The computer handling incoming email messages is known as the ____________________ email server.

Many web browsers include _____ tools to make it easier for designers to locate the source of a style that has been applied to a specific page element.?

A. ?designer B. ?planner C. ?developer D. ?creator

Write a program called valid that prints yes if its argument is a legal shell variable name and no otherwise:

$ valid foo_bar yes $ valid 123 no