We can distinguish between systems that contain:
A single processor containing a single core.
A multi-core processor, such as the Cortex-A53, with several cores capable of independent instruction execution, and can be externally viewed as a single unit or cluster, either by the system designer or by an operating system that can abstract the underlying resources from the application layer.
Multiple clusters (such as that shown in Figure 14.1), in which each cluster contains multiple cores.
The descriptions of multi-processing systems which follow define terms as they are used in this book. On other operating systems they may have different meanings.