Physical Memory and Virtual Memory

[norman]

Virtual memory is a memory management technique, used by multitasking computer operating systems wherein non-contiguous memory is presented to software as contiguous memory. This contiguous memory is referred to as the virtual address space. It is used commonly and provides great benefit for users at a very low cost. The computer hardware that is the primary memory system of a computer also called as RAM is the physical memory.

[rakesh trichy]

RAM is the amount of physical memory installed on your computer. It acts like short-term memory, enabling programs to load and operate faster. When you start a program or an application, it uses a part of that memory. Most programs will require at least 32MB of RAM. If you look in your system tray (next to the time), there are usually four or more programs running (antivirus, firewall, and so on). Those background programs alone require 128MB. Then if you use any programs, such as a Web browser or a word processor, it requires more memory.

Windows makes up the difference for that amount of RAM requirement by allocating or reserving a portion of your hard drive to act as though it were RAM. That's what is referred to as virtual memory, or page file. The less RAM you have the more virtual memory is allocated. Windows typically manages that for you. As a standard rule of thumb, Windows creates a virtual memory of 1½ times your physical RAM. So if have 256MB of actual RAM, Windows pagefile (virtual memory) will equal 384MB.