2/13: storage, input & output data storage –magnetic –optical input & output:...
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2/13: Storage, Input & Output
• Data storage– Magnetic– Optical
• Input & Output: Definitions– Examples: Input & Output devices– Keyboards– Fonts– Image File Size: Color Depth,
Resolution– Monitors
Data storage: what is it?
• Long-term storage, not immediate memory
• Not RAM (short-term memory)
• Synonyms: secondary storage, auxiliary storage, mass storage
images courtesy of dalelabs.com,, iomega.com, imation.com,
Data storage: where is it?
• Storage involves 2 parts: the device & the media
• Removable vs. fixed media
• Where can you store data?– magnetic media– optical media– magneto-optical media– solid state media
image courtesy of How Computers Work
Storage characteristics• Random vs. sequential access• Tracks & sectors• Speed
– spin rate (RPM)– seek time & latency– access time– data transfer rate
• Storage Capacity– areal density– size
Image courtesy of How Computers Work
Magnetic data storage
• Use magnets to store bits:– example: 0 = N , 1 = S
• Reading and writing
• Floppy disk drives
• Hard disk drives
PACE
image courtesy of How Computers Work
Floppy disk drives: types
• Low-density floppy drives: 5.25” floppy disks3.5” 1.44 MB floppy disks
• High-density floppy drives: Zip disks, LS-120 disks
Images courtesy of How Computers Work, Imation.com, and Iomega.com
Floppy disk drives: how they work• Shutter opens with an arm.• Cookie spins on the spindle.• Read/write heads get close
to the cookie inside• Magnetic particles generate
electric currents in the heads.
• Electric currents are interpreted as a series of bits.
Images courtesy of How Computers Work
Hard disk drives: overview
• Glass platters coated with magnetic particles
• Read/write heads like floppy drives but much smaller
• Multiple platters, multiple heads.
Image courtesy of How Computers Work
Optical Storage• Instead of using magnetism to store bits, we use light• A laser is the light
– Laser: “light amplification by stimulated emission of radiation”
– Extremely focused, narrow beam of powerful light– Depending on the wavelength, the beam can be narrower or
wider
• Lands are flat areas on the disc– Reflect light like a mirror
• Pits are holes in the disc– Scatter light
Courtesy of http://www.microserve.net/~tpetchy/DVD.shtml
CD Drives: Types and Operation
• CD-ROM drive speeds: how many times faster than the original CD-ROM drives• 2x, 4x, 6x, 8x, 16x, 32x, 48x
• Operation:• Diode generates laser• Laser bounces off mirrors, reaching the disc• Disc reflects or scatters laser• Light-sensing diode sees the reflections, comparing
them to a timing circuit to generate 0s and 1s
Image courtesy of c-cube.com
Types of Optical Discs
• Compact discs:– CD-ROM: read only memory (680 MB)– CD-R: Recordable (650 MB)– CD-RW: ReWritable (495 MB)
Image courtesy of c-cube.com
Types of Optical Discs• Digital versatile discs – higher density storage
– DVD-ROM: read only memory (4.7 – 17 GB)– DVD-R: Recordable (3.9 GB?)– DVD-ram (5.2 GB) & DVD+RW (6.0 GB): Rewritable
(still fighting)
Image courtesy of c-cube.com
Input & Output: Definitions
• Input: “to enter data into the computer for processing; the data entered.”
• Output: “to transfer data from the computer to devices that allow you to see, hear, or feel it; the data transferred.”
images courtesy of keytronic.com, viewsonic.com
What is the essential qualification?
• For something to be qualified as an input or output device, it must be an interface between the user and the computer.
• Cables, dial-up modems, etc. would NOT be input or output devices.
images courtesy of logitech.com, viewsonic.com
Input devices: examples
• keyboards fax modems
• pointing devices scanners
• microphones
images courtesy of logitech.com, keytronic.com, buy.com,
Output devices: examples
• monitors printers
• speakers feedback game controllers
Images courtesy of viewsonic.com, yamaha.com, logitech.com
The Keys on the Keyboard
• for inputting text
• Standard keyboard– alphanumeric keys – function keys (F1)– shift keys (left shift)– toggle keys (caps lock)– special function keys (enter, windows, menu, home,
end, page up/down, delete, backspace, esc)
You will be expected to know what the keys on the keyboard do.
Image courtesy of fentek-ind.com
Ergonomic Keyboards
• Ergonomics: how machines and humans interact, with an emphasis on bodily stress and fatigue.
• Ergonomic keyboards are designed to alleviate wrist strain -- particularly carpal tunnel syndrome.
images courtesy of fentek-ind.com and darwinkeyboards.com
Fonts• Types of fonts: typeface family: Arial, Times
Roman
• serifs: things on end of letters
• Types of fonts: style: regular, bold, italic, shadow
• size: measured in points (72 pts/in)
F Fserifs
Arial, 208 pt., italic
Times New Roman, 229 pt., regular
Image File Size: Contributors• Images are stored on a per-bit
basis:– Bigger the physical image =
bigger the file size– Deeper the color depth = bigger
the file size– Higher the resolution = bigger
the file size 8-bit color 35K
50% size 10K
Lower res 51K
Original 56K
Color Depth
• Color depth is the number of bits that are stored for each pixel
• 1-bit B&W– line art– halftone
• 8-bit grayscale
• 24-bit color
Pictures appear courtesy of Mustek http://www.mustek.com.tw/Support/html/scannings.html
1 bit line art 1 bit halftone
8-bit grayscale 24-bit color
Why 24-bit Color?
• Color is stored as the combination of three colors: red, green, & blue (RGB).
• Each color has a value stored for it using 8 bits.
• 3 colors x 8 bits = 24 bits total.
• How many levels for each color can be recorded?– 8 bits per color = 2 to the 8th power = ?
Resolution: Printers & Files
• resolution: dpi dots per linear inch
• horizontal resolutionmay differ from vertical resolution
• higher the resolution, the “truer” the image.
• monitors: 50-100 dpiprinters (inkjet): 100-200 dpiprinters (laser): 300-1200 dpi
George Seurat, Sunday Afternoon on La Grande Jatte from Art.com
300 dpi: no zoom, 400% zoom 150 dpi: no zoom, 400% zoom
Resolution
How Monitors Work
• Resolution
• Refresh Rate
• Raster• scan lines
• field
• Flat-panel displays
image courtesy of sonystyle.com
How many colors are there?
Name colors possible mode
Standard VGA 16 4 bit
256 color mode 256 8 bit
High Color 65,536 16 bit
True Color 16,777,216 24 bit
Terms
• Resolution: # pixels displayed horizontally and vertically
• Refresh rate: how quickly the image is redrawn
Raster scanning
• Raster: the area that is hit by the electron beams, line by line. Each line is called a scan line.
• Field: a complete sweep of the screen.
• Refresh: rate usually at least 60/sec (60 Hz)
Flat-panel LCD Displays
• Passive-matrix vs. Active-matrix
• Resolution limitations
• Considerably more expensive than CRTs
image courtesy of Viewsonic.com
Flat-panel Plasma Displays
• Brighter than LCD
• Easier to manufacture (theoretically)
• Mainly used for large-scale applications
image courtesy of Viewsonic.com
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