Chapter 3 Computer Science, Chapter 3 Data Representation, final exam cis1000
Huffman encoding
(1)text compression technique - uses variable-length binary strings to represent characters, assigning frequently used characters short codes(2)invalid for a bit string that represents a character to be the prefix of any other string used to represent a character
electronic signals
(both analog and digital) degrade as they move down a line
How is the following string represented using run-length encoding? AAAABBBCCCCCCCCDDDD hi there EEEEEEEEEFF
*A4BBB*C8*D4 hi there *E9FF
HiColor
A 16-bit color depth: five bits used for each number in an RGB value with the extra bit sometimes used to represent transparency
TrueColor
A 24-bit color depth: eight bits used for each number in an RGB value
lossy
Data compression technique which means some information may be lost in the process of compaction
lossless
Data compression technique which means the data can be retrieved without any loss of the original information
Vector graphics
Describes image in lines & geometric shapes (instead of pixels). Exp: Flash, SVG
2^n
In general, how many things can be represented by n bits?
Sampling
Recording the voltage level of an audio signal at regular intervals; used to digitize a signal
Data compression
Reduction in the amount of space needed to store a piece of data
color depth
The amount of data that is used to represent a color
what are huffman code creations based on?
The frequency of use of the character
what does it mean to digitize something?
act of breaking continuous information into discrete pieces so that we can represent each piece separately
what does color depth indicate?
amount of data used to represent a color; that is the number of bits used to represent each other colors in the RGB value
what type of data is continuos?
analog
radix point
another type of decimal point
what format does a CD store information?
binary format
what is the technique in which an application supports only a certain number of specific colors, creating a palette from which to choose?
indexed color
the representation for numbers we've used since grade school is called this
magnitude representation
Temporal compression of video
makes use of keyframes and delta frames
Limited network bandwidth
primary reason for compressing data
what is spatial video compression?
removes redundant information within a frame; good for landscapes
why is data compression an important topic today?
save storage
voltage
signal fluctuates due to environmental effects
what is lossy data compression?
some information may be lost
what is raster graphic?
stores information of a pixel-by-pixel basis
Signed-magnitude
technique for representing numeric data - has two forms of zero; sign represents the ordering, the digits represent the magnitude
Fixed-size numbers
technique for representing numeric data - uses ten's complement to represent negative values
what are the two types of video compression?
temporal & spatial
Run-length encoding
text compression technique - replaces a long series of repeated characters with a count of the repetition
Keyword encoding
text compression technique replaces a frequently used word with a single character
what is the decimal point called in a number base other than base 10?
the radix point
ASCII
used seven bits to represent each character, allowing for 128 unique characters
Unicode
uses 16 bits per character; superset of ASCII; over 65,000 characters
what is temporal video compression?
uses differences between frames as the basis for compression; a keyframe is stored in its entirety and then changes from that keyframe are stored
how does Huffman encoding represent characters?
uses variable-length binary strings
what are the techniques called that shrink the sizes of movies?
video codecs
how do humans perceive sound?
when a series of air compressions vibrate a membrane in our ear sending signals to our brain
What is the letter 'A' in Huffman code?
00
how many things can be represented with seven bits?
128
how many things can be represented with four bits?
16
how many things can be represented with five bits?
32 bits
what is the sampling rate per second that is enough to create reasonable sound reproduction?
40,000
how many things can be represented with six bits?
64
Analog data
A continuous representation, analogous to the actual information it represents
Transistors
A device composed of semiconductor material that amplifies a signal or opens or closes a circuit. Invented in 1947 at Bell Labs, they have become the key ingredient of all digital circuits, including computers. Today's microprocessors contains tens of millions of them in microscopic size.
Digital data
A discrete representation, breaking the information up into separate elements
Scientific notation
A form of floating-point representation in which the decimal point is kept to the right of the leftmost digit
Character set
A list of characters and the codes used to represent each one
real numbers
A number with a whole part and a fractional part
Microprocessor
A silicon chip that contains a CPU. It sits at the heart of all personal computers and most workstations. This brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand.
Temporal compression
A technique based on differences between consecutive frames
Spatial compression
A technique based on removing redundant information within a frame
Second Generation Computers
Although the transistor was a vast improvement over the vacuum tube, these computers still relied on punched cards for input, printouts for output and generated a great deal of heat.
Integrated Circuit
Another name for a chip, it is a small electronic device made out of a semiconductor material. The first integrated circuit was developed in the 1950s.
The Fourth Generation
As small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. GUIs, the mouse and handheld devices were also developed in this generation.
Digitize
Breaking data into pieces and representing those pieces separately
The First Generation
Computers in this generation were so enormous that they took up whole rooms. They used vacuum tubes for circuitry and magnetic drums for memory.
multimedia
Computers store, present, and modify: numbers, text, audio, images & graphics, video
Machine Language
First generation computers relied on this language, the lowest-level programming language understood by computers, to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts.
what technique does the GIF format use?
GIF uses indexed color
Binary Code
Groupings of 1's and 0's that makes information that a computer can understand.
What is the difference between HiColor & TrueColor?
HiColor uses 16 bits; TrueColor uses 24 bits
The Fourth Generation
In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the Macintosh. More and more everyday products began to use microprocessors.
what is the best format for photographic color images?
JPEG
Video codec COmpressor/DECompressor
Methods used to shrink the size of a movie to allow it to be played on a computer or over a network
n
Notation to represent number of BITS when calculating how many bits needed to represent things
2^n
Number of THINGS that can be represented with n bits
what is pulse code modulation?
Pulse Code Modulation is a signal that jumps sharply between two extremes.
Raster-graphics format
Storage of information on pixel-by-pixel basis. Examples: bitmap (BMP), GIF, JPEG
First Generation Computers
The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.
Resolution
The number of pixels used to represent a picture
Compression ratio
The size of the compressed data divided by the size of the original data
High Level Languages
This was being developed during the Second Generation. A programming language such as C, FORTRAN, or Pascal that enables a programmer to write programs that are more or less independent of a particular type of computer. These languages have their name because they are closer to human languages and further from machine languages.
The Second Generation
Transistors replaced vacuum tubes and ushered in this generation of computers. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their predecessors.
The Third Generation
Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.
Audio Formats
WAV, AU, AIFF, VQF, and MP3
when does overflow occur?
When the value that we compute cannot fit into the number of bits we have allocated for the result
MP3
Which audio format is the most popular today?
What does *X5*A9 represent using run-length encoding?
XXXXXAAAAAAAAA
Cause of numeric overflow
a calculation producing a value that won't fit into the allotted space
what is a raster-graphic?
a graphic usually consisting of a grid pixels
is a stereo speaker analog or digital?
analog because it receives an analog representation of the sound wave from the stereo
what is a vector graphic?
basically lines or shapes that don't lose quality when zoomed in
pulse-code modulation (PCM)
behavior of a digital signal which jumps between two extremes
how is an audio signal digitized?
by sampling it at regular intervals
how are various video codecs different?
codecs differ in how the blocks of frames are used/encoded
what is the perception of the various frequencies of light that reach the retinas of our eyes?
color
analog signal
continually fluctuates in voltage up and down
what is a vector graphic?
describes an image in terms of lines & geometric shapes
What does an MP3 file do to information that can't be heard by humans?
discards the information
extended ASCII
eight bits were used to represent characters; not enough for international use
what are GIF files best for?
graphics and images with few colors
digital signal
has only a high or low state, corresponding to the two binary digits
how are various video codecs alike?
most video codecs are block oriented; each frame of a video is divided into rectangular blocks
what is lossless data compression?
no information is lost
do vinyl record albums and compact disc record sound the same way?
no; vinyl record albums use an analog representation, but compact discs store audio information digitally
floating point
number of digits is fixed, but the radix point floats (exp: sign * mantissa * 10^exp)
what is resolution?
number of pixels used to represent a picture?
