Hi Rich,

this is because on VFP if a object don't have a parent,
parent isn't NULL, it isn't undefined, it is a ZOMBI property with a error trapping attacked to it.
Identical behaviour you have for _SCREEN.ActiveForm or _SCREEN.ActiveControl.

For me VFPT must change this behaviour, and set it to an object vartype
with value set to NULL.

Also VARTYPE() it needs of some improvement.

Example ( on command window ):

? VARTYPE(_screen)
? VARTYPE(_screen.Top)
? VARTYPE(_screen.xc)
? VARTYPE(_screen.parent)        && <---
? VARTYPE(_screen.ActiveForm)    && <---
? VARTYPE(_screen.ActiveControl) && <---
? VARTYPE(z)
? VARTYPE(z+1)                   && <--- VARTYPE()need improvement
z=4
? VARTYPE(z+1)
? VARTYPE(NULL+1)          
y=null
? VARTYPE(y+1)                   && <-- VARTYPE() need improvement
? VARTYPE(_screen.w[1])          && 
? VARTYPE(w[1])                  && <-- VARTYPE() need improvement

You have to use the slow function TYPE(),
this eval the expression, and for any error return "U".

Fabio