LOADHIGH
Open-knowledge reference entry
In computing, LOADHIGH (abbreviated 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.
The command was introduced with MS-DOS 5.0 / PC DOS 5.0 in 1991, copying the built-in HILOAD command earlier introduced with DR DOS 5.0 in 1990. DR DOS 6.0 added support for this naming variant as well in 1991.
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 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 LOADHIGH command.
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This entry incorporates text from “LOADHIGH” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.