FON, Generic Font File (.fon)
The FON Misc file format
One of the earliest file formats known for fonts on a Windows machine is the FON file format. These early font files have some distinct disadvantages compared to modern font files like TTF and OTF. While FON files are rarely even used anymore, they can still be opened by the Microsoft Windows Font Viewer. It was part of the Windows 3.x font library.
Technical details of FON files
FON files contain general information about a font used on a Windows computer. From a today's standard, there are severe deficiencies within this file format. Unlike TTF files, fonts stored in the FON format can not be resized. It is also possible, that they are displayed differently on screen than on paper after printing.