02 DataFormats

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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