About
Universal coded character set 2 (UCS2) (aka ucs 2) is an Unicode character set that is a subset of UTF-16 with the most common characters
The designers of Unicode historically miscalculated the total of code points and originally thought that Unicode would need no more than <math>2^{16}</math> code points. The original standard UCS-2 16-bit encoding was born.
UCS-2 is made up of individual 16-bit code unit (number), each of which corresponded to a single Unicode code point.
Indexing into a string is a cheap, constant-time operation: Accessing the nth code point of a string simply selects from the nth 16-bit element of the array.