Character Encoding

Question 1

Unicode

Answer 1

• attempt to represent all text from all languages in a single standard
• to support electronic rendering of all texts and symbols
• each grapheme assigned unique number of code point
• allow different orthographies to co-exist in a single document

Question 2

Text documents

Answer 2

• represented as series of numbers
• simplest form of encoding through fixed precision ie. fixed number of digits to represent code point for each character

Question 3

ASCII

Answer 3

• 128 characters
• 7 bit
• compact but can only encode small number of characters

Question 4

UTF-32

Answer 4

• 32 bit encoding

- can encode all unicode characters but bloated

Question 5

ISO-8859

Answer 5

• single byte encoding built on top of ASCII to include extra 128 characters
• can represent orthographies such as Thai, unable to support big orthographies e.g. Japanese

Question 6

Variable-width encoding

Answer 6

• variable bytes
• encode code points using variable number of code units of fixed size
  e. g. UTF-8, UTF-16

Question 7

UTF-8

Answer 7

• 8 bit, variable-width encoding
• compatible with ASCII, superset of ASCII
• character boundaries easily locatable, continuation bytes always start with 10
• used to represent unicode strings

Question 8

Declaring character encoding

Answer 8

• manually specify character encoding in document e..g charset = ISO8859-8
• automatically detects character encoding in terms of compatibility, user preferences, statistical model