F - stands for File Management. This is bread and butter work for SAS, with standard file handling features such as:
The upgrade of LUA in 9.4M6 opens up more possibilities for file management with access to the IO library (https://www.lua.org/manual/5.1/manual.html#5.7).
Files received from the frontend are easily captured by SAS 4GL via the automatic "_WEBIN_nameXX" and "_WEBIN_FILEREFXX" macro variable arrays (which point to copies of the received files).
Sending files back to the frontend simply involves setting the http headers ("stpsrv_header" function) and writing content directly to the "_webout" fileref.
These are the mechanisms in use in this 30 second demo video. A CSV file is uploaded to Data Controller, the data is reviewed and approved, and the table is finally downloaded as a .SAS program file.