[file system]block device vs character device

A block device is one in which the data that moves to and from it occurs in blocks (such as disk sectors) and supports attributes such as buffering and random access behavior (is not required to read blocks sequentially, but can access any block at any time). Block devices include hard drives, CD-ROMs, and RAM disks. This is in contrast to character devices, which differ in that they do not have a physically-addressable media. Character devices include serial ports and tape devices, in which data is streamed character by character.