Memory organization is one of the most important aspects of CPU design. The first thing to note is that when we say "memory organization", we do not mean its physical layout on memory chips/boards. For us, it is much more important how the CPU sees memory and how it communicates with it (on a higher level, of course, as we are not going to dive into the hardware aspects of the architecture).
However, as the book is dedicated to application programming, rather than operating system development, we will further consider the most relevant aspects of memory organization and access in this section.