HARDISK TRACK AND SECTOR EXPLAINED.
Track – this is one “ring” of the data on one side of the disk. Track record on the disk is too large to use as unit of information storage. In many drives, the capacity of more than 100 thousand bytes, and gives the unit for storing small files are very wasteful. Therefore, the tracks on the disk is divided into numbered segments called sectors.
The number of sectors may be different depending on the density of tracks and the drive type. For example, the track floppy drives can hold from 8 to 36 sectors, and track the hard drive – 380 to 700. Sectors that are created using standard programming format, have a capacity of 512 bytes, but it is possible that in the future, this value will change.
The numbering of sectors per track begins with unity, in contrast to the heads and cylinders, which is counting from zero. For example, a floppy disk HD (High Density) format 3.5-inch (1.44 MB) contains 80 cylinders, numbered 0 to 79 in the drive has two heads (with numbers 0 and 1), and each track is divided into the cylinder at 18 sectors (1-18).
When you format a disk at the beginning and end of each sector are additional areas to record their numbers, and other service information, through which the controller identifies the beginning and end of the sector. This allows us to distinguish an unformatted and formatted the disk space. After formatting the disk capacity is reduced, and this has to be reconciled, as to ensure normal operation of the drive for a disk space should be reserved for official information.
At the beginning of each sector recorded its title (or a prefix – prefix portion), that determines the beginning and the sector number, and in the end – the conclusion (or suffix – suffix portion), which contains a checksum (checksum), necessary to verify data integrity . Most new drives instead of the title, so-called entry No-ID, accommodating a larger amount of data. In addition to these areas of service data, each sector contains a data area of 512 bytes. When low-level (physical) formatting to all data bytes assigned a value, for example F6h.
