Chapter 2 Operating Systems 67
displayed while waiting for user input, and the
default operating system to load if no user input is
entered.
The Windows Boot Manager (bootmgr) replaces
bootcfg.exe
used by Windows NT-based operating
systems. The Windows Boot Manager will not
display a selection of operating systems if there
is only one operating system on the computer.
If there are two or more operating systems, the
Windows Boot Manager appears for approximately
30 seconds to allow the user to select which
operating system to boot. If no selection is made,
the default operating system is started.
When the Windows Boot Manager phase
completes, the Windows Boot Loader (winload.
exe) phase begins. First, the kernel (ntoskrnl.exe) is
loaded into memory but not executed. The
hal.dll
file and registry data are also loaded into memory.
The Windows Boot Loader phase ends by executing
the kernel. The kernel loading phase begins.
In this phase, the kernel starts the Session
Manager (smss.exe), which creates the system
environment. Up until now, the operating system
has been in a text-based mode; however, with
smss.exe
loaded, the operating system switches
to graphics mode by loading the GUI. It is at this
point that the familiar progress bar appears at the
bottom of the screen.
The kernel interacts with
hal.dll
and the
registry information in memory to load hardware
drivers and other files necessary to complete
the boot operation. The last phase in the boot
sequence is the logon phase, which is initiated by
the loading of the Logon Manager (winlogon.exe).
After a successful user logon, the desktop appears,
and the user can start using the various software
applications.
Certain files are automatically loaded into
RAM after a successful user logon. These files are
generally referred to as startup programs, and
will start quickly after they are selected from the
Start
menu or from a shortcut icon because they
are already loaded into RAM. If a program is not
a startup program, it will need to be loaded to
RAM before it starts, thus causing a short delay
in program response when selected. Figure 2-33
provides a description of the files for this boot
Windows Vista, 7, and
8 Boot Sequence File
Description
BCD The Boot Confi guration Data fi le, which is a registry fi le
containing information such as the names of the operating
systems to list in a boot menu.
BCDEdit.exe Used to edit the Boot Confi guration Data fi le. Replaces
bootcfg.exe
in Windows NT-based operating systems.
winload.exe
The Windows Boot Loader fi le, which loads
ntoskrnl.exe
and
hal.dll
into memory and scans the registry for device drivers to
load. It then passes control to the ntoskrnl.exe.
bootmgr The Windows Boot Manager fi le, which reads the BCD fi le
and displays the boot menu.
hal.dll Provides information and supports communication between
software applications and hardware devices. Software appli-
cations are not allowed to directly communicate with hard-
ware. Loads at the same stage as the kernel and then works
directly with the kernel.
ntoskrnl.exe
The core of the operating system referred to as the kernel.
smss.exe The Session Manager fi le, which creates the user session envi-
ronment and the graphical user interface.
winlogon.exe The Logon Manager fi le, which controls system logon by the
user.
Goodheart-Willcox Publisher
Figure 2-33.
Windows Vista,
Windows 7, and
Windows 8 boot
sequence and
configuration files.