C and C++ have never been independent of architecture. Especially C. C implementations have always had differences in matters such as word length, whether characters are signed or unsigned, whether "int" and "long" are the same type, which end of a byte that a bitfield starts packing from, and other issues.
Standard C by itself does not give device access. Standard C only supports buffered I/O such as fread() and fwrite(). These are, of course, inadequate for low-level control of devices such as you would like to do. The result of type-punning an integer into a pointer in order to point to an absolute address to do I/O is a common extension to C but is not part of C (and seldom works on systems that implement virtual memory.)
