Program binaries in many systems are typically structured as follows.Code's stored starting with a small fixed virtual address such as 0.What is the significance of that structured on the pure paging?

Answer 1

Question: Program binaries in many systems are typically structured as follows.

Code is stored starting with a small fixed virtual address such as 0. The

code segment is followed by the data segment that is used for storing

the program variables. When the program starts executing, the stack is

allocated at the other end of the virtual address space and is allowed to

grow towards lower virtual addresses. What is the significance of the

above structure on the following schemes:

a. contiguous-memory allocation

b. pure segmentation

c. pure paging

Answer: 1) Contiguous-memory allocation requires the operating system

to allocate the entire extent of the virtual address space to the program

when it starts executing. This could bemuch higher than the actual

memory requirements of the process. 2) Pure segmentation gives the

operating system flexibility to assign a small extent to each segment at

program startup time and extend the segment if required. 3) Pure paging

does not require the operating system to allocate themaximum extent of

the virtual address space to a process at startup time, but it still requires

the operating system to allocate a large page table spanning all of the

program's virtual address space. When a program needs to extend the

stack or the heap, it needs to allocate a new page but the corresponding

page table entry is preallocated.