.NDX file extension - ArcView fonts index
What is ndx file? How to open ndx files?
File type specification:
The ndx file extension is associated with the ArcView, a basic geographic information system software (GIS) that allows users to view and edit GIS data stored in flat file databases.
The ndx file stores fonts index.
The default software associated to open ndx file:
ArcGIS for Desktop Basic (ArcView) 
Company or developer:
Esri
ArcGIS for Desktop Basic (formerly known as ArcView) is GIS (geographic information system) application used to visualizing, managing, creating, and analyzing geographic data.
ArcGIS for Desktop Basic is a part of the ArcGIS Desktop. ArcGIS for Desktop Basic supports creation of interactive maps, spatial analysis, GIS deployment, map viewing and navigation, map printing etc.
List of recommended software applications associated to the .ndx file extension
Recommended software programs are sorted by OS platform (Windows, macOS, Linux, iOS, Android etc.)
and possible program actions that can be done with the file: like open ndx file, edit ndx file, convert ndx file, view ndx file, play ndx file etc. (if exist software for corresponding action in File-Extensions.org's database).
Unspecified and all other actions for computer programs working with ndx file - ArcView fonts index
Click on the software link for more information about ArcGIS for Desktop Basic (ArcView). ArcGIS for Desktop Basic (ArcView) uses ndx file type for its internal purposes and/or also by different way than common edit or open file actions (eg. to install/execute/support an application itself, to store application or user data, configure program etc.).
