Cog is an evolution of the Squeak Back-to-the-future Smalltalk virtual
machine that provides a number of different Smalltalk virtual
machines. The VMs are developed in Smalltalk, using all the dynamic
and reflective facilities of the Squeak/Pharo Smalltalk system. As
such, developing in Cog is a delight. The Smalltalk framework
comprising the various Cog VMs is translated into C by its Slang
component to produce VM source that is combined with platform-specific
support sources and compiled via a C compiler to obtain a fast
production VM. This directory tree includes the output of Slang for
various configurations of "Cog VM" and the associated platform support
code, plus build directories that can be used to produce production
VMs.