Conventional memory

In DOS memory management, conventional memory, also called base memory, is the first 640 kilobytes (640 × 1024 bytes) of the memory on IBM PC or compatible systems. It is the read-write memory directly addressable by the processor for use by the operating system and application programs. As memory prices rapidly declined, this design decision became a limitation in the use of large memory capacities until the introduction of operating systems and processors that made it irrelevant.