The basic rules of the command tree are as follows.
Letter case (upper and lower) is ignored.
For example,
FUNCTION: IMPEDANCE=
function:impedance
Spaces (_ used to indicate a space) must not be
placed before and/or after the colon (:).
For example,
func_:_imp func:imp
The command can be completely spelled out or in
abbreviated form. (The rules for command
abbreviation are described later in this section)
For example,
function: impedance =func:imp