Because most computers have several application programs installed
in addition to the operating system, isolating a software problem can be confusing.
Software errors can also appear to be hardware malfunctions at first. Software problems
can result from the following circumstances:
- Improper installation or configuration of a program
- Device drivers that conflict with certain application programs
- Memory conflicts resulting from the use of
terminate-and-stay-resident (TSR) programs
- Interrupt conflicts between devices
You can confirm that a computer problem is caused by software by
running the System Board Devices test group as described in "Dell Diagnostics." If all tests in the test group complete
successfully, the error condition is most likely caused by software.
This section provides some general guidelines for analyzing software
problems. For detailed troubleshooting information on a particular program, see the
documentation that came with the software or consult the support service for the software.
When you obtain software, check it for viruses with virus-scanning
software before you install it on your computer's hard-disk drive. Viruses, which are
pieces of code that can replicate themselves, can quickly use all available system memory,
damage or destroy data stored on the hard-disk drive, and permanently affect the
performance of the programs they infect. Several commercial virus-scanning programs are
available for purchase, and most bulletin board services (BBSs) archive freely distributed
virus-scanning programs that you can download with a modem.
Before you install a program, read its documentation to learn how
the program works, what hardware it requires, and what its defaults are. A program usually
includes installation instructions in its accompanying documentation and a software
installation routine on its program diskette(s) or CD(s).
The software installation routine assists you in transferring the
appropriate program files to your computer's hard-disk drive. Installation instructions
may provide details about how to configure your operating system to successfully run the
program. Always read the installation instructions before you run a program's installation
routine. You may be instructed to modify some operating system start-up files, such as config.sys
and autoexec.bat, or the installation routine may modify start-up files
automatically.
When you run the installation routine, be prepared to respond to
prompts for information about how your computer's operating system is configured, what
type of computer you have, and what peripherals are connected to your computer.
Error messages can be produced by an application program, the
operating system, or the computer. "Messages and Codes"
discusses the error messages that are generated by the system. If you receive an error
message that is not listed in "Messages and Codes," check your operating system
or application program documentation.
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 your
application program to make sure the values or characters you are entering are valid.
Make sure that the operating environment is set up to accommodate
the programs you use. Keep in mind that whenever you change the parameters of the
computer's operating environment, you may affect the successful operation of your
programs. Sometimes, after modifying the operating environment, you may need to reinstall
a program that no longer runs properly.
Some programs may leave portions of their setup information behind,
even though you have exited from them. As a result, other programs cannot run. Rebooting
your system can confirm whether or not these programs are the cause of the problem.
Programs that use specialized subroutines called device drivers
can also cause problems with your computer system. For example, a variation in the way the
data is sent to the monitor may require a special screen driver program 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. Call the support service for the software
you are using to help you with this problem.
Memory address conflicts occur when two or more devices try to
access the same address in the upper memory blocks (UMB). For example, if a network
expansion card and an expanded-memory page frame are assigned an overlapping block of
addresses, a memory address conflict arises. As a result, when you try to log in to the
network, the operation fails.
To resolve this type of conflict, you can change the address of one
of the devices. For example, in the case of the network expansion card and expanded-memory
page-frame address conflict, you can move the network card to an address block in the
range of CC000h through D0000h. To reassign the expansion card's address block, refer to
the documentation for the card.
Problems can arise if two devices attempt to use the same interrupt
request (IRQ) line. To avoid this type of conflict, check the documentation for the
default IRQ-line setting for each installed expansion card. Then consult Table 1 to configure the card for one of
the available IRQ lines.
Table 1.
Default IRQ Line Assignments
| IRQ Line |
Used/Available |
| IRQ0 |
Used by the system timer |
| IRQ1 |
Used by the keyboard to signal that the
output buffer is full |
| IRQ2 |
Used by interrupt controller 1 to enable
IRQ8 through IRQ15 |
| IRQ3 |
Used by serial port 2 |
| IRQ4 |
Used by serial port 1 |
| IRQ5 |
Available |
| IRQ6 |
Used by the diskette/tape drive
controller |
| IRQ7 |
Used by the parallel port |
| IRQ8 |
Used by the real-time clock (RTC) |
| IRQ9 |
Available |
| IRQ10 |
Available |
| IRQ11 |
Available |
| IRQ12 |
Used by the mouse port |
| IRQ13 |
Used by the math coprocessor (if
applicable) |
| IRQ14 |
Used by the primary integrated drive
electronics (IDE) controller |
| IRQ15 |
Used by the secondary IDE controller |
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