Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Squeak programming language is a Smalltalk implementation, derived directly from Smalltalk-80 by a group at Apple Computer that included some of the original Smalltalk-80 developers. Its development was continued by the same group at Walt Disney Imagineering, where it was intended for use in internal Disney projects. Some Squeak users refer to Squeak as a programming language rather than as a Smalltalk implementation. It is object-oriented, class-based, and reflective. Squeak is available for many platforms, and programs produced on one platform run bit-identical on all other platforms. The Squeak system includes code for generating a new version of the virtual machine (VM) on which it runs. It also includes a VM simulator written in itself (Squeak). For this reason, it is easily ported.