There are special folders for installing libraries, externals, objectclasses, abstractions, GUI plugins, and help files into. These folders are for things that are not included in Pd itself, and they are separate from Pd so that you can upgrade Pd without messing up your other files.

On all platforms, there is a user-specific folder and a global folder:

GNU/Linux

User-specific

~/pd-externals

Global

/usr/local/lib/pd-externals

Mac OS X

User-specific

~/Library/Pd

Global

/Library/Pd

Windows

User-specific

%AppData%\Pd

• %AppData%\Pd will be something like C:\Documents and Settings\myusername\Application Data\Pd
• this is mostly synonymous with %UserProfile%\Application Data\Pd
• %UserProfile% is your home folder, on an English system, it is usually C:\Documents and Settings\myusername

Global

%CommonProgramFiles%\Pd

• on an English system, this is usually C:\Program Files\Common Files\Pd
• en español: \Archivos de programa\Archivos comunes\Pd
• auf Deutsch: \Programme\Gemeinsame Dateien\Pd
• this is mostly synonymous for %ProgramFiles%\Common Files\Pd (%ProgramFiles% is where your programs are installed)

Other versions of Pd

This was included in Pd-vanilla in version 0.43, and in Pd-extended in version 0.41.

Discussion

These choices of directories has been discussed quite a bit. If you are interested in reading about how they were chosen, then read the:

http://lists.puredata.info/pipermail/pd-list/2008-06/063086.html

http://lists.puredata.info/pipermail/pd-list/2008-07/063769.html (?)

http://lists.puredata.info/pipermail/pd-dev/2009-04/013302.html (?)

Discussion (Linux specific)

Here are some references to discussion about storing architecture-dependent binaries somewhere in $HOME.

http://lists.freedesktop.org/archives/xdg/2009-June/010716.html (nicknaming architecture/OS)

http://lists.freedesktop.org/archives/xdg/2008-November/010010.html (.local/share, .local/lib, $HOME/lib, or what?)

http://lists.freedesktop.org/archives/xdg/2007-November/009029.html (All binaries should go to either $prefix/bin or $prefix/lib{,64} - these are the only directories guaranteed to be mounted with exec rights and not shared across different architectures (as is sometimes done for /$prefix/share))

http://lists.freedesktop.org/archives/xdg/2007-November/009030.html (If the plugins are dlopened objects, my opinion is that they are right in a subdir of $prefix/lib{,64})