[jerf]

Well... yes, but the modern sense of the term "OS" is somewhat different than what would apply to the Commodore 64. We tend to think of the OS as a management layer that tells its "processes" how many resources they can have and such, but on the Commodore 64, it's basically just a stream of assembler instructions. The distinction between "kernel" and "program" is all but nonexistent in modern terms. If you've got no use for the functions the kernel provides, then just unmap it and move merrily along.

[andyjohnson0]

Agreed. I'd say the onboard s/w was more like a simple version of what we now term a bios.

[digi_owl]

A very apt comparison.

And much like with the C64, the BIOS maintains a memory map.

http://wiki.osdev.org/Memory_Map_%28x86%29