Absolute Beginner's Guide to Digital Photography

When a disk is formatted, a number of special areas of the disk are set aside for

organization:

■ Master boot record

■ Partition table

■ Boot record

■ File Allocation Table (from which the FAT system takes its name)

■ Root directory

At a low level, disks are organized into 512-byte groups called sectors. The FAT sys-

tem allocates space for files using a unit called a cluster, made up of an integral

(side-by-side) number of sectors.

Aboot recordis a sector that contains code executed by the computer. A boot record

contains important information about the FAT filesystem, such as the cluster size

and the positions of the file allocation table, data area, and the root directory. The

master boot recordis the first boot record that the computer executes when it accesses

the hard disk.

104 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY

FIGURE 8.4

The write

process for a

FAT-based

system.

MBR (Master Boot Record)

FAT (0011 0012 0029 0030 EOF)

Boot Record

Data Area

Directory Entry

File Data

0011 0012

DATA

0022 0030

DATA

CONTRACT.DOC 0011 45691

File name First cluster Size

Further cluster numbers are found from the

file allocation table (FAT) and read from the

corresponding clusters in the data area.

System information

(file name, size, and

first cluster number)

are determined from

the directory entry.

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