Windows® via C/C++, 5th Edition

Physical Storage and the Paging File

In older operating systems, physical storage was considered to be the amount of RAM that you had in your machine. In other words, if you had 16 MB of RAM in your machine, you could load and run applications that used up to 16 MB of RAM. Today’s operating systems have the ability to make disk space look like memory. The file on the disk is typically called a paging file, and it contains the virtual memory that is available to all processes.

Of course, for virtual memory to work, a great deal of assistance is required from the CPU itself. When a thread attempts to access a byte of storage, the CPU must know whether that byte is in RAM or on the disk.

From an application’s perspective, a paging file transparently ...