A swap file enables an operating system (OS) to utilize hard disk space to simulate additional memory. Effectively, as the system goes on the low-memory mode, it swaps a certain section of the RAM that an idle program may be using onto the hard disk to release memory capacity for other vital programs. Subsequently, when the user returns to the swapped out program, it swaps places with another program in RAM. This intelligent mix of RAM and swap files is commonly referred to as virtual memory, and its use allows the system to run a far greater number of programs than possible using only the built-in RAM.
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