Vocabulary - Jobs

Are you able to describe each of these jobs?

Author
Waiter
Singer
Operator
Delivery boy
Sales assistant
Traffic warden
Architect
Doctor
Air-traffic controller
Cashier
Computer programmer
Bank teller
Vet
Artist
Graphic designer
Account
Car salesman
Teacher
Chemical engineer

Go through these exercises:
http://www.englishmedialab.com/cloze/jobs/index.html
http://www.englishmedialab.com/crosswords/what%20will%20you%20be/index.html
http://www.englishexercises.org/makeagame/viewgame.asp?id=6062