Basic Principles Of Page Organization Of

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Basic Principles Of Page Organization Of
Memory
In the case of page memory organization, a logical address is also called a
linear or virtual address. Such addresses belong to one set (for example, a
32 bits non-negative number can be a linear address). Physical memory is
divided into blocks of fixed length - frames , or page blocks
( frames ). Logical memory, in turn, divided into blocks of the same length
- page . When the process starts, its pages are loaded into available physical
memory frames from disk or other media. The paging organization must
have hardware support. Each address generated by the processor is divided
into two parts: the page number and the page offset . The page number is
used as an index in the page table.
A page table is a data structure containing page - table entries ( PTE ), each
of which contains information about the page number, the number of the
corresponding physical memory frame (or directly it's the base address) and
access rights. The page number is used to find the item in the table. After
finding it, the page frame is added to the base address of the corresponding
frame, which determines the physical address.
Page size is a power of 2, modern OS uses pages ranging from 2 to 8 KB. In
custom addressing modes, you can work with larger pages. For each
process, they create their own page table. When the process begins to run,
the OS calculates its page size and the number of frames in physical
memory. Each page is uploaded to a corresponding frame, after which its
number is written to the process page table.
The process of memory mapping is different from the actual physical
memory state. At the logical level, all memory is represented by a

continuous block and belongs only to this process, and physically it is
spread over the address space of the memory chip, alternating with the
memory of other processes. The process cannot access memory whose
address is not specified in its page table (so memory protection is
implemented) .
The operating system must have information about the current state of
physical memory (frame occupancy, frame number, etc.). This information
is usually stored in a frame table . Each element corresponds to the frame
and contains all the information about it.

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