Lecture #5:

of data in binary format
Human communication
Includes language, images and

sounds
Data formats:
Specifications for converting data into computer-usable form
Define the different ways human data may be represented, stored and processed by a computer

Example: keyboard input such as A 1+2=3 math
Keyboard generates a

binary number code for each key
Analog
Continuous data such as sound or images
Requires hardware to convert data into binary numbers

Figure 3.1 with this color scheme

source
Type of processing required
Trade-offs
Accuracy and resolution
Simple photo vs. painting

in an art book
Compactness (storage and transmission)
More data required for improved accuracy and resolution
Compression represents data in a more compact form
Metadata: data that describes or interprets the meaning of data
Ease of manipulation:
Processing simple audio vs. high-fidelity sound
Standardization
Proprietary formats for storing and processing data (WordPerfect vs. Word)
De facto standards: proprietary standards based on general user acceptance (PostScript)

multiply, divide
Types
Integer (whole number)
Real (contains a decimal point)
Covered in Chapters

4 and 5

7 9
Punctuation marks: ! ;
Special-purpose characters: $ &
Numeric characters

vs. numbers
Both entered as ordinary characters
Computer converts into numbers for calculation
Examples: Variables declared as numbers by the programmer (Salary$ in BASIC)
Treated as characters if processed as text
Examples: Phone numbers, ZIP codes

characters
Consistency: input and output device must recognize same code
Value of

binary number representing character corresponds to placement in the alphabet
Facilitates sorting and searching

scheme
EBCDIC: IBM mainframe (legacy)
Unicode: developed for worldwide use

Latin alphabet, Arabic numerals, standard punctuation characters
Plus small set

of accents and other European special characters
ASCII
7-bit code: 128 characters

by IBM
Restricted mainly to IBM or IBM compatible mainframes
Conversion

software to/from ASCII available
Common in archival data
Character codes differ from 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

upper- and lowercase codes
In ASCII, numbers collate first; in EBCDIC,

last
ASCII collating sequence for string of characters

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

keyboard
One generated when key is struck and another when key

is released
Converted to Unicode, ASCII or EBCDIC by software in terminal or PC
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

and inputs it as character data
Used to read specially encoded

characters
Example: magnetically printed check numbers
General use limited by high error rate
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 read optically using wand
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

graphs
Two approaches:
Bitmap or raster images of photos and paintings

with continuous variation
Object or vector images composed of graphical objects like lines and curves defined geometrically
Differences include:
Quality of the image
Storage space required
Time to transmit
Ease of modification

variations in shading, color, shape and texture
Examples:
Scanned photos
Clip

art generated by a paint program
Preferred when image contains large amount of detail and processing requirements are fairly simple
Input devices:
Scanners
Digital cameras and video capture devices
Graphical input devices like mice and pens
Managed by photo editing software or paint software
Editing tools to make tedious bit by bit process easier

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

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

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

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

16 million colors
Suitable for highly detailed photographs and paintings
Employs lossy

compression algorithm that
Discards data to decreases file size and transmission speed
May reduce image resolution, tends to distort sharp lines

.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

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

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

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

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

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

producing full screen 640 x 480 pixel true color image

at 30 frames/sec 27.65 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

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

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

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

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

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

0 0 3 4 0 0 0

0 1 5 8 7 0 4 3 4 0 3
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.

binary numbers
Interpreted based on
Operations computer can perform
Data types supported by

programming language used to create application

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