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Memory Managment Operating Systems

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Ricki Lambert Operating systems Assignment 2 Memory Management Introduction Memory management is a control of the operating system. Memory management is the most vital part of keeping computers resources in order. Without this kind of management the computer would experience severe problems when multiple threads are to be run, and when processes are completed and memory is to be regained. The management system is therefore capable of allocating and de-allocating memory when needed by the system. When a system has too little memory it will become unstable and therefore almost unusable. The memory managing sector of the operating system will also allocate an orderly fashion for the executable files to be dealt with, this then allows for the memory management system to determine what is in the memory for optimum performance and C.P.U utilization. It must be constantly active searching through its system and deciding what parts are being used by whom and what threads and applications need to be moved in and out of the system. When the memory becomes to full there must be an application or process to free some of it. A list can be seen below of the main purposes of the memory management sector. 1. Relocation of memory 2. Allocation of memory 3. Protection of memory 4. Sharing of memory 5. ...read more.


This diagram bellow shows how a process is taken from the CPU and sent to the memory. * The relocation register will hold the value at the base address which is owned by the process * The relocation registers contents are added to each memory address before it is sent to the memory. * A process can never see the physical address - it will just manipulate the logical address It is clear to see that the register has a limit, and if the process exceeds the register limit it will result in an address fault. If the total is less than the limit it will proceed to the base and is added to the logical address. This is how new logical addresses are designed. Fixed and Dynamic Partitioning It is also possible for memory to be partitioned when it is within its stored elements. This is for efficient storage and avoids clustering of the memory system. The memory can be partitioned in two differing ways. Firstly is fixed partitioning. Fixed memory partitioning ensures that memory blocks are split up into fixed sizes. When a process is sent for execution a space is created and a new process can enter. ...read more.


This is done by assigning it a bit, 1 bit is for writing, 1 bit is for reading and another for execution. It can therefore be said that this process is similar to that of the linking process described earlier. The only difference is that the dynamic linking always had to reside somewhere within the R.A.M, this process however can allocate virtual memory. This is done by what is known as the paging table. This then gives the logical memory two identities, the first being a page number and the second would be an offset within that page. Then when a process is to be run the memory management must look up the page number and offset and extracts the pair of them. From this is can translate the two and turn it in to the physical memory location. This then allows the process to be run. Segmentation Segmentation is where memory resides in the logical address space in groups. There are many benefits to this, but the most important is the protection. Memory can be protected in its groups rather that each individual address space. This improves efficiency of the system and makes memory allocation far easier. From here the need for external fragmentation is not needed although there is an additional need for context switching. It can also be said that there is a clear separation between the user and the system. ...read more.

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