SLR12 Coding text and graphics Flashcards
Character coding
“The process of encoding text-based characters from a character set (such as ASCII or UNICODE) and mapping them to their binary equivalents in that character set.)
Character set
“The set of symbols that may be represented in a computer at a particular time. These symbols, called characters, can be letters, digits, spaces or punctuations marks, the set includes control characters.”
ASCII
“A character set devised for early telecommunication systems but proved to be ideal for computer systems. uses 7-bits giving 32 control codes and 96 displayable characters (the 8th bit is often used for error checking).”
Unicode
“Standard character set that replaces the need for all the different character sets. It incorporates characters from almost all the world’s languages. It is a 16-bit extension of ASCII.”
Parity bits
“A bit which acts as a check on a set of binary values, calculated so that the number of 1s in the set plus the parity bit should also be even if we are using even parity or odd if we are using odd parity.”
Majority voting
“A crude method of identifying errors in transmitted data by transmitting a binary code multiple times and then looking the pattern received. If the pattern does not match, then there must be a discrepancy. Majority voting can be used to see which bit occurs the most frequently and assumptions can then be made about which bit was incorrect.”
Checksums
“A digit representing the sum of the correct digits in a piece of stored or transmitted digital data, again which later comparisons can be made to detect errors in the data.”
Check digits
“A form of redundancy check used for error detection on identification numbers, such as bank account numbers, which are used in an application where they will at least sometimes be input manually.”
Bit pattern
“A sequence of bits in memory, a communications channel or some other device.”
Analogue-to-digital converter
“A device for converting analogue signals to digital form.”
Digital-to-analogue convertor
“A device for converting digital signals into analogue form.”
Bitmap graphic
“A digital image composed of a matrix of dots. When viewed at 100%, each dot corresponds to an individual pixel on a display. Each can be assigned a different colour.”
Resolution
“The number of pixels a display unit can display.”
Colour depth
“The number of bits used to indicate the colour of a single pixel in a bitmapped image or video frame buffer or the number of bits used for each colour component of a single pixel.”
Metadata
“A set of data that describes and gives information about other data.”