chapter 3--Data representation Flashcards
What do you call it when the value that is computed cannot fit into the number of bits we have allocated for the answer?
overflow
WhAt are the first 256 characters of Unicode?
The ASCII extended charset
What type of encoding replaces frequently-used words with a single character?
keyword encoding
True/False. Run-length encoding is very good at compressing English text.
false.
What kind of encoding uses variable-length binary strings to represent characters?
Huffman encoding
True/False. The MP3 format discards information that cannot be heard by humans.
true
What does MP3 stand for? Also, describe the encoding process
MPEG-2, audio layer 3 file. Moving Picture Experts Group, an international committee that develops standards for digital audio and video compression. First, info that humans can’t hear is discarded, by comparing the file to mathematical models of of human psychoacoustics. Finally, the bit stream is compressed using a form of Huffman encoding.
How does the RGB model represent color?
Using 3 number values for red, green, and blue. 0 to 255 for each.
True/False. Bitmap, GIF, and JPEG are all examples of raster graphics formats.
true
How do vector graphics represent images?
in terms of lines and geometric shapes
True/False. A keyframe is used in temporal compression to represent the changes from one frame to another.
false. delta frame
What kind of data is a continuous representation of information?
analog
the representation for numbers you’ve used since grade school is called ______.
signed-magnitude representation
if the number system is other than base 10, we call the decimal point the ______
radix
_______ data is a discrete representation of information.
digital
Huffman codes are created based on the _____ of the character.
frequency
What is pulse-code modulation?
the way in which digital data is transmitted. it’s a square wave, that is either on or off at any given point in time, which corresponds to either a 0 or a 1.
The GIF format uses which technique?
Color indexing
What do we call the perception of the various frequencies of light that reach to retinas of our eyes?
Color
What is the best format for photographic color images?
JPEG
What are the video compression techniques?
Codecs, both spatial and temporal
What is the technique in which an application supports only a certain number of specific colors, creating a palette from which to choose?
Color indexing
Which format stores information on a pixel-by-pixel basis?
Raster graphics format
What is the difference between HiColor and TrueColor?
HiColor is 16 bit, and TrueColor is 24 but
Floating point?
Where the number of digits is fixed, but the radix floats
Discuss a common way to store numbers on a computer.
64 bits.1 for the sign, 11 for the exponent, and 52 for the mantissa
What does GIF stand for, and how does it handle color?
Graphics interchange format. 256 colors
What does PNG stand for, and how is it different than JPEG?
Portable network graphics. Greater compression ratio, but cannot support video
SVG?
Scalable vector graphics, uses vectors like Flash. Expressed in plain text.
How is SVG different from Flashplayer?
Requires no editor, expressed in plain text
Name some video codecs.
Sorenson, Cinepak, MPEG, & Real Video.
What is the main ASCII character set called? How many bits/characters?
Latin-I Extended ASCII Character Set. 8 bits, 128 characters
What are the first 32 characters in ASCII used for?
Carriage return, tabs, etc.
How many bits does Unicode have?
16
Name some audio data formats.
Wav, aU, aiff, vqf, MP3.
What’s the most popular audio format, and why?
MP3. Better compression ratio
How many bits do HiColor and TrueColor use?
HiColor is 5 bits for each color plus 1 for transparency. TrueColor is 8 bits for each color, total of 24. 0 to 255
Bob Bemer–most important accomplishment, plus others.
Escape character. Also his work on ASCII. Also FORTRANSIT, a FORTRAN compiler.
4 programming languages Bemer was involved with?
FORTRAN, COBOL CODASYL –(an early approach to database modeling and management), SIMULA–(a simulation language that had many object-oriented features)
How many computer codes did Bemer’s survey include?
over 60
What did Bemer’s use of the Escape character in ASCII allow?
an easy way to change what characters each key on the keyboard mapped to
What does ASCII stand for?
American Standard Code for Information Interchange
What color format does bit mapping support? How is it compressed?
24-bit TrueColor, although the color depth can be specified to reduce file size. It is compressed using run-length encoding
When/who GIF? How many colors? What ideal for?
Compuserve, 1987. 256 colors. Ideal for line art and images with few colors.
Discuss JPEG.
Humans are more sensitive to gradual changes of color/brightness than rapid ones. JPEG averages out the color hues over short distances.
How does a digital signal regain its shape?
By being reclocked before the 1s get below 2.5 volts
