What does A20 mean?

A20 meaning in Computer Science Dictionary

A20 may be the 21st memory target line on 80286 and later processors that enable real-mode software to achieve usage of high memory or area of memory beyond the very first megabyte. With MS-DOS and early versions of Windows this method of accessing the high memory area ended up being done by using an A20 handler. For instance, you could weight the himem.sys when you look at the config.sys file and make use of the DOS=HIGH,UMB line to have accessibility the computer systems high memory.