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Binary and Hard Disk

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PEOPLE Program Binary and Hard Disk Aslin Izmitli Outline How do Computers Store Numbers Computers are constructed of digital electronics = two states: on ... – PowerPoint PPT presentation

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Title: Binary and Hard Disk


1
Binary and Hard Disk
PEOPLE Program
  • Aslin Izmitli

2
Outline
  • How do computers store numbers
  • Hard drive and its components
  • Binary numbers

3
How do Computers Store Numbers
  • Computers are constructed of digital electronics
    gt two states on off
  • Binary number system consists of 0 and 1 only
  • On-off patterns are used to encode numbers using
    binary number system

Most computer electronics Voltage levels
CD-ROM Microscopic dark spots on disk surface
Hard disk Magnetism
Computer memory Electric charges on capacitors
4
Cassette Tape vs. Hard Disk
  • They use the same magnetic recording techniques
  • Easily erased-written
  • remember for many years

Cassette Tape Hard Disk
Recording material On plastic strip On high-precision aluminum or glass disk
To get to a point Fast forward (several minutes) You can move instantly
Read-write head Touches the tape flies over the disk
Move Spin 2 inch/second 3000 inch/second (170mph)
Info storage Magnetic domains Extremely smaller magnetic domains
5
Hard Drive
  • Hard disks are used in all desktop computers,
    servers, super computers etc. They are also VCR
    type devices or video recorders that use hard
    drives instead of tape
  • They store changing digital information in a
    relatively permanent form. They give computers
    the ability to remember things when the power
    goes out.
  • Now see what we can find in a hard drive
  • (opening a hard disk ruins it!!)

6
Electronic Board
  • A hard drive is a sealed aluminum box with
    controller electronics attached to one side.
  • The electronics are all contained on a small
    board that detaches from the rest of the drive
  • The electronics
  • control the read/write mechanism and the motor
    that spins the platters.
  • Magnetic domains -gt bytes (reading)
  • Bytes -gt Magnetic domains (writing)

7
Beneath the Board
  • the connections for the motor that spins the
    platters
  • a highly-filtered vent hole that lets internal
    and external air pressures equalize

8
Removing the cover from the drive
  • The platters
  • typically spin at 3,600 or 7,200 rpm when the
    drive is operating
  • are manufactured to amazing tolerances and are
    mirror-smooth
  • The arm
  • holds the read/write heads and is controlled by
    the mechanism in the upper-left corner
  • is able to move the heads from the hub to the
    edge of the drive
  • extremely light and fast, can move from hub to
    edge and back up to 50 times per second

9
Mechanism moving the arms
  • Incredibly fast and precise. Can be constructed
    using high-speed linear motor
  • Many derives use a voice coil approach the
    same technique used to move the cone of a speaker
    von your stereo

10
Platters and Heads
  • Multiple platters to increase information storage
    capacity
  • This drive has three platters and six read/write
    heads

11
Storing the Data
  • Data is stored on platter surface
  • Tracks -gt concentric cycles
  • Sectors -gt pie-shaped wedges on a track
  • A sector contains a fixed number of bytes (256,
    512 etc.)
  • Sectors are often grouped together into clusters
  • Low level formatting
  • The drive establishes tracks and sectors on the
    platter
  • Prepares the drive to store blocks of bytes
  • High level formatting
  • Writes the file-storage structures, like file
    allocation table into sectors
  • Prepares the drive to hold files

12
How Does Binary Work?
  • Decimal number system
  • 10 digits (0 to 9)
  • Add a second column worth 10 times the value of
    the first column
  • Expanded notation
  • 3 x 100 6 x 10 5 365
  • 1 x 1000 0 x 100 3 x 10 2 1032

1000 100 10 1
13
Binary Number System
  • Only contains two digits 0,1
  • Add a second column worth 2 times the value of
    the first column
  • To convert a number from binary to decimal, use
    expanded notation
  • 101101
  • 1x32 0x16 1x8 1x4 0x2 1x1
  • 45

      0
      1
    1 0
    1 1
  1 0 0
  1 0 1
  1 1 0
  1 1 1
1 0 0 0
1 0 0 1
32 16 8 4 2 1
14
Binary ?? Decimal
  • Any desired amount can be represented using 1 and
    0.
  • Examples
  • 1 0001
  • 3 0011
  • 6 0110
  • 1 ? a power of 2
  • 0 ? zero
  • Examples
  • 0001 ? 20 1
  • 0010 ? 21 2
  • 0100 ? 22 4
  • 1000 ? 23 8
  • 0101 0 4 0 1 5
  • 1010 8 0 2 0 10
  • 0111 0 4 2 1 7

15
Larger Numbers
  • Numbers from 1 to 15
  • 0000 0 0100 4 1000 8 1100 120001
    1 0101 5 1001 9 1101 130010 2 0110
    6 1010 10 1110 140011 3 0111 7 1011
    11 1111 15
  • Bigger whole numbers ? more bits more
    places in binary number
  • 10000101 128 0 0 0 0 4 0 1 133
  • This is 8 bits 1 byte

16
Larger Numbers
  • 10000101 128 0 0 0 0 4 1 133
  • This is 8 bits 1 byte
  • Alphanumeric characters are represented with 8
    bits
  • A 65 01000001
  • Kilobyte 1024 bytes (1024 210)
  • Megabyte a million bytes
  • Gigabyte 1000 megabytes

17
Typical Sizes
  • Typical RAM is 512 - 1024 megabyte
  • Typical Hard disks are 40 80 gigabyte
  • 1 byte 1 character
  • ? hard disk might hold 80000 million
    characters 15000 million words of raw text
  • Real numbers, fractions, very large numbers
  • ? floating point arithmetic

18
Binary numbers are great!
  • Simple to work with
  • No big addition and multiplication tables to
    learn
  • Just do same things over and over very fast
  • Just use two values of voltage, magnetism or
    other signal
  • Hardware easier to design and more resistant

19
ASCII Table
  • Write your name in ASCII Table
  • Password 5 letter word

20
Binary Addition
  • Decimal System
  • Sum gt 10 ? add 1 to the column on the left
  • Binary System
  • Sum gt 2 ? add 1 to the column on the left
  • Example 111 11
  • 1111 100
  • 110101
  • 11110
  • --------------
  • 1010011

21
Binary Addition
  • Second Way
  • Convert the numbers to decimal
  • Add the decimal numbers
  • Convert the sum to binary
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