Memory Management

Memory Management Requirements
Marian Bennett
POS/355
October 15, 2012
Jeff Rugg

Memory Management Requirements
There are two different types of programming systems; uniprogramming and multiprogramming. In uniprogramming there is just an operating system and the program that is currently being utilized. In multiprogramming, it is just as the term says, working to accommodate multiple programs. When are there is more than one program being executed at a time, there needs to be proper protocol and system checks. There are five requirements that memory management needs to satisfy: relocation, protection, and sharing, logical and physical organization.
Relocation of a program is needed if the processor needs more resources. Knowing that the main memory is shared by many different programs and processes, there will be times that some might need to be swapped out. For example, if the processor needs to swap out a program to be more efficient, the chances are that it will not be put back into the exact location therefore it would be relocated to a different area of the memory. The requirement of relocation is important because if the memory does not allow for this then the processor would not be utilized efficiently and would make your system slow and unreliable.
Protection is another requirement that is needed for memory management. “Each process should be protected against unwanted interference by other processes, whether accidental or intentional” (Stallings, 308). When the program is executed it will be checked by the processor at run time to make sure that it only has the proper memory reference of that particular program.
Another requirement for memory management is sharing. Sharing happens when a lot of processes are running the same program. Instead of each process having its own copy of the program, the processes share one copy that is protected.
Logical organization is the fourth requirement. Programs would be written in modules, which are not the same as computer systems, which are linear. There are advantages to programs being written in modules, and as noted by Stallings (p.309) the following are the benefits:
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 modest additional overhead, different degrees of protection (read only, execute only) can be given to different modules.
3. It is possible to introduce mechanisms by which modules can be shared among processes. The advantage of providing sharing on a module level is that this corresponds to the user’s way of viewing the problem, and hence it is easy for the user to specify the sharing that is desired.

The last requirement is physical organization. This requirement is important for the two levels of memory, main and secondary memory. Information will travel back and forth from each memory location. The secondary memory tends to be larger and can hold more programs and data, while the main memory is smaller and can only hold processes that are currently being used. This system responsibility is a crucial requirement and cannot be left up to the programmer because the amount of memory needed would not be known.
All of these requirements are important to the overall management of the memory. Each one is related to the next and all of the requirements must be met in order to have a processor that is utilizing space and speed effectively while maintaining the integrity of the program.

References
Stallings, W. (1998). Operating Systems Internals and Design Principles (7th ed.). Upper Saddle Rivery, NJ: Pearson Education.

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References: Stallings, W. (1998). Operating Systems Internals and Design Principles (7th ed.). Upper Saddle Rivery, NJ: Pearson Education. .