Clarified the methods used to set the state of a checkbox.

Added "Querying Button Matrices" plus a example of programmatically creating a matrix of radio buttons. Also removed "Deprecated Buttons" from "Types of Buttons".

Renamed "Using Switch Buttons" to "Using Checkboxes."

Made a small change in the organization of information. Changed title from "Buttons."

Moved information on making a button the default into a separate article.

Fixed typos.

Removed obsolete references to mnemonics.

Revision history was added to existing topic. It will be used to record changes to the content of the topic.