0xFFFE

0xFFFE is the hexadecimal representation of the 16-bit value 65534. In Unicode terminology, the corresponding code point is U+FFFE. This code point is classified as a noncharacter, meaning it is permanently reserved and not assigned to any user-visible character. Noncharacters are distinct from regular characters and are generally not intended for text interchange.

In Unicode, noncharacters include U+FFFE, U+FFFF, U+FDD0 through U+FDEF, and all code points whose final two hexadecimal digits are FFFE or FFFF. These code points should not appear in normalized text data and are typically used for internal signaling or internal processing in some systems. If encountered in text data, they are commonly treated as invalid or ignored.

0xFFFE also has a practical role in the encoding of UTF-16. The two-byte sequence FF FE is commonly encountered at the start of a UTF-16 file or stream as the byte order mark (BOM) for UTF-16 little-endian encoding. The corresponding byte sequence FE FF serves as the BOM for UTF-16 big-endian. The BOM indicates endianness but is not part of the text content and is usually stripped before processing the actual data.

In summary, 0xFFFE can refer to a specific 16-bit value that corresponds to a Unicode noncharacter (U+FFFE), and it also appears as the little-endian UTF-16 BOM in files encoded with UTF-16LE. It should not be used to represent ordinary characters in text.