This document provides an overview of Smalltalk in 3 sentences or less: Smalltalk is an object-oriented programming language where everything is an object that communicates through messages. It was developed in the 1970s and influenced many modern object-oriented languages. The document outlines Smalltalk concepts like classes, instances, and messaging and provides resources for learning more about the Smalltalk programming environment and language.

1. Smalltalk in a Nutshell
Oscar Nierstrasz
Software Composition Group
scg.unibe.ch

2. Roadmap
> Introduction
> Demo
> Exercises:
> Everything happens by sending messages
> Everything is an object
> Scripting with control constructs
> Objects are instances of classes
> Creating your own classes
> SOI 2008 sample problems
> SOI Workshop
© Oscar Nierstrasz 2

3. Programming is Modeling
Programs = Algorithms + Data
Programs = Objects + Messages
© Oscar Nierstrasz 3

4. The origins of Smalltalk
Alan Kay’s Dynabook project (1968)
Alto — Xerox PARC (1973)
© Oscar Nierstrasz 4

5. Object-oriented language genealogy
© Oscar Nierstrasz 5

6. Smalltalk-80 and Squeak
• Everything is an object
• Everything is there, all the time
• First windowing system with mouse
• First graphical IDE
Squeak: a modern,
portable, fast, open-
source Smalltalk
© Oscar Nierstrasz 6

7. Squeak resources
www.squeak.org www.seaside.st
Downloads and links One-click image
SqueakByExample.org
Free download — Print-on-demand
© Oscar Nierstrasz 7

8. Don’t panic!
New Smalltalkers often think they need to
understand all the details of a thing before they
can use it.
Try to answer the question “How does this work?”
with “I don’t care”.
—Alan Knight. Smalltalk Guru
© Oscar Nierstrasz 8

9. Everything is an object
Public interface
Private data
Everything happens by
exchanging messages
© Oscar Nierstrasz 9

10. Smalltalk architecture
Image
Virtual machine
+ +
Changes Sources
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11. Three-button mouse
Operate
Select
Window
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12. World Menu and Open Menu
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13. Three kinds of messages
> Unary messages 5 factorial
Transcript cr
> Binary messages 3 + 4
> Keyword messages
3 raisedTo: 10 modulo: 5
Transcript show: 'hello world'
© Oscar Nierstrasz 13

14. Precedence
First unary, then binary, then keyword:
2 raisedTo: 1 + 3 factorial 128
Use parentheses to force order:
1 + 2 * 3 9 (!)
1 + (2 * 3) 7
© Oscar Nierstrasz 14

15. A typical method in the class Point
Method name Argument Comment
<= aPoint
quot;Answer whether the receiver is neither
below nor to the right of aPoint.quot;
^ x <= aPoint x and: [y <= aPoint y]
Return Binary message Block
Instance variable Keyword message
(2@3) <= (5@6) true
© Oscar Nierstrasz 15

16. Statements and cascades
Temporary variables
Statement
| p pen |
p := 100@100.
pen := Pen new.
pen up.
pen goto: p; down; goto: p+p
Cascade
© Oscar Nierstrasz 16

17. One-click download
scg.unibe.ch/Teaching/ICUB
© Oscar Nierstrasz 17

18. License
> http://creativecommons.org/licenses/by-sa/3.0/
Attribution-ShareAlike 3.0 Unported
You are free:
to Share — to copy, distribute and transmit the work
to Remix — to adapt the work
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Any of the above conditions can be waived if you get permission from the copyright holder.
Nothing in this license impairs or restricts the author's moral rights.
© Oscar Nierstrasz 18