{{Use dmy dates|date=July 2019|cs1-dates=y}} {{Use list-defined references|date=January 2022}} {{Infobox software | name = LOADHIGH / LH / HILOAD | logo = | screenshot = | screenshot size = | caption = | developer = Digital Research, Novell, Microsoft, IBM, Caldera | released = {{Start date and age|1991|06|11|df=yes}} | latest release version = | latest release date = | operating system = DOS | genre = Command | license = | website = }} In computing, '''{{code|LOADHIGH}}''' (abbreviated '''{{code|LH}}''') is an internal DOS command in COMMAND.COM that is used to load a program into the upper memory area (UMA) instead of conventional memory.<ref name="Microsoft_Q95555"/>

The command was introduced with MS-DOS 5.0 / PC&nbsp;DOS 5.0 in 1991,<ref name="RUNNINGMSDOS"/><ref name="Microsoft_Q95555"/> copying the built-in '''{{code|HILOAD}}''' command earlier introduced with DR&nbsp;DOS 5.0 in 1990. DR&nbsp;DOS 6.0 added support for this naming variant as well in 1991.<ref name="Paul_1997_NWDOSTIP"/><ref name="Caldera_1998_DRDOS702"/>

==Overview== Due to design of the IBM PC, DOS suffered from what was known as the 640 KB barrier. The size of this memory area, known as conventional memory, was fixed and independent of the amount of system memory actually installed. Various schemes were developed to support extra memory (see also EMS, XMS) and DOS extenders, but conventional memory was still an issue due to compatibility issues. It was a scarce resource as many applications demanded a large part of this basic memory fragment at runtime. Therefore, it was often necessary to move high some TSR programs like the mouse driver or the disk caching driver (like SMARTDRV) prior to running a memory-hungry application. This was achieved by using {{code|LOADHIGH}} called with the program's name as the parameter.

To load TSRs high within CONFIG.SYS, the INSTALLHIGH directive must be used instead of the {{code|LOADHIGH}} command. The equivalent of {{code|LOADHIGH}} for device drivers is DEVICEHIGH (usable only within CONFIG.SYS). These are also supported since DR&nbsp;DOS 6.0. DR&nbsp;DOS 5.0 and higher also support HIINSTALL and HIDEVICE, respectively.<ref name="Caldera_1998_DRDOS702"/>

Most modern operating systems now run in protected mode with support for an unsegmented (flat) memory model and do not have a 640&nbsp;KB constraint. {{code|LOADHIGH}} and other methods of freeing conventional memory have largely become obsolete.

{{code|LOADHIGH}} is part of the Windows XP MS-DOS subsystem to maintain MS-DOS and MS OS/2 version 1.x syntax compatibility only.<ref name="Microsoft_XP"/> It is not available at all on Windows XP 64-Bit Edition<ref name="Microsoft_64"/> and also no longer available in the command interpreter of newer Windows operating systems.<ref name="Microsoft_Commands"/>{{clarify|reason=Windows 95/98/SE/ME supported it, Windows XP COMMAND.COM only supports it as compatibility dummy (non-functional). It is unclear, if Windows 3.5 - 2000 COMMAND.COM ever supported it.|date=September 2017}}

==See also== * BUFFERSHIGH / HIBUFFERS (DOS 7.0+) * STACKSHIGH / HISTACKS (DOS 7.0+) * LASTDRIVEHIGH / HILASTDRIVE (DOS 7.0+) * FILESHIGH / HIFILES (DOS 7.0+) * FCBSHIGH / HIFCBS (DOS 7.0+) * DOS / HIDOS (DOS 5.0+) * DOSDATA * HIINSTALLLAST * List of DOS commands * Self-highloading * Self-relocation

==References== <references>

<ref name="RUNNINGMSDOS">{{Cite book |author-last=Wolverton |author-first=Van |title=Running MS-DOS Version 6.22 |version=20th Anniversary Edition |edition=6th revised |date=2003 |publisher=Microsoft Press |isbn=0-7356-1812-7}}</ref> <ref name="Paul_1997_NWDOSTIP">{{cite book |title=NWDOS-TIPs &mdash; Tips & Tricks rund um Novell DOS 7, mit Blick auf undokumentierte Details, Bugs und Workarounds |language=de |trans-title=Tips & tricks for Novell DOS 7, with a focus on undocumented details, bugs and workarounds |series=MPDOSTIP |author-first=Matthias R. |author-last=Paul |date=1997-07-30 |edition=3 |url=http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |access-date=2012-01-11 |url-status=live |archive-url=https://web.archive.org/web/20161105172944/http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |archive-date=2016-11-05}} (NB. NWDOSTIP.TXT is a comprehensive work on Novell DOS 7 and OpenDOS 7.01, including the description of many undocumented features and internals. It is part of the author's yet larger MPDOSTIP.ZIP collection maintained up to 2001 and distributed on many sites at the time. The provided link points to a HTML-converted older version of the NWDOSTIP.TXT file.)</ref> <ref name="Caldera_1998_DRDOS702">{{cite book |title=Caldera DR-DOS 7.02 User Guide |publisher=Caldera, Inc. |date=1998 |orig-date=1993, 1997 |chapter=Chapter 10 Managing Memory |chapter-url=http://www.drdos.net/documentation/usergeng/10ugch10.htm |access-date=2017-08-30 |url-status=dead |archive-url=https://web.archive.org/web/20170830153325/http://www.drdos.net/documentation/usergeng/10ugch10.htm |archive-date=2017-08-30}}</ref> <ref name="Microsoft_64">{{cite web |url=https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-xp/bb490895(v%3dtechnet.10) |title=MS-DOS subsystem commands |publisher=Microsoft}}</ref> <ref name="Microsoft_Commands">{{cite web |url=https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/windows-commands |title=Windows Commands |date=26 April 2023 |publisher=Microsoft}}</ref> <ref name="Microsoft_Q95555">{{cite web |title=Overview of Memory-Management Functionality in MS-DOS |date=2001-06-06 |id=Q95555 |publisher=Microsoft |url=https://jeffpar.github.io/kbarchive/kb/095/Q95555/ |access-date=2020-02-08 |url-status=live |archive-url=https://web.archive.org/web/20200208161927/https://jeffpar.github.io/kbarchive/kb/095/Q95555/ |archive-date=2020-02-08}}</ref> <ref name="Microsoft_XP">{{cite web |title=Loadhigh |publisher=Microsoft |work=Technet |url=https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-xp/bb490692%28v%3dtechnet.10%29 |access-date=2020-02-08 |url-status=live |archive-url=https://web.archive.org/web/20190813102714/https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-xp/bb490692(v%3Dtechnet.10) |archive-date=2019-08-13 |quote=Windows XP does not use this command. It is accepted only for compatibility with MS-DOS files.}}</ref>

</references>

==Further reading== * {{cite book |author-last=Cooper |author-first=Jim |title=Special Edition Using MS-DOS 6.22 |edition=3 |date=2001 |publisher=Que Publishing |isbn=978-0-7897-2573-8}} * {{cite book |author-first1=Kathy |author-last1=Ivens |author-first2=Brian |author-last2=Proffit |date=1993 |title=OS/2 Inside & Out |publisher=Osborne McGraw-Hill |isbn=978-0-07-881871-4}}

Category:Internal DOS commands Category:DOS memory management

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