A list is any sequences of objects, such as symbols, numbers, or other lists, enclosed by parenthesis.   Much of the power and beauty of Lisp is derived from the fact that even a program is because even functions and programs are themselves lists.
 
 Something that is not a list may be generally classified as either a self-evaluating form or a symbol.  A self-evaluating form is a form, such as a number, which evaluates to itself.   A symbol is a variable which has an associated value.
 
 

 The single quote in front of a list is an abbreviation for the function quote, which returns its argument identically.   For example (where user input is blue, interpreter response underneath is black,  and comments are red):
> (quote  45)
45

> (quote "testing quote")
"testing quote"

> '(+ 1 2 3 (/ 4 5)))   ;; it does not evaluate the arithematic operations
(+ 1 2 3  (/ 4 5))

> '(a4  b4  c4)            ;; Lisp is case-insensitive.  It converts all symbols to upper case.
(A4  B4  C4)
 
 
 
 The  function setf sets the named variable to the value of the object that follows.
> (setf  zebra  '(stripes white black))
(STRIPES  WHITE   BLACK)

>zebra
(STRIPES  WHITE  BLACK)

>(setf sum (+ 8   9  10))
27

;; note that performing an operation using sum does not change the value of sum.
> (+  sum  10)
37
> sum
27
;; to destructively add 10 to the value stored in sum, you would have to type:
> (setf  sum  (+ sum  10))
37

;; you can assign multiple values using setf by listing pairs of variable names and values:
> (setf   variable1   'value1   variable2   'value2   variable3  'value3)   ;; it prints the last value assigned
VALUE3
> variable2
VALUE2