XP started in several stages

When you press the computer to start the computer, and before the Windows XP Professional operating system starts, we call it the pre-boot (pre-boot) phase, where the computer first runs Poweronselftest (POST), The current status of the total memory of the post detection system and other hardware devices.

Starting the computer by pressing the computer switch to the login to the desktop completes the following stages:

1. Pre-boot (pre-boot) phase;

2. The pilot phase;

3. Loading the kernel phase;

4. Initialize the kernel phase;

5. Landing.

Detailed introduction to each startup phase

A) Pre-boot phase

When you press the computer to start the computer, and before the Windows XP Professional operating system starts, we call it the pre-boot (pre-boot) phase, where the computer first runs Poweronselftest (POST), The current status of the total memory of the post detection system and other hardware devices. If the BIOS of the computer system (the underlying input/output system) is Plug and Play, then the computer hardware device will be inspected and configured to complete. The computer's underlying input/output system (BIOS) locates the boot device of the computer, and then the MBR (Masterbootrecord) is loaded and run. In the pre-boot phase, the computer loads the Windows XP NTLDR file.

(b) pilot phase

The Windowsxpprofessional boot phase contains 4 small phases.

First, the computer passes through the initial boot loader phase (Initialbootloader), in which NTLDR converts the computer microprocessor to 32-bit flat memory mode. In real mode, the system retains 640kb of memory for MS-DOS, while the remaining memory is treated as extended memory, whereas in 32-bit flat memory mode, the system (Windowsxpprofessional) treats all memory as available memory. Next, NTLDR launches the built-in mini-filesystemdrivers, which enables NTLDR to identify each partition formatted with the NTFS or FAT file system to discover and load windowsxpprofessional, here , the initial boot loader phase is over.

Then the system came to the operating system selection phase, if the computer installed more than one operating system (that is, multiple systems), and correctly set the Boot.ini to enable the system to provide the OS choice, the computer monitor will display an operating system menu, which is NTLDR read boot.ini results. (As for the operating system menu, because the temporary conditions are not enough, no way to screenshot, but the author simulates a, see figure one.) ）

In Boot.ini, the main contents are as follows:

[Bootloader]

Timeout=30

Default=multi (0) disk (0) rdisk (0) partition (1) WINDOWS

[Operatingsystems]

multi (0) disk (0) rdisk (0) partition (1) windows= "Microsoftwindowsxpprofessional"/fastdetect

multi (0) disk (0) rdisk (0) partition (2) winnt= "Windowswindows2000professional"

wherein, multi (0) represents the disk controller, and disk (0) rdisk (0) represents disks, and partition (x) represents partitions. NTLDR is where to look for Windowsxpprofessional's system files. (* This article will not explain the composition of boot.ini in more detail, because it has little to do with this topic, if you want to know, you can go to a number of specialized sites to query the relevant information.) If there is only one operating system option in the Boot.ini, or if the timeout value is set to 0, the system does not appear in the operating System selection menu, directing directly to that unique system or default system. After you choose to start windowsxpprofessional, the operating system selection phase ends and the hardware detection phase begins.

During the hardware detection phase, Ntdetect.com collects a list of computer hardware information and returns the list to NTLDR, which is designed to make it easier to add these hardware information to hardware under the registry HKEY_LOCAL_MACHINE later.

After hardware detection is complete, enter the configuration selection phase. If your computer contains a list of multiple hardware profiles, you can select it by pressing the up and down buttons. If you have only one hardware profile, the computer does not display this screen and uses the default profile to load the Windows XP Professional version directly.

The boot phase ends. In the boot phase, the system to use a total of the files are: Ntldr,boot.ini,ntdetect.com,ntokrnl.exe,ntbootdd.sys,bootsect.dos (optional).

c) Load kernel phase

During the load kernel phase, NTLDR loads the ntokrnl.exe called the Windows XP kernel. The system loaded the Windows XP kernel but did not initialize it. Then NTLDR loads the hardware abstraction layer (Hal,hal.dll), then the system continues to load the Hkey_local_machinesystem key, NTLDR reads the SELECT key to determine which ControlSet will be loaded. The control set contains the drivers for the device and the services that need to be loaded. NTLDR Loading Hkey_local_machinesystemservice ... The bottom start key value is 0 of the lowest device driver. When the CurrentControlSet of the mirror as ControlSet is loaded, the Ntldr pass is controlled to the kernel, and the initialization kernel phase begins.

(d) Initializing the kernel phase

At the beginning of the initialization kernel phase, the color Windows XP logo and the progress bar are displayed in the center of the screen, at which point the system completes the 4 tasks that are started:

* The kernel uses the data collected during hardware detection to create the Hkey_local_machinehardware key.

* The kernel creates clonecontrolset by referencing the default value of Hkey_local_machinesystemcurrent to copy ControlSet. The CloneControlSet configuration is a backup of the computer's data, excluding changes in startup and not being modified.

* The system completes initialization and loading device drivers, the kernel initializes those underlying drivers that are loaded during the load kernel phase, and then the kernel scans the hkey_local_machinesystemcurrentcontrolsetservice ... The device driver with the Start key value of 1. These device drivers are initialized when loading, and if there is an error, the kernel uses the ErrorControl key value to determine how to handle, the value is 3 o'clock, the error mark is a crisis/key, the system first encountered error will be restarted with Lastknowngoodcontrolset, If you still have an error using Lastknowngoodcontrolset startup, the system reports a startup failure, the error message is displayed, the system stops booting, the value is 2 o'clock error condition is serious, system startup failed and restarted with Lastknowngoodcontrolset, If the system boot is already using the LastKnownGood value, it ignores the error and continues to boot, the error is normal when the duty is 1, the system generates an error message, but it still ignores the error and continues to boot, ignoring the 0, the system does not display any error messages and continues to run

*sessionmanager starts the Windows XP advanced subsystem and services, SessionManager starts the WIN32 subsystem that controls all input, output devices, and accesses the monitor screen, as well as the Winlogon process, which completes the initialization of the kernel.

e) Landing

*winlogon.exe starts the localsecurityauthority and windowsxpprofessional the Welcome screen or Login dialog box, the system may continue to initialize the driver that has not been completed in the background.

* Prompt to enter a valid username or password.

ServiceController the final execution and scan hkey_local_machinesystemcurrentcontrolsetservives to check if there is still a service to load. ServiceController find the service with the start key value of 2 or higher, and the service is loaded according to the value of start and Dependongroup and Depandonservice values.

Only after the user successfully logged on to the computer, the start of Windows XP is considered to be completed, after the successful landing, the system copy CloneControlSet to Lastknowngoodcontrolset, after completing this step, the system will mean that has been successfully guided.