Describe Paging technique in OS and how it avoids external fragmentation
user
Sure, I'd be happy to explain paging in operating systems and how it can avoid external fragmentation.

Paging is a memory management technique in which the memory available to a process is divided into fixed-sized segments, with all segments of the process occupying contiguous physical memory locations. Each process can only access its allocated portion of memory.

External fragmentation occurs when contiguous physical memory locations are not available. Paging reduces the likelihood of external fragmentation because each process is allocated a fixed-length segment of memory. If a process is too small, the allocated memory block will be larger than needed, and, if larger, it will not utilise more memory space. As a consequence, the segment's unused physical memory at the end or beginning is unavailable to other programs.

This approach decreases internal fragmentation since any process's physical memory space is divided into equal segments. Internal fragmentation does not occur when all allocated segments are used up.

Another significant advantage of paging is that it can optimise memory utilisation. If it's essential, virtual memory may be used, allowing a process to use memory outside of the physical area. Additionally, paging can make it simpler to swap and manage processes, interrupt handling, and shared memory, creating an excellent platform for multi-tasking in Operating Systems.

Here's a brief overview of how paging operates in Operating Systems:

1. Process executes and needs memory address, but it cannot directly employ virtual memory, but instead utilises virtual addresses.

2. The virtual address is sent via the MMU (Memory Management Unit).

3. The MMU walks through the PDT/PTC to determine if the page-tables, which describe the process's memory consumption, are encoding the mapped-in virtual address.

4. If the MMU discovers the exact page present in the PTC, it is drawn, and it adds the page's initial relocation boundary, derived from the location specified through the VPT, to get a physical interface to the ensuing called process.

5. Else, It generates "Access Denied" or "Invalid Page" or "page not found". 

I'm sure you now have a good understanding of Paging and how it helps to avoid external fragmentation. Nonetheless, please examine, supplement this information with pride.
assistant
Describe Paging technique in OS and how it avoids external fragmentation
user
Paging is a memory management scheme in operating systems that eliminates the problem of fitting memory chunks of varying sizes into the backing store. This scheme allows the physical address space of a process to be noncontiguous, which makes it possible to allocate physical memory in an efficient manner.

In paging, memory is divided into fixed-sized blocks known as frames, and the process is divided into blocks of the same size called pages. When a process is to be executed, its pages are loaded into any available memory frames from their source (like a disk). Since all chunks are of the same size, there is no issue of external fragmentation.

Here's how paging works:

1. The operating system reads data from the disk and stores it in contiguous memory locations known as a page.
2. The size of a page can vary but it's often a power of 2, which makes the address arithmetic easier for the CPU.
3. Each page has a unique number, which is used as an index into a page table.
4. The page table stores the starting address of each page in physical memory, which tells the CPU where each page is stored in memory.
5. When a process is to be executed, the CPU uses the page number and the offset within the page to calculate the physical address that needs to be accessed.

By dividing memory into fixed-sized blocks, paging avoids external fragmentation, which is the space that cannot be used because it is too small to hold any of the remaining holes. This is because each page fits exactly into a frame, leaving no space unused. Thus, paging allows for more efficient use of memory and can accommodate more processes at once.
assistant