What does the Mapper do?

The mapper is the part of the operating system that translates the logical page number generated by the program into the physical page frame number where the main memory holds the page. This translation is accomplished by using a directly indexed table called the page table which identifies the location of all the program's pages in the main store. If the page table reveals that the page is, in fact, not resident in the main memory, the mapper issues a page fault to the operating system so that execution is suspended on the process until the desired page can be read in from the secondary store and placed in main memory.

The mapper function must be very fast if it is not to substantially increase the running time of the program. With efficiency in mind, where is the page table kept and how is it accessed by the mapper? The answer involves associative memory.

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