Quiz 1 IT 105 9 (chap 4) Flashcards
What are data formats?
-computers/computer-based devices process/store data in binary forms
Human comm: language images and sound.
-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
What are sources of data ?
- Binary input: begins as discrete input, ex: 1+2=3, 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 ex: 1+2=3 —-> input device ——> computer
What are common data representations?
-Alphanumeric: Unicode, ASCII, EBCDIC
- Image(bitmapped): JPEG, GIF, TIFF, PNG
- Image(object): PostScript, SVG
- Outline graphics and fonts: PostScript, TrueType
-Sound: MP3, WAV, MIDI, WMA
- Page description: PDF
Video: MPEG-2, MPEG-4, WMV
What are numeric data types and what are they used for?
-used for math manipulation
-types: integer(whole number), real (contains decimal point)
What are alphanumeric data types ?
Characters: b T ñ Ω
Number digits: 2 7 9
Punctuation marks: ! ¿ ? ;
Special-purpose characters: $ @ &
Differences between numeric characters and numbers
-both entered as ordinary characters
- computer converts into numbers for calculation ex: variables declared as numbers by the programmer
- Treated as characters if processed as text
Ex: phone number, zip codes,
What are alphanumeric codes?
- arbitrary choice of bits to represent characters
-consistency (input and output device must recognize the same code)
Value - binary number representing character corresponds to placement in the alphabet
- facilitates sorting and searching
What standards are used for representing characters?
Unicode
- Developed for worldwide use
-UTF( unicode transformation format)
- UTF-8 ( the most widely used coding scheme on the web)
- UTF- 16 (used by windows and java)
ASCII
- developed by ANSI, american national standards institute
EBCDIC
- IBM mainfram(legacy)
What is ASCII?
-created in 1963
- 7 bit code, 128 characters
Represents
- latin alphabet and arabic numerals
-standard punctuation characters
-small set of accents and other european special characters
ISO Latin I
- extended version of ASCII
- 8 bit code, 256 characters
- incorporated into unicode as the first 256 characters for forward/ backward compatibility
What is EBCDIC?
- Extended Binary Coded Decimal Interchange Code developed by IBM in 1963/1964
- restricted to mainly IBM or IBM mainframes
- conversion software to/from ASCII available
- common in archival data
- character codes differ from ASCII
What is UNICODE?
- created in 1991-1992
- most common 16 bit form /represents 65,536 characters
- ASCII Latin -I subset of Unicode(values 0-225 in unicode table)
- Multilingual defines code for: almost every character based alphabet, large set of ideographs for chinese+japanese+korean, composite characters for vowels and syllabic clusters required by some languages
- Allows software modifications for local languages
What is a collating sequence?
-alphabetic sorting if software handles mixed upper- and lowercase codes
- In ASCII , numbers collate first, in EBCDIC last
- ASCII collating sequence for string of characters
What are the two categories of codes?
-Printing characters: produced on the screen or printer
- Control characters: control position of output on screen or printer
VT= vertical tab. LF= line feed - Cause action to occur
BEL= bell rings
DEL: delete current character - Communicate status between computer and I/O device
ESC: extends character set by changing the meaning of the specific sequence of subsequent contiguous characters
What is visual data and what are the two approaches ?
- Videos, photographs, biometric images, figures, icons, drawings, charts, and graphs
Two approaches
- Bitmap or raster images of photos and paintings with continuous variation
- Object or vector images composed of graphical objects such as geometrically defined lines and curves
Visual Data Differences
- Quality of the image
- Storage space required
-Time to transmit - Ease of modification
What are bitmap images used for and what are their input devices?
- used for realistic images with continuous variations in shading, color, shape and texture
- preferred when image contains large amount of detail and processing requirements are fairly simple
Input devices
- scanners
- digital camera and video capture devices
-graphical input devices like mice and pens
-managed by photo editing software or paint software
What is the relation between bitmap images and a pixel?
- Each individual pixel for picture element, in a graphic is stored as a binary number
-Pixel: a small area with an associated coordinate location
look at example in slideshow
What is the bitmap display?
Monochrome
- black or white
- 1 bit per pixel
Gray scale
- black, white, or 254 shades of gray
- 1byte per pixel
Color graphics
- 16 colors, 4 bits
- 256 colors, 8 bits
- 16.7 million colors, 24 bit true color
8 bits on each for red, green, and blue shades
Storing Bitmap Images?
Frequently large files
-Example: 1080 rows of 1920 pixels, with one byte for each of 3 colors per pixel—-> approx. 48 MB
File size is 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
What is JPEG?
-Joint Photographers Expert Group
- Approx. 16.7 million colors
- Suitable for highly detailed photographs and paintings
- employs lossy compression algorithm that(discards data to decrease file size up to 90% and reduce transmission speed, may reduce image resolution, reduce number of the colors, and distort sharp lines)
What is a GIF?
- Graphics Interchange Format
- First developed by CompuServe in 1987
-Limited to 256 colors - Preferred for line drawings, clip art and pictures with large blocks of solid color
-LZW(Lempel-Zif-Welch) compreesion algorithm(lossless compression) - GIF89a enabled animated images
allows images to be displayed sequentially at fixed time intervals
What is PNG?
-Portable Network Graphics
Deflate compression algorithm
- lossless compression vs. JPEG’s lossy compression
- more efficient compression algorithm than GIF
- 16.7 million colors and transparency vs. GIF’s 256 colors
Up to 64-bit RGBA color
-alpha channel indicates the level of transparency
What are object images?
-created by drawing software or drawing features of microsoft office such as charts, shapes, SmartArt
- 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)
- movie series such as shrek and toy story use object images
What are object images based on?
-based on math formulas (easy to move, scale, rotate without losing shape or 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 with the exception of plotters, are bitmap
