The second step to participating in Parrot development is to get a copy of the source code. If you just want to try it out--experiment with a few features and see how it feels--the best option is to download the most recent point release for your system. Point releases are usually packaged up for easy download and install for various platforms, including Windows, Debian, and Redhat. Point releases are available from http://www.parrot.org/download.
If you plan to get involved in development, you'll want to check out the source from the git repository directly. Anyone can get anonymous access to read the files and download a working copy to explore and test. For commit access, volunteers need a https://github.com username, and need to be approved by a Metacommitter. To download the most recent version from git, type this command into your terminal This is for Linux users, on Mac or Windows systems, follow the instructions from your git client:
git clone http://github.com/parrot/parrot
There's also a web interface for viewing files in the repository at the same link.
The repository is large and complex, so it's worth taking a little bit of time to explore. The code changes constantly, but most files and functions have informative descriptions to help keep track of things.
The most important top-level directory is docs/. The content isn't always up to date, but it is a good place to start. parrot.pod provides a quick overview of what's in each documentation file. If you're a capable writer and know a thing or two about how Parrot works, the documentation is a great place to start contributing. This book that you're reading right now was created in docs/book/ by ordinary contributors. Most other documentation files found here are parsed and converted to HTML for display at http://www.parrot.org.
There are a number of existing language implementations for Parrot: Perl 6, Python ("Pynie"), Ruby ("Cardinal"), PHP ("Pipp"), Lisp, Lua, Tcl ("partcl"), WMLScript, Forth, Scheme, Befunge, BASIC, and many others. These language compilers are in various stages of partial completion. The page https://github.com/parrot/parrot/wiki/Languages provides meta information on these languages and where to find them. If you have a language you're particularly interested to see implemented on Parrot, you can see how far along the effort is, or you can start the work to implement it yourself. We'll talk more about creating new compilers in Chapter 10: High-Level Languages, if you're interested.
The lib/ directory contains Perl 5 classes currently used in developing, building, and testing Parrot. The src/pmc/ directory contains the C source code for Parrot classes (PMCs, which you'll read more about in Chapter 11).
Most Parrot development happens in src/ for the C source code, and include/parrot/ for the C development header files.
Libraries for use by programs running on Parrot are found in runtime/.
The examples/ directory contains some example Parrot PIR and Assembly code, as well as benchmarks. More discussions about these topics will be found in Chapter 3, Chapter 5, and Chapter 7 respectively.