Computer Science Illuminated Chapter 3 Vocab

Data Representation, AP Comp Sci

Analog data

A continuous representation of data

Bandwidth

The number of bits or bytes that can be transmitted from one place to another in a fixed amount of time

Character set

A list of the characters and the codes used to represent each one

Compression ratio

The size of the compressed data divided by the size of the uncompressed data (the percentage that compressed data’s size is of the original data’s)

Data

Basic values or facts

Data compression

Reducing the amount of space needed to store a piece of data

Digital data

A discrete representation of data

Digitize

The act of breaking information down into discrete pieces

Floating point

A representation of a real number that keeps track of the sign (positive or negative), the mantissa (all of the integers that make of the number), and the exponent (what place value each integer is in)

Huffman encoding

Using a variable-length binary string to represent a character so that frequently used characters have short codes (typically the most effective form of lossless data compression on this list)

Information

Data that has been organized or processed in a useful manner

Keyword Encoding

Replacing a frequently used word with a single character (replacing the word data in this textbook would be an excellent way to use keyword encoding – it shows up on 421 pages!)

Lossless compression

A data compression technique in which there is no loss of information

Lossy compression

A data compression technique in which there is loss of information

Multimedia

Several different media types

Overflow

A situation during which a calculated value cannot fit into the number of digits reserved for it

Pixels

Individual dots used to represent a picture; stands for picture elements

Pulse-code modulation

Variation in a signal that jumps sharply between two extremes

Radix point

The dot that separates the whole part from the fractional part in a real number of any base (The decimal point of base 10)

Raster-graphics format

Storing image information pixel by pixel

Reclock

The act of reasserting an original data signal before too much degradation occurs

Resolution

The number of pixels used to represent a picture

Run-length encoding

Replacing a long series of a repeated character with a count of the repetition (uses a flag, the character, and the number of times the character is repeated; in this order. Good for DNA sequences and other experimental data)

Scientific notation

An alternative floating-point representation (one whole integer with every other integer a fractional part to the right of the radix point, all raised to a power – ex. 1.2532 x 10^-5)

Signed-magnitude representation

Number representation in which the sign (negative or positive) represents the ordering of the number and the value represents the magnitude (this is the number representation we typically use in daily life and mathematics classes)

Spatial compression

Movie compression technique based on the same compression techniques used for still images (removing redundant information – grouping areas of the same color within a frame)

Temporal compression

Movie compression technique based on differences between consecutive frames (avoiding the duplication of information if it stays the same between frames)

Ten’s complement

A representation of negative numbers such that the negative of I is (I raised to k) minus I

ex) (-3) = 10^2 – 3 = 97

Vector graphics

Representation of an image in terms of lines and shapes

Video codec

Methods used to shrink the size of a movie or video