the same exact position twice with a stylus, so "double-tap" operations with a stylus are harder to perform if the system is expecting "double-click" input from a mouse. A finger can be used as the stylus on a touch-sensitive tablet surface, such as with a touchscreen.

Handwriting recognition: The tablet and stylus can be used to replace a keyboard, or both a mouse and a keyboard, by using the tablet and stylus in two modes:

• Pointing mode: The stylus is used as a pointing device as above. • On-line Handwriting recognition mode: The strokes made with the stylus are

analyzed as an "electronic ink", by software which recognizes the shapes of the

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strokes or marks as handwritten characters. The characters are then input as text, as if from a keyboard.

References:

1. Govindrajalu, IBM PC And Clones: Hardware, Troubleshooting And Maintenance, TMH.

2. Mark Mines Complete PC upgrade & maintenance guide, BPB publications.

3. Craig Zacker& John Rouske, PC Hardware: The Complete Reference, TMH.

4. Scott Mueller, Upgrading and Repairing PCs, PHI, 1999

Annexure 1

1. Intel 80386

The Intel80386 ("eighty-three-eighty-six"), also known as i386 or just 386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistors and were the CPU of many workstations and high-end personal computers of the time. The 32-bit 80386 can correctly execute most code intended for the earlier 16-bit processors such as 8088 and 80286 that were ubiquitous in early PCs. The 80386 added a 32-bit architecture and a paging translation unit, which made it much easier to implement operating systems that used virtual memory. It also offered support for register debugging.

The 80386 featured three operating modes: real mode, protected mode and virtual mode. The protected mode which debuted in the 286 was extended to allow the 386 to address up to 4 GB of memory. The all new virtual 8086 mode (or VM86) made it possible to run one or more real mode programs in a protected environment, although some programs were not compatible.

2. Intel 80486

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The Intel80486 ("eighty-four-eighty-six"), also known as the i486 or just 486 was a higher performance follow-up to the Intel 80386microprocessor. The 80486 was introduced in 1989 and was the first tightly pipelined x86 design as well as the first x86 chip to use more than a million transistors, due to a large on-chip cache and an integrated floating-point unit. It represents a fourth generation of binary compatible CPUs since the original 8086 of 1978. A 50 MHz 80486 executes around 40 million instructions per second on average and is able to reach 50 MIPS peak performance.

The instruction set of the i486 is very similar to its predecessor, the Intel 80386, with the addition of only a few extra instructions, such as CMPXCHG which implements an compare-and-swapatomic operation and XADD, a fetch-and-add atomic operation returning the original value (unlike a standard ADD which "returns" flags only).

From a performance point of view, the architecture of the i486 is a vast improvement over the 80386. It has an on-chip unified instruction and data cache, an on-chip floating-point unit (FPU) and an enhanced bus interface unit. Due to the tight pipelining, sequences of simple instructions (such as ALU reg,reg) could sustain a single clock cycle throughput (one instruction completed every clock).

3. Pentium Processor

The Pentium family of processors, which has its roots in the Intel486(TM) processor, uses the Intel486 instruction set (with a few additional instructions). The term ''Pentium processor'' refers to a family of microprocessors that share a common architecture and instruction set. The first Pentium processors (the P5 variety) were introduced in 1993. This 5.0-V processor was fabricated in 0.8-micron bipolar complementary metal oxide semiconductor (BiCMOS) technology. The P5 processor runs at a clock frequency of either 60 or 66 MHz and has 3.1 million transistors.

The next version of the Pentium processor family, the P54C processor, was introduced in 1994. The P54C processors are fabricated in 3.3-V, 0.6-micron BiCMOS technology. The P54C processor also has System Management Mode (SMM) for advanced power management.

The Intel Pentium processor, like its predecessor the Intel486 microprocessor, is fully software compatible with the installed base of over 100 million compatible Intel architecture systems. In addition, the Intel Pentium processor provides new levels of performance to new and existing software through a reimplementation of the Intel 32-bit instruction set architecture using the latest, most advanced, design techniques. Optimized, dual execution units provide one-clock execution for "core" instructions, while advanced technology, such

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as superscalar architecture, branch prediction, and execution pipelining, enables multiple instructions to execute in parallel with high efficiency. Separate code and data caches combined with wide 128-bit and 256-bit internal data paths and a 64-bit, burstable, external bus allow these performance levels to be sustained in cost-effective systems. The application of this advanced technology in the Intel Pentium processor brings "state of the art" performance and capability to existing Intel architecture software as well as new and advanced applications.

The Pentium processor has two primary operating modes and a "system management mode." The operating mode determines which instructions and architectural features are accessible.

4. Pentium Pro

Intel Pentium Pro was the first processor from the Intel Pentium II processor family. Targeted for the server and workstation market, the Pentium Pro included integrated 256KB, 512 KB or 1 MB L2 cache running at the processor speed. The L2 cache in the Pentium Pro was not located on the same die as the CPU core. The CPU was packaged in a "dual cavity" package, where one cavity contained the processor die and another contained the L2 cache. As all other members of the Pentium 2 family, the Pentium Pro was optimized to run 32-bit applications and, when running in 32-bit mode, it significantly outperformed Pentium and Pentium MMX CPUs at the same clock speed. At the same time Pentium Pro performance with 16-bit applications was poor, and often the processor was slightly slower than similarly clocked Pentium/Pentium MMX processors. Poor performance of the Pentium II core with 16-bit applications was fixed in the desktop Pentium II CPU.

The Pentium Pro processor was the only processor from the Pentium II family that didn't have MMX instructions.

5. Pentium II

The Pentium II brand refers to Intel's sixth-generation micro architecture ("P6") and x86-compatible microprocessors introduced on May 7, 1997. Containing 7.5 million transistors (27.4 million in the case of the mobile Dixon with 256 KB L2 cache), the Pentium II featured an improved version of the first P6-generation core of the Pentium Pro, which contained 5.5 million transistors. However, its L2 cache subsystem was a downgrade when compared to Pentium Pros. In early 1999, the Pentium II was superseded by the almost identical Pentium III, which basically only added SSE instructions to the CPU.

6. Celeron

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Celeron is a brand name given by Intel Corp. to a number of different IA-32 and x86-64 computer microprocessor models targeted at budget personal computers.

Celeron processors can run all IA-32 computer programs, but their performance is often significantly lower when compared to similar CPUs with higher-priced Intel CPU brands. For example, the Celeron brand will often have less cache memory, or have advanced features purposely disabled. These missing features can have a variable impact on performance, but is often very substantial. While a few of the Celeron designs have achieved surprising performance, most of the Celeron line has exhibited noticeably degraded performance. This has been the primary justification for the higher cost of other Intel CPU brands versus the Celeron range.

Introduced in April 1998, the first Celeron branded CPU was based on the Pentium II branded core. Subsequent Celeron branded CPUs were based on the Pentium III, Pentium 4, Pentium M, and Intel Core branded processors. The latest Celeron design (as of January 2014) is based on the fourth generation Core i3/i5/i7 series. This design features independent processing cores (CPUs), but with only 66% as much cache memory as the comparable Core i3 offering.

7. Pentium III

The Pentium III (marketed as Intel Pentium III Processor, informally PIII, also stylized as Pentium !!! ) brand refers to Intel's 32-bit x86 desktop and mobile microprocessors based on the sixth-generation P6 microarchitecture introduced on February 26, 1999. The brand's initial processors were very similar to the earlier Pentium II-branded microprocessors. The most notable differences were the addition of the SSE instruction set (to accelerate floating point and parallel calculations), and the introduction of a controversial serial number embedded in the chip during the manufacturing process.

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Annexure 2

1. Patch Cables

A patch cable connects two network devices. Patch cables are typically CAT5 / CAT5e Ethernet cables linking a computer to a nearby network hub, switch or router. Ethernet patch cables are useful to those building home computer networks and also to travelers who need wired access to Internet connections such as those provided in hotel rooms. They are normally manufactured using stranded rather than solid sheathing in order to give them pliability that reduces risk of breakage when unplugging or carrying them.

2. Ethernet Crossover Cables

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A crossover cable directly connects two network devices of the same type to each other over Ethernet. Ethernet crossover cables are commonly used when temporarily networking two devices in situations where a network router, switch or hub is not present

3. USB Cable

A universal serial bus (USB) cable connects between a computer and a peripheral device such as a printer, monitor, scanner, mouse or keyboard. It is part of the USB interface, which includes types of ports, cables and connectors. Many USB devices have a captive, or attached, USB cable, such as the Apple USB Keyboard. Other devices come with a standard USB cable that has a Type A connector on one end and a Type B connector on the other end.

Type AType A ports and connectors are small and rectangular and are typically used to plug a device into a Type A USB port on a computer or a hub. Type A ports and connectors are sometimes referred to as "upstream".

Figure 1 USB Type A port and connectorType B

Type B ports and connectors are small and square and are used to attach a USB cable to a USB device. Type B ports and connectors are sometimes referred to as

"downstream".

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Figure 2 USB Type B port and connector

4. Unshielded Twisted Pair (UTP) Cable

Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks. The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated six categories of wire (additional categories are emerging).

5. Shielded Twisted Pair (STP)

Although UTP cable is the least expensive cable, it may be susceptible to radio and electrical frequency interference (it should not be too close to electric motors, fluorescent lights, etc.). If you must place cable in environments with lots of potential interference, or if you must place cable in extremely sensitive environments that may be susceptible to the electrical current in the UTP, shielded twisted pair may be the solution. Shielded cables can also help to extend the maximum distance of the cables.

Shielded twisted pair cable is available in three different configurations. Each pair of wires is individually shielded with foil. There is a foil or braid shield inside the jacket covering all wires (as a group). There is a shield around each individual pair, as well as around the entire group of wires (referred to as double shield twisted pair).

6. Coaxial Cable20

Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield. The metal shield helps to block any outside interference from.Although coaxial cabling is difficult to install, it is highly resistant to signal interference. In addition, it can support greater cable lengths between network devices than twisted pair cable. The two types of coaxial.

Thin coaxial cable is also referred to as thin net. 10Base2 refers to the specifications for thin coaxial cable carrying Ethernet signals. The 2 refers to the approximate maximum segment length being 200 meters. In actual fact the maximum segment length is 185 meters. Thin coaxial cable has been popular in.

7. Fibre Optic Cable

Fibre optic cabling consists of a centre glass core surrounded by several layers of protective materials. It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It has also made it the standard for connecting networks between Fibre optic cables has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The cost of fibre optic cabling is comparable to copper cabling; however, it is the centre core of fibre cables is made from glass or plastic fibres. A plastic coating then cushions the fibrecentre help to strengthen the cables and prevent breakage

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Annexure 3

1. PS/2 port and its specification

Connect a PC to its keyboard and mouse. Though both ports look identical as shown in Fig. 1, the mouse (green) and keyboard (purple) ports are not interchangeable. Usually both ports are color coded or labelled.

Fig. 1

2. VGA Port and its specification

Connect a PC to a monitor. This is a venerable but now completely standard monitor interface. The original VGA monitors could do no more than 640×480. During the mid 1990’s, more advanced monitors were called “SVGA” (for Super). Since all monitors can display more than 640×480 today, the two terms are now interchangeable. This HDD-15 port seems to have evolved facing upside-down on most machines as shown in Fig. 2.

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Fig. 2

3. Serial port and its specification and applications

This port connects a PC to an external modem, serial mouse, etc. DOS calls these ports COM1-COM4. You can refer to Fig. 3. The small version is slightly more popular than the large version. Dating from the PC XT, these are ubiquitous but rarely used.

Fig. 3

Both the small (male DB-9) and large (male DB-25) versions are electrically identical, and can be interchanged with a simple adapter.They both speak RS-232, a relatively slow (around 105Kbps max) and error-prone protocol. The default controller is CPU-intensive and low data rate. A better UART, common on modern machines, is the 16550A, which has a 1KB buffer.

4. Parallel Ports and its specification

This port connects a PC to a printer. DOS calls this port LPT1. Another PC XT holdover, this port is virtually always used to connect to a printer. A slow but bidirectional 8-bit clocked or unclocked port, this DB-25 port can also be used by scanners, tape drives, and other peripherals. It looks like a Mac SCSI port, but isn’t. When connected to a printer, it always terminates in a Centronics 36 connector. Refer to Fig. 4.

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Fig. 4

5. USB Port and its specification

Connect a PC to a USB printer, hard drive, scanner, CD drive, keyboard, mouse, etc. First introduced around 1997, and famously not supported by MS Windows 95 and NT 4.0 (one of the few reasons to use Windows 98 or 2000).This port may eventually replace everything except the VGA port. These ports are available at the front or back of the cabinet and shown in the Fig. 5.

Fig. 5USB uses a 4-wire parasitic serial protocol, running at 12 Mbps. It is not daisy-chainable but is hub-able and hot-pluggable. Most PC USB peripherals can also be used on Macs without any extra setup; but a few lack the necessary drivers.

6. RJ45 connector

RJ45 is a standard type of connector for network cables. RJ45 connectors are most commonly seen with Ethernet cables and networks. RJ45 connectors feature eight pins to which the wire strands of a cable interface electrically. Standard RJ-45 pinouts define the arrangement of the individual wires needed when attaching connectors to a cable.

7. Ethernet port

An Ethernet port is an opening on computer network equipment that Ethernet cables plug into. These ports are alternatively called jacks or sockets. Ethernet ports accept cables with RJ-45 connectors. Most computers include one built-in Ethernet port for connecting the device to a wired network.A computer's Ethernet port is connected to its internal Ethernet network adapter.

8. DVI Monitor port

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The DVI connector on a device is given one of three names, depending on which signals it implements: DVI-D (digital only, single link or dual link) DVI-A (analog only) DVI-I (integrated, combines digital and analog in the same connector; digital may be single or dual link)

9. Most DVI connector types

The exception being DVI-A – contain pins that pass digital video signals. These come in two varieties: single link and dual link. Single-link DVI employs a single 165 MHz transmitter that supports resolutions up to 1920 × 1200 at 60 Hz. Dual-link DVI adds six additional pins (located in the center of the connector) for a second transmitter increasing the bandwidth and supporting resolutions up to 2560 × 1600 at 60 Hz.

10.

Modem RJ-11 port

RJ-11 is a standard Phone Jack.It is possible to connect the telephone line to the RJ11 port on a computer to receive calls. This configuration requites call management software that is compatible with the network adapter. Such software usually provides the capability to receive faxes and store them as computer files. It usually also enable the user to create a switchboard structure with extensions and voice mail. Calls can be directed to an automated message, or placed on hold where the caller listens to music or a message recorded on the computer.

The RJ11 port contains six channels at the bottom, each with a copper metal strip. This strip is a contact and creates a connection when corresponding metal strips in the plug tough the socket strips. The plug is held in place with a plastic spring at the top. A phone line travels over two wires, and so only the the two central contacts actually connect to anything. The remaining four contacts can be used to add in two more lines entering the computer or telephone.

11.

DB-9 connector

The DB9 (originally DE-9) connector is an analog 9-pin plug of the D-

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Subminiature connector family (D-Sub or Sub-D).

DB9 connectors are designed to work with the EIA/TIA 232 serial interface standard, which determined the function of all nine pins as a standard, so that multiple companies could design them into their products.  DB9 connectors were commonly used for serial peripheral devices like keyboards, mice, joysticks, etc. Also they are used on DB9 cable assemblies for data connectivity. Today, the DB9 has mostly been replaced by more modern interfaces such as USB, PS/2, Fire wire, and others.

12.

DB-25 connector

The DB25 (originally DE-25) connector is an analog 25-pin plug of the D-Sub miniature connector family (D-Sub or Sub-D). As with the DB9 connector, the DB25 is mainly used for serial connections, allowing for the asynchronous transmission of data as provided by standard RS-232 (RS-232C). It is also used for parallel port connections, and was originally used to connect printers, and as a result is sometimes known as a "printer port" (LPT for short).

Annexure 4

1. Ethernet Card

An Ethernet card is one kind of network adapter. These adapters support the Ethernet standard for high-speed network connections via cables. Ethernet cards are sometimes known as network interface cards (NICs).

The Ethernet card was created to build a Local Area Network (LAN). Once Ethernet cable is connected to the Ethernet cards of two or more computers over the LAN, one can transfer files and data. This can be carried out for external hardware such as printers and scanners when information from one computer needs to be transferred to another computer.

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2. Sound Card

A sound card (also known as an audio card) is a computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation, education, and entertainment (games). Many computers have sound capabilities built in, while others require additional expansion cards to provide for audio capability.

4. Video/Graphics Card

A video card, video adapter, graphics-accelerator card, display adapter or graphics card is an expansion card whose function is to generate and output images to a display. Many video cards offer added functions, such as accelerated rendering of 3D scenes and 2D graphics, video capture, TV-tuner adapter, MPEG-2/MPEG-4 decoding, FireWire, light pen, TV output, or the ability to connect multiple monitors (multi-monitor). Other modern high performance video cards are used for more graphically demanding purposes, such as PC games.

5. Network Interface card

A network interface card provides the computer with a dedicated, full-time connection to a network. Personal computers and workstations on a local area network (LAN) typically contain a network interface card specifically designed for the LAN transmission technology. In computer networking, a NIC provides the hardware interface between a computer and a network. A NIC technically is network adapter hardware in the form factor of an add-in card such as a PCI or PCMCIA card. Some NIC cards work with wired connections while others are wireless. Most NICs support either wired Ethernet or WiFi wireless standards. Ethernet NICs plug into the system bus of the PC and include jacks for network cables, while WiFi NICs contain built-in transmitters / receivers (transceivers).

6. TV Tuner Card

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It allows television signals to be received by a computer. Most TV tuners also function as video capture cards, allowing them to record television programs onto a hard disk much like the digital video recorder (DVR) does. The interfaces for TV tuner cards are most commonly either PCI bus expansion card or the newer PCI Express (PCIe) bus for many modern cards. These cards typically include one or more software drivers to expose the cards' features, via various operating systems, to software applications that further process the video for specific purposes. As a class, the cards are used to capture baseband analog composite video, S-Video, and, in models equipped with tuners, RF modulated video. Unlike video editing cards, these cards tend to not have dedicated hardware for processing video beyond the analog-to-digital conversion. Most, but not all, video capture cards also support one or more channels of audio.

7. Accelerator card

Aprinted circuit board that enhances a computer's performance by substituting a faster microprocessor without replacing the entire motherboard and associated components. A graphic accelerator is a type of video adapter that contains its own processor to boost performance levels. These processors are specialized for computing graphical transformations, so they achieve better results than the general-purpose CPU used by the computer. In addition, they free up the computer's CPU to execute other commands while the graphics accelerator is handling graphics computations.

The popularity of graphical applications, and especially multimedia applications, has made graphics accelerators not only a common enhancement, but a necessity. Most computer manufacturers now bundle a graphics accelerator with their mid-range and high-end systems.

Annexure 5

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1. Floppy disk drive

A floppy disk drive is a hardware device that reads one of the first types of portable data storage media — floppy diskettes, also known as floppy disks. The circuitry of this drive is shown in Fig.1.

Fig. 1The floppy disk drive has many parts that are needed in order for it to work properly. Among the most important of these are the read and write heads. Most floppy drives have two of these heads. These are used to get information from the disk and transfer information to the disk. Some floppy disks have tabs that can be moved to prevent the writing of information on a disk, even if an attempt is made. A motor spins the disk and does so at a rate of at least 360 revolutions per second.

The other major parts of a floppy disk drive include the stepper motor and circuit board. The stepper motor is responsible for moving the read/write heads where they need to be. The circuit board is responsible

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for taking the information and transferring it between the computer and floppy disk drive. The circuit board is also responsible for controlling the motors of the floppy disk drive.

2. Hard disk

In any computer system the hard disk is considered as the secondary memory device that is used for the primary data storage. The hard disk drive is the most popularly used secondary memory device is because the access speed and the reliability of the data it can offer. In the case of the tape drives the access speed is much low and the data transfer is comparatively low than the hard disk drive. The components of hard disk are shown in Fig.2.The primary function of the primary memory is to load the programs so that the CPU – Central Processing Unit can easily and speedily access and execute the instructions. The primary memory can only boot the computer system; but it is the hard disk drive that is responsible for the loading and the proper functioning of any operating system. The operating system is a necessary for the computers to run to the expectations of the user. Hence the hard disk is a must for the loading of the hard disk drive. The importance of the primary memory is that it is a compulsion that is necessary for the start-up of the computer. A computer can start up even without a hard disk. But since there is no operating system that is present in the computer hence it is not possible to load the operating system. The computer will display a message usually in such a situation stating that “Disk Boot Failure”.

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Fig. 2The information that is required to boot a computer is stored in the hard disk boot sector. Also the importance of the hard disk drive is to store the backup of the data or any information that is created by the user. Apart from the hard disk drives the other storage devices like the optical disks that are the CD ROM, DVD ROM etc. can be used for the purpose of the backup of the data or user information. The floppy disks can also be used for the backup of the data. The hard disk specification should also match the expectations of the computers; that is the storage capacity and access speed.

3. CD ROM

These drives are necessary today for most programs. A single CD can store up to 650 MB of data (newer CD-Rs allow for 700 MB of data, perhaps more with “over burn”). Fast CD-ROM drives have been a big topic in the past, but all of today’s CD-ROM drives are sufficiently fast. Of course, it’s nice to have the little bits of extra speed. However, when you consider CD-ROM drives are generally used just to install a program or copy CDs, both of which are usually done rarely on most users’ computers, the extra speed isn’t usually very important. The speed can

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play a big role if you do a lot of CD burning at high speeds or some audio extraction from audio CDs (i.e. converting CDs to MP3s).

4. CD-R/RW

CD-R/RW (which stands for Recordable / Rewritable) drives (aka burners, writers) allow a user to create their own CDs of audio and/or data. These drives are great for backup purposes (backup your computers’ hard drive or backup your purchased CDs) and for creating your own audio CD compilations (not to mention other things like home movies, multimedia presentations, etc.).

5. DVD-ROM

DVD-ROM drives can store up to 4 GB of data or about 6 times the size of a regular CD (not sure on the exact size, but suffice to say it’s a very large storage medium). DVDs look about the same and are the same size as a CD-ROM. DVD drives can also read CD-ROM drives, so you don’t usually need a separate CD-ROM drive. DVD drives have become low enough in price that there isn’t much point in purchasing a CD-ROM drive instead of a DVD-ROM drive. Some companies even make CD burner drives that will also read DVDs (all in one). DVD’s most practical use is movies. The DVD format allows for much higher resolution digital recording that looks much clearer than VCR recordings.

6. DVD recordable drives

DVD recordable drives are available in a couple of different formats – DVD-R or DVD+R with a RW version of each. These are slightly different discs and drives (although some drives support writing to both formats). One is not much better than the other, so it really boils down to price of the media (and also availability of the media).

7. DUAL LAYER DVD+/-RW

DVD+R DL discs employ two recordable dye layers, each capable of storing nearly the 4.7 GB capacity of a single-layer disc, almost doubling the total disc capacity to 8.5 GB. Discs can be read in many DVD devices

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(older units are less compatible) and can only be created using DVD+R DL and Super Multi drives.

A dual-layer disc differs from its usual DVD counterpart by employing a second physical layer within the disc itself. The drive with dual-layer capability accesses the second layer by shining the laser through the first semi-transparent layer. The layer change can exhibit a noticeable pause in some DVD players, up to several seconds.This caused more than just a few viewers to worry that their dual-layer discs were damaged or defective, with the end result that studios began listing a standard message explaining the dual-layer pausing effect on all dual-layer disc packaging.

Annexure 6

1. CRT (Cathode Ray Tube)

A CRT monitor contains millions of tiny red, green, and blue phosphor dots that glow when struck by an electron beam that travels across the screen to create a visible image. In a cathode ray tube, the "cathode" is a heated filament. The heated filament is in a vacuum created inside a glass "tube." The "ray" is a stream of electrons generated by an electron

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gun that naturally pour off a heated cathode into the vacuum. Electrons are negative. The anode is positive, so it attracts the electrons pouring off the cathode. This screen is coated with phosphor, an organic material that glows when struck by the electron beam.

There are three ways to filter the electron beam in order to obtain the correct image on the monitor screen: shadow mask, aperture grill and slot mask.

2. LCD (Liquid Crystal Display)

A liquid crystal display (LCD) monitor is a computer monitor or display that uses LCD technology to show clear images, and is found mostly in laptop computers and flat panel monitors. This technology has replaced the traditional cathode ray tube (CRT) monitors, which were the previous standard and once were considered to have better picture quality than early LCD variants.

Various different LCD technologies are used today, including:• In Plane Switching (IPS) Panel Technology: These panels are considered to have the best color accuracy, viewing angles and image quality in LCD technology.

• Super Plane to Line Switching (PLS): Developed by Samsung, this LCD panel is very similar to the IPS panel but reportedly, it is 10 percent brighter, has wider viewing angles and is cheaper to produce.

• Vertical Alignment (VA) Panel Technology: These panels are considered to be in the middle of TN and IPS technology. Compared to TN panels, they offer wider viewing angles and better color quality but have slower response times. They have higher contrast ratios, compared to the other panels but have a downside, in terms of color shifting, where the brightness display is unevenly distributed throughout the screen.

• Twisted Nematic (TN) Panel Technology: These panels are the most commonly used type of panel in LCD technology. They are cheaper and offer faster response times, making them a preferred choice for gamers. The downside is that the viewing angles, contrast ratios and color production are considered the lowest of LCD panel types.

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3. LED (Light-Emitting Diodes)

An LED is an electronic device that emits light when an electrical current is passed through it. Early LEDs produced only red light, but modern LEDs can produce several different colors, including red, green, and blue (RGB) light. Recent advances in LED technology have made it possible for LEDs to produce white light as well. LEDs are commonly used for indicator lights (such as power on/off lights) on electronic devices. They also have several other applications, including electronic signs, clock displays, and flashlights. Since LEDs are energy efficient and have a long lifespan (often more than 100,000 hours), they have begun to replace traditional light bulbs in several areas.

4. Plasma

A plasma display panel (PDP) is a type of flat panel display common to large TV displays 30 inches (76 cm) or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent lamps.

Plasma displays are bright (1,000 lux or higher for the module), have a wide color gamut, and can be produced in fairly large sizes—up to 3.8 metres (150 in) diagonally. They had a very low-luminance "dark-room" black level compared with the lighter grey of the unilluminated parts of an LCD screen at least in the early history of the competing technologies.

Power consumption varies greatly with picture content, with bright scenes drawing significantly more power than darker ones – this is also true for CRTs as well as modern LCDs where LED backlight brightness is adjusted dynamically. The plasma that illuminates the screen can reach a temperature of at least 1200 °C (2200 °F). Typical power consumption is 400 watts for a 127 cm (50 in) screen. 200 to 310 watts for a 127 cm (50 in) display when set to cinema mode.

5. OLED

OLED, or Organic Light-Emitting Diode, a display device that sandwiches carbon-based films between two charged electrodes, one a metallic cathode and one a transparent anode, usually being glass. It is able to

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deliver sharper and brighter images than LCDs, while also using less power. Unlike an LCD, which requires a backlight, OLED screens can emit their own light. This allows OLED screens to display brighter, sharper images and text, and to offer better viewing angles. It also means that OLED screens are thinner and consume less power than their LCD counterparts.

OLED screens also offer faster refresh rates than LCDs, so they can deliver smoother video playback. But there are a few drawbacks to OLED displays. For one, the organic materials used to make them have a more limited lifetime than the components of other display types. OLED screens also have the potential to be more easily damaged by water or other liquids. Also, when viewed in direct sunlight, the images on an OLED display are not as bright as what you'd see on an LCD.

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