Computer hardware components Input Devices Output Devices

I have given a brief over view about computer hardware terminology in our last article. Now in this article I would discuss about hardware components of computer.

Hardware components

Input devices -

accept data or commands in a form useable by computers

Output devices

display the processed information - printers, monitors, speakers.

Processing devices

in system unit and are comprised of circuitry.

Storage devices -

Drives read from and write to storage media (the physical material that can store data and programs).

Communication devices

provide connections between computers and communication networks, allowing for exchange of information and data with other computers via transmission media such as cables, telephone lines, and satellites

Input Devices

• Keyboards
• Pointing Devices mouse, trackballs, joysticks, touchpads and light pens
• Source Entry devices Scanners, Audio input devices, video input devices, digital cameras

Output Devices

Softcopy

Monitor /Display Screens CRT and Flat Panel (LCD), EL and gas plasma

Monitor /Display Screen clarity

Resolution
refers to the number of dots displayed in the X (across) and Y (down) co-ordinates.
expressed in terms of horizontal pixels X vertical pixels.
Typical screens are capable of displaying 640x480 dots

Dot Pitch
measurement of how close together the pixels, or phosphor dots, are that make up an image.
The smaller the dot pitch, the crisper the image,0.31 or less provides a sharp image, especially when displaying text.

Refresh rate
the vertical frequency, or the rate at which each pixel on a screen is re-drawn. A low refresh rate results in an image that flickers, resulting in eye-strain.
A refresh rate of 60Hz means the images is redrawn 60 times a second. Typical refresh rates are 60Hz, 72Hz and 75Hz.

Video Display Adapters

Display graphics - Visual output from your system.
Works between the system's processor and monitor
Relays the information received from the programs and applications running on the system to the monitor

VDAs come with their own memory chips (RAM or VRAM for video RAM) which determines how fast the card processes images, the resolution, and how many colours it can display.
VDA embody certain standards.
Todays PCs commonly use VGA and SVGA standards

Hardcopy Output : Printers

Impact Printers

The general features of impact printers are uses force by applying hammer pins to strike the paper

• slow speed
• prints on most paper types
• transparencies not supported
• multiple copies may be printed at once

Advantages : Less expensive, Fast (some types) , Can make multiple copies with multipart paper

Disadvantages : Noisy! Print quality lower in some types. Poor graphics or none at all.

Dot-Matrix and Daisy-Wheel.

Dot matrix printers form characters using row(s) of pins, 9, 18, or 24 which impact the ribbon on top of the paper.

Daisy wheel printers use a spoked wheel with characters placed at the end of each spoke. A print hammer is used to strike the desired character onto the ink ribbon and then the paper.

Hardcopy Output : Printers

Non Impact Printers

General features print head does not make contact with the paper

• higher speed in characters per second is possible
• prints on most paper types but better quality obtained with better paper
• transparencies usually supported
• Uses ink spray or toner powder
• Offer superior quality and greater options (in terms of the number of fonts and quality of graphic pictures)

Disadvantages : more expensive.

The three main types of non-impact printers are laserjet, inkjet and thermal

Characters of printers

Speed: The speed of a printer is measured in: cps= characters per second, lpm= lines per minute ppm= pages per minute The faster the printing, the more expensive the printer.

Resolution: A more numerical measure of print quality is printer resolution. Measured in dots per inch (dpi), this determines how smooth a diagonal line the printer can produce.

Cable connection:

Serial Cables- send data only 1 bit at a time- Distance from PC 1000 ft

Parallel Cables- send data 8 bits at a time. Distance from PC 50 ft.- Most popular - USB cable which has a maximum data transfer speed of 12 megabits/s (1.5 MBYTES/s).