Various techniques of low level format and high level format

Format is also an MS-DOS command that prepares a blank diskette or hard drive to hold data. To prepare a storage medium, usually a disk, for reading and writing. When you format a disk, the operating system erases all bookkeeping information on the disk, tests the disk to make sure all sectors are reliable, marks bad sectors (that is, those that are scratched), and creates internal address tables that it later uses to locate information. You must format a disk before you can use it.

Note that reformatting a disk does not erase the data on the disk, only the address tables. Do not panic, therefore, if you accidentally reformat a disk that has useful data. A computer specialist should be able to recover most, if not all, of the information on the disk. You can also buy programs that enable you to recover a disk yourself.

There are two types of formatting the any digital storage media.

1) Low level formatting: Low level formatting is a hard disk operation that should make recovering data from your storage devices impossible once the operation is complete. It sounds like something you might want to do if giving away a hard disk or perhaps discarding an old computer that may have contained useful and important, private information. All right, let's take a closer look and try to figure out how we can go about geeking, safely and smartly.

Low level formatting, as opposed to high level formatting is an operation performed directly against disk sectors. You skip the file system layer and you go directly for the underlying storage. Let me elaborate.

Normally, operations against storage devices are performed using a logical abstraction layer called the file system. Humans do not think in terms of bits and sectors and such, they think in terms of file names and possibly file sizes. This is exactly what file systems do, plus a few other things, like keep relations between files and directories, optimize read and writes, maintain integrity of operations, and more.

Low-level formatting is a procedure where you write data directly to the storage medium, bypassing the file system layer. You do not care if the hard disk has one partition or more, NTFS or BTRFS or anything else. You are using the device driver, which can be IDE or SCSI or SATA or others, and you're writing data to physical sectors. More importantly, low level formatting will write to each and every bit on the storage device, making sure the old states are destroyed forever, and with them, any trace of former data previously stored.

2) High level formatting: Method of formatting a hard drive that initializes portions of the hard drive and creates important file system areas on the disk. A good example of a high-level format is using the format command in MS-DOS.

A high-level format is commonly done if a user wishes to erase the hard drive and reinstall the operating system back onto the hard drive. If errors are present on the hard drive, or a high-level format is unable to be completed, a low-level format may need to be done first.

High-level formatting is the process of writing the file system structures on the disk that let the disk be used for storing programs and data. If you are using DOS, for example, the DOS FORMAT command performs this work, writing such structures as the master boot record and file allocation tables to the disk. High-level formatting is done after the hard disk has been partitioned, even if only one partition is to be used. See here for a full description of DOS structures, also used for Windows 3.x and Windows 9x systems.

The distinction between high-level formatting and low-level formatting is important. It is not necessary to low-level format a disk to erase it: a high-level format will suffice for most purposes; by wiping out the control structures and writing new ones, the old information is lost and the disk appears as new. (Much of the old data is still on the disk, but the access paths to it have been wiped out.) Under some circumstances a high-level format won't fix problems with the hard disk and a zero-fill utility may be necessary.

Different operating systems use different high-level format programs, because they use different file systems. However, the low-level format, which is the real place where tracks and sectors are recorded, is the same.