How to manage your AUTOEXEC.BAT and CONFIG.SYS. (MS-DOS Featuring DOS 5.0)
by Tony Roberts

The system startup files, AUTOEXEC.BAT and CONFIG.SYS, are central to your PC's personality. Whenever you turn on your computer, it spends a few seconds checking the hardware; then it reads your drive's CONFIG.SYS file and sets up the computer according to the instructions it finds there. After that, the system reads your drive's AUTOEXEC.BAT and performs the commands that are included in that file.

One Sings; the Other Doesn't

Although these two files seem to have similar functions, there a distinct difference between them: CONFIG.SYS describes and sets up hardware resources, and AUTOEXEC.BAT mainly runs software.

In addition, the CONFIG.SYS parameters normally can't be changed without your having to reboot, while the AUTOEXEC.BAT commands often can be changed without rebooting.

FILES is an example of a common CONFIG.SYS command. FILES specifies the number of open files the system can maintain. For each open file, the system sets aside a small amount of memory to track that file.

Even if you don't use all the allocated files, you can't reclaim the memory set aside for them without rebooting.

CONFIG.SYS is also used to install memory managers and device drivers--specialized software needed to operate such devices a scanners, CDROM drives, and mice.

While CONFIG.SYS describes your system's physical characteristics and personality, AUTOEXEC.BAT takes care of the routine tasks of getting the day started.

For example, when I wake in the morning, I put on a pot of coffee, shower, brush my teeth, dress, and eat breakfast. You could call this my personal AUTOEXEC.BAT program. Your computer's AUTOEXEC.BAT handles its routine chores in much the same way.

Remove Control

If you're going to control your computer, you need to understand and be able to modify your CONFIG.SYS and AUTOEXEC.BAT files. These files are usually very short and are found in the root directory of your system boot disk.

To edit or modify your startup files, you need an ASCII text editor or a word processor that can save files as text only. Most power users load their favorite text editor when they need to edit their startup files, but there's better way.

After all, what's the point of using a full-blown word processing program with a dictionary, a thesaurus, and a raft of other features when all you want to do is make a quick change in a ten-line file?

If you have DOS 5.0, you can use its excellent little text editor, EDIT. Earlier versions of DOS included EDLIN, a more difficult-to-use line editor.

When you install new software on your system, you're usually asked to make sure certain lines appear in your startup files. In some cases, the programs will modify the startup files for you; other times you'll have to make the changes yourself.

In either case, always make backup copies of your AUTOEXEC.BAT and CONFIG.SYS files before you install the new software. If your system suddenly starts actin flaky, you can compare the old and new startup files and determine if the changes made during the installation are causing a problem. Then you can revert to the old version if necessary.

DOS Boot

To start working with your startup files, examine the FILES and BUFFERS commands in your CONFIG.SYS. These common commands set aside areas of memory to handle file access and data transfer from disk to CPU.

Software installation programs often set these parameters high, just to be on the safe side. If you're facing a memory crunch, you may be able to reduce the number of buffers and files without suffering ill effects.

In your AUTOEXEC.BAT file, you'll want to have a PROMPT command and a PATH command as well as any commands needed to run your memory-resident utilities and set up the proper environment for your application.