Keyboard
ü The most familiar input device
ü Used to enter letters, numbers and special characters
Ø Standard keyboard
Ø Ergonomic keyboards
q To address possible medical problems
Ø Wireless keyboard
Ø Folding keyboards
q Used with palm-sized computers
Ø One-handed keyboards
Ø Keyboards printed on membranes
Pointing Devices
ü Mouse
ü Touchpad
ü Pointing stick
ü Trackball
ü Joystick
ü Graphics tablet
ü Touch screen
ü Stylus
Reading Tools
ü Read marks representing codes specifically designed for computer input
Ø Optical-mark readers
Ø Magnetic-ink character readers
Ø Bar-code readers
Ø Pen scanners
Ø Tablet PC
Ø Smart whiteboard
Ø Radio Frequency Identification Readers (RFID)
Digitizing the Real World
ü Scanners capture and digitize printed images.
Ø Flatbed
Ø Slide
Ø Drum
Ø Sheet-fed
ü Digital camera
Ø Snapshots captured as digital images
Ø Digital images stored as bit patterns on disks or other digital storage media
ü Video digitizer
Ø Capture input from a:
q Video camera
q Video cassette recorder or television
Ø Convert it to a digital signal
q Stored in memory and displayed on computer screens
ü Videoconferencing
Ø People in diverse locations can see and hear each other
q Used to conduct long-distance meetings
Ø Video images transmitted through networks
ü Audio digitizers
Ø Digitize sounds from
q Microphones
q Other input devices
Ø Digital signals can be
q Stored
q Further processed with specialized software
Ø A digital signal processing chip compresses the stream of bits before it is transmitted to the CPU.
ü Speech recognition software
Ø Converts voice data into words that can be edited and printed
ü Sensors
Ø Designed to monitor physical conditions
q Temperature, humidity, pressure
Ø Provide data used in:
q Robotics
q Environmental climate control
q Weather forecasting
q Medical monitoring
q Biofeedback
q Scientific research
Output: From Pulses to People
ü Screen Output
Ø A monitor or video display terminal (VDT) displays characters, graphics, photographic images, animation and video.
q Video adapter—connects the monitor to
the computer
q VRAM or video memory—a special portion of RAM to hold video images
Ø The more video memory, the more picture detail is displayed.
Color depth
- 1-bit depth
- 4-bit depth
- 8-bit depth
- 16-bit depth
Ø Monitor classes
q CRTs (cathode-ray tubes)
q LCDs (liquid crystal displays)
• Overhead projection panels
• Video projectors
• Portable computers
ü Paper Output
Ø Printers produce paper output or hard copy.
Ø Two basic groups of printers:
q Impact printers
• Line printers
• Dot-matrix printers
q Non-impact printers
• Laser printers
− Laser beam reflected off a rotating drum to create patterns of electrical charges
− Faster and more expensive than dot matrix printer
− 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
Ø Multifunction printer or MFP combines a scanner, printer and a fax modem.
Ø A plotter can produce large, finely scaled engineering blueprints and maps.
ü Fax Machines and Fax Modems
Ø Facsimile (fax) machine
q 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
q Receiving:
• uses the signals to reconstruct the image
• prints black-and-white facsimiles or copies of the originals
Ø Fax modem
q Connect from PC to fax machine via modem and phone line
ü
ü Output You Can Hear
Ø Sound card
q Enables the PC to:
• Accept microphone input
• Play music and other sound through speakers or headphones
• Process sound in a variety of ways
Ø Synthesizers
q Used to produce music, noise
ü Controlling Other Machines
Ø Output devices take bit patterns and turn them into non-digital movements.
q Robot arms
q Telephone switchboards
q Transportation devices
q Automated factory equipment
q Spacecraft
q Force feedback joystick
Rules of Thumb:
Ergonomics and Health
ü Choose equipment that’s ergonomically designed.
ü Create a healthy workspace.
ü Build flexibility into your work environment.
ü Rest your eyes.
ü Stretch to loosen tight muscles.
ü Listen to your body.
ü Seek help when you need it.
Storage Devices: Input Meets Output
ü Magnetic Tape
Ø Can store large amounts of information
in a small space at a relatively low cost
Ø Limitation: sequential data access
Ø Used mainly for backup purposes
ü Magnetic Disks
Ø Random data access
Ø Floppy disks
q Provide inexpensive, portable storage
Ø Hard disks
q Non-removable, rigid disks that spin continuously
and rapidly
q Provide much faster access than a floppy disk
Ø Removable media (Zip & Jaz disks)
q Provides high-capacity portable storage
ü Optical Disks
Ø Use laser beams to read and write bits of information on the disk surface
q Not as fast as magnetic hard disks
q Massive storage capacity
q Very reliable
Ø CD-ROM
q Optical drives that read CD-ROMs
Ø CD-R
q WORM media (write-once, read many)
Ø CD-RW
q Can read CD-ROMs and write, erase and rewrite data onto CD-R & CD-RW disks.
Ø DVD (Digital Versatile Disks)
q Store and distribute all kinds of data
q Hold between 3.8 and 17 gigabytes of information
Ø DVD-ROM drives
q Can play DVD movies, read DVD data disks
q Read standard CD-ROMs, and play audio CDs
q Read-only: can’t record data, music, or movies
Ø DVD-RAM drives
q Can read, erase, and write data (but not DVD video) on multi-gigabyte
DVD-R (but not CD-R or CD-RW) media
ü Solid-State Storage Devices
Ø Flash memory is an erasable memory chip:
q Sizes range from 16 MB to 1 GB
q Compact alternative to disk storage
q Contains no moving parts
q Designed for specific applications such as storing pictures in digital cameras.
q Likely to replace disk and tape storage
Computer Systems: The Sum of Its Parts
Personal Computer Design Classes
ü Tower systems
Ø Tall, narrow boxes, generally have more expansion slots and bays than other designs.
ü Flat desktop systems
Ø Designed to sit under the monitor like a platform.
ü All-in-one systems (like the iMac)
Ø Combine monitor and system unit into a single housing.
ü Laptop computers
Ø Include all the essential components, including keyboard and pointing device, in one compact box.
ü Ports and Slots Revisited
Ø The system or motherboard includes several standard ports:
q Serial Port for attaching devices that send/receive messages one bit at a time (modems)
q Parallel Port for attaching devices that send/receive bits in groups (printers)
q Keyboard/Mouse Port for attaching a keyboard and a mouse
Ø Other ports are typically included on expansion boards rather than the system board:
q A video port is used to plug a color monitor into the video board.
q Microphones, speakers, headphones, MIDI ports are used to attach sound equipment.
q An SCSI port allows several peripherals to be
strung together and attached to a single port.
q A LAN port uses faster connections to a local-area network (LAN).
Ø Expansion Made Easy
q With the PC open architecture and the introduction of new interfaces, you can hot swap devices.
Ø USB (Universal Serial Bus) transmits a hundred times faster than a PC serial port
Ø Firewire (IEEE 1394) can move data between devices at 400 or more megabits per second. The high speed makes it ideal for data-intensive work, like digital video.
q FireWire 800, which offers 800 Mbps transfer speeds, was recently introduced on high-end Macintosh systems.
ü Putting It All Together
Ø A typical computer system might have several different input, output, and storage peripherals—the key is compatibility.
Ø Networks blur the boundaries between computers.
Ø Networked computers may have access to all the peripherals on a system.
Ø The computer is, in effect, just a tiny part of a global system of interconnected networks.
Inventing the Future: Tomorrow’s Peripherals
ü Tomorrow’s Storage
Ø Smaller disks that hold more
q A single electron memory chip the size of a thumbnail that can store all of the sounds and images of a full-length feature film
ü Tomorrow’s Output
Ø Flat-panel screens replacing desktop CRTs
Ø Retinal displays that work without a screen
ü Tomorrow’s Input: Sensors
Ø More sophisticated devices will serve as eyes, ears, and other types of sense organs for computer networks.
ü Peripherals allow computer to communicate with the outside world and store information for later use information.
ü The most common input devices today are the keyboard and the mouse. A variety of other input devices can be connected to the computer.
ü Output devices perform the opposite function: They accept strings of bits from the computer and transform them into a form that is useful or meaningful outside the computer.
ü Storage devices are capable of two-way communication with the computer. Because of their high-speed random access capability, magnetic disks are the most common forms of storage on modern computers.
ü Network connections make it possible for computers to communicate with one another directly.
