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Case Study: Memory Management And Virtual Memory For Operating System

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This document highlights the topics required by Project 2 – Research – Memory Management and Virtual Memory for Operating Systems class of 2014. This paper is presenting a case study of Microsoft’s Windows 7 64 Bit Professional Operating System.

2. Memory
2.1 Description:
The main memory is the central hub where all programs are executed. It consists of a large array of bytes, each with its own address. The amount of main memory is a limiting factor in a computer system, the more memory we have, the more addressable space the Operating System has, increasing the number of programs that can be executed and how much information is ready to be put into execution. When the instructions are ready to be executed, the scheduler sends them to the CPU. This process can take more than one transition between the memory and the processor. The memory unit acknowledges only a stream of memory addresses, it has no understanding on how they are generated or what their purposes are.

2.2 Physical Memory:
Most current Operating systems today support 64 bit addressing, that includes our case study, Windows 7 x64 Professional. Hardware and software limitations of
32 bit chips which are constrained to a maximum of 2 GB user addressable or 4 GB of RAM access, sped up this transition. A 64-bit chip addressing space is increased to 2^64 bytes of RAM and can greatly increase system performance and the way programs can be written without having to take in consideration the above constraints.
- Windows 7 Professional 64 bit has a limit of 192 GB in addressing space.

2.3 Virtual memory:
Virtual memory is a memory management technique implemented with the help of both hardware and software. It maps memory addresses used by a program, called virtual addre...

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...e is assigned an age value consisting of three bits that determines the age of a page thus helping the operating system to decide which memory page can be discarded from the physical memory. The reference counter used in the aging algorithm and the way it is used ensure that pages referenced more recently, though less frequently referenced, will have higher priority over pages more frequently referenced in the past: thus, when a page needs to be swapped out, the page with the lowest counter will be chosen.

3. Conclusion:
Windows 7 is the first widely adopted 64 bit Operating System in the Microsoft family. It addressed a lot of security issues and greatly improved performance and some of the features from its predecessors. It has matured to a stable and reliable Operating System and holds the majority stake of being installed on most personal computers worldwide.
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