[2 As we shall see in the following chapters the 3 GB linear address space is an upper limit but a User Mode process is allowed to reference only a subset of it

Let's start with the 10 most significant bits of the linear addresses assigned to the process, which are interpreted as the Directory field by the paging unit. The addresses start with a 2 followed by zeros, so the 10 bits all have the same value, namely 0x08 0 or 128 decimal. Thus the Directory field in all the addresses refers to the 129th entry of the process Page Directory. The corresponding entry must contain the physical address of the Page Table assigned to the process (see Figure 2-8). If no other linear addresses are assigned to the process, all the remaining 1,023 entries of the Page Directory are filled with zeros.

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