The Virtual Memory Manager (VMM)
The Difference between virtual memory and physical memory Physical memories are the RAM chips purchased and placed in a slot on the computer motherboard. The RAM is the first memory used when the computer requires memory usage, such as for loading an application or opening a document.
 Virtual
Virtual memory is stored on the hard drive. Virtual memory is used when the RAM is filled. Virtual memory is slower than physical memory, so it can decrease the performance of applications.
 Allocation
Physical memory allocates information in a "first in, last out" process. The information is placed on the stack. Virtual memory uses a process called paging. These pages are laid across the hard drive in fixed sizes.
 Size
1. Physical memory is limited to the size of the RAM chips installed in the computer. Virtual memory is limited by the size of the hard drive, so virtual memory has the capability for more STORAGE.
2. Virtual memory is a memory management technique developed for multitasking kernels.
3. In virtual memory Operating systems have memory areas that are pinned (never swapped to secondary storage). For example, interrupt mechanisms rely on an array of pointers to their handlers, such as I/O completion and page fault. If the pages containing these pointers or the code that they invoke were pageable, interrupt-handling would become far more complex and time-consuming, particularly in the case of page fault interruptions. Hence, some part of the page table structures is not pageable (SPECTORA).
1) Physical Memory is the actual memory chips inside your computer. It's a very fast type of memory that the computer can access very quickly and efficiently.

2) Virtual Memory is a space on your hard drive. The computer uses this from time to time instead of using the physical memory. As this is space on the hard