An extended memory manager for use with MS-DOS. In essence it coordinates the use of your computer's extended memory, including the high memory area (HMA), so that no two applications or device drivers use the same memory at the same time.

HIMEM is installed by loading himem.sys in the config.sys configuration file of MS-DOS.

HIMEM can also act as an A20 handler and under no circumstances should it be be confused with hymen.