In modern computers there are several memory systems and hardware components that are used for the internal use and storage of data. These memory components are separated by different types of physical and programming partitions.

The principle types of system memory include, but are not limited to, random-access memory (RAM memory), read-only memory (ROM memory), programmable read-only memory (PROM), specialized types of PROM memory, and virtual memory. System memory is further separated into several component areas, each with their own unique block of addresses. The types of separation are, in many cases, remnants of earlier computer hardware and software designs (i.e., they are traditional designations) made necessary by the small memory capacity of early computer systems.

Conventional memory designates the first 640 KB of system memory, and it is this memory that is utilized by DOS-based programs. Upper memory is the next 384 KB...