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Thursday, January 12, 2012

Computer Hardware Familiarization Part-5.

For part 5 of this post we now go into the external components of the computer hardware. We three primary items for these post, the monitor, pointing device and keyboard.

The Computer monitor

A monitor or display (also called screen or visual display unit) is an electronic visual display for computers. The monitor comprises the display device, circuitry, and an enclosure. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) thin panel, while older monitors use a cathode ray tube about as deep as the screen size.

Originally, computer monitors were used for data processing while television receivers were used for entertainment. From the 1980s onwards, computers (and their monitors) have been used for both data processing and entertainment, while televisions have implemented some computer functionality. The common aspect ratio of televisions, and then computer monitors, has also changed from 4:3 to 16:9.

New LCD 22Image by freefotouk via Flickr

Transparent Computer Monitors  [explore #38]Image by Louish Pixel via Flickr

LG L194WT-SF LCD monitorImage via Wikipedia

CRT computer monitor. Price: 139 Euro (19th No...Image via Wikipedia

The first computer monitors used cathode ray tubes (CRT). Until the early 1980s, they were known as video display terminals and were physically attached to the computer and keyboard. The monitors were monochrome, flickered and the image quality was poor In 1981, IBM introduced the Color Graphics Adapter, which could display four colors with a resolution of 320 by 200 pixels. In 1984 IBM introduced the Enhanced Graphics Adapter which was capable of producing 16 colors and had a resolution of 640 by 350.

CRT remained the standard for computer monitors through the 1990s. CRT technology remained dominant in the PC monitor market into the new millennium partly because it was cheaper to produce and offered viewing angles close to 180 degrees.

Liquid Crystal Display

There are multiple technologies that have been used to implement Liquid Crystal Displays (LCDs). Throughout the 1990s the primary use of LCD technology as computer monitors was in laptops where the lower power consumption, lighter weight, and smaller physical size of LCDs justified the higher price versus a CRT. Commonly, the same laptop would be offered with an assortment of display options at increasing price points (active or passive) monochrome, passive color, active matrix color (TFT). As volume and manufacturing capability have improved the monochrome and passive color technologies were dropped from most product lines.

The pointing device

A pointing device is an input interface (specifically a human interface device) that allows a user to input spatial (i.e., continuous and multi-dimensional) data to a computer. CAD systems and graphical user interfaces (GUI) allow the user to control and provide data to the computer using physical gestures — point, click, and drag — for example, by moving a hand-held mouse across the surface of the physical desktop and activating switches on the mouse. Movements of the pointing device are echoed on the screen by movements of the pointer (or cursor) and other visual changes.

While the most common pointing device by far is the mouse, many more devices have been developed. A "rodent" is a technical term referring to a device which generates mouse-like input. However, the term "mouse" is commonly used as a metaphor for devices that move the cursor.

A computer mouseImage via Wikipedia

Touchpad and a pointing stick on an IBM LaptopImage via Wikipedia

English: iPad with on display keyboardImage via Wikipedia

English: An HTC Touch2 being operated with a s...Image via Wikipedia

English: A Sun branded Mouse Systems optical m...Image via Wikipedia

 The mouse is the most common representation of the computer pointing device. Most of us point to the mouse as the only pointing device, but based on the picture above pointing  cane vary in size and form. Another type of pointing device that is similar to the mouse is the Trackball.

A trackball is a pointing device consisting of a ball housed in a socket containing sensors to detect rotation of the ball about two axes, similar to an upside-down mouse: as the user rolls the ball with a thumb, fingers, or palm the pointer on the screen will also move. Tracker balls are commonly used on CAD workstations for ease of use, where there may be no desk space on which to use a mouse. Some are able to clip onto the side of the keyboard and have buttons with the same functionality as mouse buttons. There are also wireless trackballs which offer a wider range of ergonomic positions to the user.

The computer keyboard

In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches. Following the decline of punch cards and paper tape, interaction via teleprinter-style keyboards became the main input device for computers.
Despite the development of alternative input devices, such as the mouse, touchscreen, pen devices, character recognition and voice recognition, the keyboard remains the most commonly used and most versatile device used for direct (human) input into computers.

A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or computer commands.

English: IBM AT KeyboardImage via Wikipedia

English: IBM AT KeyboardImage via Wikipedia

SAN FRANCISCO - JANUARY 27:  An event guest pl...Image by Getty Images via @daylife

English: SGI Indy Workstation with original 17...Image via Wikipedia

SAN FRANCISCO - JANUARY 27:  An event guest pl...Image by Getty Images via @daylife

Standard "full-travel" alphanumeric keyboards have keys that are on three-quarter inch centers (0.750 inches, 19.05 mm), and have a key travel of at least 0.150 inches (3.81 mm). Desktop computer keyboards, such as the 101-key US traditional keyboards or the 104-key Windows keyboards, include alphabetic characters, punctuation symbols, numbers and a variety of function keys. The internationally common 102/105 key keyboards have a smaller 'left shift' key and an additional key with some more symbols between that and the letter to its right (usually Z or Y). Also the 'enter' key is usually shaped differently. Computer keyboards are similar to electric-typewriter keyboards but contain additional keys. Standard USB keyboards can also be connected to some non-desktop devices.

We are now almost complete in our familiarization series post about the basic computer hardware. My next will tackle some hardware accessories that you might be interested to really dress up your computer.

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