is used to indicate files, directories, commands and
program names when they appear in the body of a paragraph.
Constant Width
is used in examples to show the contents of
files or the output from commands, and to indicate
environment variables and keywords in the body of a
paragraph.
Constant Bold
is used in examples to show input that is typed
literally by the user.
[ ]
surrounds optional elements in a description of program syntax.
(The brackets themselves should never be typed.)