The base library is the scripts and other files installed under the system subdirectory. These are primarily required for the development system, but for historical reasons also contain examples and other non-essential files. Subdirectories of system are:
main - main scripts needed for J applications
packages - supporting packages, e.g. Files, Printing
classes - class definitions. e.g. Grid, Plot
extras - utilities for the development system, but not required for applications
examples - various examples
Migration To Addons
Some non-essential scripts in J602 are being migrated to the Addons, see Migration To Addons.