After looking in detail at startup files, it would perhaps be a natural step to discuss a couple of disks you may need if you run into trouble.
A boot disk is also called a system disk. A setup disk, on the other hand, is something different; it is a floppy disk that installs a program ? in this case DOS ? from the floppy to the hard disk. You may have a setup diskette but you don?t necessarily have a boot diskette.
Boot disks can give you a helping hand in times of real trouble. Experience proves it is better to be safe than sorry ? especially if you have DOS 5. If you begin experimenting with the contents of CONFIG.SYS, you must have a boot disk. Often in my experiments, I just couldn?t boot from the hard disk. An error in the CONFIG.SYS file can stall your computer, i.e. prevent it from completing the startup procedure. Luckily, DOS 6 has solved this problem.
A corrupt COMMAND.COM file can also cause the PC to crash. I remember once "just" opening the COMMAND.COM with the editor in Norton Commander (I only wanted to take a look) and then closing it without poking around. My computer went on strike. Moral: never touch COMMAND.COM.
Unfortunately, a PC can?t simply be switched on like an electric toaster and work ? it would be great if it could. It must first activate the operating system. Even though you have DOS, and one of the setup disks can start your PC, it still won?t do the job of a boot disk. So I suggest you make one. A PC can only start (boot) from drive A or C. Format a floppy like this:
Place an empty, formatted floppy disk in drive A and type:
The screen shows system transferred, which means that two "hidden" system ? or boot ? files and COMMAND.COM have been copied to the disk (DBLSPACE.BIN will also be copied, if you have DOS 6). These are the files necessary for DOS to start working, i.e. be read into memory. If you use DBLSPACE, you will also need DBLSPACE.BIN if you want to be able to read files on a disk that it has compressed. Copy sys.com to the disk:
C:\DOS>COPY SYS.COM A:
Label the disk Clean Boot.
Now you have a boot disk that will always start your PC if it refuses to start from the hard disk. This boot disk only contains the 3-4 files essential to the operating system, and booting from it results in a clean boot. Note that this can change the position of certain symbols on your keyboard as no keyboard drivers or codepages have been loaded. The new positions will correspond to those on an American (US) keyboard.
If you want to see which files are on the disk, you can use this undocumented DIR that includes a comma and shows hidden files:
Some games need a clean boot, so you can use your boot disk. It can also solve two problems you might run into.
You are unable to boot from your hard disk, and get the message Non-system disk. If the problem is just that there is something wrong with one of the system files or COMMAND.COM, then boot with your disk, and after booting write
which copies the 3-4 files to C:\. When you see the message system transferred, you should be able to boot from your hard disk again.
If you get the error message missing or bad Command Interpreter, then something has gone wrong with COMMAND.COM. If this happens, boot with your clean boot disk and write:
A:\>copy command.com C:\
A:\>copy command.com C:\DOS
which copies a working copy of COMMAND.COM from the diskette to the two relevant directories on the hard disk. You might actually need a copy only in a single location but put it in both to start off. Remove the disk from the drive and boot again.
Take another formatted floppy and do the same as you did with the first one.
This diskette will be used to boot your machine in the same way as a boot from the hard disk ? except that it will be done by the floppy. All the essential files should be on the floppy (here?s the advantage of having startup files without C: in front of the commands). The startup files are identical on both hard disk and diskette, with the exception of the PATH command.
All the following copying is easier to do with a program like NC, but here are the DOS commands so that nobody feels left out. If you can boot from the hard disk, then copy the startup files over to the diskette.
C:\>copy config.sys a:
C:\>copy autoexec.bat a:
Change the PATH command in A:AUTOEXEC.BAT to PATH=\;\DOS
(The commands given below may appear unusual to some readers because they specify a directory as the default directory by using the CD command but if you think about it, this is actually what CD does. The commands also make and switch to a directory in A without actually being on the A: drive. But this is perfectly acceptable.)
Create the directory A:\DOS.
Set this directory as the default on A:
Set C:\DOS as the default on C:
Copy the files that appear in your startup files to A:\DOS. You can use F3 after every command and edit the next command a little. The first commands should look something like this:
C:\DOS>copy himem.sys a:
C:\DOS>copy emm386.exe a:
C:\DOS>copy display.sys a:
Continue until all the files mentioned in your startup files are copied.
This disk can boot your PC with the same configuration as a boot from your hard disk but without using any of the files from your hard disk. Similarly, copy these files from C:\DOS to A:\DOS: UNFORMAT.COM, FORMAT.COM, CHKDSK.EXE, (SCANDISK.EXE), UNDELETE.EXE, FDSK.EXE and SYS.COM. You might want to copy other utility programs to the diskette. Check that it works, write-protect it, keep it in a safe place ? and remember where the safe place is!
It can be used in a situation where your hard disk breaks down to the extent that you cannot access or read the files on it (cannot read drive C: or error reading drive C:).
If you install a CD-ROM, sound card or a similar device, which add lines to your start files, then do not forget to copy the new start files to this boot diskette.
In addition, I would suggest you test your boot diskette at least once a month. Try it now!! It is a bit of a disaster if you really need it sometime next year and it does not work. It can happen!!
So, keep your boot diskette up to date. The work is minimal compared to the amount of time it can save you.
If disaster strikes and the only solution seems to be a repartition and/or a format or UNFORMAT of your hard disk, you can use this diskette. Fortunately, only a small minority of users ever have to face such a traumatic experience ? but if you are one of them, it is no consolation knowing that you are one of only a very few. If you are fortunate enough to know someone who may be able to help you, this is a situation where you should ask for his or her assistance.
Your rescuer will be able to give you much more help if you have made one of these disks. If you are an expert who helps others, then I recommend you make such a disk yourself. Check that it works by booting from it before you need to use it.
Losing contact with your hard disk can also occur if something happens to your CMOS, which we describe in the next section.