I am wondering if anyone here knows where the source code for the Arduino "firmware" is available for reading? I think it must be more than the 'boot loader' but I am not sure. Thanks!

p.s. I assume this kind of question is ok here, even though it's not ok on StackOverflow?

I am wondering if anyone here knows where the source code for the Arduino "firmware" is available for reading? I think it must be more than the 'boot loader' but I am not sure.