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Harvard University CSCI E-2a Life, Liberty, and Happiness After the Digital Explosion

Harvard University CSCI E-2a Life, Liberty, and Happiness After the Digital Explosion. 3A: Data Representation. Representation. How do you represent “things” with bits Anything Text Documents Pictures Sounds. Representation. How do you represent “things” with bits

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Harvard University CSCI E-2a Life, Liberty, and Happiness After the Digital Explosion

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  1. Harvard UniversityCSCI E-2aLife, Liberty, and HappinessAfter the Digital Explosion 3A: Data Representation

  2. Representation • How do you represent “things” with bits • Anything • Text • Documents • Pictures • Sounds

  3. Representation • How do you represent “things” with bits • Why does representation matter? • Power • Money

  4. Bits (“Binary digITs”) • There are two bits: 0 and 1 • Everything else is a sequence of bits • I.e. a “bit string” • 0010101, 111100010100101011

  5. Digital representations are, by definition, approximations. They leave out a lot.

  6. Representing Things

  7. Representing Things

  8. Representing Things

  9. Representing Things

  10. Representing Things

  11. How many bits for “n” things • Each bit doubles the number • 1 bit = 2, 2 bits = 4, 3 bits = 8 • N bits = 2n things • 10 bits = 1024 etc. Another example of exponential growth

  12. How many bits does it take to represent the 2007 Red Sox Season?

  13. Red Sox 2007 • 162 games = 162 bits (96 “1”s and 66 “0”s • Add 4 bits / game for opponent • Add Inning results • Add at-bat results • Add pitch details • Stop when you’ve had enough

  14. Representing Text • 8 bits per character • “A” = 01000001 • “(” = 00101000 • How many combinations of 8 bits? 2· 2· 2· 2· 2· 2· 2· 2 = 28 = 256

  15. Hexadecimal Digits

  16. ASCIIAmerican Standard Code for Information InterchangeCharacter represented by Hex xy, e.g. 4B is “K”

  17. ASCII Underneath • Emails • Web pages

  18. What if you need more than 256 characters? • Unicode • 32 bits per character (roughly 4 billion different characters)

  19. What about documents? Representation + Interpretation

  20. Word Processors • DisplayWrite • Document Editor • EasyWriter • FullWrite Professional • geoWrite • Gypsy • lexicon • LocoScript • MacWrite • Magic Wand • MindWrite • MultiMate • PaperClip • pfs:Write • Protext • SpeedScript • Sprint • Taste • TJ-2 [3] • Transwrite • WordMARC • WordStar • Wordsworth • WriteNow • XyWrite 602PC Suite AppleWorks Applix Word - Atlantis Ocean Mind EasyWord FrameMaker Han/Gul Lotus Word Pro Mellel Microsoft Word - Nisus Writer - Pages - Papyrus – PolyEdit StarOffice TextMaker WordExpress WordPerfect Hieroglyph Jarte Madhyam Amí AtariWriter Bravo Bank Street Writer DeskMate

  21. Why not pick one?

  22. Why representation matters • Loss of data and the inability to exchange is the primary deterrent to switching vendors. • Control the representation and your control what can be seen and what can be done.

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