||Lance, I'm not doubting your expertise. I think I'm miscommunicating somehow. When I'm talking about NULLs in AV3.2, I'm not talking about true NULL, rather the simulation of such. I'm talking about how you can have "blanks" in number columns in AV3.2, which are recognized as NULL by the software. Excel has the same capability with dBase files. If you look at the link that I posted in the post right below this one, you will see what I mean.
I realize that dBase does not support NULL values. This is a workaround to that that some software manufacturers have found (which I am trying to find out about).
ESRI technical support think that their white paper on shapefile architecture will answer this question, so I am about to go read through that again. I don't remember ever seeing this there, but maybe because I was looking for something else then.
And, yes, I very much realize that this was a design decision. That is why I am having to write this software, after all. ESRI seems very clear that they have no interest in developing this technology for ArcGIS.