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Binary and Hard Disk

PEOPLE Program. Binary and Hard Disk. Aslin Izmitli. How do computers store numbers Hard drive and its components Binary numbers. Outline. How do Computers Store Numbers. Computers are constructed of digital electronics => two states: “on” “off”

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Binary and Hard Disk

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  1. PEOPLE Program Binary and Hard Disk Aslin Izmitli

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

  3. How do Computers Store Numbers • Computers are constructed of digital electronics => 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 -> bytes (reading) • Bytes -> 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. 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 Removing the cover from the drive

  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. Data is stored on platter surface Tracks -> concentric cycles Sectors -> 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 Storing the Data

  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 • 1  a power of 2 • 0  zero • Examples • 0001  2^0 = 1 • 0010  2^1 = 2 • 0100  2^2 = 4 • 1000  2^3 = 8 • Any desired amount can be represented using 1 and 0. • Examples • 1 == 0001 • 3 == 0011 • 6 == 0110 • 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 = 2^10) • 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 >= 10  add 1 to the column on the left • Binary System • Sum >= 2  add 1 to the column on the left • Example: 1+1+1 = 11 1+1+1+1 = 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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