AutoCAD uses a configuration file with the name acadxxxx.cfg to store device and application information.
The xxxx in the file name refers to the AutoCAD release number. The AppData section of this file is provided for users and developers to store configuration information pertaining to their applications. The getcfg and setcfg functions allow AutoLISP applications to inspect and change the value of parameters in the AppData section.
The setcfg function requires two strings that represent the section and parameter, and the value to assign. The value returned by setcfg is nil if the value could not be stored or the value that was being assigned to the parameter. The getcfg function requires the section and parameter to retrieve a value from and returns the value if the parameter exists.
(setcfg "AppData/ArchStuff/WallThk" "8") "8"
(getcfg "AppData/ArchStuff/WallThk") "8"