Learning Objectives
• When you finish this chapter, you
will:
– Recognize major components of an
electronic computer.
– Understand how the different
components work.
– Know the functions of peripheral
equipment.
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Learning Objectives
• Be able to classify computers into
major categories, and identify their
strengths and weaknesses.
• Be able to identify and evaluate key
criteria when deciding what computers
to purchase.
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The Central Tool of Modern
Information Systems
• Four Basic Functions of Computers
– Accept data
– Process data
– Store data and instructions
– Output data
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The Central Tool of Modern
Information Systems
Figure 4.1 All computers have the same basic components.
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The Central Tool of Modern
Information Systems
Figure 4.2 Organizations have moved from using large mainframes to using
networked PCs.
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The Central Tool of Modern
Information Systems
Figure 4.3 A timeline of computing
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The Central Tool of Modern
Information Systems
Figure 4.3 (continued) A timeline of computing
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Computers Communicating:
Bits And Bytes
• Computer recognizes two states: on or
off
– Each on or off signal represents a bit
(binary digit)
• Encoding Schemes
– Representation of symbols by unique
strings of bits
• Counting Bases
– Decimal system is “base 10”
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– Binary systemMISis175“base
2”
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Computers Communicating:
Bits And Bytes
Figure 4.4 Binary encoding
schemes
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A Peek Inside the Computer
Figure 4.5 A look inside a computer
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A Peek Inside the Computer
• The Central Processing Unit (CPU)
– The brain of the computer
– Microprocessor
• Carries signals that execute all
processing
– Two Components:
• Control unit
• Arithmetic logic unit (ALU)
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A Peek Inside the Computer
• Microprocessor
– Silicon chip embedded with
transistors, or semiconductors
Figure 4.6 Schematic of how circuits on a chip would be
open and closed to represent the letter D in EBCDIC
(11000100)
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A Peek Inside the Computer
Figure 4.7 What happens inside the CPU in one machine cycle executing the
operation 7 + 5
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A Peek Inside the Computer
• Machine Cycle
– CPU’s execution of four functions:
• Fetch
• Decode
• Execute
• Store
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Time Measurements
Functions measured in small fractions of
a second
“Clock speed” determines the number of
the smallest operations performed per
second
Figure 4.8 Computer time
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Speed Measurements
Measured in terms of cycles per second
1 hertz (Hz) = one clock cycle per second
1 MHz (megahertz) = 1,000,000 clock cycles per
second (1 million)
1 GHz (gigahertz) = 1,000,000,000 clock cycles per
second (1 billion)
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Moore’s Law
• States that
– Chip density will double every 18 months
• This has driven incredible decreases in
cost per unit of computing power and
memory
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A Peek Inside the Computer
• Memory
– CPU Registers (part of the CPU)
– Internal Memory
• Random access memory (RAM)
• Read-only memory (ROM)
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A Peek Inside the Computer
• Computer Power
– Clock rate (measured in cycles per
second)
– Amount of information the CPU can
process in each cycle
• This is determined by the word
length and bus size
– Effective speed determined only by
combination of both factors
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Input Devices
•
•
•
•
•
•
Keyboard
Mouse, Trackball, and Track Pad
Touch Screen
Source Data Input Devices
Imaging
Speech Recognition
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Input Devices
Figure 4.9 Banks use magnetic-ink character recognition (MICR) to automate
their input procedures.
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Output Devices
• Soft-Copy Output Devices
– Cathode-Ray Tube (CRT) Monitor
– Flat-Panel Monitor
– Speech Output
• Hardcopy Output Devices
– Nonimpact Printers (most common)
– Impact Printers
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External Storage Media
External Memory (Storage)
• Magnetic disks, magnetic tapes, optical
discs
• Important Properties to Consider
– Capacity
– Speed
– Cost
– Reliability and permanence
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External Storage Media
•
•
•
•
Magnetic Tapes
Magnetic Disks
Optical Discs (Compact Discs)
Optical Tapes
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External Storage Media
• Business Considerations of
Storage Media
– Trade-offs
– Modes of Access
• Sequential Access
• Direct Access
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External Storage Media
Figure 4.11 Characteristics of storage media for business consideration
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External Storage Media
Figure 4.12 Sequential and random data organization
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Classification of Computers
• Supercomputers
– The largest, most powerful, and most
expensive
– Used by universities, research institutions,
large corporations, and the military
• Mainframe Computers
– Less powerful and less expensive than
supercomputers
– Used by businesses with large amounts of
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2002
data that needMIS
to175be
stored
in a central
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Classification of Computers
• Minicomputer
– Often used as the host computer in a
network of smaller computers
– Priced in the tens of thousands to a
few hundred thousand dollars
– Manufacturers: Compaq (VAX), IBM
(AS/400), and Hewlett-Packard
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Classification of Computers
• Servers
– Minicomputers used for specialized
purposes on a network
– Example: file server, printer server,
database server, web server
– Optimized for processing tasks and
I/O with other computers
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Classification of Computers
• Personal Computers / Clients
• Laptop and Handheld Computers
Figure 4.13 PC sales continue to grow.
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Importance of Standards
• Compatibility
– Software and peripheral devices from one
computer can be used with another computer.
– In a networked environment, computers need to
communicate to share databases and other
computing resources.
– In addition to power and cost, compatibility is an
extremely important factor in purchasing
decisions.
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Considerations in Purchasing
Hardware
• What should you consider when
buying personal computers?
– Power -- speed, size of memory, storage capacity
– Expansion and upgrade capability
– Ports for external devices like printers, hard
disks, communication devices
– Ergonomics: Keyboard, Monitor
– Vendor reliability, warranty policy, vendor support
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