Time for a system tuneup. (making changes to startup files using MS-DOS) (Column)
by Tony Roberts

Startup-file phobia is a condition every computer user should try to outgrow. Your system is defined by the CONFIG.SYS and AUTOEXEC.BAT files, so you can't ignore these files and hope to run a well-tuned operation. The more you learn about your startup files, the better computer user you'll be.

Most of today's software installation programs are able to modify your startup files to include the necessary instructions for the software to run, but these automatic modifications aren't always the most efficient. Even if you let software modify your startup files, it's a good idea to review the changes carefully and tidy things up when necessary.

Let's look at what's involved: CONFIG.SYS contains instructions that define your system at boot-up. After you turn on your computer, it performs its system and memory check, loads the hidden DOS files and COMMAND.COM to get its basic operating instructions, and turns to CONFIG.SYS to see how you want things set up.

The instructions in CONFIG.SYS define how your computer will operate until it's rebooted. Memory allocation and the computer's rlationship with various devices--the screen, scanners, network cards--are defined here.

Once CONFIG.SYS puts everything in place, AUTOEXEC.BAT takes over. It fine-tunes DOS the way you like it and runs your regular programs. Unlike the commands issued in CONFIG.SYS, most of the instructions in AUTOEXEC.BAT can be changed during a computing session without rebooting.

To examine or edit your startup files, you need a text editor. The Edit command, which is part of DOS 5.0, will do just fine. To allay any fears that you might do something that will upset the balance of your system, make printouts and/or backup copies of CONFIG.SYS and AUTOEXEC.BAT before you begin.

Now, take a look at CONFIG.SYS and focus on the lines that begin device= or devicehigh. These lines install drivers that control your hardware. Each of these drivers takes up memory that could be used for other purposes, so there's no sense installing drivers you don't need. You might check for drivers that control devices, such as a scanner and fax board, that you're no longer using.

If you're not sure whether you can safely remove a line from CONFIG.SYS, you can insert the keyword Rem, just ahead of the command, as in rem device=c:/dos/cdr.sys.

This is known as commenting out the line. Rem is used to insert remarks or comments in a program. These comments don't execute when the program runs. By commenting out a line, you prevent the line from being executed. If you find that your system won't run properly without that particular line, you can reinstate it quickly by deleting the Rem.

While you're perusing CONFIG.SYS, make note of the Buffers and Files commands. These commands set aside areas of memory that are used to speed up data transfer and to keep track of open files. Some software installation programs set these to very high levels, probably on the better-safe-than-sorry theory. Unfortunately, each buffer and file allocated consumes memory that can't be used elsewhere.

Depending on how you use your computer, you may be able to lower the number of files and buffers allocated. My system--which I'd classify as an active one with plenty of Windows multitasking and network activity--allocates 40 files and 40 buffers.

On the AUTOEXEC.BAT side, make sure you have a Prompt statement and a Path statement. A good basic Prompt statement is prompt $p$g. This gives you a system prompt that includes the current disk drive and subdirectory. It's possible to get more elaborate with the prompt, but $p$g is a good start.

The Path statement tells the system where to look when it's trying to find executable files. Every time a Path statement is executed, the current path is replaced with the new path. If you have two Path statements in your AUTOEXEC.BAT, the second one overwrites the first one, so there's no point in having two. A few software installation routines, in their attempt to modify your Path statement, actually create a second Path statement.

If you were to type xxxyyyzz at the DOS prompt, your system would check every directory listed on the path before returning with the Bad command or filename message. Out-of-date subdirectory references in the path don't hurt anything; they just waste time.

The Path statement can be only 127 characters long, but you can usually keep it to less than that. A bare minimum Path statement includes the root directory, the directory where you keep your DOS programs, and the directory where you keep your batch files. By using batch files to switch to the subdirectory where a program resides, you can skirt the need to have that subdirectory on the path.

So why not shed your fear of startup files and give your system a tuneup?