XMLVARS supports storing and retrieving a total of 2048 different variables, with names up to 64 char, numeric values of type FLOAT64 and string values up to 128 char. It can minimize the use of repetitive code in complex gauges like FMS, Navigation Display, TCAS and similar as one of its strongest points is the ability to maintain variable values across the different gauges, like Lvars do (and most gpsvars don't). However, unlike LVars, those values still remain even after an aircraft reload, aircraft change or flight reset; something that could be useful for debugging purposes. In this case, making a RELOAD_USER_AIRCRAFT in FSX equals to make RELOAD_PANELS in FS9 (a powerful event for developers that was lost in FSX).
XMLVARS was tested in FSX and FS9 (FS2004) under Windows Vista and Windows 7 64 bits.