Overview of the Windows XP startup process

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, in which the computer first runs the Power On Self Test (POST), The total memory of the post detection system and the status of other hardware devices.

Start the computer from the press of the computer switch to the desktop to complete the boot, after a total of the following stages:

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

2. The boot phase;

3. Load the kernel stage;

4. Initialize the kernel phase;

5. Login.

Detailed description of 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, in which the computer first runs the Power On Self Test (POST), The total memory of the post detection system and the status of 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 the configuration completed. The computer's underlying input/output system (BIOS) locates the computer's boot device, and then the MBR (Master Boot Record) is loaded and run. During the pre-boot phase, the computer will load the Windows XP NTLDR file.

b) Boot phase

The Windows XP Professional boot phase contains 4 small stages.

First, the computer passes through the initial boot loader phase (Initial boot Loader), during which NTLDR converts the computer microprocessor from the actual mode to the 32-bit planar memory mode. In real mode, the system retains 640kb of memory for MS-DOS, while the rest of the memory is considered extended memory, whereas in 32-bit planar memory mode, the system (Windows XP Professional) treats all memory as free memory. Next, NTLDR launches the built-in Mini-file system drivers, which allows NTLDR to recognize every partition formatted with the NTFS or FAT file system to discover and load Windows XP Professional, here , the initial boot loader phase is over.

Then the system came to the operating system selection stage, if the computer installed more than one operating system (that is, multi-system), and the correct set of boot. INI so that the system provides operating system selection conditions, the computer monitor will display an operating system menu, which is NTLDR read the results of the boot. Ini. (As for the operating system menu, because the temporary conditions are not enough, there is no way to screenshot, but the author simulates one, see figure one.) )

In boot. INI, the following are mainly included:

[boot loader]

Timeout=30

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

[Operating Systems]

multi (0) disk (0) rdisk (0) partition (1) windows= "Microsoft WINDOWS XP Professional"/fastdetect

multi (0) disk (0) rdisk (0) partition (2) winnt= "Windows Windows $ Professional"

where multi (0) represents the disk controller, disk (0) rdisk (0) represents the disks, and partition (x) represents the partition. NTLDR is where the system files from the Windows XP Professional are located. (* This article does not explain in more detail the structure of the boot. INI, because it is not related to this topic, if you want to know, you can go to some specialized sites to inquire about the relevant information.) If there is only one operating system option in boot. ini, or if the timeout value is set to 0, the system does not appear in the operating System selection menu and directs directly to that unique system or default system. After you choose to start Windows XP Professional, the operating system selection phase ends and the hardware detection phase begins.

During the hardware detection phase, Ntdetect.com collects the list of computer hardware information and returns the list to NTLDR, which is intended to facilitate the subsequent addition of these hardware information to hardware in the registry HKEY_LOCAL_MACHINE.

After the hardware detection is complete, enter the configuration selection stage. If your computer has more than one hardware profile list, you can select it by pressing the up and down buttons. If there is only one hardware profile, the computer does not display this screen and loads the Windows XP Professional Edition directly using the default configuration file.