HyperC is a new variant of C, released under the Gnu public license by Hyperon Software. The User's Guide (PDF) may be viewed online, and the source code (tar.gz) may be downloaded.
The HyperC compiler is an add-on to the gcc-4.1.1 compiler, which must be downloaded in source form from http://gcc.gnu.org or a mirror site. The file needed is gcc-4.1.1.tar.bz2. One location, at one point in time anyway, is ftp://mirrors.kernel.org/gnu/gcc/gcc-4.1.1/gcc-4.1.1.tar.bz2