Paging In OS with Examples

Paging is a technique of Non-Contiguous where one process can reside at different locations of main memory. So, spanning is totally possible. In this post we will see all bout paging with examples.

Need of Paging

The main disadvantage in Contiguous Dynamic Partitioning was External fragmentation. Although, External fragmentation may remove by Compaction but it makes the system inefficient.

In paging, external fragmentation was totally remove without compaction.

Explain with Example

P1 requires 3 MB space to load in the main memory. We have two holes of 2MB and 1MB respectively available at different locations in main memory. And still Process 1 can load successfully. It is because of non-contiguous memory allocation.

Non contiguous memory allocation

Concept of Paging

 In which processes are organized in equal size blocks called pages and the main memory is organized in equal sized blocks called frames.

Pages at secondary memory and frames at main memory both have the same size. As, CPU does not generate absolute address. But it generates the logical address.

But the actual data required to CPU present in main memory. Physical address is requiring to access actual data in main memory. For this purpose, system use the MMU. MMU further use the Page table. Every process has its own page table.

Entries of page table of each process = total no of pages of that process

Paging is a technique in which the main memory is organized in equal sized blocks. These blocks also known as pages. In this technique, the address of occupied pages of physical memory is stored in a table, which is known as page table.

Through Paging, OS can get the physical memory location without specifying the lengthy memory address in the instruction. In this technique, the virtual address is use to map the physical address of the data. The length of virtual address is specified in the instruction and is smaller than physical address of the data. It consists of two different numbers, first number is the address of page which is known as virtual page in the page table. Second number is the offset value of the actual data in the page. Let explain with diagram


Lets Explain with example.

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