GNU C Compiler is one of the compilers of GNU Compiler collection and was released by Free Software Foundation. GNU C Compiler is a totally *nix oriented compiler for C language which can be operated through commands from its command line interface.
This compiler comes by default with most *nix based operating systems, so if you have installed and/or using Unix or Linux based operating system, in your system, then you can find and use it easily.
For compiling your source code using GNU C compiler, you need to write like this:
GCC, which was originally abbreviated as GNU C Compiler, because before 1987, there was only one compiler provided by GNU, and that was C compiler, but after 1987, it extended its compilers and language support and hence formed a package, which is now abbreviated as GNU Compiler Collection (GCC). The recent publishing of GCC supports C++17, and this support started in 2017.