Welcome developers! You have come to the right place to get a comprehensive concise guide that explains paging and how to convert logical addresses to physical addresses.
Logical addresses refer to the addresses seen by the user whereas physical addresses are the addresses seen by the main memory. Logical addresses are generated in the CPU while physical addresses are seen by the main memory. Virtual memory is used to translate logical addresses to physical addresses. This is what paging is all about. Paging allows us to divide the physical memory into pages and then divide the logical memory into page frames of equal size. This way, a portion of physical memory or page is mapped to each page frame. This mapping is done with the help of page tables.
Now let us find out how to convert a logical address to physical address:
Step 1: Obtaining the Page Number
The translation of the logical address to physical address requires two components: the Page Number (PN) and Page Offset (PO). The PN is obtained by dividing the logical address by the size of the page frame size. This can be done using the following formula:
PN = Logical Address/Page Frame Size
Step 2: Obtaining the Page Offset
Once the page number has been obtained, the page offset can be calculated by obtaining the remainder of the logical address divided by the page size as follows:
PO = Logical Address % Page Frame Size
Step 3: Using Page Tables
Once the page number and page offset have been obtained, the user will then have to access the page table. The page table contains the details of all the page frames and it can be used to look up the page number to determine the physical address. The physical address will then consist of the page frame number and the page offset calculated in the above steps.
Physical Address = Page Frame Number + Page Offset
FAQ
What is paging?
Paging is a method of mapping the logical memory to physical memory. It allows us to divide the physical memory into pages and then divide the logical memory into page frames of equal size. This way, a portion of physical memory or page is mapped to each page frame.
What are the components of a logical address?
The components of a logical address are the page number and the page offset. The page number is obtained by dividing the logical address by the size of the page frame size and the page offset is obtained by taking the remainder of the logical address divided by the page size.
What is the purpose of page tables?
Page tables are used to store a mapping of page numbers to physical addresses. The tables can be used to look up the page number to determine the physical address.
What is the formula for obtaining the page number and page offset from a logical address?
The formula for obtaining the page number from a logical address is:
- PN = Logical Address/Page Frame Size
The formula for obtaining the page offset from a logical address is:
- PO = Logical Address % Page Frame Size
What is the formula for obtaining the physical address from a logical address?
The formula for obtaining the physical address from a logical address is:
- Physical Address = Page Frame Number + Page Offset