Final answer:
Virtual memory is normally implemented by demand paging, which is a technique used by operating systems to efficiently manage memory.
Step-by-step explanation:
Virtual memory is normally implemented by demand paging, which is a technique used by operating systems to efficiently manage memory. Demand paging allows the system to transfer pages of data from secondary storage (such as a hard disk) to main memory only when they are needed.
This technique is commonly used because it allows programs to run efficiently, even when the required memory exceeds the available physical memory. It also allows for better multitasking, as multiple programs can share the same physical memory while using their own virtual memory spaces.
While virtual memory can indeed be implemented by other means, such as through virtualization or using buses, demand paging is the most common method used in modern operating systems.