The formatting is the action to format , i.e. to prepare a data-processing data carrier (Disquette, Hard drive, etc) by registering a Filesystem there, so that he is recognized by the Operating system of the Ordinateur. There exist many different filesystems: FAT, NTFS, HFS, Ext2, Ext3, UFS, etc

The mass storage units can receive several filesystems, divided into logical partitions; one speaks then about partitioning. In theory, only the hard drives can be partitionnés, the other peripherals of storage usually do not have a sufficient space or present compatibility issues.

The formatting makes the access impossible to the data previously present on the disc. It is thus essential to proceed to a safeguard of the important data.

However, as for any traditional suppression of data, it is always possible to try a recovery, in so far as the disc was not formatted in a protected way. The formatting of low level is often confused with the formatting with zero , during which each bit of data is replaced by zeros (what causes to restore the disc in its state at the exit of factory).

The formatting calls upon two processes different known under the names from formatting from low level and high level formatting . The formatting of low level deals with returning the surface of the disc in conformity so that the controller waits while the high level formatting relates to software information suitable for the operating system.

In order to avoid the accidents, the utilities of formatting require at least a confirmation on behalf of the operator. In several versions of MS-DOS, there exists a parameter not documented entitled /autotest which forces the formatting without confirmation.

Formatting of a diskette

Formatting of low level

The formatting of low level of a Disquette 1.44MB generally writes 18 sectors of 512 bytes on each of the 160 tracks (80 on each face) of the peripheral. That gets 1 ' 474 ' 560 bits of storage - the sectors are actually larger than 512 bytes because they include/understand numbers of sector, bits CRC and other necessary informations to identify and check the sectors during the reading and of the writing. The formatting of low level registers properties such as the numbers of the sectors, necessary for the material and the disk controller. Moreover, it is possible to resort to several formats of low level on the same peripheral. For example, it can be useful to increase the size of the sectors to reduce space between the recordings.

High level formatting

On the other hand, the high level formatting is specific to each filesystem. MS-DOS requires for example the writing of a sector of starting, which will indicate if it is possible to start the computer on the diskette, like two copies of the table of allowance of the files and an empty root directory.

In the case of a diskette, the formattings of bottom and high level are generally carried out on the only one way.

Formatting of low level of an hard drive

The first hard drives were relatively similar to the diskettes but it was most of the time the BIOS which took care of the formatting of low level. On MS-DOS, the process implied the program debug to transfer control to a routine dissimulated at several addresses in the various BIOS.

With the beginning of the year 1990, the formatting of low level of the hard drives became more complex and more advanced:

• recourse to various numbers of sector per track;
• longer external tracks;
• encoding of the numbers of track the surface of the disc to simplify the material and to increase the rate of travel of the play-back heads, etc

In order to avoid the increasing difficulties due to the various versions of the BIOS, manufacturing them started to carry out the formatting of low level at the exit of factory. It any more but did not remain to launch a high level formatting to register the filesystem.

Today, it is improbable that an end user has to carry out a formatting of low level of a disc IDE or ATA. Simple rebootstrapping is enough in the majority to the cases.