Allownull

Allownull indicates that an actual parameter may also be 0. No matter what type the formal parameter is.

Example

dll "some.dll"
  "DoAllowNull"
    function DoAllowNull(nParam1 : out number allownull,
                         nParam2 : in number);

dcltrans
  transaction TMain
  begin
    // although a variable should be set as first parameter,
    // we can also
    // specify 0, as the formal parameter
    // is declared allownull
    DoAllowNull(0, 12);
  end TMain;