BOOTING PROCESS

The steps involved in the booting process, starting from the time the computer is switched ON, are described below.

For computers running on Windows 9x. (FAT)

1. The reset control is transferred to the ROM BIOS which has the set of instructions. The control is transferred to the routine of POST. POST is the power on self-test. This checks the memory, system internals and external peripherals.

2. The initialization of hardware, additional ROM BIOS and interrupt vector table then take place.

3. The first level bootstrap Loader tries to load another bootstrap loader from disk in the RAM. Then the ROM monitor first tries to load the first physical sector (partition table). If this drive fails then a similar read attempt is made on the hard disk's first physical sector. When found, then control is transferred to that sector.

4. The first bootstrap loader then loads the boot sector of the active partition and DBR in case of DOS partition. This DBR contains another loader for loading DOS called DBSL, which is the second level loader. This loader searches for two internal files IO.SYS and MS-DOS.SYS.

5. The IO.SYS file, which consists of new drivers and their initialization, and the second file is the SYSINIT that loads the rest of the operating system and gives logical access to the disk.

6. When MS-DOS.SYS is loaded, the DOS file system services are made available to the loader.

7. SYSINIT gives control to the CONFIG.SYS file if it exists. This is used to load some

drivers and memory management routines.

8. COMMAND.COM the user command interface is executed.

9. The AUTOEXEC.BAT file is run which contains some programs to run at the time of booting.