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10/10: Input & Output
• Definitions
• Input devices: examples
• Output devices: examples
• Keyboards
• Scanners: OCR
• Fonts
• Image File Size: Color Depth,Resolution
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 aredesigned to alleviate wriststrain -- particularly carpaltunnel syndrome.
images courtesy of fentek-ind.com and darwinkeyboards.com
Scanners: OCR
• Optical Character Recognition
• We see characters, and recognize them as letters
• Paper copy becomes– Scanned image becomes– Bitmapped image (bitmap)– Via feature extraction
process becomes– Text file
AA
A
AA
AAA
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
• 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