Hi! Is Cardinal a type, or what is it?

I tried to blockwrite a cardinal variable but the compiler (sorry, it was Delphi, not FPC, I din't try it in FPC yet) complained, that he wants a variable.
--> blockwrite(var f :file; var X; <-- VAR is the problem, but it shouldn't be a problem, 'cause I wanted to write a
var

  cardinalvar : cardinal;

to disk).

Why does he complain?!

Thanx in advance
Tobi