Smalltalk

1
Smalltalk

• Mark Colangelo
• CMSC-631, Fall 2002
• 10 December 2002

2
History of Smalltalk

• Alan Kay designed and build the first OOP-based
  personal Computer called FLEX in 1967-68
• In 1967 Simula 67 was designed
• In 1972 Alan Kay and other and XEROX PARC Created
  Smalltalk 72 with roots tied to Simula 67
• Followed by Smalltalk 76 (Completely OOPL)
• Followed by Smalltalk 80 which became available
  as the first commercial release of Smalltalk

3
Smalltalk in the Real World

• Financial
• Chubb
• Chrysler
• Dunn and Bradstreet, several other
• Manufacturing and Engineering
• Texas Instruments
• Romax (Simulation Software)

4
Free Implemenations of Smalltalk

• Squeak (Smalltalk for Win , Mac and others)
• http//www.squeak.org/download/index.html
• GNU Smalltalk (Unix systems only)
• http//www.gnu.org/software/smalltalk/smalltalk.ht
  ml

5
Installation of Squeak

• Installation of Squeak is trivial
• Download zip file
• Squeak3.2.image
• Squeak3.2.changes
• SqueakV3.sources
• Squeak VM for your system, version 3.2
• Doubleclick Squeak image. No other installation
  is required

6
Squeak Install Files
7
Squeak Desktop
8
Hello World
9
Exending Hello World

• hello
• 1 to 3 do i (Transcript show 'Hello
  World') cr
• Gives
• Hello World
• Hello World
• Hello World

10
Adding Logic to Hello World

• hello times
• (times gt 100)
• ifTrue Transcript show 'You will get
  bored!' ifFalse 1 to times do i
  (Transcript show 'Hello World') cr

11
Final Hello World

• hello times say text
• (times gt 100)
• ifTrue Transcript show 'You will get
  bored!' ifFalse 1 to times do i
  (Transcript show text) cr

12
Syntax Observations

• Any variable can store any object. Object keeps
  track of what it is.
• Could pass an integer into the text parameter.
  No error until the Transcript tried to show it.

13
Messaging

• Always pass messages to an object
• the colon syntax for parameter passing looks a
  lot like the colon syntax for loops--and logic,
  for that matter. That's because it's exactly the
  same.
• hellosay, ifTrueifFalse and todo are all
  messages.

14
Blocks of Code are Objects

• i (Transcript show text) cr is an object
• Code block can be passed as an argument to todo
• Transcript is a global variable that contains an
  object which understands the show message.
• In addition to show, the Transcript object
  understands the message cr, which puts a newline
  in the Transcript window.

15
References

• Smalltalk home page
• www.smalltalk.org
• Squeak home page
• www.squeak.org
• Smalltalk Industry Council home page
• www.whysmalltalk.com