F# is a functional programming language for the .NET Framework. It combines the succinct, expressive, and compositional style of functional programming with the runtime, libraries, interoperability, and object model of .NET.
Files with the FSX extension identify saved spreadsheet files created in the Lotus 1-2-3 application utilized on the DOS operating platform. FSX files store text data utilized in a spreadsheet. Setting and formatting changes made in the spreadsheet will be saved with the FSX extension. FSX files may be opened and edited with the Lotus spreadsheet applications.