查看“HIMEM.SYS”的源代码

{{Infobox Windows component	
|name = HIMEM.SYS	
|type = Device driver	
|logo = 98DLLIcon.png	
|screenshot = <!-- Image of HIMEM.SYS file properties needed -->
|other names = HIMEM (often simply referred as such)
|introduced in = [[Windows/386 2.1]]<br>[[MS-DOS 5]]<br>[[IBM PC-DOS|IBM DOS 5]]
|included in = [[MS-DOS]]<br>[[IBM PC-DOS]]<br>[[Windows 3.0]]<br>[[Windows 3.1x]]<br>[[Windows 9x]]
|last included in = [[Windows Me]]	
}}
'''<code>HIMEM.SYS</code>''' (often simply referred to as '''<code>HIMEM</code>''') is a device driver file for [[MS-DOS]] and other DOS systems that enables them to use extended memory (i.e. memory above the 1MB conventional memory barrier) on 80286 machines and above. It implements the Extended Memory Specification, providing control over the A20 line, access to both the High Memory Area (the 65520 bytes immediately following the 1MB line, starting at <code>FFFF:0010</code>) and the rest of extended memory, allocating it and copying between extended and conventional memory. If loaded in <code>CONFIG.SYS</code>, it can be used to load DOS into the HMA, freeing up conventional memory.

It is required by Windows/386 2.1x and Windows 3.x to run in 386 Enhanced Mode. An EXE version of the driver is included on the Windows 9x distribution media that can load after DOS startup if no XMS driver is available, <code>XMSMMGR.EXE<code>.