NTLDR

NTLDR is launched by the volume boot record of system partition, which is typically written to the disk by the Windows FORMAT or SYS command.

Windows NT was originally designed for ARC-compatible platforms, relying on its boot manager support and providing only osloader.exe, a loading program accepting ordinary command-line arguments specifying Windows directory partition, location or boot parameters, which is launched by ARC-compatible boot manager when a user chooses to start specific Windows NT operating system.

However, because IBM PC compatible machines lacked any of the ARC support, as that platform preceded ARC, the additional layer was added specifically for that platform: custom boot manager code presenting text menu allowing the user to choose from one or more operating system and its options configured in boot.ini configuration file, prepended by special StartUp module which is responsible for some preparations such as switching the CPU to the protected mode.

For a harddisk the code in the Master Boot Record (first sector) determines the active partition.

For NT and NT-based operating systems, it also allows the user to pass preconfigured options to the kernel.

For NT-based OSs, the location of the operating system is written as an Advanced RISC Computing (ARC) path.