I will report a behavior that I believe is a bug in IBO Version 5.9.7 Build 2754:

In TIBODataset.SysDefineParams(), line 5730, the conditional below:

if ( not VarSameValueEx( v, tmpPrm.Value )) then

Returns True when (v = 0) and (tmpPrm.Value = Unassigned).

This keeps the tmpPrm.Value = null instead of the value zero when I do in the code somethink like:

var

  vDouble: Double;

...

  vDouble := 0;

  TIBOQuery.ParamByName('FIELDNAME').Value := vDouble;

...

In case of any doubt, I will respond promptly,

Best regards,