Pharo is an open source, cross-platform implementation of the classic Smalltalk-80 programming language and runtime.^[3] It is based on the OpenSmalltalk virtual machine called Cog (VM), ^{[4][5][6][7]: 16} which evaluates a dynamic, reflective, and object-oriented programming language with a syntax closely resembling Smalltalk-80.

Quick Facts Paradigm, Developer ...

Pharo

Paradigm	Object-oriented
Developer	Pharo community
First appeared	2008; 16 years ago (2008)
Stable release	11.0.0[1]  / 11 May 2023; 11 months ago (11 May 2023)
Typing discipline	Dynamic
Implementation language	Smalltalk
OS	Windows, Linux, macOS, others
License	MIT license, partly Apache License 2.0[2]
Website	pharo.org
Influenced by
Smalltalk (Squeak)

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Pharo is shipped with source code compiled into a system image that contains all software necessary to run Pharo.^[7]: 16 Like the original Smalltalk-80, Pharo provides several live programming features such as immediate object manipulation, live updates, and just-in-time compilation. The image includes an IDE-like software to modify its components.

Pharo was forked from Squeak v3.9 in March of 2008.^{[8][3][7][7]: 10 [9]}

Pharo is a pure object-oriented dynamically typed and reflective language. The stated goal of Pharo is to revisit Smalltalk design and enhance it.

The name Pharo comes from the French word "phare" (French pronunciation: [faʁ]) which means lighthouse. This is why the Pharo logo shows a drawing of a lighthouse inside the final letter O of the name.

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.^[how?]

The Pharo syntax is based on Smalltalk-80 language syntax with several extensions. Some of these are common among modern Smalltalk dialects.

• literals for dynamic arrays. The expressions that specify the array content are evaluated in time of the program execution

{1. 2. 1+2}

• literals for byte arrays that can be composed only of integer numbers in the range from 0 to 255

#[1 2 3 4]

• literals for scaled decimals, a representation of fixed point decimal numbers able to accurately represent decimal fractions

3.14s2

• pragmas. In Smalltalk-80 the pragmas are used only for primitive methods. In Pharo they are fully capable method annotations

<gtInspectorPresentationOrder: 30>

• two double quotes inside a comment are interpreted as a single double quotes character that is part of the content of the comment

The Pharo language syntax is supposed to be very simple and minimalistic. The basic language elements are often presented on a single 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 serialization format.

Pharo emerged as a fork of Squeak, an open-source Smalltalk environment created by the 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.^{[citation needed]} Pharo is supported by the Pharo consortium (for legal entities) and the Pharo association for physical persons .

Pharo relies on a virtual machine that is written almost entirely in Smalltalk itself. Beginning in 2008, a new virtual machine (Cog) for Squeak, Pharo and Newspeak has been developed that has a level of performance close to the fastest Smalltalk virtual machine.^[31] 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.^[32]

• Amber Smalltalk
• GNU Smalltalk
• Squeak
• VisualWorks