HIMEM.SYS is a

DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

device driver In computing, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabling operating systems and ot ...

which allows DOS programs to store data in

extended memory In DOS memory management, extended memory refers to memory above the first megabyte (220 bytes) of address space in an IBM PC or compatible with an 80286 or later processor. The term is mainly used under the DOS and Windows operating systems. D ...

according to the Extended Memory Specification (XMS). The memory beyond the first 1 MB of

address space In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity. For software programs to save and retrieve st ...

is required by

Windows 9x Windows 9x is a generic term referring to a series of Microsoft Windows computer operating systems produced from 1995 to 2000, which were based on the Windows 95 kernel and its underlying foundation of MS-DOS, both of which were updated in subs ...

/ Me in order to load; therefore, these versions of

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

require HIMEM.SYS to be loaded to be able to run. HIMEM.SYS was first included with

Windows 2.1 Windows 2.1 is a major release of Microsoft Windows. It was released to manufacturing on May 27, 1988, as a successor to Windows 2.0. It was released with two different variants with differing CPU compatibility, also known as Windows/286 and ...

(1988). In

MS-DOS 5.0 MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few ope ...

(1991) and later, HIMEM.SYS can be used to load the DOS

kernel Kernel may refer to: Computing * Kernel (operating system), the central component of most operating systems * Kernel (image processing), a matrix used for image convolution * Compute kernel, in GPGPU programming * Kernel method, in machine learn ...

code into the

High Memory Area In DOS memory management, the high memory area (HMA) is the RAM area consisting of the first 65520 bytes above the one megabyte in an IBM AT or compatible computer. In real mode, the segmentation architecture of the Intel 8086 and subsequen ...

(HMA) to increase the amount of available

conventional memory In DOS memory management, conventional memory, also called base memory, is the first 640 kilobytes of the memory on IBM PC or compatible systems. It is the read-write memory directly addressable by the processor for use by the operating system ...

by specifying

DOS 

 DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems.

DOS may also refer to:

 Computing
*  Data over signalling (DoS), multiplexing data onto a signalling channel
* Denial-of-service attack (DoS), an attack on a communicat ...
=HIGH

CONFIG.SYS 


CONFIG.SYS is the primary configuration file for the DOS and OS/2 operating systems. It is a special ASCII text file that contains user-accessible setup or configuration directives evaluated by the operating system's DOS BIOS (typically residing  ...

. In DR DOS 5.0 (1990) and 6.0 (1991), the driver is named HIDOS.SYS rather than HIMEM.SYS, like the corresponding

DCONFIG.SYS 


CONFIG.SYS is the primary configuration file for the DOS and OS/2 operating systems. It is a special ASCII text file that contains user-accessible setup or configuration directives evaluated by the operating system's DOS BIOS (typically residing  ...

or CONFIG.SYS directive HIDOS=ON. In

FreeDOS FreeDOS (formerly Free-DOS and PD-DOS) is a free software operating system for IBM PC compatible computers. It intends to provide a complete MS-DOS-compatible environment for running legacy software and supporting embedded systems. FreeDOS can ...

, the matching file is named HIMEM.EXE and can be loaded from the FreeDOS configuration file named FDCONFIG.SYS or CONFIG.SYS. In Windows 3.1 and

, there is also a command-line loadable version of HIMEM.SYS called XMSMMGR.EXE. It can load extended memory services after the system boots into the command prompt. This allows Windows Setup to load even if HIMEM.SYS is not loaded.

See also