Title: Binary and Hard Disk
1Binary and Hard Disk
PEOPLE Program
2Outline
- How do computers store numbers
- Hard drive and its components
- Binary numbers
3How 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
4Cassette 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
5Hard 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!!)
6Electronic 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)
7Beneath the Board
- the connections for the motor that spins the
platters - a highly-filtered vent hole that lets internal
and external air pressures equalize
8Removing 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
9Mechanism 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
10Platters and Heads
- Multiple platters to increase information storage
capacity - This drive has three platters and six read/write
heads
11Storing 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
12How 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
13Binary 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
14Binary ?? 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
15Larger 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
16Larger 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
17Typical 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
18Binary 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
19ASCII Table
- Write your name in ASCII Table
- Password 5 letter word
20Binary 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
21Binary Addition
- Second Way
- Convert the numbers to decimal
- Add the decimal numbers
- Convert the sum to binary