Categories of Computer

â–º Personal computers
Personal computers are desktop computers designed for an individual's use. They run programs designed to help individuals accomplish their work more productively.
â–º Servers
Servers are not designed to be used directly. They make rmgrams and data available for people hooked up to a computer network, a collection of computers connected together so that they can exchange data.
â–º Minicomputers
Minicomputers are multi-user systems that can handle the computing needs of a smaller corporation or organization. Many people use them simultaneously by means of remote terminals or personal computers.
â–º Personal computers
Mainframes are huge, multi-user systems designed to handle gigantic processing jobs in large corporations or government agencies.
â–º Supercomputers
Supercomputers are ultra fast computers designed to process hugh amounts of scientific data then display the underlying patterns that have been discovered.
Input Devices
An input device lets you communicate with a computer. You can use input devices to enter information and issue commands. A keyboard, mouse, scanner, digital camera, touch pads and joystick are examples of input devices.
Some Common Computer Input Devices:
â–º Keyboard
Used to type data into the computer
Most common input device today
Has special keys for giving the computer commands
o Commands tell the computer to do something, like save the file
o These special keys are calledcommandor function keys
â–º Pointing Devices
Pointing devices move some object on the screen and can do some action - ..
Common pointing devices
o Mouse - most common pointing device
o Track ball - basically an upside down mouse
o Joystick
o Game controller
â–º Scanner
A scanner allows you to scan documents, pictures, or graphics and view them on the computer. You can also use software to edit the items you scan.
Used to put printed pictures and text into a computer
Converts an image into dots that the computer can understand
To scan text, optical character recognition (OCR) software is needed
â–º Digital Camera
Used to take electronic pictures of an object
The pictures taken by a digital cameracan be used directly by a computer
â–º Microphone
Used to put sound into a computer
Need sound recording software
â–º CD-ROM/DVD-ROM
Can be used to put both sound and images into a computer
Use a laser to read a Compact Disk (CD) or a DVD disk
â–ºVideo Capture Card
Usually place inside the computer's case
Use to put video into a computer
Need a video source, either a video camera or video recorder
Output Devices
An output device displays infonnation on a screen, creates printed copies or generates sound A monitor, printer, and speakers are examples of output devices.
Some Common Output Devices:
â–º Monitors and Displays
Shows the processed information on a screen
o A monitor uses a Picture Tube like a television with the image displayed on the front of the tube, which is called the screen.
o Displays are flat and use plasma, LCD, active-matrix, or some other technology.
Monitors used to be called Cathode Ray Tubes (CRTs) because of the picture tube, which is a large vacuum tube.
A monitor or display produce a soft copy. When the device is turned off the information goes away.
Monitors are slowly being replaced by flat panel displays
â–º Printers
Printers produce a hard copy
The information is printed on paper and can be used when the device is off.
It is also called a printout
Do-matrix printers (impact printer)
o Uses metal pins to strike an inked ribbon to make dots on a piece of paper
o Can see the dots that make up the letters or images.
o Lowest print quality of all of the printers.
o Very low in cost per page to use.
o Rarely used today because of the poor print quality, but still used in business to print multi-part forms.
Ink jet printers (non-impact printer)
o .Use drops of magnetic ink to produce dots on a page to produce text or Images.
o The print quality is almost the same as a laser printer's.
o Problems with the ink
• The ink is very expensive
• The ink is water soluble and will run if the paper gets wet
o Highest cost per page of all the printer.s
o For producing color documents, it' has the highest quality at a reasonable price.
Laser printers (non-impact printer)
o How the laser printer produces an image
• A laser or LEDs make dots on a light sensitive drum
• Toner (very tiny particles of plastic) stick to the drum where the dots where made
• Paper is pressed against the drum and the toner is placed on the paper
• The paper is heated and the toner melts into the paper
o Produces the highest quality printout
o For black and white printouts, very low cost per page
o Printout is permanent
o Color laser printers are still fairly expensive ($3,000 to $10,000)
â–º Speaker
used to output sound