Changes and/or reads a system setting. When the value for <lAdditive> is .T. (true), the corresponding files are opened in append mode and new data is added to the end of the respective file. If the value is .F. (false) and the files already exist, they are first truncated to zero length before being opened. The default value is .T. (true).
Set( <nDefine>, [<xNewSetting>], [<lAdditive>] ) --> xOldSetting