Beginner s knowledge of bootstrap files, a basic overview of bootstrap files

During the preboot phase, the computer does the following things: it runs the POST program, which detects the total memory of the system and other hardware devices, loads the first physical sector of the disk into memory, loads the hard disk master boot record and runs it, and the master boot record looks for the start location of the active partition. The boot sector of the active partition is then loaded and executed, and finally the NTLDR file is loaded and initialized from the boot sector.

During the boot phase, Windows XP will go through four smaller phases: the initial bootloader phase, the operating system selection phase, the hardware detection phase, and the configuration selection phase.

1) In the initial bootloader phase, NTLDR will convert the computer's microprocessor from real mode to 32-bit flat memory mode, in real mode, the system will reserve 640KB memory space for MS DOS, the rest of the memory is treated as extended memory, in 32-bit flat mode the system will treat all memory as available memory, and then NTLDR executes the appropriate small file system driver, At this point, NTLDR recognizes every file system partition in NTFS or FAT format, and this is the end of the initial bootloader phase.

2) When the initial bootloader phase is over, it will enter the operating system selection stage, if there are multiple operating systems installed on the computer, since ntldr has loaded the correct files, then a menu will appear at startup asking to select the operating system, ntldr is the partition location from the file to the system file. If the NT system is selected, then NTLDR will run the file, otherwise NTLDR will load and then hand over control. If there is only one operating system in the file or the timeout value in it is 0, then the menu screen for selecting the operating system will not appear, and if the file is illegal or does not exist, then NTLDR will attempt to boot the system from the default system volume.

Tip: After NTLDR starts, if an existing file is delivered to the root directory of the system and the file is valid, NTLDR will read the information in the file and restore the system to the state before hibernation, and the file will not be processed.

3) When the operating system selection phase is over, it will enter the hardware detection stage, at this time, the file will collect the list of hardware information in the computer, and then return the list to NTLDR, so that NTLDR will load these hardware information into the hardware in the registry "hkey local machine".

4) After the hardware detection phase is over, it will enter the configuration selection stage, if there is more than one hardware configuration list, then the profile selection menu will appear, if there is only one, it will not be displayed.