Windows 9X Boot Sequence

Windows 95 Boot Process

Overview

If you select another type of boot from the Startup Menu shown in Figure A, the boot sequence will vary accordingly.

If you want to observe each step of the boot process we’ll describe, you should begin by pressing the [F8] key when Windows 95 displays the Starting Windows 95 . . . message.

When you see the Microsoft Windows 95 Startup Menu, choose the Step-by-step confirmation option. Windows 95 will check with you before performing each step that it automatically executes in the normal boot sequence.

Since you’ll want to observe the entire process, you should answer Yes to all prompts. However, since we’re describing a normal boot sequence, we won’t include these prompts in our discussion.

Figure A: If you boot your system using any Startup Menu option other than Step-by-step confirmation, your boot process will differ from the procedure we explain here.

Microsoft Windows 98 Startup Menu
==========================

1. Normal
2. Logged (\BOOTLOG.TXT)
3. Safe Mode
4. Step-by-step confirmation
5. Command prompt only
6. Safe mode command prompt only
7. previous version of MS-DOS

Enter a choice: 1       Time remaining: 30

F5=safe mode  Shift+F5=Command Prompt  Shift+F*=Step-by-step confirmation  [N]

Windows 95 versus DOS

Many people argue over whether Windows 95 is a true operating system—some say it is, and others contend it’s just Windows 4 riding atop DOS 7.

Both sides of the debate make convincing arguments, but that’s because your stance on the issue depends largely on your definitions of DOS and Windows.

There’s no question that the GUI, which many people equate with Windows, functions on top of a lower-level operating system that looks and behaves much like DOS.

However, even though this subordinate part of the OS looks like DOS, its system files are very different from those in all previous DOS releases.

Through version 6.22, DOS loaded the IO.SYS and MSDOS.SYS files. These files were hidden system files that you couldn’t reconfigure unless you knew how to use a hex editor.

In Windows 95, IO.SYS and MSDOS.SYS still exist, but they play dramatically different rolls than they once did.

IO.SYS

The 32-bit IO.SYS is really a combination of DOS’s IO.SYS, MSDOS.SYS, CONFIG.SYS, and AUTOEXEC.BAT files. The new IO.SYS contains all the instructions the operating system needs to initially interact with your hardware. IO.SYS also loads some default CONFIG.SYS and AUTOEXEC.BAT commands, and it controls much of the remaining boot sequence.

Windows 95 can run without a CONFIG.SYS or an AUTOEXEC.BAT file. That’s because these files are built into IO.SYS, which automatically executes a set batch of commands.

(These commands are listed at the end of this article under the table “Commands Included in IO.SYS,”) Even though you can’t edit the IO.SYS file, you can use your CONFIG.SYS and AUTOEXEC.BAT files to override these commands. For example, IO.SYS automatically sets your file handles to a maximum of 60.
If you wanted to change this value to 100, you’d add to your CONFIG.SYS file the line FILES=100, which would override the FILES=60 command in IO.SYS.

MSDOS.SYS

After it finishes loading MSDOS.SYS, IO.SYS loads the system’s Registry (as long as you haven’t told it not to do so).

Windows 95 stores the Registry in two hidden files—USER.DAT and SYSTEM.DAT—in the \WINDOWS directory.

After Windows 95 processes the Registry, it creates backup copies of each of these files, called USER.DA0 and SYSTEM.DA0, respectively.

If Windows 95 can’t load the Registry through normal means, it will try to use these backup files.

If you’ve requested a logged boot or if your last boot was unsuccessful, Windows 95 will next copy BOOTLOG.TXT to BOOTLOG.PRV and then create a BOOTLOG.TXT file as the operating system loads.

CONFIG.SYS and AUTOEXEC.BAT

The next step in Windows 95’s boot sequence is to load COMMAND.COM, CONFIG.SYS, and AUTOEXEC.BAT.
Since Windows 95 can run without a CONFIG.SYS or AUTOEXEC.BAT file, you may be wondering about their purpose. By default, Windows 95 loads protected-mode drivers for your hardware along with the settings we detail in the sidebar “Commands Included in IO.SYS.”

Booting Windows 95 without loading CONFIG.SYS and AUTOEXEC.BAT is the preferred method because it increases your machine’s speed by loading 32-bit drivers instead of 16-bit DOS-based drivers. This technique also saves conventional memory in a DOS session.

For example, in our test, we added the 16-bit CD-ROM driver NEC_IDE to our CONFIG.SYS file and the MSCDEX command to the AUTOEXEC.BAT file.

Next, we rebooted and opened an MS-DOS Prompt window. When we executed the MEM/C command, we could see the added files loaded in conventional memory. At that point, Windows 95 reported that the system had 555 KB of free conventional memory, as Figure B shows.

Figure B: When we loaded the CD-ROM drivers from CONFIG.SYS and AUTOEXEC.BAT, the MEM utility reported 555 KB of free conventional memory.

Then, we removed the two commands and repeated the procedure. When our PC rebooted, we opened an MS-DOS Prompt window. We could still access our CD-ROM drive because Windows 95 detected the drive and loaded its own 32-bit protected-mode drivers. However, this time when we executed the MEM/C command, the utility didn’t list the files, and it reported that our system had 603 KB of free conventional memory, as shown in Figure C.

Figure C: When we let Windows 95 automatically detect the CD-ROM drive and load its own real-mode drivers, the MEM utility reported 603 KB of available conventional memory.

Since omitting the CONFIG.SYS or AUTOEXEC.BAT file increases conventional memory and processing speed, you may wonder why Microsoft even includes these files in Windows 95. The main reason is to ensure compatibility with legacy hardware and software.

Not all hardware manufacturers include Windows 95 drivers with their products, so Microsoft included CONFIG.SYS and AUTOEXEC.BAT to enable you to load a DOS-based driver and use the hardware anyway.
In addition, some software may require special commands in the CONFIG.SYS or AUTOEXEC.BAT file. For example, many older programs require that file handles be set to at least 20.
Windows 95 automatically sets file handles to 60, but some programs actually read the CONFIG.SYS file and check for the existence of a FILES command. If you had a program like this, you could add the line

FILES=60

to CONFIG.SYS to make your program run correctly. If you decide to delete your CONFIG.SYS and AUTOEXEC.BAT files, remember that Windows 95’s protected-mode drivers are available to all Windows and DOS-based programs.

However, if you select the Restart the computer in MS-DOS mode option in the Shut Down Windows dialog box, none of the drivers will be available to you unless you’ve loaded them in CONFIG.SYS or AUTOEXEC.BAT.

If you have a specific need that requires you to use the Restart the computer in MS-DOS mode option but you don’t want to limit yourself by using a CONFIG.SYS or an AUTOEXEC.BAT file, remember that this option automatically executes the DOSSTART.BAT file.

You won’t be able to execute CONFIG.SYS-type commands in DOSSTART.BAT, but you can include anything else you’d normally put in an AUTOEXEC.BAT file, such as a path, a prompt, and calls to other programs.

Graphical User Interface

Windows 95 Root Directory Files

Commands Included in IO.SYS