> So if I look at the var_data section I should see
> <tag> = Type of data to follow. Is this a byte in size ? Also, what are
> the values I can expect and their meanings please.
> <length> = Word ?
> <value> = Pretty obvios

From www.ibphoenix.com download GLINK utility which comes with C source code.
Look at procedure show_db_header().
Or if you want more code to study, download IB/FB source ...

Ivan
http://www.volny.cz/iprenosil/interbase