What is an input mask? What can an input mask do for you?

What is a regular expression? What can you use it for?

What is a validator? What is it used for?

Describe three different kinds of validators.

What is a regular expression meta-character? There are four kinds of metacharacters: quantifier, character set, group, and anchor. Give examples of each type and explain what they mean.

Why would you want to extend QValidator?