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Overview
Squeak is a modern implementation of Smalltalk-80 that is available for free via the Internet, at (http://www.research.apple.com/research/proj/learning_concepts/squeak/) and other sites.
It includes platform-independent support for color, sound, and image processing. Originally developed on the Macintosh, members of its user community have since ported it to numerous platforms including Windows 95 and NT, Windows CE, all common flavors of UNIX, and the Acorn.
Squeak stands alone as a practical Smalltalk in which a researcher, professor, or motivated student can examine source code for every part of the system, including graphics primitives and the virtual machine itself, and make changes immediately and without needing to see or deal with any language other than Smalltalk. It also runs bit-identical images across its wide portability base. Three strands weave through this paper:
- the design of the Squeak virtual machine, which differs in several interesting ways from the implementation presented in the Smalltalk "Blue Book" [Gold83] and explored in the "Green Book" [Kras83];
- an implementation strategy based on writing the Squeak virtual machine in Smalltalk and translating it into C, using an existing Smalltalk for bootstrapping until Squeak was able to debug and generate its own virtual machine; and
- the incremental development process through which Squeak was created and evolved over the course of a year.
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