Output and Storage Chapter 3 of Computers: Understanding Technology 1Bill Pegram - September 15, 2009

Output and Storage

Chapter 3 of Computers: Understanding Technology

1Bill Pegram - September 15, 2009

Types of Output

• Text

• Graphics

• Audio

• Video

Bill Pegram - September 15, 2009 2

Output Devices

• Monitors

• Screen projector

• Printers

• Plotters

• Televisions

• Speakers

Bill Pegram - September 15, 2009 3

Monitors

• Sizes are measured diagonally – 15, 17, 19, and 21 inches for desktop PCs

• Cathode ray tube (CRT) monitors utilize the same technology used in television sets

• Monitor screen consists of dots of phosphor material, with each dot containing a red, green, and blue phosphor


CRT Technology

• Electron beam moves back and forth across the rear of the screen causing the dots on the front of the screen to glow

• Graphics card (video adapter) inside computer converts digital signals in computer to analog signals and sends them to the monitor


Liquid Crystal Display (LCD)

• LCD monitors utilize digital signals

• Liquid crystals are sandwiched between two sheets of material. Electric current causes these crystals to twist, which blocks some light waves.

• Notebook computer LCDs use either passive matrix or active-matrix displays. The latter permit viewing from any angle.


LCD Advantages over CRT

• Thinner (7” vs 17”)• Lighter (12 lbs. vs. 31-41 lbs)• Larger viewable screen size (17” vs. 16”)

for same size• Consume less power• Generate less heat• Flicker-free

*Comparing 2 17” monitors on May 28, 2007 on Best Buy website


CRT Advantages over LCD

• Less expensive ($115 vs. $170-200)*• Precise color matching• Blur-free movement• Can adjust screen resolutions without affecting

image sharpness whereas LCDs best at the native screen size**

• Price comparison of 17” monitors – Best Buy website, May 28, 2007** Monitor Guide on Best Buy website


Screen Resolution, Dot Pitch

• 640x480, 800x600, 1024x768, etc. screen resolution (in pixels)

• Can be changed in Control Panel>Display• The higher the resolution, the smaller

something will appear• Dot pitch: the distance between the

centers of pixels on a display – lower values are better (values range from 0.25-0.31 mm)


Refresh Rate

• Refresh rate should be at least 72 hertz to avoid flicker


Screen Projectors

• Screen projectors display what is displayed on the computer monitor on a large screen

• Used in classrooms and speakers making presentations at meetings, conventions, conferences, etc.


Printers

• Printers can usually print in both portrait and landscape format

• Dot-matrix printers are impact printers; print head strikes an inked ribbon; impact printers are useful for making copies or Braille output

• The number of dots per linear inch is a measure of print quality – draft quality (~300 dpi) and letter quality (~1200 dpi)

• Line printers print an entire line at one time, utilizing a chain of rotating characters. These printers typically use 11 x 17 inch, tractor-fed, continuous-form paper. A fast printer can print 3000 lines per minute


Printers (cont.)

• Ink-jet printers are non-impact printers and provide greater resolution than dot-matrix printers – spray tiny droplets of electrically charged ink – typically use a cartridge for black and one or more for color printing

• Laser printers are nonimpact printers that utilizes technology similar to photocopy machines


Ink-Jet vs. Laser Printer Comparison

• Ink jet advantages– Printers less expensive, particularly for color– Print cartridges less expensive

• Laser printer advantages– Faster– Ink (toner) costs per page less than ink jet


Other output devices

• Thermal printers – used in some fax machines, thermal dye transfer printer can do very high quality

• Plotters – maps, diagrams, charts

• Fax/modem card

• Speakers

• Speaker headsets

• Synthesized human speech15Bill Pegram - September 15, 2009

Storage Devices and Media

• Devices are the hardware component which houses the medium on which data is recorded (e.g. VCR is the device, VCR tape is the medium)

• Speed of storage device measured by access time (to locate file) and data transfer rate

• Magnetic storage devices – floppy disks, hard disks, zip disks, tape cartridges, USB flash drives


Floppy Disks and Disk Drives

• Track: numbered concentric circle• Sector: numbered section of disk, similar to slice

of pie• Cluster: Group of sectors; the smallest unit of

storage that is assigned a memory address• File Allocation Table (FAT) – name of each file,

its size, and the sector in which it begins• Both floppy and hard disks spin, but floppy disk

only spin when data is being accessed or stored


Zip Disks

• Zip disks initially had 100MB capacity, then 250 and later 750MB versions introduced

• Introduced in 1994 by Iomega, the drive was $200 and each 100MB disk was $20; prices declined over time

• Have completely been replaced by writable CDs and flash drives


USB Flash Drive

• Also known as jump drive, thumb drive, and pen drive

• Electronic with no moving parts (unless floppy or hard drive)


Tape Cartridges and Tape Drives

• Magnetic tape was one of the first types of secondary storage for computers

• Tape storage is appropriate for storing large amounts of data that are no longer actively used but need to be saved for historical purposes

• Tape cartridges are used with personal computers to back up the contents of a hard drive


Optical Storage Devices

• Compact Discs (CDs) and Digital versatile (or video) discs (DVD’s) are both 4.75” in diameter and about 1/20” thick

• Lasers are used to write and read discs; light is reflected from the nonburned areas (0) but not from burned areas (1’s)

• Unlike floppy and hard disks, which store data in concentric circles, optical disk data is usually stored in a single track which spirals from the center of the disk to the outer edge

• Some are rewritable and some are not – the designation of R means it can only be written to once, whereas RW means it is is rewritable


CD, DVD Capabilities

• Data transfer rates for CDs expressed as multiple of speed of first drive (150KB/second)

• CD – 700MB capacity

• DVD – from 4.7GB to 17GB (double sided, double layered) capacity


Documents

Output and Storage Chapter 3 of Computers: Understanding Technology 1Bill Pegram - September 15, 2009