Check for table existence

Hi group

First, let me say that I am new to postgres. I used MySQL before, but..
ehm..

I am trying to do a small program (in C), and I have stumbled on to some
problems:
1. How can I check if a given table exists?2. How can I check if a given existing table has the right layout? (Correct
column names and types)

Currently, I check using something like:
select * from giventable limit 0;

but that only helps checking if the table exists and if the number of
columns is correct. I'm sure, there must be a smoother way to do this, but I
cannot seem to find it. Anyone out there with good ideas?

M.
-- 
Rumour is information distilled so finely that it can filter through
anything.
-- (Terry Pratchett, Feet of Clay)