PC Boot Sequence
This collection of pages describes how a PC boots.
The boot sequence consists of these steps:
- The PC hardware or the user initiates the boot sequence.
Reset or Other
- BIOS (Basic Input Output System)
POST (Power On Self Test). The POST
tests and initializes the hardware.
- BIOS Boot. The
BIOS Boot routine selects a boot devices and boots it. For the
hard disk this reads the MBR into memory.
- Master Boot Record (MBR). The MBR selects the active partition
and reads the PBR from that partition
- Partition Boot Record (PBR). The PBR loads
the next stage of the boot loader into memory.
- Boot Loader. The boot loader reads the kernel and selected
drivers into memory. The details depend on the OS being loaded.
Windows NT and later, Windows Vista and later, Linux
- Kernel Intialization. The kernel initializes internal state
and other data structures to begin normal operation.
- System Process Initialization. Once the
kernel is initialized it begins dispatching processes. The initial
process continues the system initialization. Windows Linux
- Login. Part of
system initialization is to start the mechanism to allow users to
log in. Windows Linux
- User Process Startup. Once
a user logs on, additional processing occurs to initialize the
user's desired configuration. Windows Linux
Links to information on booting other types of systems may be found
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