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Data Types and Data Storage
Published in Julio Sanchez, Maria P. Canton, Microcontroller Programming, 2018
Julio Sanchez, Maria P. Canton
The three encoding forms of the Unicode Standard allow the same data to be transmitted in a byte, word, or double word format, that is, in 8-, 16- or 32-bits per character. UTF-8 is a way of transforming all Unicode characters into a variable length encoding of bytes. In this format the Unicode characters corresponding to the familiar ASCII set have the same byte values as ASCII. By the same token, Unicode characters transformed into UTF-8 can be used with existing software.UTF-16 is designed to balance efficient access to characters with economical use of storage. It is reasonably compact and all the heavily used characters fit into a single 16-bit code unit, while all other characters are accessible via pairs of 16-bit code units.UTF-32 is used where memory space is no concern, but fixed width, single code unit access to characters is desired. In UTF-32 each Unicode character is represented by a single 32-bit code.
Feature Engineering for Text Data
Published in Guozhu Dong, Huan Liu, Feature Engineering for Machine Learning and Data Analytics, 2018
Chase Geigle, Qiaozhu Mei, ChengXiang Zhai
If the text is written in English, these individual bytes might be sufficient to represent the individual characters that occur in the text—this is commonly referred to as ASCII-encoded text. This particular byte-encoding for the characters of predominately English text is compatible with the UTF8 encoding standard: any ASCII-encoded text document is a valid UTF-8 encoded text document (but this relationship is only one way). UTF-8 encoded text supports a much broader range of characters1 than ASCII, and it has been continuously updated to be able to be utilized to represent text in nearly every written language on the planet. It does this by representing individual characters with a variable-length sequence of bytes. UTF-8 encoding is arguably the most commonly encountered encoding of text today (as it is the most common encoding for HTML content), but there are other variants of UTF encodings such as UTF-16 (commonly used in Windows) and UTF-32. The basic idea remains the same across all encodings, however: the document is a sequence of bytes that can be interpreted according to some encoding standard to eventually correspond to the written characters or glyphs that we eventually see displayed on a screen or physical printout.
Character Mapping and Code Sets
Published in Cliff Wootton, Developing Quality Metadata, 2009
These are the implications of using the different Unicode Transformation Formats: A document encoded in UTF-32 could be twice as large as a UTF-16 encoded version, because the UTF-32 scheme requires four bytes to encode any character, while UTF-16 only uses two bytes for the characters inside the basic multilingual plane. Characters outside the Basic Multilingual Plane are rare. You’ll seldom need to encode in UTF-32.The character encoding in UTF-8 is a variable length format and uses between one and four bytes to encode a character. UTF-8 may encode more or less economically than UTF-16, which always encodes in 2 or more bytes. UTF-8 is more economic than UTF-16 when characters having a low (one byte) value predominate.UTF-7 encoding is more compact than other Unicode encodings with quoted-printable or BASE64 encodings when operated in a 7-bit environment but it is difficult to parse.
Extending brain-computer interface access with a multilingual language model in the P300 speller
Published in Brain-Computer Interfaces, 2022
P Loizidou, E Rios, A Marttini, O Keluo-Udeke, J Soetedjo, J Belay, K Perifanos, N Pouratian, W Speier
An additional technical complication when using a non-English language is that characters may not be in the ASCII character encoding used by most computer programs (including BCI2000) and programming languages. As an alternative, the 8-bit Unicode Transformation Format (UTF-8) can be used to represent these characters. However, an added difficulty arises because this format has a variable bit-width that can be difficult to represent in a system dependent on string lengths and character locations. We handled this situation by creating a lookup table where each character was represented by a single 8-bit code. These codes were used for the character representations within the language model and during the computation of character probabilities. Lookups were performed at the input and output stages of the system so that it would be able to read in the language model in UTF-8 format and then present the output as Greek characters through the graphical interface.