What are the memory addresses from 0 to 640kb known as?

The memory addresses from 0 to 640 KB are known as conventional memory. This range was primarily used in early personal computers, specifically in the context of the x86 architecture. It was the area of RAM available for use by MS-DOS and older operating systems, where most applications and programs would operate. Beyond this range, from 640 KB to 1 MB, is known as upper memory.