Sets the default value of a class's variable. If the class is designated as configurable (using the "config" keyword in UnrealScript or CLASS_Config in C++), and so is the variable, this function updates the Unreal.ini file to reflect the new default value. If any instances of objects belonging to are in memory, all of those objects are updated. When an object's config variables are updated, they are notified as follows: The object's PreEditChange() function is called, basically saying "Get ready to be modified!"
The object's configurable variables are updated with the newly configured values.
The object's PostEditChange() function is called, saying "You've been modified, so validate and update yourself". This procedure enables objects to validate their configurable properties and update themselves. For example, the audio subsystem's PostEditChange() function clamps the sound volume to a safe range of 0.0 - 1.0 (because the SET command enables users to set it to ridiculous values) and then updates the actual volume of the sound effects that are playing.