1. ITEC 1000 “Introduction to Information Technology”
Lecture 4
Data Formats

2. Lecture Template: Data Forms Data conversion and representation
Data Formats
Alphanumeric Data
Image Data
Audio Data
Data Input
Data Compression
Internal Computer Data Format

3. Data Forms Human communication Computers
Includes language, images and sounds
Computers
Process and store all forms of data in binary format
Conversion to computer-usable representation using data formats
Define the different ways human data may be represented, stored and processed by a computer

4. Data conversion and representation

5. Standards (evolve in two ways):
Data formats
Proprietary formats
Unique to a product or company
E.g., Microsoft Word, Word Perfect
Standards (evolve in two ways):
Proprietary formats become de facto standards (e.g., Adobe PostScript)
Invented by an international standard organization (e.g., Motion Pictures Experts Group, MPEG)

6. Common Data Representations
Type of Data
Standard(s)
Alphanumeric
Unicode, ASCII, EDCDIC
Image (bitmapped)
GIF (graphical image format)
TIF (tagged image file format)
PNG (portable network graphics)
Image (object)
PostScript, JPEG, SWF (Macromedia Flash), SVG
Outline graphics and fonts
PostScript, TrueType
Sound
WAV, AVI, MP3, MIDI, WMA
Page description
PDF (Adobe Portable Document Format), HTML, XML
Video
Quicktime, MPEG-2, RealVideo, WMV

7. Alphanumeric Data
Characters (r, T), number digits (0..9), punctuation (!, ;), special purpose characters ($, &)
Four codes/standards to represent letters and numbers:
BCD (Binary-Coded Decimal)
Unicode
ASCII (American Standard Code for Information Interchange)
EBCDIC (Extended Binary Coded Decimal Interchange Code)

8. Standard Alphanumeric Formats
BCD
ASCII
EBCDIC
Unicode
Next 2 slides

9. Binary-Coded Decimal (BCD)
Four bits per digit
Digit
Bit pattern
0000 1
0001 2
0010 3
0011 4
0100 5
0101 6
0110 7
0111 8
1000 9
1001
Note: the following 6 bit patterns are not used:

10. BCD: Example
= ? (in BCD)

11. Standard Alphanumeric Formats
BCD
ASCII
EBCDIC
Unicode
Next 13 slides

12. ASCII Features
Developed by ANSI (American National Standards Institute)
Defined in ANSI document X
7-bit code
8th bit is unused (or used for a parity bit or to indicate “extended” character set)
27 = 128 different codes
Two general types of codes:
95 are “Printing” codes (displayable on a console)
33 are “Control” codes (control features of the console or communications channel)
Represents
Latin alphabet, Arabic numerals, standard punctuation characters
Plus small set of accents and other European special characters (Latin-I ASCII)

13. ASCII Table

14. ASCII Table
Most significant bit
Least significant bit

15. ASCII Table
e.g., ‘a’ =

16. ASCII Table
95 Printing codes

17. ASCII Table
33 Control codes

18. ASCII Table
Alphabetic codes

19. ASCII Table
Numeric codes

20. ASCII Table
Punctuation, etc.

21. ASCII Table 7416 111 0100 | MSD LSD 1 2 3 4 5 6 7 NUL DLE SP @ P p SOH1 2 3 4 5 6 7
NUL
DLE SP @ P p
SOH
DC1 ! A Q a W
STX
DC2 “ B R b r
ETX
DC3 # C S c s
EOT
DC4 $ D T d t
ENQ
NAK % E U e u
ACJ
SYN
& F V f v
BEL
ETB ‘ G g w 8 BS
CAN ( H X h x 9 HT EM ) I Y i y LF
SUB * : J Z j z VT
ESC + ; K [ k { FF FS ,
< L \ l | CR GS - = M ] m } SO RS .
> N ^ n ~ SI US / ? O _ o
DEL
7416

22. Example: “Hello, world”=
Binary
Hexadecimal 48 65 6C 6F 2C 20 77 67 72 64
Decimal
101
108
111 44 32
119
103
114
100 H e l o , w r d

23. Common Control Codes CR 0D carriage return LF 0A line feed
HT 09 horizontal tab
DEL 7F delete
NULL 00 null
Hexadecimal code

24. ASCII Table: Common Control Codes

25. Standard Alphanumeric Formats
BCD
ASCII
EBCDIC
Unicode
Next 3 slides

26. EBCDIC 8-bit code Developed by IBM IBM and compatible mainframes only
Rarely used today (common in archival data)
Character codes differ from ASCII
Conversion software to/from ASCII available
ASCII
EBCDIC
Space
2016
4016 A
4116
C116 b
6216
8216

27. EBCDIC Table (1 out of 2)

28. EBCDIC Table (2 out of 2)

29. Standard Alphanumeric Formats
BCD
ASCII
EBCDIC
Unicode
Next 2 slides

30. Unicode Most common 16-bit form represents 65,536 characters
ASCII Latin-I subset of Unicode
Values 0 to 255 in Unicode table
Multilingual: defines codes for
Nearly every character-based alphabet
Large set of ideographs for Chinese, Japanese and Korean
Composite characters for vowels and syllabic clusters required by some languages
Allows software modifications for local-languages

31. Two-byte Unicode Assignment Table

32. Collating Sequence
Collating Sequence – the order of the codes in the representation table
Determines sorting and selection of the alphanumeric data
Collating Sequences are different in ASCII and EBCDIC:
Small letters precede capitals in EBCDIC; reverse in ASCII
Numbers collate first in ASCII; in EBCDIC, last

33. Two Classes of Codes Printing characters Control characters
Produced output on the screen or printer
Control characters
Control position of output on screen or printer
Cause action to occur
Communicate status between computer and I/O device

34. Control Code Definitions (ASCII Table)

35. Escape Sequences Extend the capability of the ASCII code set
For controlling terminals and formatting output
Defined by ANSI in documents X and X
The escape code is ESC = 1B16
An escape sequence begins with two codes: ESC [
1B16
5B16

36. Escape Sequences: Examples
Erase display: ESC [ 2 J
Erase line: ESC [ K

37. Alphanumeric Input: Keyboard
Scan code
Two different binary scan codes generated
when key is struck and when key is released
Converted to Unicode, ASCII or EBCDIC by software in terminal or PC
Received by the host as a stream of text and other characters, i.e. in the sequence typed
Advantage
Easily adapted to different languages or keyboard layout
Separate scan codes for key press/release for multiple key combinations
Examples: shift and control keys

38. inhibits bit 5 in the ASCII code
Shift Key
inhibits bit 5 in the ASCII code
Key(s)
ASCII code
Character a A a
Shift a

39. inhibits bits 5 & 6 in the ASCII code
Control Key
inhibits bits 5 & 6 in the ASCII code
Key(s)
ASCII code
Character c
ETX c
Ctrl c
Control code

40. Keyboard Input
Three letters are typed: “D”, “I”, “R”, followed by the carriage return
Four scan codes translated to ASCII binary codes: , , ,

41. OCR (optical character recognition)
Scans text and inputs it as character data
Special OCR software required
Used to read specially encoded characters
Example: magnetically printed check numbers
Attempts to recognize hand-written input (limited, only carefully printed)

42. Bar Code Readers
Used in applications that require fast, accurate and repetitive input with minimal employee training
Examples: supermarket checkout counters and inventory control
Alphanumeric data in bar code (i.e., ) read optically using wand that converts them into electrical binary signals
A bar code translation module converts the binary input into a sequence of number codes , one code per digit, then translated to Unicode or ASCII.

43. Other Alphanumeric Input
Magnetic stripe reader: alphanumeric data from credit cards
Voice
Digitized audio recording common but conversion to alphanumeric data difficult
Requires knowledge of sound patterns in a language (phonemes) plus rules for pronunciation, grammar, and syntax

44. Image Data Photographs, figures, icons, drawings, charts and graphs
Two approaches:
Bitmap or raster images of photos and paintings with continuous variation (e.g., GIF, JPEG)
Object or vector images composed of graphical shapes like lines and curves defined geometrically
Differences include:
Quality of the image
Storage space required
Time to transmit
Ease of modification

45. Image Input
Image scanning (moves over the image converting dot by dot into a stream of binary numbers, pixels, representing black or white, or levels of gray, or of a colour) – bitmap image
Digital/video cameras – bitmap image
Pointing devices (mouse, pen)- object image

46. Bitmap Images
Each individual pixel (pi(x)cture element) in a graphic stored as a binary number
Pixel: A small area with associated coordinate location
Example: each point below represented by a 4-bit code corresponding to 1 of 16 shades of gray

47. Bitmap Display Monochrome: black or white
1 bit per pixel
Gray scale: black, white or 254 shades of gray
1 byte per pixel
Color graphics: 16 colors, 256 colors, or 24-bit true color (16.7 million colors)
4, 8, and 24 bits respectively

48. Storing Bitmap Images Frequently large files File size affected by
Example: 600 rows of 800 pixels with 1 byte for each of 3 colors ~1.5MB file
File size affected by
Resolution (the number of pixels per inch)
Amount of detail affecting clarity and sharpness of an image
Levels: number of bits for displaying shades of gray or multiple colors
Palette: color translation table that uses a code for each pixel rather than actual color value
Data compression

49. GIF (Graphics Interchange Format)
First developed by CompuServe in 1987
GIF89a enabled animated images
allows images to be displayed sequentially at fixed time sequences
Color limitation: 256
Image compressed by LZW (Lempel-Zif-Welch) algorithm
Preferred for line drawings, clip art and pictures with large blocks of solid color
Lossless compression

50. GIF (Graphics Interchange Format)

51. JPEG (Joint Photographers Expert Group)
Allows more than 16 million colors
Suitable for highly detailed photographs and paintings
Employs special compression algorithm that
Discards data to decreases file size and transmission speed
May reduce image resolution, tends to distort sharp lines

52. Other Bitmap Formats
TIFF (Tagged Image File Format): .tif (pronounced tif)
Used in high-quality image processing, particularly in publishing
BMP (BitMaPped): .bmp (pronounced dot bmp)
Device-independent format for Microsoft Windows environment: pixel colors stored independent of output device
PCX: .pcx (pronounced dot p c x)
Windows Paintbrush software
PNG: (Portable Network Graphics): .png (pronounced ping)
Designed to replace GIF and JPEG for Internet applications
Patent-free
Improved lossless compression
No animation support

53. Object Images
Created by drawing packages or output from spreadsheet data graphs
Composed of lines and shapes in various colors
Computer translates geometric formulas to create the graphic
Storage space depends on image complexity
number of instructions to create lines, shapes, fill patterns
Movies Shrek and Toy Story use object images

54. Object Images Based on mathematical formulas
Easy to move, scale and rotate without losing shape and identity as bitmap images may
Require less storage space than bitmap images
Cannot represent photos or paintings
Cannot be displayed or printed directly
Must be converted to bitmap since output devices except plotters are bitmap

55. Popular Object Graphics Software
Most object image formats are proprietary
Files extensions include .wmf, .dxf, .mgx, and .cgm
Macromedia Flash: low-bandwidth animation
Micrographx Designer: technical drawings to illustrate products
CorelDraw: vector illustration, layout, bitmap creation, image-editing, painting and animation software
Autodesk AutoCAD: for architects, engineers, drafters, and design-related professionals
W3C SVG (Scalable Vector Graphics) based on XML Web description language
Not proprietary

56. PostScript
Page description language: list of procedures and statements that describe each of the objects to be printed on a page
Stored in ASCII or Unicode text file
Interpreter program in computer or output device reads PostScript to generate image
Scalable font support
Font outline objects specified like other objects

57. PostScript Program

58. Representing Characters as Images
Characters stored in format like Unicode or ASCII
Text processed and stored primarily for content
Presentation requirements like font stored with the character
Text appearance is primary factor
Example: screen fonts in Windows
Glyphs: Macintosh coding scheme that includes both identification and presentation requirement for characters

59. Bitmap vs. Object Images
Bitmap (Raster)
Object (Vector)
Pixel map
Geometrically defined shapes
Photographic quality
Complex drawings
Paint software
Drawing software
Larger storage requirements
Higher computational requirements
Enlarging images produces jagged edges
Objects scale smoothly
Resolution of output limited by resolution of image
Resolution of output limited by output device

60. Video Images Require massive amount of data
Video camera producing full screen 640 x 480 pixel true color image at 30 frames/sec MB of data/sec
1-minute film clip 1.6 GB storage
Options for reducing file size: decrease size of image, limit number of colors, reduce frame rate
Method depends on how video delivered to users
Streaming video: video displayed as it is downloaded from the Web server
Example: video conferencing
Local data (file on DVD or downloaded onto system) for higher quality
MPEG-2: movie quality images with high compression require substantial processing capability

61. Audio Data
Transmission and processing requirements less demanding than those for video
Waveform audio: digital representation of sound
MIDI (Musical Instrument Digital Interface): instructions to recreate or synthesize sounds
Analog sound converted to digital values by A-to-D converter

62. Waveform Audio
Sampling rate normally 50KHz

63. Sampling Rate
Number of times per second that sound is measured during the recording process.
1000 samples per second = 1 KHz (kilohertz)
Example: Audio CD sampling rate = 44.1KHz
Height of each sample saved as:
8-bit number for radio-quality recordings
16-bit number for high-fidelity recordings
2 x 16-bits for stereo

64. MIDI
Music notation system that allows computers to communicate with music synthesizers
Instructions that MIDI instruments and MIDI sound cards use to recreate or synthesize sounds.
Do not store or recreate speaking or singing voices
More compact than waveform
3 minutes = 10 KB

65. Audio Formats
MP3
Derivative of MPEG-2 (ISO Moving Picture Experts Group)
Uses psychoacoustic compression techniques to reduce storage requirements
Discards sounds outside human hearing range: lossy compression
WAV
Developed by Microsoft as part of its multimedia specification
General-purpose format for storing and reproducing small snippets of sound

66. .WAV Sound Format

67. Data Compression
Compression: recoding data so that it requires fewer bytes of storage space.
Compression ratio: the amount file is shrunk
Lossless: inverse algorithm restores data to exact original form
Examples: GIF, PCX, TIFF
Lossy: trades off data degradation for file size and download speed
Much higher compression ratios, often 10 to 1
Example: JPEG
Common in multimedia
MPEG-2: uses both forms for ratios of 100:1

68. Compression Algorithms
Repetition
Example: large blocks of the same color
Pattern Substitution
Scans data for patterns
Substitutes new pattern, makes dictionary entry
Example: 45 to 30 bytes plus dictionary
Peter Piper picked a peck of pickled peppers.
 t   p    a   of  l   pp  s.  Pe  pi  ed  er  ck  pe  Pi

69. Internal Computer Data Format
All data stored as binary numbers
Interpreted based on
Operations computer can perform
Data types supported by programming language used to create application

70. Five Simple Data Types
Boolean: 2-valued variables or constants with values of true or false
Char: Variable or constant that holds alphanumeric character
Enumerated
User-defined data types with possible values listed in definition
Type DayOfWeek = Mon, Tues, Wed, Thurs, Fri, Sat, Sun
Integer: positive or negative whole numbers
Real
Numbers with a decimal point
Numbers whose magnitude, large or small, exceeds computer’s capability to store as an integer