Systems Architecture, Sixth Edition

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Systems Architecture, Sixth Edition

Systems Architecture,

Sixth Edition

Chapter 7

Input/Output Technology

Systems Architecture, Sixth Edition

Chapter Objectives


In this chapter, you will learn to:


Describe basic concepts of text and image
representation and display, including digital
representation of grayscale and color, bitmaps,
and image description languages


Describe the characteristics and implementation
technology of video display devices


Understand printer characteristics and technology

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Systems Architecture, Sixth Edition

Chapter Objectives (continued)


Describe the main manual input technologies


Describe types of optical input devices


Identify the characteristics of audio I/O devices
and explain how they operate

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Systems Architecture, Sixth Edition

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FIGURE 7.1 Topics covered in this chapter

Courtesy of Course Technology/Cengage Learning

Systems Architecture, Sixth Edition

Basic Print and Display Concepts


Share many features


Character representation methods


Measurement systems


Methods of generating color

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Systems Architecture, Sixth Edition

Matrix
-
Oriented Image Composition


Display surfaces vary wide in size and
composition


Divided into rows and columns similar to a large
matrix


Each cell (pixel) represents one simple
component of an image


Resolution


Number of pixels displayed per linear
measurement unit


Stated in dots per inch (dpi)

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Systems Architecture, Sixth Edition

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FIGURE 7.2 Text displayed in two resolutions: 50 dpi (top) and 200
dpi (bottom)

Courtesy of Course Technology/Cengage Learning

Systems Architecture, Sixth Edition

Fonts


Collection of characters of similar style and
appearance


Usually measured in points (one seventy
-
second
of an inch), which refers to height of characters

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Systems Architecture, Sixth Edition

FIGURE 7.3 The letters p and A represented in an 8x16 pixel
matrix

Courtesy of Course Technology/Cengage Learning

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Systems Architecture, Sixth Edition

FIGURE 7.4 Sample characters printed in a variety of fonts

Courtesy of Course Technology/Cengage Learning

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Systems Architecture, Sixth Edition

FIGURE 7.5 A font (Times Roman) printed in different point sizes

Courtesy of Course Technology/Cengage Learning

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Systems Architecture, Sixth Edition

Color


RGB (additive colors)


Generates color by mixing red, green, and blue


CMY (subtractive colors)


Generates color using cyan (absence of red),
magenta (absence of green), and yellow
(absence of blue)


CMYK color


Four
-
dye scheme using a separate black dye (K)

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Systems Architecture, Sixth Edition

Numeric Pixel Content


Bitmap


Stored set of numeric pixel descriptions


Monochrome display


Displays one of two colors


Requires only one bit per pixel


Grayscale display


Displays black, white, and shades of gray


Chromatic depth or chromatic resolution

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Systems Architecture, Sixth Edition

Numeric Pixel Content (continued)


Palette


A table of colors


Number of bits used to represent each pixel
determines table size


Dithering


Generates color approximations by placing small
dots of different colors in an interlocking pattern


Half
-
toning (grayscale dithering)

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Systems Architecture, Sixth Edition

Image Storage and Transmission
Requirements


Depends on number of bits that represent each
pixel and on image height and width in pixels


Can be reduced with bitmap compression


Graphics Interchange Format (GIF)


Joint Photographic Experts Group (JPEG)


Moving Pictures Experts Group (MPEG)


All compression methods are lossy, resulting in
some loss of image quality

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Systems Architecture, Sixth Edition

Image Description Languages (IDL)


Address drawbacks of bitmaps (large size and
device dependence) by storing images
compactly


Can represent image components in several
ways


Embedded fonts


Vectors, curves, and shapes


Embedded bitmaps

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Systems Architecture, Sixth Edition

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FIGURE 7.6 Elements of a vector (top) and two complex shapes built
from vectors (bottom)

Courtesy of Course Technology/Cengage Learning

Systems Architecture, Sixth Edition

Adobe PostScript and Portable
Document Format

PostScript

PDF


Used in printing and
publishing and as graphic
file interchange format
and embedded printer
technology


Lacks features needed to
generate and manage
documents as an
integrated whole


Ability to distribute
compressed documents
with complete authorial
control over exact format
of the printed and
displayed document,
regardless of end user’s
specific computer, OS, or
printer

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Systems Architecture, Sixth Edition

Video Display


Character
-
oriented video display terminals
(VDTs)


Connected through dedicated low
-
speed
communication links


Only display text and primitive graphics

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Systems Architecture, Sixth Edition

Video Controllers


Enables communication between computer
system and monitor


Accepts commands and data transmitted via a
bus from the CPU


Generates analog or digital video signals, which
are transmitted to the monitor


Terms:


Refresh cycle and refresh rate; video RAM; dual
porting; graphics accelerators

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Systems Architecture, Sixth Edition

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A video controller contains
RAM, a microprocessor, and
embedded software.

FIGURE 7.8 Video controller with monitor and bus connections

Courtesy of Course Technology/Cengage Learning

Systems Architecture, Sixth Edition

Video Monitors


Separate from keyboards


Common types


Cathode ray tubes (CRTs)


Flat panel displays


Liquid crystal displays (LCDs)


Plasma displays


LED displays

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Systems Architecture, Sixth Edition

LCD


Contains matrix of liquid crystals sandwiched
between two polarizing filter panels


Active and passive matrix displays


Manufactured with thin film transistor (TFT)
technology

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Systems Architecture, Sixth Edition

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FIGURE 7.9 Light entering the
rear filter can’t pass through the
front filter if the liquid crystal is
electrically charged (top);
removing the charge returns the
liquid crystal to its twisted state,
allowing light to pass (bottom)

Courtesy of Course Technology/Cengage
Learning

Systems Architecture, Sixth Edition

Plasma Displays


Combine elements of CRT and LCD technology


Flat panel, active matrix devices


Actively generate colored light near surface of
the display


Good brightness and viewing


Require more power than LCDs

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Systems Architecture, Sixth Edition

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FIGURE 7.10 A plasma display pixel

Courtesy of Course Technology/Cengage Learning

Systems Architecture, Sixth Edition

Printers

Impact (dot
matrix)



Slow, noisy


Relatively poor
-
quality
output


Inexpensive

Inkjet



Relatively slow


Excellent
-
quality output

Laser


Relatively fast


Excellent
-
quality output

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Systems Architecture, Sixth Edition

Inkjet Printers


Most common printing technology


Prints with liquid ink placed directly onto paper


Uses mechanical movement or heat to force ink
out of nozzle


Paper is drawn past moving print head


Resolution is up to 600 dpi

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Systems Architecture, Sixth Edition

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FIGURE 7.12 Ink drop formation and ejection in a thermal inkjet chamber

Courtesy of Hewlett
-
Packard Company; reproduced with permission

Systems Architecture, Sixth Edition

Printer Communication


Impact printers


Can print each character as it’s received


Commonly uses small buffers


Inkjet and laser printers


Use pixels as fundamental output unit


Have relatively large buffers


IDLs are commonly used to improve printer
performance

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Systems Architecture, Sixth Edition

Laser Printers


Operates with an electrical charge and the
attraction of ink to this charge


Color laser output uses three separate print
generators


Laser


Drum


Laser modulators

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Systems Architecture, Sixth Edition

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FIGURE 7.13 Components of a laser print engine

Courtesy of Course Technology/Cengage Learning

Systems Architecture, Sixth Edition

Plotters


Printers that generate line drawings on wide
sheets or rolls of paper


Use inkjet technology


Can produce any large output, including posters
and banners


Also called large format printers

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Systems Architecture, Sixth Edition

Manual Input Devices

Keyboards


For entering text and commands

Pointing
devices


For pointing and selecting buttons or
menu items


For drawing


For moving the position of cursor

Input pads


For many of same functions as mice


Also used for signature pads and
touch screens

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Systems Architecture, Sixth Edition

Keyboards


Translate keystrokes directly into electrical
signals


Generate bit stream outputs (scan code) with a
keyboard controller


Can connect to computer in various ways

(e.g., PS/2, USB, wireless)

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Systems Architecture, Sixth Edition

Pointing Devices


Include:


Mouse


Trackball


Joystick


Input pads (e.g., digitizer tablet)


Infrared detector


Photosensor


Pressure
-
sensitive pad


Magnetic fields

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Systems Architecture, Sixth Edition

Optical Input Devices


Detect light reflected off a printed surface or
object into a photosensor


Categories


Mark and pattern sensors


Image capture devices

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Systems Architecture, Sixth Edition

Mark Sensors and Bar
-
Code Scanners


Mark sensor


Scans for light or dark marks at specific locations
on a page (e.g., standardized multiple
-
choice
test)


Bar code scanner


Detects specific patterns of vertical bars of
varying thickness and spacing


Typically used to track large numbers of inventory
items

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Systems Architecture, Sixth Edition

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FIGURE 7.15 A PDF417 bar code

Courtesy of Course Technology/Cengage Learning

Systems Architecture, Sixth Edition

Optical Scanners


Generate bitmap representations of printed
images


Bright white light shines on the page; reflected
light is detected by an array of photosensors


Optical character recognition (OCR) devices


Combine optical
-
scanning technology with a
special
-
purpose processor or software to interpret
bitmap content

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Systems Architecture, Sixth Edition

Digital Cameras


Digital still cameras, video cameras, and
Webcams use a 2D photosensor array placed
behind lenses to capture reflected and focused
ambient light


Digital still camera


Captures one image at a time


Can configure to store images in a compressed
format, such as JPEG


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Systems Architecture, Sixth Edition

Portable Data Capture Devices


Used for warehouse inventory control and
package routing, tracking and delivery


Simpler devices function only as I/O devices


More complex devices are portable computers
with embedded I/O devices


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Systems Architecture, Sixth Edition

Audio I/O Devices


Sound: an analog signal that must be converted
to digital form for computer processing or
storage


Various mathematical transformations convert
complex sounds to a single numeric
representation


Sampling and playback rely on analog
-
to
-
digital
converters (ADC) and digital
-
to
-
analog
converters (DAC)

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Systems Architecture, Sixth Edition

Audio I/O Devices (continued)


Used in computer systems for:


General
-
purpose sound output (e.g., warnings)


General
-
purpose sound input (e.g., digital
recording for voice email messages)


Voice command input


Speech recognition


Speech generation


Monophonic and polyphonic

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Systems Architecture, Sixth Edition

Speech Recognition


Conceptually simple, but complicated by
speaker variability, phoneme transitions and
combinations, and real
-
time processing


Most current systems are speaker dependent


Digital signal processor (DSP)


Specialized to process continuous streams of
audio or graphical data


Commonly embedded in audio and video
hardware

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Systems Architecture, Sixth Edition

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FIGURE 7.18 The process of speech recognition

Courtesy of Course Technology/Cengage Learning

Systems Architecture, Sixth Edition

Speech Generation


Audio response unit


Generates spoken messages based on textual
input (e.g., automated call routing)


Speech synthesis


Stores individual phonemes within the system


General
-
purpose audio hardware (sound card,
multimedia controller)

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Systems Architecture, Sixth Edition

General
-
Purpose Audio Hardware


Typically packaged as an expansion card that
connects to the system bus of a workstation


Sound cards include an ADC, DAC, low
-
power
amplifier, and connectors (jacks) for microphone,
speaker, or headphone


Musical Instrument Digital Interface (MIDI)


Compact storage format

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Systems Architecture, Sixth Edition

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FIGURE 7.19 Components and connections of a typical sound card

Courtesy of Course Technology/Cengage Learning

Systems Architecture, Sixth Edition

Summary


Concepts, technology, and hardware used in
communication between people and computers


Print and display concepts


Video display devices


Printers


Manual input devices


Optical input devices


Audio I/O devices

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