Paging and segmentation are ways for operating systems to manage memory, but they handle things differently.

Basic Concept

• Paging breaks memory into equal-sized blocks called pages. Each page fits into a part of the physical memory called a frame. This makes memory management simpler because everything is the same size, and it helps reduce gaps in memory.
• Segmentation, however, divides memory into different-sized segments. These segments are based on how a program is organized, like different functions or data types. This method reflects the way programs are built in a more natural way.

Addressing Mechanism

• In paging, the address (or location in memory) is split into a page number and an offset. This makes it easy to connect logical addresses (what the program sees) to physical addresses (what the memory uses) through a page table. The formula looks like this: $Physical\ Address = Page\ Number \times Page\ Size + Offset$.
• Segmentation also uses a segment number and an offset, but it needs a segment table. This table shows the starting point and size of each segment, which makes the process of finding addresses more complex.

Fragmentation

• Paging reduces external fragmentation, which are empty spaces in memory. But it can create internal fragmentation, meaning that some pages might not be fully used.
• Segmentation usually ends up with more external fragmentation because the segments can vary in size, which can waste memory.

In simple terms, paging is about keeping things uniform and simple with equal-sized parts. Segmentation offers more flexibility and aligns better with how a program is structured, but it can lead to more memory waste.