DOS HIMEM.SYS

Starting with DOS 5 and Windows 3.0, the HIMEM.SYS driver is included, which manages extended memory (memory beyond one megabyte). To free up more conventional memory, HIMEM.SYS also allows part of DOS to be loaded into the first 64K block of extended memory known as the high memory area (HMA). To do this, the dos=high line must follow the activation of HIMEM.SYS (see below).

HIMEM.SYS is also required if EMM386.EXE is used. HIMEM.SYS is activated in the CONFIG.SYS file and must precede all drivers that use extended memory; for example:

     device=himem.sys        activate HIMEM.SYS
     device=emm386.exe       EMS memory manager
     device=smartdrv.sys     disk cache
     device=ramdrive.sys /e  RAM disk
     dos=high                load DOS into HMA

Note: Windows requires extended memory and installs its own HIMEM.SYS driver. DOS 6's HIMEM.SYS supersedes the HIMEM.SYS from Windows 3.1. Thus, if you install Windows 3.1 on a DOS 6 machine, the installation will reference the HIMEM.SYS that it put in the Windows directory. For better operation, change the line in CONFIG.SYS to reference the more current HIMEM.SYS in the DOS directory, rather than the Windows directory. See DOS Dos and DOS EMM386.EXE.