ok - GCC, glibc, bash, binutils, coreutils. That is the GNU operating system.
i don't think that would be completely right. GNU is not a production ready operating system(yet). Only with a kernel like Linux, xBSD, etc... can you call it an operating system. Though it is said that when HURD is production ready, that entity can be called the GNU operating system.
Regards,
- vihan