Filename extensions (.something at the end of a filename) tell programs and users what type of data a file contains.

In QNX Neutrino filesystems, extensions are just an ordinary part of the filename and can be any length, as long as the total filename size stays within the 505-byte filename length limit.

Most of the time, file extensions are simply naming conventions, but some utilities base their behavior on the extension. See Filename extensions for a list of some of the common extensions used in a QNX Neutrino system.