What is virtual memory and why is it used?

Virtual memory is a memory management technique that allows a computer to use more memory than what is physically available in the system's RAM. By creating a layer that combines both physical RAM and a portion of the hard drive (or SSD), virtual memory provides the illusion to the user and the applications that there is a larger amount of RAM available for their tasks.

When a program requires more memory than is available in the physical RAM, the operating system can move some of the data to a reserved space on the hard drive, commonly referred to as the page file or swap space. This process is transparent to the user and allows multiple applications to run simultaneously without running out of physical memory. The system efficiently manages which data needs to be held in RAM and which can be temporarily stored on the hard drive, balancing the needs of active processes and optimizing performance.

The other options either describe benefits that are not directly correlated to the core function of virtual memory or present concepts that do not reflect its primary purpose. For instance, while virtual memory can indirectly influence costs by reducing the need for physical RAM upgrades, its primary function is to extend the capacity for applications to utilize memory effectively, making it a foundational element in modern operating systems.