Low Level Formatting is conducted by the manufacturer, and identifies the cylinders, heads, and sectors. The field technician may do this under special circumstances if the software has been acquired from the manufacturer’s web site.

Medium Level formatting is preparing the hard disk to receive the operating system, and may be done with either the FDISK program from DOS or Windows 9.x or 'diskpart' with NT, which partitions the disk. The disk has to be partitioned before we can perform the actual medium level format procedure. Medium level formatting creates the File Allocation Table (FAT) and the root directory. The DOS FORMAT.COM utility is used to perform this function.
The format command will write the status code 0000 to identify all good sectors or status code FFF7 to identify bad sectors to the FAT.

High Level Formatting is commonly called just “formatting”. and is essentially installing the operating system on the hard disk after it has been medium level formatted.

The File Allocation Table (FAT) is a table on the disk that keeps track of which file is stored in which sector. Older hard drives used FAT16, then we transitioned to FAT32. With today’s Microsoft® Windows 2000 and XP operating systems, NTFS (New Technology File System) is the most common file system in use.

A Cluster is a set of contiguous sectors (minimum of two) and treating them as a single unit in the FAT. Keep in mind that a sector is 512 bytes.