Memory management is the act of managing computer memory. In its simpler forms, this involves providing ways to allocate portions of memory to programs at their request, and freeing it for reuse when no longer needed.

Virtual memory systems separate the memory addresses used by a process from actual physical addresses, allowing separation of processes and increasing the effectively available amount of RAM using disk swapping. The quality of the virtual memory manager can have a big impact on overall system performance.

Garbage collection is the automated allocation, and deallocation of computer memory resources for a program. This is generally implemented at the programming language level and is in opposition to manual memory management, the explicit allocation and deallocation of computer memory resources.

History

In addition to standard memory management, the 640 KB barrier of MS-DOS and compatible systems led to the development of programs known as memory managers when PC main memories started to be routinely larger than 640KB in the late 1980s (see conventional memory). These move portions of the operating system outside their normal locations in order to increase the amount of conventional or quasi-conventional memory available to other applications. Examples are EMM386, which was part of the standard installation in DOS's later versions, and QEMM. These allowed use of memory above 640 KB barrier, where memory was normally reserved for RAMs, and high and upper memory.