Lehekülgitabel

Lehekülgitabel, also known as a page table, is a fundamental data structure used in modern operating systems to implement virtual memory. It translates virtual addresses generated by a running program into physical addresses in the computer's RAM. Each process in the system has its own page table, which maps its virtual address space to physical memory.

The page table is typically organized as an array or a tree. Each entry in the page table, called a page table entry (PTE), contains information about a virtual page. This information usually includes the corresponding physical frame number where the virtual page is stored, as well as various control bits. These bits can indicate whether the page is valid (currently in memory), whether it has been modified (written to), and access permissions (read, write, execute).

When a program accesses a virtual address, the memory management unit (MMU) consults the process's page table to find the corresponding physical address. If the page is not present in physical memory (a page fault occurs), the operating system must fetch it from secondary storage (like a hard drive) and load it into an available physical frame. The page table is then updated to reflect the new location of the page. This process of translating virtual addresses to physical addresses allows for efficient memory management, enabling larger address spaces than physically available RAM, memory protection between processes, and efficient sharing of memory.