C_866.NLS

National Language Support data Reference

An .nls file contains National Language Support data for Windows. The tables define code pages, character classes, and sort orders. The system loads .nls files to convert text between encodings and to compare strings. Examples are code page files such as C_1252.NLS. The files stay in the System32 directory.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.