This refers to an operating system which is capable of processing 16 bits (or 2 bytes ) at any one time. Windows 3.1 is an example. File names can be no more than 8 characters in 16 bit operating systems.
16 BIT OPERATING SYSTEM
Meaning of 16 BIT OPERATING SYSTEM in English
English glossary of Internet and PC terminology. Английский глоссарий Интернет и ПК терминологии. 2012