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

4
Cassette Tape vs. Hard Disk

• They use the same magnetic recording techniques
• Easily erased-written
• remember for many years

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

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

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