The DOS and Microsoft Windows device that manages the use of extended memory and the high memory area on IBM-compatible computers. HIMEM.SYS not only allows your application programs to access extended memory, it also oversees that area to prevent other programs from trying to use the same space at the same time. HIMEM.SYS must be loaded by a DEVICE command in your CONFIG.SYS file; do not use DEVICEHIGH.
A device driver that manages memory above conventional memory (the first 640K). In DOS and Windows 3.x it had to be loaded in the CONFIG.SYS file. Win9x loads it automatically but it has to be present on your hard drive.
The DOS and Windows 9x memory manager extension that allowed access to memory addresses above 1 MB.