A sector (data block, block) is the smallest readable/writable unit of a hard disk. The regular size of a sector for hard drives is 512 bytes, for newer hard drives the sectors are 4096 bytes. The so-called 4K sectors (Advanced Format) correspond to the minimum size of the data blocks (Windows: Cluster, Linux: blocks) of modern operating systems. All sectors can be addressed individually and uniquely (LBA addressing). The 4K sectors are now almost standard for all hard drives over 2 TB capacity.