10.9.4 The ucs2 Character Set (UCS-2 Unicode Encoding)

In UCS-2, every character is represented by a 2-byte Unicode code with the most significant byte first. For example: LATIN CAPITAL LETTER A has the code 0x0041 and it is stored as a 2-byte sequence: 0x00 0x41. CYRILLIC SMALL LETTER YERU (Unicode 0x044B) is stored as a 2-byte sequence: 0x04 0x4B. For Unicode characters and their codes, please refer to the Unicode Consortium website.

The ucs2 character set has these characteristics:

Supports BMP characters only (no support for supplementary characters)
Uses a fixed-length 16-bit encoding and requires two bytes per character.