An error message returns a reference to "RDB$INDEX_2"

Are IB indeces zero based, i.e., the above message
refers to the 3rd index or does it refer to the
actual 2nd index.

...and what criteria are used to base other types
of count/index values?

As a Delphi programmer, I find it confusing to try
to remember which values are zero based and which
are one based.

I think IB is in 'C,' so are they all zero based?