Character Set

• Is a collection or list of characters
• Any given character set contains the characters needed to support a specific language (or languages)
• Character Sets are often given names

For example:

The Latin Character Set is used by English and most Western European languages, though the Greek Character Set is used only by the Greek language.

Code Point

• The characters of a Character Set are represented by numbers​
• A Code Point is any one of the numbers used to represent a valid character of the Character Set​
• The set of Code Points that represent all of the characters of a Character Set is a Code Point collection​
• A Code Point collection has a name, e.g. ASCII, Unicode, Windows-1252​

For example:​

The letter ‘A’ might be represented by the number 1 and the letter ‘Z’ by 26, therefore the range 1 through 26 are the Code Points for letters ‘A’ through ‘Z’.​

Code Unit

• Is a sequence of bits used to represent a given Code Point​

For example:​

Representing our A-Z Character Set with Code Points 1 through 26 and using a sequence of 5-bits for each Code Point obtains Code Units such as:​ 00001 == 1 == A​ 00011 == 3 == C​ 11010 == 26 == Z

Encoding

• Is the method used to map between a Code Point and its respective Code Unit​
• Encodings are given names​
• Confusingly some Encoding names are the same/similar to the name of a Character Set, e.g. ASCII and ASCII-7​
• Even more confusingly many Encodings are commonly referred to as Character Sets, e.g. UTF-8​
• Most confusing of all, some names represent a Character Set, a Code Point collection and an Encoding, e.g. ISO-8859-1 (Latin Western European, single byte encoding)​

Locale

• A Locale is a set of parameters defining the User’s language, region and any particular preferences that the User wants to see in their user interface​
• Locales are given a name, e.g. en, en-GB , cy-GB​

Affects​

• Character set and orientation (left-to-right)​
• Date-time representation and time zone selection​
• Formatting of numbers and currency​

Note: can affect the active NLS settings used by an Oracle​ Data Server/Database

National Language Support

• National Language Support (NLS) is part of Oracle​ Data Server
• NLS allows storage, processing and retrieval of data in native languages​
• NLS ensures that database utilities and error messages, sort order, date, time, monetary, numeric, and calendar conventions automatically adapt to the native language and locale​
• NLS settings on the Client and the Server can differ and Oracle will convert between the two​

ASCII

• ASCII is 128 characters including: A through Z, a through z, 0-9, punctuation and certain special characters​
• The Code Point collection for ASCII uses numbers ranging from 0 to 127​
• The characters are arranged such that the “English” sort order of characters (ASCII-betical) is preserved in its numerical sequence, e.g. A (65), B(66), C(67)​
• The ASCII-7 Encoding uses a 8-bit sequence for each Code Point where the binary value is equivalent to the Code Point value​

For example:​

A == Code Point 65 == 0100 0001​

ISO-8859

• ISO-8859 is both an Encoding, a set of Code Point specifications and 15 character sets (covering Latin-based languages)​
• The encoding is an 8-bit sequence using all 256 possible values, i.e. every Code Point is represented by a byte​
• All Code Point collections have the same 1st 128 characters and they are equivalent to ASCII​
• The next (higher-order) 128 characters represent additional characters​
• There are 15 different sets of these higher order 128 characters, ISO-8859-1 thro’ ISO-8859-11 and ISO-8859-13 thro’ ISO-8859-15​
• The ISO-8859 Standard is no longer being maintained/developed​

ISO-8859-1

• This is the Character Set, Code Point collection and Encoding method that many ‘C’ applications used to use
• It consists of 191 characters from the Latin script. ​
• It is used throughout the Americas, Western Europe, Oceania, and much of Africa​
• It is commonly used in most “romanizations” of East-Asian languages​
• Forms the basis for popular Code Point collections, including Windows-1252 and the first block in Unicode​

UTF-8

• Is an Encoding scheme for the Unicode Character Set/Code Point collection​
• It uses between 1 and 4 bytes to represent each Code Point​
• It is backwards compatible with ASCII-7​
• More than 90% of all Web Pages can be said to be UTF-8 (probably because they are boring, old, generic English text entirely represented in ASCII?​)
• UTF-8 is the default encoding for XML

UTF-8 Encoding

An Encoding Example

An example of UTF-8 Encoding for the Letter A:

• Unicode character UPPERCASE A has a Code Point of 65 (0x41)​
• As that falls in the range of 0x00 thro’ 0x7F, 1 byte is needed to store the encoding​
• Therefore, A == 0x41 == 0010 0001​

An example of UTF-8 Encoding for the Letter ä:​

• Unicode character LATIN SMALL LETTER A WITH DIAERESIS ä has a Code Point of 228 (0x00E4)​
• As that falls in the range of 0x0080 thro’ 0x07FF, 2 bytes are needed to store the encoding​
• Therefore, ä == 0xC3A4 == 1100 0011 1010 0100

Last modified on 2018-02-05