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Computer Hardware and Architecture


Computer Hardware and Architecture * Secondary Storage Purpose The purpose of secondary storage is to: retain data and programs while the computer system is turned ... – PowerPoint PPT presentation

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Title: Computer Hardware and Architecture

Computer Hardware and Architecture
  • Objectives
  • By the end of this session, the student will be
    able to
  • Name and define 5 categories of Computer
  • Show how these categories inter-relate
  • Define the function of input devices
  • List and describe the operation of the input
    devices described in the course
  • Define the function of output devices
  • List and describe the operation of the output
    devices described in the course
  • Define Primary Storage
  • List 2 types of primary storage
  • List the two parts of the CPU
  • Describe the function of each part of the CPU
  • List the factors that affect processor speed
  • Describe how each of these factors affects
    processor speed
  • List the 3 operating modes of the Intel processor
  • Describe the traits of these modes
  • Define Secondary Storage
  • List 2 types of secondary storage, give examples
    of each
  • List the 3 structures of magnetic secondary

Computer Systems
History 1642 Pascaline was invented by Blaise
Pascal in 1642. The device is able to add two
decimal numbers. Using ten's complement it is
also possible to subtract. Pascal had started
production of his calculator (about 50 machines
were produced), but there was no interest, so he
had to stop.
Computer Systems
History 1671 First calculator with
multiplication and division 1801 Joseph-Marie
Jacquards loom- introduction of punch
cards 1822 Analytical Engine invented by
Charles Babbage
Computer Systems
History 1939 Atanasoff-Berry Computer. First
computer built with vacuum tubes.
Computer Systems
History 1940 Prototype of the Bombe developed by
Alan Turing (Enigma code)
Computer Systems
History 1943 Mark I. Developed in the U.S., with
the help International Business Machines IBM)
Computer Systems
History 1944 Colossus, designed by Tommy Flowers
was operational (Lorenz code)
Computer Systems
History 1946 ENIAC developed to calculate
missile trajectories originally. Computers began
to achieve manageable size.
Computer Systems
History 1951 UNIVAC, first commercially sold
computer 1954 First completely transistorized
computer 1963 DEC PDP-8 1971 Intel 4004,
first true CPU 1975 Altair Sphere 8800, sold as
kits to hobbyists 1977 Apple II, Commodore
PET 1978 Atari 400 and 800 1981 IBM PC
Computer Systems
  • Definition
  • A computer system is hardware that contains
    software to transform data into information.
    This transformation requires four aspects of data
  • Input
  • Processing
  • Output
  • Storage

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Computer Architecture
Computer Architecture The architecture of a
computer can be broken down into 5 categories.
These 5 categories interrelate with each other in
a structured way. Categories The categories of
the architecture of a computer system are
Computer Architecture, Continued
Interrelation of Categories The categories
interrelate in the following way
Computer Systems
Diagram This is a diagram of the elements of a
computer system
Computer Systems
Diagram This is a diagram of the elements of a
computer system, inside the chassis
  • Purpose
  • The purpose of input is to take data that is
    external to the computer system, and transform it
    into data that is internal to the computer
  • Some of the devices that perform this function
  • Keyboard
  • Mouse
  • Barcode scanner
  • Optical Mark Recognition (OMR)
  • Optical Character Recognition (OCR)
  • Hand-written characters
  • Voice recognition
  • Touch screens

Input Keyboard
Keyboard The keyboard is probably the most common
way to get data into a computer system. What it
does A keyboard converts the keys pressed by the
user into electrical patterns that represent the
letter or symbol that was pressed on the
keyboard. Diagram Below is a diagram of a
keyboard, with different regions labelled
Input Mouse
Mouse The mouse has become a very popular means
of providing input to a computer system. What it
does The mouse is used to position a pointer over
a symbol on the screen. The buttons on the mouse
can then be used to perform a defined
action. Diagram Below is a picture of a typical
Input Barcode scanner
Barcode scanner Barcode scanners are a means to
read some data (numbers and letters) very quickly
and enter them into a computer system faster and
more accurately than a human. What it does A
laser is reflected off of a label consisting of
different width lines and into a photocell. The
electronics of the barcode scanner convert the
patterns of light and dark into an equivalent
keyboard character. Diagram Below are pictures
of typical barcode scanner applications
Input OMR
  • Optical Mark Recognition
  • Optical Mark Recognition (OMR) is another means
    to get data into a computer system faster and
    more accurately that a person.
  • Example
  • Common examples of the use of OMR are
  • the bubble-sheets used in tests
  • old style computer cards
  • What it does
  • The OMR reader recognizes marks on paper based on
    their position and converts them into data that
    is meaningful to the computer system.

Input OMR, Continued
Diagram Below is a picture of a computer card
that reads 'WELCOME TO ICS124SB!'
Input OCR
Optical Character Recognition Optical Character
Recognition (OCR) is another way to quickly and
accurately input data into a computer system, yet
the data itself is also readable by humans. What
it does The characters used in OCR are very
structured. Again a laser is reflected off a
label containing the characters and into a
photocell. The electronics in the OCR reader
convert the patterns into equivalent keyboard
characters. Diagram Below are OCR symbols
Input Hand-written characters
Hand-written characters The complexity of
computer systems and electronics has advanced to
the point where hand writing can be recognized by
the computer. The purpose of this is to
eliminate transcribing hand-written forms into
electronic format through data entry
operators. What it does The hand-written word is
scanned and the pattern of lines compared to
'model' characters. When a match is found, that
character is sent as a keyboard
character. Diagram Below are samples of
hand-written characters and the rules to write
Input Voice recognition
Voice recognition Is means to provide some
convenience when entering data into a computer
system. What it does The process of voice input
Input Voice recognition, Continued
Diagram Below is a picture of the process
Input Touch-screens
Touch screens Touch screens are a means to allow
a user to simply choose among a list of
predefined choices, and provide the selection to
the computer system. What it does A grid of
light beams are projected vertically and
horizontally across the surface of a screen.
When a finger interrupts a horizontal and
vertical light beam, the position of the finger
is known. This information is passed to the
computer system. Diagram Below is a picture of a
touch-screen installation
  • Purpose
  • The purpose of output is to take information that
    is internal to the computer system, and transform
    it into information that is external to the
    computer system, and therefore available for the
    user to use.
  • Some of the devices that perform this function
  • Monitor
  • Dot-matrix printer
  • Bubble-jet printer
  • Laser printer
  • Voice

Output Monitors
Monitors Monitors are the most common means to
display information to a user. When viewing
information on a monitor, it is said to be in
'soft copy' format. What it does The monitor
consists of a Cathode Ray Tube, or CRT, that
projects a stream of electrons across the back of
its screen. The electron beam sweeps back and
forth from the top to the bottom of the screen.
The back of the CRT has a phosphorous coating
that glows when hit by the electrons.
Output Monitors, Continued
Attributes of a monitor There are various
attributes of monitors that need to be considered
when comparing one monitor to another
Output Monitors, Continued
LCD Technology LCD is an acronym for Liquid
Crystal Display. The crystals are sandwiched
between two layers of polarizing film, set at
right angles. The natural twist of the crystals
causes light passing through them to reorient its
plane of vibration. By passing an electric
current though the crystals, the crystals will
straighten out- losing their twist. If the twist
of the crystals causes the light to reorient
itself by 90o, then it can get through the second
polarizing film layer. If the twist has been
eliminated, the light is not reoriented
(maintains its original plane of vibration), and
fails to get through the second polarizing film.
Output Monitors, Continued
Light entering first polarizing film layer. The
right-most light wave is blocked.
Output Monitors, Continued
Light passing through first polarizing film, top
wave enters crystal that has an electric current
applied, the middle wave missed a crystal, the
bottom wave enters a crystal with its natural
Output Monitors, Continued
Only the wave that was reoriented by the crystal
escapes, and will be visible.
Output Monitors, Continued
LCD Panels There are three elements of a 'pixel'
in an LCD screen Red Green Blue By turning
on combinations of the elements of a pixel, 256
colours are available By altering the amount
of light that gets through the backlit screen or
reflective screen, 256 shades per element are
possible, therefore 16 million colours are
Output Monitors, Continued
Diagram Below is a picture of a monitor
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Output Ink jet printers
  • Ink jet printers
  • The ink jet printer is very popular due to its
  • lost cost
  • high resolution (300dpi)
  • reasonable print speed
  • use of colour
  • low noise
  • What is does
  • The ink jet printer sprays ink onto the paper to
    form the images of characters or graphics.

Output Ink jet printers, Continued
Diagram Below is a picture of an ink jet printer
Output Laser printers
  • Laser printers
  • The laser printer is a high end printer that
  • superior resolution (600dpi - 1200dpi)
  • fast print speed
  • Is capable of colour, if you are willing to pay
    the price
  • What it does
  • A laser is used to neutralize points on a
    positively charged drum inside the printer. As
    the drum passes by a toner cartridge, toner
    sticks to the neutral spots on the drum. The
    toner is then transferred to paper and heated to
    fuse it in place.

Output Laser printers, Continued
Diagram Below is a picture of a laser printer
Output Audio
  • Audio
  • The output of audio information can take two
  • Speech synthesis
  • Music
  • Speech synthesis
  • There are two methods of speech synthesis
  • synthesis by analysis
  • synthesis by rules
  • Synthesis by analysis uses pre-recorded words
    stored and retrieved when needed. This method is
    limited by the number of words that were
  • Synthesis by rules uses a device that applies
    linguistic rules to create artificial speech.
    This method is not as natural sounding as using
    pre-recorded words, however it is not as

Output Audio, Continued
Music MIDI (Musical Instrument Digital Interface)
is a set of rules designed for recording and
playing back music on digital synthesizers.
Primary Storage
Purpose The purpose of primary storage is to
store data for a short period of time while it is
being manipulated. The term 'memory' is also
used when referring to Primary Storage, however
this term also includes forms of memory that are
not Primary Storage.
Primary Storage, Continued
  • Types of memory
  • The types of memory are listed below
  • RAM (Primary Storage)
  • DRAM
  • SRAM
  • External cache
  • ROM (not Primary Storage)
  • PROM

Primary Storage, Continued
  • Measuring memory
  • The smallest unit of memory is the byte. A byte
    can used to represent a single character or
    symbol. When evaluating memory size the
    following aggregates are also used
  • KB - kilobyte 1,024 bytes
  • MB - megabyte 1,048,576 bytes
  • GB -gigabyte 1,073,741,824 bytes
  • A typical modern home computer will have 512MB or

Primary Storage, Continued
RAM RAM is an acronym for Random Access Memory.
RAM is volatile, in that when power is removed
from the circuit, the contents of RAM are
lost. SRAM SRAM is Static RAM. When data is
written to SRAM, it is retained by the memory
without any further intervention by the computer
system. DRAM DRAM is Dynamic RAM. When data is
written to DRAM, it must be periodically
refreshed or it will loose its contents. DRAM
may be slower than SRAM, however due to its size
and cost, it is used in most PCs.
Primary Storage, Continued
DRAM, Continued This is a picture of DRAM
Primary Storage, Continued
External cache Cache is a a small amount of
memory, typically 512KB, that is very fast. By
keeping instructions or data that is frequently
used or most recently used in cache memory, there
is a chance that the processor will not need to
access the slower RAM memory to process the next
ROM ROM is an acronym for Read Only Memory. ROM
is non-volatile, in that when power is removed
from the circuit, the contents of ROM are
retained. The data on ROM is written once, or
the ROM is manufactured with the data already
present. PROM PROM is Programmable ROM. This is
a memory chip that is manufactured with no data,
however it can be written to once. EPROM EPROM
is Erasable PROM. The contents of the ROM can be
erased by exposing the circuit to UV radiation
for 20 minutes. The EPROM is now ready to have
new data written to it.
ROM, Continued
EEPROM EEPROM is Electrically Erasable PROM. The
contents of the ROM can be erased by sending an
erase signal to the EEPROM circuit. The EEPROM
is now ready to have new data written to it.
  • Purpose
  • The processor, or Central Processing Unit (CPU)
    is where the computer system performs the
    manipulation of data. Every computer must have
    at least one CPU to function.
  • A processor is composed of
  • control unit
  • Arithmetic / logic unit (ALU)
  • Control unit
  • The control unit oversees the operation of the
    CPU by performing
  • Fetch - get an instruction from memory
  • Decode - decide what the instruction means and
    direct the necessary data be moved from memory
    to the ALU
  • The combination of Fetch and Decode is called,
    Instruction Time or I-Time

Processor, Continued
  • Arithmetic / Logic Unit
  • The ALU performs two classes of operations
  • Arithmetic operations
  • Logical operations
  • The ALU is responsible for
  • Execute
  • Store
  • The combination of Execute and Store is call
    Execution-Time, or E-Time

Processor, Continued
  • Arithmetic operations
  • The arithmetic operations performed by the ALU
  • Addition
  • Subtraction
  • Multiplication
  • Division
  • Older ALUs could only perform addition and
    subtraction. The multiplication and division
    operations were performed through a set of

Processor, Continued
  • Logic operations
  • The logic operations, or tests, performed by the
    ALU are
  • Equal-to
  • Greater than
  • Less than
  • These can be combined to create an additional
    three tests
  • Greater than or equal
  • Less than or equal
  • Greater than or Less than (not equal)

Processor, Continued
Machine cycle A machine cycle is the combination
of I-Time and E-Time. The I-Time and E-Time
differs from instruction to instruction,
therefore the machine cycle will also be
different. Diagram of a machine cycle This a
diagram of the steps in a machine cycle
Processor, Continued
  • Processor speed
  • The speed of a processor is based on different
  • Clock speed
  • Number of instructions
  • Internal cache
  • Clock speed
  • The operations that are taking place in a CPU
    need to be organized to prevent chaos. For
    example, an addition operation cannot be executed
    until the data has finished being read from RAM.
  • To control the timing within the CPU, a clock is
    used to synchronize the operations. The clock
    simply supplies a stream of pulses at a very fast
    fixed rate.

Processor Clock speed, Continued
  • Clock speed, continued
  • The speed of the processor might be measure based
  • the speed of the clock
  • Megahertz - millions of cycles per second,
    abbreviated MHz
  • Gigahertz - billions of cycles per second,
    abbreviated GHz
  • the number of machine cycles per second
  • MIPS - million instructions per second
  • BIPS - billion instructions per second

Processor, Continued
  • Number of instructions
  • Within a conventional processor there are many
    instructions that are rarely used. By
    eliminating the rarely instructions, processor
    speed can be increased.
  • Processors are now also classed based on their
    instruction set
  • CISC - Complex Instruction Set Computer
  • RISC - Reduced Instruction Set Computer
  • RISC processors can outperform CISC processors by
    a factor of 4 to 10.
  • Internal cache
  • Internal cache is a small block of very fast
    memory manufactured into the processor. It
    behaves the same way as external cache memory

Processor, Continued
  • Operating modes of the Intel processor
  • An Intel processor has several operating modes
  • Protected mode
  • Real mode
  • Virtual mode
  • Protected mode
  • This is the native operating mode of the
    processor, and provides facilities for
  • Real mode
  • The processor emulates an 8086 or 8088 processor,
    but at a higher speed.
  • Virtual mode
  • Emulates 8086 / 8088 processor in a protected,
    multitasking environment.

Processor, Continued
The Intel evolution The following history and
commentary is taken from Intel's web
site http//
hof/hof_main.htm11 1978 - 8086 / 8088
Microprocessor A pivotal sale to IBM's new
personal computer division made the 8088 the
brains of IBM's new hit product--the IBM PC. The
8088's success propelled Intel into the ranks of
the Fortune 500, and Fortune magazine named the
company one of the "Business Triumphs of the
Seventies." 1982 - 80286 Microprocessor The
286, also known as the 80286, was the first Intel
processor that could run all the software written
for its predecessor. This software compatibility
remains a hallmark of Intel's family of
microprocessors. Within 6 years of it release,
there were an estimated 15 million 286-based
personal computers installed around the world.
Processor, Continued
The Intel evolution, continued 1985 -
Intel386 The Intel386(TM) microprocessor featured
275,000 transistors--more than 100 times as many
as the original 4004. It was a 32-bit chip and
was "multi-tasking," meaning it could run
multiple programs at the same time. 1989 -
Intel486 The 486(TM) processor generation really
meant you go from a command-level computer into
point-and-click computing. "I could have a color
computer for the first time and do desktop
publishing at a significant speed," recalls
technology historian David K. Allison of the
Smithsonian's National Museum of American
History. The Intel 486(TM) processor was the
first to offer a built-in math coprocessor, which
speeds up computing because it offloads complex
math functions from the central processor.
Processor, Continued
The Intel evolution, continued 1993 -
Pentium The Pentium processor allowed computers
to more easily incorporate "real world" data such
as speech, sound, handwriting and photographic
images. The Pentium brand, mentioned in the
comics and on television talk shows, became a
household word soon after introduction. These
are pictures of a Pentium microprocessor
Processor, Continued
The Intel evolution, continued 1997 - Pentium
II The 7.5 million-transistor Pentium II
processor incorporates Intel MMXTM technology,
which is designed specifically to process video,
audio and graphics data efficiently. It was
introduced in innovative Single Edge Contact
(S.E.C) Cartridge that also incorporated a
high-speed cache memory chip. With this chip, PC
users can capture, edit and share digital photos
with friends and family via the Internet edit
and add text, music or between-scene transitions
to home movies and, with a video phone, send
video over standard phone lines and the
Internet. 1999 - Pentium III The Pentium III
processor features 70 new instructions--Internet
Streaming SIMD extensions-- that dramatically
enhance the performance of advanced imaging, 3-D,
streaming audio, video and speech recognition
applications. It was designed to significantly
enhance Internet experiences, allowing users to
do such things as browse through realistic online
museums and stores and download high-quality
video. The processor incorporates 9.5 million
transistors, and was introduced using 0.25-micron
Processor, Continued
The Intel evolution, continued 2001 - Pentium
4 The Intel Pentium 4 processor, Intel's most
advanced, most powerful processor, is based on
the new Intel NetBursttm micro-architecture.
The Pentium 4 processor is designed to deliver
performance across applications and usages where
end users can truly appreciate and experience the
performance. These applications include Internet
audio and streaming video, image processing,
video content creation, speech, 3D, CAD, games,
multi-media, and multi-tasking user environments.
The Intel Pentium 4 processor delivers this
world-class performance for consumer enthusiast
and business professional desktop users as well
as for entry level workstation users
Secondary Storage
  • Purpose
  • The purpose of secondary storage is to
  • retain data and programs while the computer
    system is turned off
  • hold data and programs that cannot fit into
    primary storage
  • Types of secondary storage
  • Secondary storage is composed of two main groups
    of media, within each group are many types of
    secondary storage. The most common are
  • Magnetic media
  • floppy diskette
  • hard disk
  • Optical media
  • CD-ROM

Secondary Storage, Continued
  • Measuring storage capacity
  • Secondary storage devices use the same units of
    measurement as primary storage.
  • How magnetic media works
  • Although there are other magnetic media-based
    secondary storage devices, the most common are
    disks. This is a description of how a disk
  • The data is stored on the disk as magnetized
    spots, and is read or written using a 'read/write
  • To read the data, the spots are converted into
    electrical impulses to represent the data.
  • To write data, electrical pulses are converted
    into magnetized spots on the disk to represent
    the data.

Secondary Storage, Continued
Disk layout Disks are flat, round platters housed
in a case that protects their surface from
contamination. Tracks The logical structure of
disk consists of a series of concentric rings,
called tracks. Sectors These tracks are
subdivided into sectors. The Sectors contain the
Secondary Storage, Continued
Sectors, continued This is a diagrammatic
representation of tracks and sectors No
te that the outer sectors are bigger than the
inner sectors. The track layout is optimized by
assigning more sectors to outer tracks than inner
tracks. This is called Zone Recording.
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Secondary Storage, Continued
Contamination of disk surfaces The read/write
head that is responsible for placing the
magnetized spots on the disk, is very close to
the surface of the disk. Any slight
contamination will cause disk failures, sometimes
referred to as head crashes. This is a diagram
showing relative sizes of contaminants on a disk
Secondary Storage, Continued
Floppy diskette A floppy diskette derives its
name from the nature of the platter that data is
stored on it is flexible Mylar Typical
capacity The typical floppy diskette can hold
1.44MB Diagram This is a diagram of the parts of
a floppy diskette
Secondary Storage, Continued
Hard disk A hard disk derives its name from the
nature of the platter that data is stored on it
is non-flexible metal platter. Typical
capacity Capacity ranges based on how much you
are willing to spend. 40GB to 250 GB hard disks
are not uncommon. Diagram This is a diagram of a
hard disk that has had its cover
removed. Caution do not do this with a
functional hard disk.
Secondary Storage, Continued
How optical media works Unlike magnetic media,
the write technology is different than the read
technology for optical media. When writing
optical media, laser heat produces tiny spots on
the metallic surface of the disk. When reading
optical media, a laser reflected off the surface
picks up the spots. Disk layout The layout of
optical disks is the same as for magnetic
disks. CD-ROM CD-ROM derives its name from
'Compact Disk- Read Only Memory'. The
significance of 'ROM' in its name means that once
written (usually during manufacture), the
contents of the disk cannot be altered.
Secondary Storage, Continued
Typical capacity The contemporary CD-ROM can
store up to 700MB. Access speed terms There are
common terms used when defining the speed of
operation of a disk Seek Time The time it
takes the Read/Write head to be positioned over a
track Rotational Delay The time it takes for a
sector to rotate under the read/write head
Computer Systems
  • Input / output
  • Although there are elements of computer systems
    that can be easily categorized as either input or
    output, there are other devices that can be used
    for either
  • Serial port
  • Parallel port
  • USB port
  • SCSI port
  • Serial port
  • A serial port is used to send/receive data one
    bit at a time.
  • Typical speed 14.4KB/second
  • Maximum number of devices concurrently attached

Input / Output, Continued
  • Parallel port
  • A parallel port was originally for output only.
  • Typical speed 50KB/second - 150KB/second
  • Maximum number of devices concurrently attached
  • New versions allow for input and output of data.
  • USB port
  • USB is an acronym for Universal Serial Bus. This
    is a relatively new technology. The intent is to
    be able to attach devices without having special
    interface cards for each device.
  • Typical speed 1.5MB/second
  • Maximum number of devices concurrently attached

Input / Output, Continued
  • SCSI port
  • SCSI is an acronym for Small Computer System
    Interface. This was the original high speed
    interface for computers.
  • Typical speed 320MB/second (new technology)
  • Maximum number of devices concurrently attached
    16 (new technology)

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