case - one of the following: uppercase or lowercase.

The concept of case as used here derives from the notion that each character may be printed using one or more types or fonts. Case now has semantic value.

case classification - character classification in which the character classes being considered are limited to the case classes.

case classes - the character classes uppercase and lowercase. For the purposes of case classification, a character is either an uppercase character, or it is a lowercase character, or it is neither.

The isupper() and islower() functions are used to determine membership in the case classes.

case conversion - for a given character, the process by which the case conversion character is determined.

case conversion character - the character returned by toupper() or tolower().

toupper() -

tolower() -

_toupper() -

_tolower() -

An N-to-1 collation unit does not possess a case conversion character.

Given a subject character, if a case conversion character is not specified, then the default case conversion character is the subject character itself.