This directory contains source code for the GNU Project's C
preprocessor.  

Unlike this preprocessor, the compilers bundled with some systems have
arbitrary limits on the number of significant characters in
identifiers which make them unable to compile GNU Emacs.  The Emacs
build process tries to detect when it is running on such a system; if
it is, it builds this C preprocessor, and then uses it to edit the
Emacs source code into a form that the system's compiler can handle.
