Dell Latitude LM - Manual (Page 43)

Troubleshooting Your Computer 3-9
When you boot the computer, MS-DOS recognizes
memory in excess of 1 MB as extended memory. Some,
but not all, programs are able to use extended memory.
For example, the Windows operating system and Lotus
®
1-2-3 take advantage of extended memory.
Other programs are able to use extended memory only if it
is first converted into expanded memory by an expanded
memory manager (EMM).
Under the following conditions, expanded memory can
greatly enhance the computer’s ability to use application
programs that require more memory than is available in
the conventional memory area:
• The application program is written for use with
expanded memory.
• The EMM driver is installed and properly initialized.
Improper use of an EMM can lead to conflicts between
the expanded-memory operation and any installed PC
Cards, which may be assigned memory areas that overlap
memory areas that the EMM is using.
Using Software
The following subsections discuss errors that can occur
while using software.
Error Messages
Error messages can be produced by an application program,
the operating system, or the computer. “Messages and
Codes,” found earlier in this chapter, discusses the error
messages generated by the computer. If you receive an error
message not listed in “Messages and Codes,” check the
operating system or application program documentation.
Input Errors
If a specific key or set of keys is pressed at the wrong
time, a program may give you unexpected results. See the
documentation that came with the application program to
make sure the values or characters you are entering do
not conflict with the application program you are using.
Make sure the operating environment is compatible with
the programs you use. Keep in mind that whenever you
change the parameters of the computer’s operating envi-
ronment, you may affect the successful operation of the
programs. Sometimes, after modifying the operating
environment, you may need to reinstall a program that no
longer runs properly.
Memory-Resident Programs
There are a variety of utilities and supplementary pro-
grams that can be loaded either when the computer boots
or from an operating system prompt. These programs are
designed to stay resident in system memory and thus
always be available for use. Because they remain in the
computer’s memory, memory conflicts and errors can
result when other programs require use of all or part of
the memory already occupied by these TSR programs.
Typically, the operating system’s start-up files contain
commands to start TSR programs when you boot the
computer. If you suspect that one of these TSR programs
is causing a memory conflict, remove the commands that
start them from the start-up file. If the problem you were
experiencing does not recur, one of the TSR programs
probably created the conflict. Add the TSR commands
back into the start-up files one at a time until you identify
which TSR program is creating the conflict.
Program Conflicts
Some programs may leave portions of their setup infor-
mation behind, even though you have exited from them.
As a result, other programs cannot run. Rebooting the
computer can confirm whether or not these programs are
the cause of the problem.
Other programs use specialized subroutines called device
drivers that can cause problems in the computer. For
example, a variation in the way the data is sent to an
external monitor may require a special screen driver pro-
gram that expects a certain kind of video mode or
monitor. In such cases, you may have to develop an
alternative method of running that particular program—
the creation of a boot file made especially for that
program, for example. For help with this situation, call
the support service offered by the manufacturer of the
software you are using.
Avoiding Interrupt Assignment Conflicts
Problems can arise if two devices attempt to use the same
interrupt request (IRQ) line. To avoid this type of con-
flict, check the documentation for the default IRQ line