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In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. For most disks, each sector stores a fixed amount of user-accessible data, traditionally 512 bytes for hard disk drives (HDDs), and 2048 bytes for CD-ROMs, DVD-ROMs and BD-ROMs. [1]
Floppy disks and controllers had used physical sector sizes of 128, 256, 512 and 1024 bytes (e.g., PC/AX), but formats with 512 bytes per physical sector became dominant in the 1980s. [ 3 ] [ 4 ] The most common physical sector size for hard disks today is 512 bytes, but there have been hard disks with 520 bytes per sector as well for non-IBM ...
Still later, magnetic hard disks employed an evolution of LBA where the size of the addressable disk sectors can differ from the physical block size. For example, Advanced Format (AF) 512e HDDs use 4096-byte physical sectors, while their firmware provides emulation for a virtual sector size of 512 bytes; thus, "512e" stands for "512-byte ...
If the actual size of the disk exceeds the maximum partition size representable using the legacy 32-bit LBA entries in the MBR partition table, the recorded size of this partition is clipped at the maximum, thereby ignoring the rest of the disk. This amounts to a maximum reported size of 2 TiB, assuming a disk with 512 bytes per sector (see 512e).
Common floppy disk formats, logical characteristics by platform Platform Size Density Sides Tracks/ side Sectors/ track Bytes/ sector Sectoring Capacity rpm Encoding Note Acorn: 5 1 ⁄ 4 inch Single 1 40 10 256 soft 100 kB 300 FM 80 200 kB Double 1 40 16 256 160 kB MFM 80 320 kB 2 640 kB 3 1 ⁄ 2 inch Double 2 80 16 256 640 kB 300 MFM
For hard disk drives working in the 4K native mode, there is no emulation layer in place, and the disk media directly exposes its 4096, 4112, 4160, or 4224-byte physical sector size to the system firmware and operating system. That way, the externally visible logical sectors organization of the 4K native drives is directly mapped to their ...
Although other sector sizes have been known in the past, formatted sector sizes are now almost always set to powers of two (256 bytes, 512 bytes, etc.), and, in some cases, disk capacity is calculated as multiples of the sector size rather than only in bytes, leading to a combination of decimal multiples of sectors and binary sector sizes.
The sector unit is the smallest size of data to be stored in a hard disk drive, and each file will have many sector units assigned to it. The smallest entity in a CD is called a frame, which consists of 33 bytes and contains six complete 16-bit stereo samples (two bytes × two channels × six samples = 24 bytes).