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Unformatted text preview: ysical memory size of the system. 2. It enables the execution of a process on a system whose main memory size is less than the total memory required by the process. 3. It enables a process's execution to be started even when sufficient free memory for loading the entire process is not available. This helps in greatly improving the process's turnaround time. 4. With virtual memory, a program would no longer be constrained by the amount of physical memory that is available. This makes programming task much easier, since the programmer no longer needs to worry about the size limitations of the physical memory available, but can concentrate instead on the problem to be programmed. 5. An analysis of the execution of real programs shows that programs often do not execute all parts of their code during a typical execution run. For example, depending on the data, a large part of the code may be skipped on some condition check and may never be executed during that execution run. Similarly, certain options and features of a program, such as those for handling unusual error conditions, may be rarely used, and are generally not needed during most execution runs of the program. With virtual memory mechanism, since the parts of a program are loaded on demand, the parts that are not needed during a particular execution run of a program may never get loaded. This in turn leads to less I/O activity than in the case when the whole program is loaded before execution. With less I/O, each user program would run faster leading to better throughput, turnaround time, and response time. 6. Virtual memory enables a process's execution to be started even when sufficient free memory for loading the entire process is not available. Due to this, virtual memory can be effectively used to simultaneously accommodate program segments of a large number of users in the main memory. This increases the degree of multiprogramming resulting in increased CPU utilization and system throughput. Disadvantages Virtual memory typically has the following disad...
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