Pharo is a cross-platform implementation of the classic Smalltalk-80 programming language and runtime system. It is based on the OpenSmalltalk virtual machine (VM) named Cog,16 which evaluates a dynamic, reflective, and object-oriented programming language with a syntax closely resembling Smalltalk-80. It is free and open-source software, released under a mix of MIT, and Apache 2 licenses.
Pharo is shipped with source code compiled into a "system image" that contains all software needed to run Pharo.16 Like the original Smalltalk-80, Pharo provides several live programming features such as immediate object manipulation, live updates, and just-in-time compilation (JIT). The system image includes an integrated development environment (IDE) to modify its components.
Pharo was forked from Squeak v3.9 in March of 2008.10
Overview.
Pharo is a pure object-oriented, dynamically typed, and reflective language. The stated project goal is to revisit Smalltalk design and enhance it.
The name Pharo comes from the French word "phare" () which means lighthouse. This is why the Pharo logo shows a drawing of a lighthouse inside the final letter "O" of the name.
Relation to Smalltalk.
Pharo is based on general concepts of Smalltalk but seeks to improve on them, so does not limit itself to them. The basic syntax of the language has a close resemblance to Smalltalk. However, the way classes are defined in Pharo differs from other Smalltalk dialects.
Language syntax.
The Pharo syntax is based on Smalltalk-80 language syntax with several extensions. Some of these are common among modern Smalltalk dialects.
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The Pharo language syntax is supposed to be very simple and minimalist. The basic language elements are often presented on one postcard as a showcase for the language's brevity. The grammar is classified as LL(1).
The language grammar does not specify directly how the code should be stored in files. Pharo uses Tonel as the preferred code serializing format.
History.
Pharo emerged as a fork of Squeak, an open-source Smalltalk environment created by the original Smalltalk-80 team (Dan Ingalls and Alan Kay). Pharo was created by S. Ducasse and M. Denker in March 2008. It focuses on modern software engineering and development techniques. Pharo is supported by the Pharo consortium (for legal entities) and the Pharo association for physical persons .
Use of Pharo.
Companies and consultants.
Some companies use Pharo for their development projects. In particular, they use:
The Pharo consortium was created for companies wishing to support the Pharo project. The Pharo association was created in 2011 for users wishing to support the project.
Performance and virtual machine (VM).
Pharo relies on a virtual machine that is written almost entirely in Smalltalk. Beginning in 2008, a new virtual machine (Cog) for Squeak, Pharo and Newspeak has been developed that performs nearly as well as the fastest Smalltalk virtual machine. In 2014/2015 the VM community is working on Spur, a new Memory Manager for Cog that should again increase performance and provide better 64-bit VM support.
References.
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