Stored Procedures in PostgreSQL

[admin]

I use postgreSQL 7.1, and need to implement a stored procedure with the purpose of running three insert statements to three seperate tables in a database, so that if one of the three don't run, the procedure would rollback to it's previous state (that is how I understand stored procedures work, correct me if I'm wrong). I have looked far and wide on the web for documentation on how I would do this in postgreSQL, and I have read that I would have to use functions to accomplish this.

Is this correct? How would I do this, to accomplish the goals above?

Thanks