2.1 Memory Organization and Segmentation

The physical memory of an 80386 system is organized as a sequence of 8-bit
bytes. Each byte is assigned a unique address that ranges from zero to a
maximum of 232-1 (4 gigabytes).
80386 programs, however, are independent of the physical address space.
This means that programs can be written without knowledge of how much
physical memory is available and without knowledge of exactly where in
physical memory the instructions and data are located.
The model of memory organization seen by applications programmers is
determined by systems-software designers. The architecture of the 80386
gives designers the freedom to choose a model for each task. The model of
memory organization can range between the following extremes:

80386系统的物理内存是由一串8位字节组织的。每个字节分配一系列同意的地址从0到4g

尽管如此 80386的程序是不依赖物理内存地址的。这就意味这其实处理器程序是不需要知道到底

有多少内存还有指令和数据到底在哪。

由应用程序看来内存的组织模式是由系统软件设计者决定的。80386架构让设计者可以自由选择每个任务

的模式。
● A "flat" address space consisting of a single array of up to 4
gigabytes.

● A segmented address space consisting of a collection of up to 16,383
linear address spaces of up to 4 gigabytes each.
Both models can provide memory protection. Different tasks may employ
different models of memory organization. The criteria that designers use to
determine a memory organization model and the means that systems programmers
use to implement that model are covered in Part II──Systems Programming.