Unit 01 - Information Representation Flashcards
CAMBRIDGE INTERNATIONAL A-LEVEL COMPUTER SCIENCE 9618
Hexadecimal
A number system that uses 16 distinct symbols (the numbers 0-9 and the letters A-F) to represent a number. Also called hex or base-16.
Denary
Decimal numbers written with the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.
Bit
A digit in the binary number system written using either of the symbols 0 and 1. Bit is short for binary digit.
Byte
A group of eight bits treated as a single unit. 0000 0000
Nibble
A group of four bits 0000
Decimal prefix
A prefix to define the magnitude of a value. Examples are kilo, mega, giga and tera. They represent factors of 10^3, 10^6, 10^9 and 10^12 respectively.
Binary prefix
A prefix to define the magnitude of a value. Examples are kibi, mebi, gibi and tebi. They represent factors of 2^3, 2^6, 2^9 and 2^12 respectively.
One’s Complement
The binary number obtained by subtracting each digit in a binary number from 1.
Two’s Complement
A method of representing signed (i.e. negative and positive) numbers where the most significant bit has a negative place value.
Overflow
A condition when the result of a calculation is too large to fit into the number of bits defined for storage.
Binary coded decimal (BCD)
Storage of a binary value representing one denary digit in a nibble (4 bits)
Packed BCD
When two BCD (binary coded decimal) nibbles are stored in one byte
ASCII
American Standard Code for Information Interchange. An encoding format that allocates a numeric code to characters (e.g. digits, letters, punctuation marks, etc.) in order for them to be represented in binary within a computer system
Unicode
An encoding format that allocates a numeric code to characters in order for them to be represented in binary within a computer. Unicode covers the characters for the most known alphabets and special symbols (e.g. mathematical operators, geometric shapes, arrows, emojis, etc.)
Bitmapped graphic
A type of digital image that is stored as pixels. Each pixel is represented by a single colour code. Also called bitmapped image.
Colour depth
Also known as bit depth. The number of bits used to represent the colour of a pixel in a bitmapped graphic. Represents each of the red, green and blue colours.
Pixel
Short for picture element. The smallest addressable part of a bitmap image that corresponds to a single colour
Image resolution
The number of pixels in the bitmap file defined as the product of the width and height values
Screen resolution
The product of the width and height values for the number of pixels that the screen can display
Vector Graphic
An image that is stored as a set of instructions to recreate it. Uses a drawing list made up of a set of objects and their properties.
Drawing Object
A component defined by geometric formulae and associated properties
Drawing list
Contains one set of values for each drawing object
Property
Defines one aspect of the appearance of the drawing object
Metadata
Data about data. Data that provides information about other data.
File Header
A set of bytes at the beginning of a bitmap file which identifies the file and contains information about the coding used.
Analogue Data
Data obtained by measurement of a physical property which can have any value from a continuous range of values. For instance sound made by the human voice.
Digital Data
Data that has been stored as a binary value which can have one of a discrete range of values.
Sample Resolution
The number of bits used to encode each sample. Determines how accurately the sample can be represented. Also called bit depth.
Sampling Rate
The number of samples captured per second. Expressed in hertz (where 1Hz is 1 sample per second)
Sampling
A method of capturing analogue data sot that it can be converted to digital form, for example, by measuring sound at fixed intervals
Sampling interval
The amount of time (measured in seconds) between two consecutive samples.
Bit pattern
A unique string of binary digits used in a representation.
Compression
The process of reducing file size by applying a compression algorithm
Lossy Compression
A method where data is permanently lost during the compression process and must be approximated when the file is decompressed
Lossless compression
Coding techniques that allow subsequent decoding to recreate exactly the original file
Encoding
The process of representing data in binary form
Dictionary-based method
A lossless method of compression where each different word or group of characters is assigned a code. When the file is compressed, the words or character groups are substituted by the codes.
RLE
Run Length Encoding. A lossless compression method where repeated runs of binary data are represented by a single instance of the data and the number of repetitions.
