What is CD-ROM Drive and How it Works

CD ROM stands for "Compact Disc Read Only Memory".  A CD-ROM drive is the same size as a floppy disk drive.  It is a storage device that accepts data CD ROM’s (Compact Discs).  It is a box shaped device that fits into the case of the computer. A CD-ROM drive is an optical device which means it uses a laser to record information. Most new computers DVD drives have replaced CD ROM drives. A CD ROM drive will only play CD’s, not for DVD’s. 

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What is Floppy Drive and How it Works

Floppy drives are most advanced storage devices and it reads and writes data on floppy disks. Floppy Drive connects to the motherboard with a ribbon (data) cable and also power cable attached to it. Presently new computers do not have this floppy drives because USB flash drives and optical drives have replaced floppy drives in newer systems, it can be added internally to your computer (or) externally with a USB cable. It is a removable media or removable drive you can remove whatever disk is currently in the drive, and replace with another.

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What is Zip Drive and How it Works

Zip Drive introduced by Iomega Corporation in late 1994. Zip drive is a medium portable removable device looks like a floppy drive. A zip drive is needed to read and write 3.5 inch zip disk. Zip Drives are very expensive when compared to coast of other storage devices.

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What is Speakers and How it Works

These are connected to the mother board through a cable. Speakers allow you to listen to music and hear sound effects that are played through programs on computer, it usually played through speakers. And also speaker is used to produce beeps by POST (Power-On-Self -Test) to indicate certain results.

There are different types of speaker systems available in the market.

Some of them are described below.

2.0 Speakers : It is a two speaker sound system. it is commonly used on desktop speakers.

2.1 Speakers : It uses two stereo speakers and a subwoofer

5.1 Speakers : It is also called as surround sound speakers. It used two front speakers, two rear speakers and center speaker plus one subwoofer

Home Theater Speakers : Home Theater Speakers are all in one speaker system, includes  front left and front right center speakers, surround sound speakers (it also called for rear channel speakers) and other subwoofer.

Surround Speakers : This type of speakers will enhance your experience and you will hear a much realistic sound.

Wireless Speakers : This type of speakers fully wireless connectivity amongst stereo speakers and surround sound speakers.

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What is Keyboard and How it Works

The commonly used input device is a keyboard. It is the most important device for communicating between the operator and the computer. This is connected to the CPU. The keyboard is used to input data and instructions into the computer. A computer keyboard is very much like a standard type writer keyboard with few additional keys. It consists of the standard typewriter keys as well as a numeric keypad and It contains alphabets, digits, special characters and some control keys.

Keyboards are available in three types:
(i) Standard Keyboard with 83/84 keys.
(ii) Enhanced Keyboard with 101 / 102 keys.
(iii) Windows Keyboard with 104 keys.

Described below are the keyboard keys along with their different functions

 → Typewriter keys :These are normal keys on the key board. These include letters, numbers and punctuation symbols.

→ Function keys :These are the keys labeled F1 to F12. These carry our different functions. These are identified as FI through F2 on the top most row of the keyboard. These keys are programmed to perform special functions.

→ Cursor keys :These keys are marked and are called the left, right, up and down arrow keys(←, →, ↑, ↓). The keys are used to move the cursor left, right, down or up around the screen. These are present on the right hand side of the key board.

→ Numeric Key Pad :It allows numeric digits to be entered. These keys which are arranged like a calculator, have two different functions according to the status of the Num Lock key. While the num lock is not locked, these keys are used.

→ Caps lock key :It allows to enter capital letters. If we press caps lock once, any letter you type will appear in upper case. When pressed once, the caps lock light comes on, and any character you type appears as a capital letter. When this key is pressed again, the character you type appears in a lower case.

→ Shift key :It allows the capital alphabetical characters, on certain keys to be appeared. when an alphabet is typed, it is shown in the lower case, Holding down Shift key and then pressing an alphabet key causes it will appear in upper case.
Example: when you press Shift-d, you get a capital D. However, if the Caps lock is ON than this effect is reversed.

→ Ctrl and Alt keys :
These keys are often used in combination with other keys, to produce special actions.
Example: when you pressing Ctrl and C simultaneously, aborts the current task or command being executed and returns you to DOS prompt. If you are  pressing Ctrl, Alt and Del keys simultaneously, the machine is automatically restarted.

→ Enter key :
The Enter key is used for two main purposes. It represents the end of the current line, and takes you back to the first column of the next line. It is also used to represent the end of the command data. Enter key is also referred to as Return key.

→ Pause :
Pressing the pause key instructs Dos to stop the scrolling of information on the screen. When pressed enters the computer in pause mode. You can use this key to read the contents of a large file.

→ Tab Key :It is used to move the cursor position faster than the space bar key. It is also used  for  moving  from one option to another option in a menu. When pressed together with the Shift key, the cursor is moved to the next tab stop on the left. Default tab stops are at every eight columns.

→ Esc Key : (Escape Key)You can use this key to cancel or ignore the entry or command you have just entered. In many programs, the Esc key returns you to the previous menu screen or exit from the program.

→ Prtscr : (Print Screen key)
It this key is pressed then whatever is being displayed in the screen gets printed on the printer. Prints out all information currently appearing on the screen to the printer, when pressed together with the Shift key.

→ Del Key : (Delete  key )
Erases the character that the cursor is currently on. If this key is pressed, then it deletes
a character at the current cursor position on the screen.

→ Backspace Key :This key erases the character to the left, moving the cursor back one character at a line, erasing what you typed. When pressed once, erases any character to the left of the cursor.

→ Spacebar  : Spacebar is the longest key in the last row of the keyboard. Presenting spacebar shifts the cursor one position to the right

→ Alphanumeric keys: These keys have functions identical to those of an ordinary typewriter & are used for entering alphanumeric information, it is a combination of the words, alphabet and numeric.

→ Home key : Shifts the cursor to the top of the document or the beginning of the line.

→ End key : Shifts the cursor to the end of the document or the end of the line.

→ Pgup (page - up) key : Moves the cursor to the previous or page of the document.

→ Pgdn (page-down key ) : Moves the cursor to the next screen or page.

→ Ins (Insert key) : It allows insertion of characters to the left of the cursor. This is a toggle key. Pressing once brings the insert mode "ON" and pressing again will toggle position on the screen.

→ Special keys : These keys may have different functions depending on the software that is being used.

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What is Mouse and Types of Mouse

A Mouse is hand held pointing device that allows you to control your computer without having to type in instructions at the keyboard. It connected to computer by a cable. It usually contains two or three buttons.

The mouse is kept on a flat surface. When you move the mouse on the flat surface, the mouse pointer also moves in the same direction on the screen. It is used to move the cursor on the screen. And pressing the buttons on the mouse lets you select options and to execute commands on the screen. The cursor moves very fast with mouse giving you more freedom to work in any direction. Mouse is very useful and easy to choose specific options from the menu.

 There are many different types of mouse available today in the market
  

Serial Mouse : This type of mouse with a serial connector, it requires a free serial port on your PC.

PS/2 Mouse : This type of mouse is connected  to a PS/2  port.

Optical Mouse : This type of mouse uses a laser for detecting the mouse movement. It doesn’t need a mouse pad. And they are more reliable and require less maintenance.

USB Mouse : This type of mouse is connected to the USB connector and requires a free USB port.

Cordless Mouse : This type of mouse has no cable, it used batteries for its power supply. This type of mouse not connected to the computer. They used infrared or radio waves to communicate with the computer.

Wireless Mouse : A wireless mouse is connected to the computers using Bluetooth technology, except that no cable is used to connect the mouse to the computer.

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What is Monitor and different types of Monitors

Monitor is also known as VDU (Visual Display Unit) or Screen. It is Similar  to  a  television, monitor  is a commonly used output device. A Keyboard is used to input data and receive massages from the computer. Whatever is typed on keyboard gets displayed on the monitor. The monitor displays text, pictures, graphics and other items from the computer on a screen.  A monitor has its own box which is separated from the main computer system and it is connected to the computer by cable. A basic monitor displays up to 24 lines of 80 columns of standard characters..

There are different types of monochrome (single color) and color monitors available in the market.

(i) Monochrome Graphics Adopter (MGA):
It works as a color graphics adopter without a color card.

(ii) Monochrome Display Adopter (MDA):It does not have color or graphics capability. It can display only text characters in one color, bright or dim underlined in the reverse image.

(iii) Color Graphic Adopter (CGA):It can display both text and graphics. It can display upto 16 different colors. It cannot display text characters clearly as the MDA.

(iv) Enhanced Graphics Adopter (EGA) :It can also perform in its own modes display upto 64 colors and monochrome graphics and text characters.

(v) Herculer Graphics Adopter (HGA) :It can produce both quality text images and very high revolution of color graphics. It can display only 2 colors of graphics.

(vi) Visual Graphics Adopter (VGA):It has a range of high resolution. It also supports upto 256 colors of grey. Today the upper end varieties of this adopter called super Visual Graphics Adopter (SVGA) are also available.

There are different types of computer monitors  available  in a variety of colors, shapes and designs

Look at the Three main types of monitors:

1) CRT (Cathode Ray Tube monitor)
2) LCD monitor (Liquid Crystal Display)

3) TFT monitor (Thin Film Transistor)

CRT Monitor (Cathode Ray Tube):

CRT stands for cathode ray tube. The cathode ray tube made up of metal and glass. Cathode Ray Tube technology was invented more than 100 years ago. A CRT monitor contains millions of tiny red, green, and blue phosphor dots. It uses the pixels created to project an image on the screen. The CRT monitor comes in 15 inch to 21 inch sizes and larger, It looks like TV screen. It resolution up to 2048 x 1536 pixels.

-> Measuring Quality of CRT Monitor
The quality of CRT monitor depends on the following factors.
i)   Resolution
ii)  Dot pitch
iii) Refresh rate

- Different types of CRT Monitors measurements

Screen Size (Diagonal)	Width (inches)	Height  (inches)
9”	7.2	5.4
14”	11.2	8.4
15”	12.0	9.0
17”	13.6	1.2
21”	16.8	12.6

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LCD Monitor (Liquid Crystal Display) :

In 1888, the Austrian botanist Friedrich Reinitzer discover liquid crystals. This type of monitors based on LCD (liquid crystal display) technology. LCD also called flat panels.   LCD monitor is also called an Flat Panel Monitor because they are flat and thin. Liquid Crystal Displays are smaller size and use less energy than a CRT (cathode ray tube) monitor. These types of monitors are most popular for flat panel desktop monitors.

- Different types of LCD Monitors Size and  Resolution.

LCD Size	Resolution
13.5”	800X600
14.5”	1024X768
18”	1600X1200

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TFT Monitor (Thin Film Transistor) : 

It Stands for Thin Film Transistor. TFT monitor that uses thin film transistor (TFT) technology. The color per pixel is due to the frequency of power put through the pixel. TFT technology is much secure, reliable and generates better picture quality.

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- Different types of Display Standards :

MDA	Monochrome Display Adapter
CGA	Color Graphics Adaptor
EGA	Enhanced Graphics Adaptor
VGA	Video Graphics Array
SVGA	Super Video Graphics Array
WVGA	Wide Video Graphics Array
FWVGA	Full Wide Video Graphics Array
QVGA	Quarter Video Graphics Array
WQVGA	Wide Quarter Video Graphics Array
HQVGA	Half  Quarter Video Graphics Array
QVGA	Quarter Video Graphics Array
HVGA	Half-size Video Graphics Array
WSVGA	Wide Supper Video Graphics Array
XGA	Extended Graphics Array
WEGA	Wide Extended Graphics Array
SEGA	Super Extended Graphics Array
UEGR	Ultra Extended Graphics Array
WUXGA	Wide Ultra Extended Graphics Array
QEGA	Quad Extended Graphics Array
WQXGA	Wide Quad Extended Graphics Array
QWXGA	Quad Wide Extended Graphics Array
QSXGA	Quad Super Extended Graphics Array
WQSXGA	Wide Quad Super Extended Graphics Array
QUXGA	Quad Ultra Extended Graphics Array)
WQUXGA	Wide Quad Ultra Extended Graphics Array
HXGA	Hex Extended Graphics Array
WHXGA	Wide Hex Extended Graphics Array
HSXGA	Hex Super Extended Graphics Array
WHSXGA	Wide Hex Super Extended Graphics Array
HUXGA	Hex Ultra Extended Graphics Array
WHUXGA	Wide Hex Ultra Extended Graphics Array
WQHD	Wide Quad High Definition
QFHD	Quad Full High Definition

- Display Standards Color and Resolutions (in pixels)

Display	Resolution	Color
MDA	720x350	1
VGA	640x480	16
XGA	1024x768	8 bits 256 16 bits 65,536
SVGA	800x600 1024x768 1280x1024 1600x1200	16.7 million 16.7 million 16.7 million 16.7 million
SXGA	1280 x1024	16.7 million
WSXGA	1600 x 1024	16.7 million
UXGA	1600x1200	16.7 million
WUXGA	1920x1200	16.7 million

What is Tablet PC and How it Works

Tablet computers are typically designed to provide similar functionality to desktops except within a portable device. It designed specifically for portability. Note books and tablet PC’s are must utilize an integrated monitor and be capable of operation off an integrated battery or other portable power source. There are generally two formats, a convertible model with an integrated keyboard or a slate style, with a removable keyboard. The Microsoft Windows operating system designed for tablet PC technology.

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What is Personal Digital Assistants (or) Handheld PC

A handheld PC is a very small computer usually weighing less than a pound that you can hold comfortably in your hand or carry in a pocket. A handheld PC is also called a Personal Digital Assistant (PDA). Most of the people use a Personal Digital Assistant to store their schedules and check their e-mail while out of the office. PDAs function as a cellular phone, Web browser, fax, and personal organizer. They also provide handwriting recognition and voice recognition technologies.

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What is Palmtop and How it Works

Palmtop is a hand sized computer. Palmtops have no keyboard but the screen serves both as an input and output device. Palmtops accept handwritten inputs using an electronic pen which can be used to write on a palmtop’s screen. It used as a mobile phone, fax and email purpose.
 
Operating Systems : Windows CE, Psion OS, Plam OS  

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What is Laptops (or) Note book Computers and How it Works

Laptops also known as Note book computers. It consists of a Keyboard flat screen, and power Processor, which weight around 2 Kgs. Notebook and laptops both portable computers that usually feature integral keyboards and monitors. It is generally smaller in size than a desktop computer and larger than a notebook computer. The main purpose of laptop computer is it can be used at the time of traveling.

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