Memory Mapping in Operating System

We haven't heard that primary and secondary memory have same capacities.Generally, main memory is available in configurations of 1 GB, 2 GB, 4 GB, 8 GB, 16 GB or some multiples ahead. But secondary memory ranges start from 128 GB, 1 TB and more.

What is memory mapping? Why do we need memory mapping? From where, arrived the term mapping?

The answer to above questions is the very limited size of main memory, RAM and cache that are available in the computers while there is a very large secondary memory. But secondary memory cannot be used for the execution of the tasks, it can only store the data. The execution of tasks can only be performed by main memory.

Since, there are tasks that may be small or big in size. There is no problem with the execution of smaller tasks as they can be easily accommodated in main memory. But the problem arises with the ones who have size even larger than the primary memory. Due to the limited size of the main memory, we have to use mapping techniques.

There are three types of mapping techniques in computer architecture and operation systems. They are listed below.

1. Direct mapping


2. Associative Mapping


3. Set Associative mapping

The picture shown depicts the memory bits distribution in different types of memory.