Squeak

Squeak is an open- source implementation of the Smalltalk programming language along with the usual for that language development environment. It was developed by a working group at Apple Computer, which included some of the original Smalltalk-80 developers like Alan Kay, Dan Ingalls et al. This group continued this development continues at Walt Disney Imagineering, where Squeak should be used for internal projects. Squeak is now developed by a global independent community, with the building on Squeak 3-dimensional multi- user environment Croquet is an important branch of this development, which is supported by the original Smalltalk-80 developers, renowned scientific institutions and IT companies. Since 2009, the development now in Open Cobalt project will be continued.

Squeak allows computer simulations which children can develop and carry out yourself. The development of Squeak was funded partly by the company " Walt Disney Imageneering " because Squeak should be a tool among others to help preschoolers learn. It was expressly not to bring children early experience technology.

An advantage is the rapid and constant reprogramming and improvement of existing. In addition, Squeak does not require abstract programming but can be controlled by simple graphical options. The graphical user interface is, in Squeak Morphic.

E -Toys

Squeak was extended especially by Alan Kay to be usable by children. This part of Squeak he calls E- Toys.

The example of a car simulation input to E toys to be illustrated below: First, the child creates a graphical object, such as a car. Thereafter drawing a further object, such as a colored line. Finally, only the corresponding logical condition have yet to be set, so the car starts itself up on this color road. After entering the conditions the child can then start and see what the results bring forth its logical instructions the simulation. By trial-and- error method children are enabled to perceive logical relationships between statement and response figuratively and thus directly.

The simulation created can be stored in the Smalltalk language then also. The written programs are conveniently grouped in folders (called the changeset ) to allow easy replacement of the developed simulations of the children themselves.

100 dollar laptop

Squeak is available within the project " 100 dollar laptop " on the student laptops. The student laptops will thereby be provided with a basic package of so-called eToys in order to give the students from the beginning to the age-appropriate introduction to logical thinking and computer programming can. For the student laptop Squeak was relizenziert under the free Apache license.

History

The design of Squeak largely follows the books by Adele Goldberg and David Robson (known as the Blue Book) and Glen Krasner ( Green Book). There, the Smalltalk programming environment is defined, with some variations, such as an additional different syntax, provides Squeak.

The plan to develop Squeak, was established in December 1995. This software should be developed, the user can teach without requiring much prior knowledge.

Squeak was first published in September 1996 as the first free Smalltalk. Dan Ingalls, Ted Kaehler, John Maloney, Scott Wallace, Alan Kay and write in that they felt that here was successful, which failed in 1980. Three weeks later, the first UNIX port of Ian Piumerta was published. To date (March 2010) it is continually evolving. The most important development in this period is the modularization of the code parts have been that solves some of the problems that arise from the exchange of programs by changesets.

The functionally equivalent to version 3.10.2 Version 4.0 has long been prepared, the step completed for licensing under the MIT license, with parts remained under the Apache License 2.0. Previously own -Apple license was used. During the Relizenzierungsprozesses made ​​further developments of the software have been integrated into version 4.1.

Construction

This was based on the Apple Smalltalk-80 implementation, which was, however, over long distances from 68020 assembler which was not portable. To achieve portability, we used the C programming language, which was indeed appreciated by the authors because of the portability that one but still not fond of. That's why they built first a translator who SMACC was called who could translate a subset of Smalltalk code into C code, so you could enjoy the portability of C code without having to write the language.

This structure allows the once with a C compiler translated and executed code to interpret itself, which facilitates the search for errors in the interpreter.

Memory management is very complex in favor of the effectiveness, as emphasis was placed on ensuring that an integer variable should only occupy 32 bits in memory. Also for other object classes special rules have been introduced to reduce the memory consumption. It must therefore be checked for each object only once, whether it is an integer or any other object, for which a bit is used each reference. Therefore, Squeak can be only integers up to 31 bits calculated as real integers from the processor.