Biostar 865G MICRO 775 Spécifications télécharger pdf (Page 35)

133

How Startup BIOS Controls the Boot Process

the drive has, where each partition begins and ends, and which partition is used for

booting (called the active partition). A partition is sometimes called a volume. The

ﬁrst volume on the hard drive used to boot the OS is called drive C. Chapter 6 covers

partitions in more detail.

At the beginning of the boot drive (usually drive C) is the OS boot record. This

512-byte sector is physically the second sector on the hard drive right behind the

MBR. This OS boot record contains a small program that points to a larger OS

program ﬁle that is responsible for starting the OS load. (A program ﬁle contains a

list of instructions stored in a ﬁle.) For Windows Vista, the OS boot record program

points to BootMgr. For Windows XP, that program is Ntldr. Figure 3-36 shows the

steps the BIOS follows to ﬁnd this ﬁrst OS program.

Step 2

MBR

boot

record

BootMgr

I’m the beginning

of the OS. I’ll take

it from here!

BIOS

RAM on CMOS

chip

Where do I

find an OS?

Step 1

Drive C

starts here

boot record

BootMgr

Hard drive

BIOS

MBR, can you

start the OS boot?

Master Boot

Record

Only if I can

find BootMgr.

Only if I

can find the OS

boot record.

Step 3

First look on drive C

and then drive E.

MBR

program

Figure 3-36 Numbered steps show how BIOS searches for and begins to load an operating

system (in this example, Windows Vista is the OS)

Courtesy: Course Technology/Cengage Learning

Notes

Program ﬁles can be a part of the OS or applications and have a .com, .sys, .bat, or .exe ﬁle

extension. BootMgr and Ntldr are exceptions to that rule because they have no ﬁle extension.

A+ 220-701

A+

220-701

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Biostar 865G MICRO 775 Spécifications Page 35

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