example of ABSOLUTE usage as code optimization trick: this function uses a longword integer type at the float parameter address to treat data as integer in order to perform bit operations without typecasting or conversion, this code will beat "result:= x > 0" any time.

Code:
// true = positive, false = positive
function GetSign(x: single): boolean;
var
  i: longword absolute x;
begin
  Result := i and $80000000 = 0; // integer operator tricks
end;
You can also come up with code like this, which will use a single vector type and work with ANY memory compatible vector formats (think compatibility between glscene vector types and some other code vector types)

Code:
function DotProduct(const vA, vB): single; overload;
var
  A: Vector absolute va;
  B: Vector absolute vb;
begin
  Result := A.X * B.X + A.Y * B.Y + A.Z * B.Z;
end;