Get the name of the character set. This simply returns the name that was given to construct the character set.

Determine if a character or string of characters is mappable to this character set. If the input is an integer, it represents the Unicode character code for a single character; if the input is a string, each character in the string is checked. This returns true if every character given has a valid mapping in the local character set, nil if not. Note that if a string is given, and even one character is not mappable, this returns nil.

Determine if the mapping is known. This returns true if the character set has a known local mapping, nil if not. Note that it doesn't matter whether or not the character set is actually in use on the local platform; all that matters is that a T3 mapping file is available on this machine.

Determine if a character or string of characters is "round-trip" mappable to this character set. If the input is an integer, it represents a Unicode character code to be tested; if the input is a string, each character in the string is tested. Returns true if every character given has a valid round-trip mapping, nil if not.

A character has a round-trip mapping if it can be mapped to this local character set and then back to Unicode to yield the original character. If a character has a round-trip mapping, then in general the character has an exact representation in the local character set (as opposed to an approximation: if 'a-umlaut' maps to a simple unaccented 'a', or to 'ae', then it has only an approximated representation).