The range of Unicode code points is 0x0 to 0x10FFFF. However, some values within this range are reserved and are not valid characters. RWUCharTraits provides the static method RWUCharTraits::isCharacter(), which returns true if a given RWUChar32 value is a valid Unicode character code point.

RWUCharTraits::isDefined() returns true if a given value RWUChar32 is defined as the code point for a named character in the Unicode Character Database. A defined character is assigned various properties under the Unicode Standard. These properties can be accessed using other methods provided by RWUCharTraits, as described in the following sections.

RWUCharTraits::isCharacter()tests whether a code point is valid, and hence may be a defined character. RWUCharTraits::isDefined() tests whether a code point has already been defined.

In UTF-16, most Unicode characters can be represented with a single 16-bit code unit. Only characters in the range 0x10000 to 0x10FFFF must be represented with a surrogate pair of two UTF-16 code units. RWUCharTraits provides the static method RWUCharTraits::requiresSurrogatePair(), which returns true if a given RWUChar32 code point requires a surrogate representation.

Similarly, RWUCharTraits::isHighSurrogate() returns true if a given RWUChar16 code unit is the first, or high, code unit of a surrogate pair. A high surrogate has a value in the range U+D800 to U+DBFF. The function RWUCharTraits::isLowSurrogate() returns true if a given RWUChar16 code unit is the second, or low, code unit of a surrogate pair. A low surrogate has a value in the range U+DC00 to U+DFFF. The method RWUCharTraits::isSurrogate() returns true if a given RWUChar16 is a surrogate in the range U+D800 to U+DFFF. Surrogates are not characters themselves; they are reserved for use as the low or high code unit in a surrogate pair.

Finally, RWUCharTraits::isSingle() returns true if a given RWUChar16 code unit corresponds to a single code point, or false if the value is part of a surrogate pair.