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Memory Management Requirements

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Memory Management Requirements Efficient memory management is vital in a multiprogramming system. Memory management is the process in which, the operating system subdivides the user part of the main memory to accommodate multiple ready to go processes. Having multiple processes available in the main memory will allow the processor to be used to its full potential instead of waiting idly for the input/output devices to complete their jobs. Listed below are the requirements that memory management are expected to satisfy.
Relocation Requirement Having the ability to swap active processes back and forth from the main memory to disk provides a group of executable processes to keep the processor busy working. It is not to be expected for a programmer to pinpoint ahead of time which programs will be in main memory at the time of implementation of his or her program. When a program is swapped out of the main memory, it would be difficult to figure out when the next swap back into the main memory will be. By the time the process is swapped back into the main memory the area where the process was may be occupied by another process. This location unavailability creates a need to move the process to a different memory location. When a process has been moved to a different location, the processor hardware, and the operation system software work together to decipher the memory references found in the code of the program. This working together of the OPS and the processor hardware keeps track of the current location of the relocated program in the main memory (Stallings, 2015). The operating system identifies the location of process control information, the execution stack, and the entry point to begin execution of the program for this process (Stallings, 2015). The processor deals with the memory references within the program (Stallings, 2015). "Branch instructions contain an address to reference the instruction to be executed next" (Stallings, 2015). "Data reference instructions provide the address of the byte or word of data referenced" (Stallings, 2015).
Protection Requirement
Each process must be protected from interference by other programs. Programs in other processes should not have accesses to memory locations for reading or writing purposes without permission. Usually, a user process cannot access any part of the operation system, program or data. The processor hardware must have the capacity to provide memory protection requirement since the OS cannot predetermine all of the many memory references a program will make.
Sharing Requirement The sharing requirement allows several processes to access the same portion of main memory without compromising protection. One example where sharing is needed is when different processes are working on the same job and will need to access the same data structure.
Logical organization Requirement The majority programs are structured into modules by the operation system and computer hardware. Some of the modules are read/execute only, and others have data that can be changed. The advantages of modules according to Stallings, (2015):
1. Modules can be written and compiled independently, with all references from one module to another resolved by the system at run time.
2. With modes addition overhead, different degrees of protection can be given to different models.
3. Make it possible to introduce mechanisms by which modules can be shared among processes.

Physical organization Computer memory is structured into main memory and secondary memory. Main memory has fast access, high cost and does not provide permanent storage (Stallings, 2015). The main memory holds program and data currently in use (Stallings, 2015). The Secondary memory is slower and cheaper than main memory but provides a larger capacity of long term storage of programs and data (Stallings, 2015). Memory management requirements are good guides to evaluate if the memory is managed efficiently. There is nothing more agonizing than a program not executing its job or a slow process.

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