LOADHIGH

LOADHIGH (also often abbreviated as LH) is a DOS command used to load a program into the upper memory area (UMA). This is a region of memory between 640KB and 1MB in real mode DOS systems. The purpose of using LOADHIGH is to free up conventional memory (the first 640KB), which is crucial for running DOS applications.

The command works in conjunction with a memory manager like HIMEM.SYS (extended memory manager) and EMM386.EXE (expanded memory emulator). These managers must be loaded first in the CONFIG.SYS file to provide access to extended and expanded memory, respectively, and to enable the use of the UMA.

By loading programs, especially Terminate-and-Stay-Resident (TSR) programs and device drivers, into the UMA, more conventional memory becomes available for the primary DOS application, potentially preventing "out of memory" errors or improving performance.

The syntax of the command is generally:

LOADHIGH [drive:][path]programname [arguments]

Where:

• drive: specifies the drive where the program is located.
• path specifies the directory path to the program.
• programname is the name of the executable file.
• arguments are any command-line parameters required by the program.

LOADHIGH attempts to load the specified program into the largest available UMB (Upper Memory Block). If there is insufficient space or if the memory manager is not properly configured, the program may not load into the UMA, or may fail to load entirely.

The success of LOADHIGH loading a program into upper memory depends on the size of available UMBs and the amount of memory the program requires. Careful planning and optimization of CONFIG.SYS and AUTOEXEC.BAT are often necessary to maximize the use of upper memory. Alternate memory management tools could be utilized to analyze UMB usage and identify loading optimizations.