Chapter 3
Hardware:
Input, Processing, &
Output Devices
Hardware
 Hardware
Any machinery (most of which uses digital circuits) that
assists in the input, processing, storage, & output
activities of an information system
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Hardware Components (1)
 Central Processing Unit (CPU)
A hardware component that performs computing
functions utilizing the ALU, control unit, &
registers
 Arithmetic/Logic Unit (ALU)
Performs mathematical calculations & makes logical
comparisons
 Control Unit
Sequentially accesses program instructions, decodes
them, coordinates flow of data in/out of ALU,
registers, primary & secondary storage, & various
output devices
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Hardware Components (2)
 Registers
– High-speed storage areas used to temporarily hold
small units of program instructions & data immediately
before, during, & after execution by the CPU
– Primary Storage
– Holds program instructions & data (a.k.a. main
memory)
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Hardware Components (Figure 3.1)
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Execution of an Instruction
See also Figure 3.2
Machine Cycle
- Instruction phase
- Execution phase
 Instruction Phase
– Step 1: Fetch instruction
– Step 2: Decode instruction
 Execution Phase
– Step 3: Execute instruction
– Step 4: Store results
Instruction time: The time to complete the instruction phase.
Execution time: The time to complete the execution phase.
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Machine Cycle Time
See Figure 3.3
 Machine Cycle Time
Time it takes to execute an instruction
 Slow machines
Measured in microseconds (one-millionth of a second)
 Fast machines
Measured in nanoseconds (one-billionth of a second) to
picoseconds (one-trillionth of a second)
 MIPS
Millions of instructions per second.
 Pipelining
A CPU operation in which multiple execution phases are
performed in a single machine cycle
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Clock Speed
 Clock Speed
Predetermined rate a CPU produces a series of electronic
pulses.
 Hertz
One cycle or pulse per second
 Megahertz (MHz)
Millions of cycles per second
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Wordlength
 Wordlength
Number of bits the CPU can process at any one time
 BIT
Binary Digit - 0s & 1s that combine to form a “word”
 Computer word
What the computer processes
 Microcode
Predefined, elementary circuits & logical operations that
the processor performs when it executes an
instruction.
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Bus Line
 Bus Line
Physical wiring connecting computer
components
 Bus Line Width
Number of bits a bus line can transfer at one
time.
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Moore’s Law (Figure 3.4)
Moore’s Law
A hypothesis that states
transistor densities in a
single chip will double
every 18 months
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Instruction Sets
 Complex instruction set computing (CISC)
A computer chip design that places as many microcode
instructions into the central processor as possible
 Reduced instruction set computing (RISC)
A computer chip design based on reducing the number of
microcode instructions built into a chip to an essential
set of common microcode instructions
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Byte
Eight bits together that represent a single character
of data.
Bytes are stored in
memory. Memory
provides working
storage for program
instructions.
Storage
Data is represented
in on/off (0/1)
circuit states.
1 2 3 4 5 6 7 8
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Memory Characteristics &
Functions (Figure 3.5)
 Temporary & volatile: RAM - Random
Access Memory
• SRAM
• DRAM
 Permanent & non-volatile: ROM - Read
Only Memory
• PROM
• EPROM
 Cache memory (See Figure 3.6)
High speed memory that a processor can access more
rapidly than main memory.
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Multiprocessing
 Multiprocessing
The simultaneous execution of two or more
instructions at the same time.
 Coprocessor
Speeds processing by executing specific types of
instructions while the CPU works on another
processing activity.
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Parallel Processing (Figure 3.7)
 Parallel processing
– A form of multiprocessing that speeds the
processing by linking several processors to
operate at the same time or in parallel
– Splits task to be processed by multiple
processors, then solutions are compiled/
combined to provide a result
– e.g., www.google.com uses both cached
information & parallel processing via
hundreds of desktop computers.
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Secondary Storage
Stores large amounts of data, instructions, & information
more permanently than main memory.
Devices for Secondary Storage
•Magnetic tape
•Magnetic disks
•Compact Disk Read-Only
•Memory (CD-ROM)
•Write Once Read Many - (WORM)
•Magneto-optical disks
•Redundant Array of Independent /
Inexpensive Disks (RAID)
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•Optical disks
•Digital Video Disks
•Memory cards
•Flash memory
•Removable storage
•See Figures 3.9, 3.10, 3.11
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Access Methods & Storage
Devices
 Sequential
Data retrieved in the order stored.
 Direct
Data retrieved without the need to read or pass
other data in sequence.
 Storage Devices
– Sequential Access Storage Devices (SASDs)
– Direct Access Storage Devices (DASDs)
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Input & Output Devices
 Data entry
The process by which human-readable data is
converted into machine-readable form
 Data input
The process of transferring machine-readable data
into the computer system
 Source data automation
Capturing & editing data where the data is
originally created & in a form that can be
directly input to a computer
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Input Devices
•PC input devices
•Voice recognition devices
•Digital computer cameras
•Terminals
•Scanning devices
•Optimal data readers
•Magnetic Ink Character Recognition (MICR)
•Point Of Sale (POS) devices
•Automatic Teller Machine (ATM)
•Pen input devices
•Light pens
•Touch sensitive screens
•Bar code scanners
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Output Devices
• Display monitors
• Liquid crystal displays (LCDs)
• Printers & plotters
• Computer output microfilm (COM)
• Disks & diskettes
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Types of Computer Systems (1)
 Personal Computers (PCs) or Microcomputers
– Small, relatively inexpensive
– Desktop , laptop, or notebook
– Different degrees of power & cost
• Network Computers for accessing networks, especially the
Internet (also known as network appliances)
• Workstations are high-end microcomputers
 Minicomputers
– Size of a three drawer file cabinet plus peripherals
– accommodates several users at one time
– Useful for departments of large orgs. or entire mid-size
orgs.
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Types of Computer Systems (2)
 Mainframe Computers
– Large & powerful
– Shared by hundreds/thousands concurrently
– Useful for large orgs., massive transaction processing
(e.g., Internet gateway, credit card authorisation)
 Supercomputers
– Most powerful
– with fastest processing speeds
– Useful for massive number crunching (e.g., simulating
wind tunnel)
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Types of Computer Systems (3)
 Computer System Architecture
The structure, or configuration, of the hardware
components of a computer system
 Multimedia Computer System (See Figure 3.17)
– Marriage of sound, animation, & digitized video
– What is the multimedia part of the Internet commonly
known as?
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Annual Cost of PC Ownership
(TCO) (See Figure 3.16)
 Hardware
 Technical support
 Administration services
 End user operations
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15%
15%
15%
55%
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Industry Standards in Common
Use
Computer standards: reference models used by various
groups to establish interoperability between computer
components
• Multimedia Extension (MMX)
• Multimedia PC Council (MPC)
• Ultimedia Solution
• Musical Instrument Digital Interface (MIDI)
• Plug ‘n’ Play (PnP)
• Small Computer System Interface (SCSI)
• Fibre Channel
• Personal Computer Memory Card International Association
(PCMCIA)
•Universal Serial Bus (USB)
•Firewire
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Case
 Unisys - customer service, pages 132-133
Next Class
Chapter Four: Software
Case: Gap uses object-oriented programming
pp. 184-185
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