freepascal.compiler/docs/refex/ex24.pp

Program Example24;

{ Program to demonstrate the FileSize function. }

Var F : File Of byte;
    L : File Of Longint;

begin
  Assign (F,paramstr(1));
  Reset (F);
  Writeln ('File size in bytes : ',FileSize(F));
  Close (F);
  Assign (L,paramstr (1));
  Reset (L);
  Writeln ('File size in Longints : ',FileSize(L));
  Close (f);  
end.