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Memory Management Requirements

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Memory Management Requirements
POS/355 Introduction to Operating Systems
March 3, 2014
Paul Rouk

Introduction The main memory of a computer is divided into two categories; the operating system and programs that are currently being executed. Memory management itself is the task of subdivision. There are also four basic requirements to memory management which include; relocation, protection, sharing, logical organization and physical organization.
Relocation
Main memory is generally shared among a number of various processes. Since programmers cannot know in advance what other programs will be using the main memory when their program is executed thus creates the need for having the ability to swap processes in and out of the main memory. During swapping it is possible that the memory may be placed within different memory regions.
Protection
Each process should be protected against unwanted interference by other processes. This means programs in other processes should not be able to reference memory locations in a process for reading or writing purposes without permission. Since the operating system is unable to anticipate all of the memory references that a program will make it is important; the hardware rather than the software must satisfy the memory protection requirements.
Sharing
When it comes to sharing the protection mechanism must have the flexibility to allow several processes to access the same portion of the main memory. The memory management system must allow controlled access to shared areas of memory without compromising essential protection.
Logical Organization The organization of memory is closely mirrored to the actual machine hardware. Main memory is linear or one-dimensional; whereas secondary memory is just organized. These programs are organized into modules that are either modifiable or un-modifiable. There are a few advantages to this; modules can be written and compiled independently; different degrees of protection can be given to different modules and providing sharing on the module level.
Physical Organization The physical computer memory is divided between main and secondary. With main memory there is a much faster response time but with a high price tag. While this memory is not to be used for permanent storage. Secondary memory is slower to access but much more budget friendly. This type of memory is not volatile and can then be used for long-term storage of programs and data.

References

Stallings, William. "Memory Management." Operating Systems: Internals and Design Principles. Boston: Prentice Hall, 2012. 305-10. Print.

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