>I also read the help file. It wasnt very clear to me.
>
>What I wanted to know was what is "dual interface" and what does "turn on VFP's optimization" mean?

The controls supporting dual interface store a virtual table (VTable) of their internal functions and allow more direct access to those functions. SYS(2333,1) allows foxpro to use VTable for faster access to the control's functions.