This file contains an overview of the Plus/4 runtime system as it comes with the cc65 C compiler. It describes the memory layout, Plus/4 specific header files, available drivers, and any pitfalls specific to that platform.
Please note that Plus/4 specific functions are just mentioned here, they are described in detail in the separate function reference. Even functions marked as "platform dependent" may be available on more than one platform. Please see the function reference for more information.
Since the Plus/4 and the Commodore 16/116 are almost identical (the latter are missing the 6551 ACIA and do only have 16KB of memory), the C16 documentation is also worth a look. The difference between both cc65 targets is that the Plus/4 runtime uses banking to support full 64K RAM, while the C16 does not use banking and supports up to 32K RAM. Because banking is not needed, most C16 programs will be somewhat smaller than the same program compiled for the Plus/4. However, programs compiled for the C16 will always run on the Plus/4, while the reverse is not necessarily true.