The question mark "?" is used as a format modifier in order to signify that a
help string is supplied. By default, the help string is displayed at the bottom
of the window. The help string is either surrounded by square brackets, or an
"@" character is placed in the format string to indicate that the help string
is supplied as an extra argument. In addition to "?", %bh, %th and %he are used
to change the manner in which a help string is presented.