3 + 4 7  

30.45 + 22.5e7
 2.2500003e8  

'a string, don''t laugh!' 

#aSymbol
#aSymbol:composed:ofKeywords:   
#* #+       "also symbols" 

$a  "the character a

#(1 2 3)
 (1 2 3)   

#(foo bar 'and a string' 3 $a)
 (foo bar 'and a string' 3 $a)
                                                
#(a quoted thing inside)

undefinedfoo

"unary messages"
1 negated
  -1
Pen new home green
      (((Pen new) home) green)

"binary messages"
3 + 4
 7
5 - 4 * 2
 2

"keyword messages"
3 max: 2
3

(Array new: 5) at: 2 put: 3
 3
 
| i anArray  |
  anArray := Array new: 5.
  anArray at: 2 put: 3.
  i := 2.
  anArray at: i
          3

 nil  class   UndefinedObject
 nil isNil      true