how to get the field types of a(n empty) table?

Hello,

is there a possibility to get the field types of an empty table?

I made a class for editing tables in a html form. The data is inserted
or updated by something like

  "update $table set $row='$DATA'::$ftype[$row] where oid=$oid"

The type of the fields is gotten by a "select $rows from $table limit
1" -- but this is only possible, if there is at least one row inside a
table (for an "insert", "update" is no problem, of course).

It should be possible by reading something out of the postgres' system
tables, but I didn't found it.

Thank in advance,
Knut Sübert