COMPACT DISK DRIVE

• The Compact Disk Drive installs in one of the external drive bays in the front of the PC case. It is secured by screws. It is a drive used for running CD-ROM in the computer.

• CD-ROM (Compact Disc Read Only Memory) is a disc that contains data accessible by a computer.

• CD-ROM’s were originally designed for storing music. But later on they were adapted to store any form of computer data.

• A CD-Drive consists of some additional components such as jumpers, LED’s (for indicating data transfer or data read and writes) etc.

• A common CD has capacity of around 650-700 MB and they ended the era of floppy disks as common removable storage devices.

• Two types of Compact Disk Drives are available in the market :-

1. CD-ROM : The common CD-Drives are only readable and they cannot write CD’s. They cost near about 700-800 rupees.

2. CD-RW : These CD-Drives can write and read. Ordinary CD’s cannot be re-written. There are special CD’s which can be re-written. They cost near 1000 rupees.

DVD DRIVE

• DVD (Digital Video Disk) Drive is installed in one of the external drive bays in the PC cabinet. It is secured with the help of screws.

• DVD Drive is designed to optically access data stored on a DVD. A laser moves back and forth near the disk surface and accesses data at a very fast rate.

• DVD is a popular optical disc storage that can be used for data storage. DVD resembles CD’s but DVD’s are encoded in a different format of much greater density, allowing a data storage capacity 8 times greater than CD’s.

• There are two types of DVD-Drives available in the market these days :-

1. DVD-ROM : These drives can only read the DVD’s and cost about 1200-1300 rupees.


2. DVD-RAM : These drives can read and write the DVD’s also. They cost about 1600-1700 rupees.

MONITOR

Monitor is the main output device of the computer. It is just like a simple screen which is used to display. Two types of monitors are mainly used – CRT and LCD.

CRT MONITORS

• CRT (Cathode Ray Tube) Monitors are the monitors which were mostly used till a few years ago.

• They are relatively big (14” to 16” deep) and heavy (5-10 KGs) .

• They are available in screen sizes from 14” to 21’’. A 17” display means that it is measured diagonally from one corner of the tube to the other. The actual viewing area is smaller than 17” (about 16”) because the electron gun can’t sweep completely to the tube edge.

• CRTs send a stream of electrons at the screen, which is charged to about 25000 volts. As they strike it they cause phosphor on the backside of the screen to glow creating light which you see. The electron stream is swept back and forth, up and down at about 60 sweeps per second and turned off and on at the right time to make text and graphics appear.

• They are available in different colors also but black monitor is costlier than others. A CRT monitor costs around 2000-3000 rupees.


LCD MONITORS


• LCD (Liquid Crystal Display) Monitors are common these days. They are replacing CRT monitors very rapidly.

• LCD technology was used in laptops only, till a few years back. But now they are available for desktop PCs also.

• LCD monitors have no electron gun and are therefore not very deep like CRT monitors. The text and images you see are created by a back light behind the panel, that shines through pixels (picture elements). Each pixel is made up of three chambers- red, green and blue. The chambers in each pixel must be opened enough and in the proper proportion to produce the correct brightness and color.

• LCD monitors are much costlier than the CRT monitors. They almost cost 3-4 times the CRT monitors. They are more stylish and light in weight.

KEYBOARD

A Keyboard is an input device which resembles a type- writer. It is used to input text and characters and also to control operations of a computer. It consists of keys. The different keys according to their categories are:

• Modifier keys
# Control key
# Shift key
# Alt key
# Command key
# Windows key
# Fn key

• Lock keys
# Scroll lock
# Num lock
# Caps lock

• Navigation keys
# Arrow keys
# Page scroll keys (Page up /Page down)
# Home key
# End key

• Edit keys
# Return key/Enter key
# Backspace key
# Insert key
# Delete key
# Tab key

• SysRq/Print screen key

• Break key/Pause key

• Escape key

• Menu key

• Space Bar

• Numeric keypad

• Function keys

• Alphabetic keypad

• Power management keys
# Power key
# Sleep key
# Wake key

• Internet keys
# Internet (Web browser) key
# E-mail key

• Multimedia keys
# Volume keys

MOUSE

• Mouse is the most common pointing device used in PCs. It functions by detecting two-dimensional motion relative to its supporting surface.

• The name mouse, coined at the Stanford Research Institute, derives from the resemblance of early models (which had a cord attached to the rear part of the device, suggesting the idea of a tail) to the common rodent.

• The first integrated mouse – shipped as a part of a computer and intended for personal computer navigation – came with Xerox Star 1981.

• Generally every mouse has two buttons and one or two scroll buttons.

• By default the Left button is used to select items. The right button is assigned as an alternate menu. A single scroll wheel is set to scroll up and down. If a second wheel is present, it is usually assigned to scroll left and right.

• There are two types of mouse available in the market – track ball and optical. Track ball mouse uses a rolling ball for its functioning whereas optical mouse uses an infrared transmitter/receiver pair to optically detect the motion of the mouse.


SPEAKERS & HEADPHONE

• Speakers and headphones are the basic audio output devices for the computer.

• Sometimes speakers are inbuilt in monitors but generally they are free standing.

• Headphones have small speakers and are put on our ears directly. They are single person use only.

• We can get better output quality from speakers by attaching woofers, amplifiers etc. with them.

• Simple and ordinary speakers are smaller in size and less costly.



PRINTER

• A Printer produces a hard copy (permanent human- readable text and/or graphics) of documents stored in electronics form, usually on physical print media such as a paper or transparencies.

• The world’s first computer printer was a 19th century mechanically driven apparatus invented by Charles Babbage for his Difference Engine.

• Modern printers have scanners and/or fax machines combined with them in a single unit. A printer which is combined with a scanner can essentially function as a photocopier.

• Many types of printers are available in the market. The main types of printers are :

# Laser printers

# Liquid Inkjet printer

# Solid Ink printers

# Dot-matrix printers

• The most popular printers are of HP Company. Some others are Canon, Epson etc.

WEB CAMERA

• A web camera (or webcam) is a real-time camera (usually, though not always, a video camera) whose images can be accessed using instant messaging or a PC video calling application.

• The term webcam is also used to describe the low- resolution digital video cameras designed for such purposes, but which can also be also used to record in a non-real-time fashion.

MODEM

• A modem (from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.

• The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data.

• The most common modem is a voice band modem that turns the digital ‘1s and 0s’ of a personal computer into sounds that can be transmitted over telephone lines and once received on the other side, converts those 1s and 0s back into the form used by a USB, Serial or Network connection.

• Modems are generally classified by the amount of data they can send in a given time, normally measured in bits per second, or “bps”.

• Optical modems routinely have data rates in excess of a billion (109) bits per second.

USB FLASH DRIVE

• USB flash drives are flash memory data storage devices integrated with a USB (Universal Serial Bus) interface.

• They are typically small, lightweight, removable and rewritable.

• One end of the USB Flash Drive is fitted with a single male type-A USB connector. Inside the plastic casing is a small printed circuit board. Mounted on this board are some simple power circuitry and a small number of surface-mounted integrated circuits (ICs). Typically, one of these ICs provides an interface to the USB port, another drives the onboard memory and the other is the flash memory.

• USB Flash Drives are available in different storage capacities. The most common are 512MB, 1GB, 2GB etc. But they are available upto 64GB of memory.