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02 DataFormats

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Information about 02 DataFormats
Education

Published on February 27, 2008

Author: Elliott

Source: authorstream.com

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2. Data Formats:  2. Data Formats Chapt. 3 Introduction:  Introduction Examples pp. 59.-61 Input device Format must be appropriate:  Format must be appropriate The internal representation must be appropriate for the type of processing to take place (e.g., text, images, sound) Rules/Conventions:  Rules/Conventions Proprietary formats Unique to a product or company E.g., Microsoft Word, Corel Word Perfect, IBM Lotus Notes Standards Evolve two ways: Proprietary formats become de facto standards (e.g., Adobe PostScript, Apple Quick Time) Committee is struck to solve a problem (Motion Pictures Experts Group, MPEG) pp. 61-62 Standards Organizations:  Standards Organizations ISO – International Standards Organization CSA – Canadian Standards Association ANSI – American National Standards Institute IEEE – Institute for Electrical and Electronics Engineers Etc. Examples of Standards:  Examples of Standards Why Standards?:  Why Standards? Standard are “arbitrary” They exist because they are Convenient Efficient Flexible Appropriate Etc. Alphanumeric Data:  Alphanumeric Data Problem: Distinguishing between the number 123 (one hundred and twenty-three) and the characters “123” (one, two, three) Four standards for representing letters (alpha) and numbers BCD – Binary-coded decimal ASCII – American standard code for information interchange EBCDIC – Extended binary-coded decimal interchange code Unicode pp. 63-69 Standard Alphanumeric Formats:  Next 2 slides Standard Alphanumeric Formats BCD ASCII EBCDIC Unicode Binary-Coded Decimal (BCD):  Binary-Coded Decimal (BCD) Four bits per digit Note: the following bit patterns are not used: 1010 1011 1100 1101 1110 1111 Example:  Example 709310 = ? (in BCD) 7 0 9 3 0111 0000 1001 0011 Standard Alphanumeric Formats:  Next 22 slides Standard Alphanumeric Formats BCD ASCII EBCDIC Unicode The Problem:  The Problem Representing text strings, such as “Hello, world”, in a computer Codes and Characters:  Codes and Characters Each character is coded as a byte Most common coding system is ASCII (Pronounced ass-key) ASCII = American National Standard Code for Information Interchange Defined in ANSI document X3.4-1977 ASCII Features:  ASCII Features 7-bit code 8th bit is unused (or used for a parity bit) 27 = 128 codes Two general types of codes: 95 are “Graphic” codes (displayable on a console) 33 are “Control” codes (control features of the console or communications channel) ASCII Chart:  ASCII Chart Slide18:  Most significant bit Least significant bit Slide19:  e.g., ‘a’ = 1100001 Slide20:  95 Graphic codes Slide21:  33 Control codes Slide22:  Alphabetic codes Slide23:  Numeric codes Slide24:  Punctuation, etc. “Hello, world” Example:  “Hello, world” Example Common Control Codes:  Common Control Codes CR 0D carriage return LF 0A line feed HT 09 horizontal tab DEL 7F delete NULL 00 null Hexadecimal code Terminology:  Terminology Learn the names of the special symbols [ ] brackets { } braces ( ) parentheses @ commercial ‘at’ sign & ampersand ~ tilde Escape Sequences:  Escape Sequences Extend the capability of the ASCII code set For controlling terminals and formatting output Defined by ANSI in documents X3.41-1974 and X3.64-1977 The escape code is ESC = 1B16 An escape sequence begins with two codes: ESC [ 1B16 5B16 Examples:  Examples Erase display: ESC [ 2 J Erase line: ESC [ K Standard Alphanumeric Formats:  Next 1 slides Standard Alphanumeric Formats BCD ASCII EBCDIC Unicode EBCDIC:  EBCDIC Extended BCD Interchange Code (pronounced ebb’-se-dick) 8-bit code Developed by IBM Rarely used today IBM mainframes only Standard Alphanumeric Formats:  Next 2 slides Standard Alphanumeric Formats BCD ASCII EBCDIC Unicode Unicode:  Unicode 16-bit standard Developed by a consortia Intended to supercede older 7- and 8-bit codes Unicode Version 2.1:  Unicode Version 2.1 1998 Improves on version 2.0 Includes the Euro sign (20AC16 = ) From the standard: …contains 38,887 distinct coded characters derived from the supported scripts. These characters cover the principal written languages of the Americas, Europe, the Middle East, Africa, India, Asia, and Pacifica. http://www.unicode.org Keyboard Input:  Keyboard Input Key (“scan”) codes are converted to ASCII ASCII code sent to host computer Received by the host as a “stream” of data Stored in buffer Processed Etc. pp. 69 Shift Key:  Shift Key inhibits bit 5 in the ASCII code a a Shift Control Key:  Control Key inhibits bits 5 & 6 in the ASCII code c c Ctrl Controlcode Other Input:  Other Input OCR – optical character recognition Bar code readers Voice/audio input Punched cards Images / objects Pointing devices pp. 69-86 OCR:  OCR Hello, world Page of text Optical scan 10110110… Computer file Other Input:  Other Input OCR – optical character recognition Bar code readers Voice/audio input Punched cards Images / objects Pointing devices pp. 69-86 Bar Codes:  Bar Codes An automatic identification (Auto ID) technology that streamlines identification and data collection See http://www.digital.net/barcoder/barcode.html Other Input:  Other Input OCR – optical character recognition Bar code readers Voice/audio input Punched cards Images / objects Pointing devices pp. 69-86 Voice/audio Input:  Voice/audio Input Input device: microphone Audio input is “digitized” and stored Processed in two ways As is (no recognition) Recognized and converted to alphanumeric data (ASCII) Digitize 10110010… Other Input:  Other Input OCR – optical character recognition Bar code readers Voice/audio input Punched cards Images / objects Pointing devices pp. 69-86 Punched Cards:  Punched Cards Invented by Herman Hollerith (founder of IBM) Each card holds 80 characters Other Input:  Other Input OCR – optical character recognition Bar code readers Voice/audio input Punched cards Images / objects Pointing devices pp. 69-86 Images:  Images Typically images are pictures that are optically scanned and saved as a “bit map” or in some other format Many formats gif, jpeg, … Typical “Save As” Dialog:  Typical “Save As” Dialog Objects:  Objects Images made of geometrically definable shapes Offer efficiency, flexibility, small size, etc. Other Input:  Other Input OCR – optical character recognition Bar code readers Voice/audio input Punched cards Images / objects Pointing devices pp. 69-86 Pointing Devices:  Pointing Devices Originally used for specifying coordinates (x, y) for graphical input Today used as general purpose device for “graphical user interfaces” (GUIs) Thank you:  Thank you

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