Gary,
You'll probably need the Equates for the assembler, as well as a linker, and
perhaps libraries as well. EQU.ARC, EQUATE.ARC and SMALLI.ARC will probably
get you started with the assembler, and there is a linker here, BLINK67.ARC,
that is the early version of BLINK.
For the C, however, you're going to need the header files. Both they, and
the libraries, may be purchased from Commodore for about $40. They are NOT
public domain, and Commodore retains copyright to them.
Your best course of action is to purchase a commercial compiler. It is
expensive, but you have the comfort of knowing that (almost) any bugs are your
code, and you don't have to worry about the compiler itself. C on the Amiga is
a bit difficult at first, as there are many new concepts introduced by the
system itself. However, it is worth the effort to learn as the rewards for
that effort are great.
Doug