@3246251196
Another commonly used C compiler on the classics is
VBCC. It is a free download but you'll need the Amiga Developer CD (preferably v2.1) for the programming documentation unless you happen to have the Rom Kernal Reference Manuals around. You'll also need the Developer CD if you decide to use GCC.
Furthermore you're A1200 will likely need some extra expansion (such as an IDE splitter) to get a CD-ROM drive to work with your A1200 when it comes.