Assignment: (Understand only)

1. Learn the basic input and output devices of the computer

The Mouse- The mouse has become the de-facto standard for Windows based systems. As the mouse is moved in the hand across a flat surface, its relative position and movement is visually tracked on the screen by a graphic called the cursor.

Game Pads- Gamepads are hand held devices which are used to send position information and button presses to the computer. The position information is derived from a joystick device, and usually controls some component in a game, like a plane or car. Buttons allow selection and in games are used to fire weapons, open doors and perform other tasks.

Scanners- Scanners are devices which scan documents containing text or graphics and convert them into a bitmap (picture image). The image may be in black and white, gray scale, or color depending upon the features of the scanner. The resolution of a scanner refers to how many pixels (dots) per inch it can detect and reproduce in the final bitmap image. Scanners are also used with OCR (Optical Character Recognition) to scan text documents as graphic images, then convert them back to text again, saving the user having to retype the entire document.

Monitors- Monitor screens are devices used to display information from the computer. In fact, Television sets include monitor screens, though in general, the monitor screens used in computer systems are of a much higher quality. Monitors come in various sizes, commonly starting at 14", then 15", as well as 17" and 19". This is the size of the viewable screen measured across the diagonal from corner to corner. The larger the size the more expensive the monitor. Larger sizes are required for higher resolutions. Resolution refers to the number of dots displayed in the X (across) and Y (down) co-ordinates. Typical screens are capable of displaying 640x480 dots. Larger screens are required for higher resolutions, for example, 1024x768 resolutions displayed on a 14" screen look very small, but the same resolution on a 17" screen is much easier to read. Another term used with monitors is refresh rate. This refers to the number of times per second that the image is redrawn on the monitor screen. A refresh rate of 60Hz means the images is redrawn 60 times a second. Typical refresh rates are 60Hz, 72Hz and 75Hz. Higher refresh rates are required for larger resolutions, else the viewer tend to notice the image on the screen flicker. The images on the screen have to be refreshed at a reasonable rate (greater than 50Hz), otherwise the human eye perceives the image as flickering.

Printers- A device that prints text or illustrations on paper. There are many different types of printers.

• Impact
  In impact printers, the print head mechansim strikes an inked ribbon located between the print head and the paper. The general features of impact printers are
  • uses force by applying hammer pins to strike the paper
  • slow speed in characters per second
  • prints on most paper types
  • transperancies not supported
  • multiple copies may be printed at once

  The two main types of impact printers are Dot-Matrix and Daisy-Wheel.

• Non-Impact
  With non-impact printers, the print head does not make contact with the paper, and no inked ribbon is necessary. The general features of non-impact printers are
  • 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
  • transperancies usually supported

  The three main types of non-impact printers are laserjet, ink-jet and thermal.