Dropping Fields In A Table

Thanks for the response to the last question, and also please let me know if
these questions are going to the right group, you all seem alot better than
these questions.

In what version of Postgre are you able to drop fields in a table (7.1?),
and is this the correct syntax:
ALTER TABLE tablename DROP COLUMN columnname;

And is their a way to change the type of column that a column is for
instance from CHAR to INT, and what is the syntax for that.  I looked up one
side of the documentation and down the other and their does not seem to be a
way.

Thanks again.