When a new process is created (details in Chapter 10, Process Creation), its VAS must be set up by the OS. All modern OSes divide up the process VAS into homogeneous regions called segments (don't confuse these segments with the hardware-segmentation approach mentioned in the, Addressing 2 – paging in brief section).
A segment is a homogeneous or uniform region of the process VAS; it consists of virtual pages. The segment has attributes, such as start and end addresses, protections (RWX/none), and mapping types. The key point for now: all pages belonging to a segment share the same attributes.
Technically, and more accurately from the OS viewpoint, the segment is called a mapping.
From now on, when we use the word segment, ...
