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Smalltalk

Smalltalk. Aaron Bloomfield CS 415 Fall 2005. Evolution of Smalltalk. Alan Kay – grad student at Utah Dynabook Xerox PARC. Influenced by Lisp, Simula, Ivan Sutherland’s Sketchpad, LOGO, Dewey, Montessori, Piaget . Smalltalk. Interpreted Everything is an object

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Smalltalk

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  1. Smalltalk Aaron Bloomfield CS 415 Fall 2005

  2. Evolution of Smalltalk • Alan Kay – grad student at Utah • Dynabook • Xerox PARC. • Influenced by Lisp, Simula, Ivan Sutherland’s Sketchpad, LOGO, Dewey, Montessori, Piaget

  3. Smalltalk • Interpreted • Everything is an object • Dynamically & Strongly Typed • Rich programming environment • Window-oriented display management • Mouse, Menus • Example of a pure Object-Oriented Language

  4. Smalltalk and Squeak • Smalltalk – commercial product • Squeak – free version, used for education

  5. Bindings x <- 3 x <- x + 1 In Squeak, write <-as underscore OR := X is bound to 4

  6. Objects and Messages • Everything is an Object • Everything is done by sending messages to objects x * 2 • Sends the message *2 to the object x.

  7. Other Examples 3 + 2 * 5

  8. Inheritance • Superclass • Subclass • Object • Overriding • No multiple Inheritance

  9. Implementation • Mostly written in Smalltalk • Main loop: true whileTrue: [Display put: user run] Class - userTask run || Keyboard read eval print

  10. Virtual Machine • Storage Manager • Interpreter • Primitive Subroutines

  11. Storage Manager • Collects and manages free space • Handles requests to: • Create new objects • Fetch class of an object • Fetch and store fields of an object • Uses reference counting

  12. Concurrency • Easy to implement • Handy for simulations • Each activation record is a Smalltalk object sched map: [:Task | Task run]

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