The 'or' special form evaluates a sequence of expressions and returns the
effect of a logical 'inclusive-or' operation on the expressions. If all of
the expressions are 
(or NIL NIL NIL)                    ; returns NIL
(or NIL T NIL)                      ; returns T
(or NIL (princ "hi") (princ "ho"))  ; prints  hi  and returns "hi"
(or T T T)                          ; returns T
(or)                                ; returns NIL
(setq a 5)  (setq b 6)              ; set up A and B
(if (or (< a b) (< b a))            ; if
   (print "not equal")              ;   then
   (print "equal"))                 ;   else
                                    ; prints  "not equal"
See the
or
special form in the