Embed Size (px)
Citation preview
Chapter 7
Input/Output Technology
Chapter goals Describe common concepts of text and
image representation and display including digital representation of grayscale and color, bitmaps, and image compression techniques
Describe the characteristics and implementation technology of video display devices
List and describe the three predominant manual input technologies
Chapter goals Understand printer characteristics
and technology Describe various types of optical
input devices including mark sensors, bar code readers, scanners, and digital cameras
Identify the characteristics of audio I/O devices, and explain how they operate
Print vs. video display Print has a thousand year history Techniques have developed for the
design and representation of characters
Most of these techniques have been transported to video display
Matrix oriented image composition Representing text starts with the
display surface Paper, video, television, computer
screens Display can be subdivided into
rows and columns (a table or matrix)
Each cell in matrix is a pixel
Pixel Smallest element of graphical
representation of text or image Print – can be empty or contain
one or more inks or dyes Video – empty or display light of
varying color and intensity
Pixels and Paper Traditionally pixel size corresponds
to smallest drop of ink that can accurately placed on page
This is called a point, i.e. 12 pt, 14 pt
Printer’s standard is 72 pts per inch This measurement is now standard,
although modern printing can apply ink in smaller quantities
Pixels and computer display Pixel size for modern video display
is typically between 0.2 and 0.3 millimeters
Number of pixels on a surface depends on the size of the surface (height and width) and size of the pixels
Using pixels to display text
Resolution Important factor in the quality of
image For print resolution is expressed as
dots per inch (dpi) Laser printers - 600 dpi Commercial printing - 1200 dpi Screen resolution varies from
640x480 to 800x600
Poor resolution & computers Computer uses binary information
to store graphical images For each pixel, binary information
must describe the appearance of the pixel
Binary information is a representation of the color of each pixel
Color in video vs. print Human eye interprets different
light frequencies as different colors Video – color is generated directly
by the display device Print – color is the light frequency
reflected by the page
Color cont. Display – three primary colors are
Red Green blue RGB. These three are mixed together to produce all colors.
Print uses subtractive colors – cyan (absence of red) magenta (absence of green) and yellow (absence of blue) plus black, or CMYK
Representing colors Colors are represented in
computers using 0s and 1s Each pixel is assigned a fixed
amount of bits to represent its color, i.e. 24 bits
Collection of colors that can be represented in the available bits is called the color palette
Color coding examples
Display restrictions Size of color palette (number of possible
colors)http://www.lynda.com/hex.html
Resolution of the screendemo storage requirements (excel)..\..\Desktop\newmonitor.xls
Image representation can be improved through image compression formats (.GIF, .JPEG, .MPEG)
Fonts Collection of characters in a similar
style is called a font Fonts have evolved over the
centuries http://www.will-harris.com/type-fun
.htm
Sample fonts
Font in different sizes
Vector – a line segment that has a specific angle and length with respect to a point of origin
Basic Concepts of Print and Display
Basic Concepts of Print and Display
Technology Focus
Basic Concepts of Print and Display
Video Display Character-Oriented Video Display
Terminals: Commonly used during 1970s and 1980s.
Terminal – consist of an integrated keyboard and television screen.
Used today primarily in systems such as retail checkout counters and factory floor environments.
Video Display
Video Display
Thin Client – a hybrid device with a mix of VDT and microcomputer characteristics. They execute applications within an operating environment such as Java, a Web browser, or Windows Terminal Services
Video Display
Video Display
Video Controller – accepts the commands and data transmitted via a bus from the CPU and generates a TV-style analog video signal which is transmitted to the monitor
Video Display
Video Display
Monitor Types: Cathode Ray Tube (CRT) Liquid Crystal Display (LCD) Plasma Displays
Video Display
Printers
Printer Types: Impact – dot matix
Nearly obsolete expect for printing multiple forms
Laser Inkjet
Printers
Ink-Jet: The print head of an ink-jet printer
consists of an ink cartridge, a set of ink chambers and a set of ink nozzles
Each ink nozzle can print a single pixel and nozzles are arranged in short vertical rows similar to those of a dot matrix printer
PrintersLaser: Operates differently from other types
of printers No print head or ink ribbon is used An internal image of the entire page is
stored in an internal buffer as a bit map.
Once filled, the buffer contents are sent to the print driver for generation
Printers
Manual Input Devices
Input Devices: Keyboards Pointing Devices
Manual Input Devices
Keyboard Input: Keyboard devices translate keystrokes
directly into electrical signals. A keyboard controller is used to
generate bit stream outputs. The controller generates a bit stream
output according to an internal program or lookup table.
Manual Input Devices
Pointing Devices: Mouse Trackball Joystick Digitizer Tablet
Manual Input Devices
Pointing Devices:Translates the spatial position of a pointer, stylus, or other selection device into numeric values within a system of two-dimensional coordinates
Manual Input Devices
Pointing Devices: Mouse – a pointing device that is
moved on a flat surface such as a table, desk or rubber pad.
Trackball – a mouse with the roller ball on the top. The roller ball is moved by the fingertips, thumb or palm of the hand.
Manual Input Devices
Pointing Devices: Joystick – used as an input device
with computer games. Digitizer Tablet – uses a pen, or
stylus, and a digitizing tablet. The tablet is sensitive to the placement of the stylus at any point on its surface.
Manual Input Devices
Manual Input Devices
Optical Input Devices
Mark Sensors and Bar Code Scanners:
Mark Sensors – scans for light or dark marks at specific locations on a page
The mark sensors uses preprinted bars on the edge of the page to establish reference points
Optical Input Devices
Optical Input Devices
Optical Input Devices
Optical character recognition (OCR): Combine optical scanning technology
with hardware or software interpretation of bit map content
The bit mapped representation is searched for patterns corresponding to printed characters
Optical Input Devices
Audio I/O Devices
Sound generation and recognition can be used in a number of ways General-purpose sound output, such as
warnings, status indicators, and music General-purpose sound input, such as
digital recording Voice command input
Audio I/O Devices
Speech recognition: The process of recognizing and
appropriately responding to the meaning embedded within human speech.
Human speech consists of individual sounds called phonemes.
Audio I/O Devices
Audio I/O Devices
Speech Generation: A device that generates spoken
messages based on textual input is called audio response unit
Simple audio response units digitally store and play back words or word sequences
Summary Manual input devices include keyboards,
mice and other pointing devices A stored set of numeric pixel descriptions
is called a bit map Video display terminals consist of an
integrated keyboard and television screen Commonly used paper output devices
include dot matrix printer, ink-jet printer, laser printers, and plotters
Summary Optical input devices include optical
scanners, mark sensors, bar code readers, and optical character recognition devices
General-purpose speech recognition systems can be used for command and control, or for the input of large amounts of textual material
Sound cards include converters, amplifiers, microphone, speaker and headphone connectors
