Some of the older or simpler programs distributed by the IGWMC have been compiled for computers based on Intel 8088 and 80286 cpu's running under MS-DOS and will only run in conventional or low memory, i.e., using less than 640 Kb RAM. These programs will not use extended or expanded memory, even if it is available, nor do they access Intel 80386/80486 protected mode. They are often designed to use the maximum available memory after DOS has been loaded and compete for this limited memory with other system software (e.g., disk-cache), memory-resident programs, memory managers, and device drivers (including network drivers). This may cause some problems, such as:

• Inability to run the program; the program returns to DOS without proper execution.
• .Computer locks up after starting the program requiring a warm or even a cold reboot.
• The program will run correctly until functions or program modules are called which require more memory, such as graphics, additional executables called from the program's main module or shell, and creating graphics output files. The program may abort, lock-up the keyboard, or returns to DOS while the output created is incomplete, or even not saved at all.
• Other runtime errors may occur, such as inability to open files, too many open files, too many units connected, stack overflow, not enough space for environment, abnormal program termination, and unexpected heap error, preventing correct running or continuation of the program.

Although these errors are frustrating, often, they can be easily solved. Installing low-memory DOS programs provided by IGWMC requires the user to check, and when necessary, to make changes in the AUTOEXEC.BAT and CONFIG.SYS files on the boot disk of your computer system. In addition, when problems, as listed above, occur, additional modification of these system files may be necessary to free up memory for the IGWMC program. Some of these changes are specified in the IGWMC-produced documentation file distributed with each program. This file can be viewed by making the distribution disk (or the work directory) current and typing "readme" at the DOS prompt. A hardcopy version of this documentation file is included in the front of each IGWMC-prepared documentation package.

Typical changes in the CONFIG.SYS file include modification of the FILES and BUFFERS statements in the CONFIG.SYS file, adding a STACK statement to the CONFIG.SYS file, and including the statement DEVICE=[path]ANSI.SYS where path refers to the DOS directory on your hard drive and ANSI.SYS to a DOS driver in the DOS directory. If this does not solve the problem, ram cache, memory managers and other programs using low memory need to be removed or loaded in high memory (under DOS 5.0 or higher). If you have DOS 6.0 or higher, you may run the DOS program MEMMAKER to optimize memory use. Programs requiring maximum low memory resources may not run on a network or as a DOS application under MS WINDOWS. IGWMC specifies in the documentation file if the program runs under MS Windows in a typical application (e.g., requiring less than 500-550 Kb of low memory.

Sometimes, an IGWMC-distributed program require changes to the AUTOEXEC.BAT file. Possible modifications include the PATH statement, and addition of SET statements. Newer PC's often come with many peripherals requiring additional device drivers (e.g., for CD-ROM, sound), complex PATH statements, and memory-resident programs. It might be necessary to detach some of these devices to allow the DOS-type software to run. If you are not familiar with these DOS options, it is advisable to confer with your system manager or the person/organization who have set up your computer to determine the specifics of such modifications.

Before you make any changes to your CONFIG.SYS and AUTOEXEC.BAT files, make a backup copy, e.g., "COPY AUTOEXEC.BAT AUTOEXEC.OLD" and "COPY CONFIG.SYS CONFIG.OLD". These backup copies can be copied back to the AUTOEXEC.BAT and CONFIG.SYS files when the runs with the IGWMC-provided program have been completed. After creating the back up copies, the existing AUTOEXEC.BAT and CONFIG.SYS files can be modified using a line editor, e.g., the DOS program EDIT. After saving the changed files, the computer needs to be rebooted (CTL-ALT-DEL) to make the changes effective. To see how much low memory is available, type the DOS command "MEM" at the DOS prompt. For older versions of DOS (3.0 or earlier) you need to use "CHKDSK" command instead. In an optimal configuration, close to 600 Kb of low RAM may be available for the IGWMC-distributed program, especially when DOS is loaded high (DOS 5.0 or later) and MS Windows is not running. Also, if you use a disk-file compression program, such as DOS DBLSPACE, you may not have enough free low memory left. The maximum memory requirement for any of the IGWMC conventional memory programs is about 580 Kb of low RAM (e.g., some ASM solvers, WHPA GPTRAC, etc.).

If the above mentioned modifications are not successful:

• make sure that you have the correct number of disks;
• the disks contain all files on the packing list (see "readme" file)
• you have followed the installation instructions correctly
• the disks have not been damaged in shipping; this may be checked by using NORTON, PCTOOLS or other disk utilities.

If problems persist, or you expect a bad or incomplete disk, fax your problem to Technical Support, IGWMC, 303/384-2037, with specifics and nature of the problem. If possible, provide the error message(s) displayed when trying to run the program, as well as the results of the memory check. Note that obtaining new disks will not solve low memory problems, so check the memory usage first before contacting IGWMC.

An example of generic CONFIG.SYS and AUTOEXEC.BAT files that will work for most applications and leave much of the low memory available for application programs is presented below. Individual systems may differ, so confer with your system manager when using these examples.

Sample CONFIG.SYS

Shell=C:\COMMAND.COM /p /e:1024
Dos=High
Device=C:\DOS\ANSI.SYS
Files=50
Buffers=30

Sample AUTOEXEC.BAT

@ECHO OFF
Loadhigh C:\DOS\DOSKEY
Path=c:\;c:\dos;c:\(your program name)
@PROMPT $P$G

It should be noted that some of the forementioned problems might not be caused by shortage of memory, but by incorrect data entry. Often, this results in "divide by zero", "integer overflow", "real math overflow", "invalid integer", "invalid real", or "end of file encountered" error messages. Other typical problems are "no space left on device" (no storage space on current disk or hard drive; use other disk or free-up space on your hard drive), and "file not found" (program expects a file with a particular name and can not find it; consult the program documentation for file requirements and conventions).

Fore more information contact:

International Ground Water Modeling Center
Colorado School of Mines, Golden, CO 80401
phone: 303/273-3103, fax: 303/384-2037
email: igwmc@mines.edu