>In the C language there were separate logical and bitwise AND, OR and NOT operators -- getting them confused would usually result in confusing results.
>
>Of course the potentially confusing thing about BIT would be that if truly implemented as a single-bit value, there can only be 0 or 1 values. However if you want to have NULL values, then it can't actually bit a single bit in implementation.

In VFP dbfs there's a hidden bitmapped field, in tables with at least one nullable field, which contain a 1 for every null in the fields, so technically the bit field is still as it was, but there's an extra bit outside, set when it's null. I guess other databases apply a similar scheme.