It’s well worth your time to learn more about Oracle’s data dictionary views. Anything you want to know about the structure of your database and the objects within it can be found by querying the appropriate view. The definitive reference for these views is the Oracle8 Server Reference manual. However, if you don’t have that manual close by, you can get a quick list of useful views by executing the following query:

SELECT *
  FROM dictionary
ORDER BY table_name;

Use the DESCRIBE command on any views of interest. The column names tend to be reasonably self-explanatory.