A units expression is a unit name, such as
a number such as
2.5, a product of two or more unit expressions
(* expr1 ... exprn),
or a quotient of two unit expressions
(/ expr1 expr2).
Common abbreviations such as
ft are allowed.
An example is
(/ (* atto parsec) (* micro fortnight)).
When the program is started, a window is created containing a command menu and input and output areas. Click the appropriate menu items to run the demo.