Written for the Technical Communication course at Mälardalens högskola: Process description.

The IBM PC boot process

Peter Karlsson, <pk@mds.mdh.se>

April, 1999

The IBM PC, and its compatibles, can run a multitude of different operating systems, like Linux, IBM OS/2 or Microsoft Windows. To facilitate this, the boot procedure has been standardized. This text gives an overview of this procedure.

Firstly, the ``BIOS'', the Basic Input/Output System, takes control over the system. It starts by performing a self-check of the computer, to ensure that everything works the way it should. It then checks the system configuration, and decides what to do next.

The second step is normally to load the partition table from the hard disk. This contains a list of divisions, or ``partitions'', one of which is marked as ``bootable''. The partition table can also contain some code that is executed, such as a virus guard, which is then executed.

When the system has scanned the partition table, it loads the first data unit, ``sector'', of the designated starting partition. This sector is called the ``boot sector'', and normally contains a small program that locates the system files for the operating system being started. It might also give the user some sort of choice of which version of the operating system to start.

The program in the boot sector then loads the system files, which are the ``core'' of the operating system that is being started. This core is more intelligent than the boot sector, and is normally responsible for loading routines for this particular computer's setup, so called ``device drivers''. These device drivers initialize the various system units, and ensures that the operating system knows how to communicate with them.

The next step, after the drivers have been loaded, is to enable the computer user to actually do something. How this is accomplished differs from system to system. Some systems, like Linux, brings up a ``login prompt'', where the user is asked to identify himself, so that he, or she, can be granted access to the computer. Systems that are not ``multi-user'', i e, only meant to be used by one person at a time, like OS/2 or Windows, may give the user access to the computer right away.

How the user then interacts with the computer is, however, beyond the scope of this text.

About this document ...

The IBM PC boot process

This document was generated using the LaTeX2HTML translator Version 98.2 beta6 (August 14th, 1998)

Copyright © 1993, 1994, 1995, 1996, Nikos Drakos, Computer Based Learning Unit, University of Leeds.
Copyright © 1997, 1998, Ross Moore, Mathematics Department, Macquarie University, Sydney.

The command line arguments were:
latex2html -no_navigation -html_version 3.2 -split 0 pcboot

The translation was initiated by peter karlsson on 1999-05-18

peter karlsson