Chapter 3 Hardware Basics: Peripherals

INPUT DEVICES

Keyboard

• Used to enter letters, numbers and special characters
• Standard keyboard
• Ergonomic keyboards 
• To address possible medical problems  
• Wireless keyboard
• Folding keyboards 
• Used with palm-sized computers
• One-handed keyboards  
• Keyboards printed on membranes 

Pointing Devices

• Mouse
• Touchpad
• Pointing stick
• Trackball
• Joystick
• Graphics tablet
• Touch screen
• Stylus

Reading Tools

    Read marks representing codes specifically designed  for computer input

• Optical-mark readers
•   Magnetic-ink character readers
•   Bar-code readers
•  Pen scanners
•   Tablet PC
•  Smart whiteboard
•  Radio Frequency Identification Readers (RFID)

Scanners

Scanners capture and digitize printed images.

•  Flatbed
•   Slide
•  Drum
• Sheet-fed

 Digital camera

• snapshots captured as digital images 
•  stored as bit patterns on disks or other digital storage media

Video Digitizer

• capture input from a video camera or video cassette recorder or TV
• convert it to a digital signal
• stored in memory and displayed on screen

Video Conferencing

• people in diverse locations can see and hear each other
•   Used to conduct long-distance meetings
•  video images transmitted through networks 

Audio Digitizer

• digitize sounds from microphones and other input devices  
• digital signals can be stored and/or  further processed with specialized software
•  a digital signal processing chip compresses the stream of bits before it is transmitted to the CPU

Video Digitizing

• capture input from a video camera or video cassette recorder or tv 
• convert it to a digital signal
• stored in memory and displayed on screen 

Speech Recognition Software

• converts voice data into words that can be edited and printed 

Sensors

• designed to monitor physical conditions  
• for example: temperature, humidity, pressure 

• provide data used in:
• robotics
• environmental climate control
• weather forecasting 
• medical monitoring
• biofeedback
• scientific research

OUTPUT DEVICES

Screen Output

• a monitor or video display terminal (VDT) displays characters, graphics, photographic images, animation and video
• video adapter—connects the monitor to the computer
•  VRAM or video memory—a special portion of RAM to hold video images

Color Depth- 1-bit, 4-bit, 8-bit, 16-bit 

Monitor Classes

• CRTs (cathode-ray tubes) 
•   LCDs (liquid crystal displays)
• overhead projection panels 
• video projectors
• portable computers 

Paper Output

Printers produce paper output/ hard copy

• impact printers 
•  line printers
• dot-matrix printers 
•   Non-impact printers:laser printers and inkjet printer
• Laser printers 
• laser beam reflected off  a rotating drum to create patterns of electrical charges 
•  faster and more expensive
• high-resolution output
• Inkjet Printers
• sprays ink onto paper to produce printed text and graphic images 
•  prints fewer pages/minute than laser printer 
• high-quality color; costs less than laser printer

Fax Machines and Fax Modems

• Facsimile (fax) machine  
• Sending:  scans each page as an image, converts the image into a series of electronic pulses, sends those signals over phone lines to another fax 
• Receiving:  uses the signals to reconstruct the image,  prints black-and-white facsimiles or copies of the originals 
•  Fax modem 
• connect from PC to fax machine via modem and phone lines 

Controlling Other Machines

Output devices take bit patterns and turn them into non-digital movements:

• Robot arms
• Telephone switchboards
• Transportation devices
• Automated factory equipment
• Spacecraft
•   Force feedback joystick

Storage Devices: Input Meets Output

Magnetic Tape-can store large amounts of information in a small space at a relatively low cost

• imitation: sequential data access 
• used mainly for backup purposes

Magnetic Discs

• Random data access  
• Floppy disks 

•   Provide inexpensive, portable storage  
• Hard disks
• Non-removable, rigid disks that spin continuously
• Provide much faster access than a floppy disk
• Removable media (Zip & Jaz disks) 
•   Provides high-capacity portable storage

 Optical Discs

• Use laser beams to read and write bits of   information on the disk surface 
• Not as fast as magnetic hard disks
• Massive storage capacity 
• Very reliable

CD-Rom - read only

CD-R- only writes once and reads many times

CD-RW -  rewritable

DVD  (Digital Versatile Disks)-  holds between 3.8 and 17 gigabytes of info

DVD-ROM drives-

• Can play DVD movies, read DVD data disks  
• Reads standard CD-ROMs, and plays audio CDs 
• Read-only: can’t record data, music, or movies  

DVD-RAM drives

• Can read, erase, and write data (but not DVD video) on multi-gigabytes
• DVD-R (but not CD-R or CD-RW) media

--Video port- uses to plug a color monitor into the video board

--Microphones, speakers, headphones, MIDI ports- used to attach sound equipment

--SCSI port- allows several peripherals to be strung together and attached to a single port

--LAN port uses faster connections to a local-area network (LAN)