I/O Hardware General
- Input devices: translate data going into the computer to
either ASCII or binary.
- Output devices: take ASCII or Binary information and
translate it into a form usable by people or other devices.
Hardware communicates directly to the OS.
When adding a new device usually a device driver
must be installed.
Device driver: software that allows the OS to
understand the signals sent by the I/O device.
I/O devices may require a card be inserted onto a
Provides a port and local high speed data bus to the
- Mouse, trackball, touchpad, light pen.
- Allow user to point at an object and perform a task, usually
Source-data entry devices:
- Move data entry as close to the source as possible thus
reducing human data entry error and time it takes to process
- Scanning devices.
- Audio input devices.
- Video input devices.
- Biological input devices.
- Output device that prints characters, symbols, and
graphics on paper.
- Impact printers: produce output by using a
mechanism to strike the paper.
• Dot matrix: uses pins to form letters.
• Line printers: print a whole line of characters at once.
- Nonimpact printers: do not strike the paper.
• Laser printer: produce output similar to the way a
photocopy machine works.
• Ink-jet or bubble-jet printers:
– Spray ink on the paper to form the output image.
Monitors: display output on a screen for viewing.
- Usually connected to the computer via a graphics display
card on the motherboard.
- Comes with its own RAM called VRAM.
- Screens are broken down into Pixels.
- Screen Clarity:
• Resolution: how clear or sharp an image may be displayed on a
– Determined by the number of pixels, how close each pixel is (dot
pitch) and how often the screen is refreshed (refresh rate).
• Monochrome: one color displayed on black but shades of the
color can exist.
• Color: can display between 16 and 16.7 million colors.
- Converts digital sounds into speech like sounds.
- Not like a tape recorder that records your voice and replays
- Speech coding uses an actual human voice and uses those
words when a digital pattern is recognized.
- Speech synthesis: uses a set of 40 basic speech sounds to
electronically create words.
- Produces digitized sounds.
- Requires a sound card or use of a midi-port for more
Perform both input and output.
- ATM, POS.
Smart and Optical Cards:
- Smart Cards: Used to purchase goods and
- Optical cards Contain huge amounts of
information using CD like optical data.
- Like those used in restaurants.
Lots of memory