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In Unix-like operating systems, a device file or special file is an interface for a device driver that appears in a file system as if it were an ordinary file. There are also special files in MS-DOS, OS/2, and Microsoft Windows. They allow software to interact with a device driver using standard input/output system calls, which simplifies many tasks and unifies user-space I/O mechanisms. Device files often provide simple interfaces to peripheral devices, such as printers and serial ports. But they can also be used to access specific resources on those devices, such as disk partitions. Finally, device files are useful for accessing system resources that have no connection with any actual device such as data sinks and random number generators. MS-DOS borrowed the concept of special files from Unix, but renamed them ''devices''. Because early versions of MS-DOS did not support a directory hierarchy, devices were distinguished from regular files by making their names reserved words. This means that certain file names were reserved for devices, and should not be used to name new files or directories. The reserved names themselves were chosen to be compatible with "special files" handling of PIP command in CP/M. There were two kinds of devices in MS-DOS: Block Devices (used for disk drives) and Character Devices (generally all other devices, including COM and PRN devices). PIPE, MAILSLOT, and MUP are other standard Windows devices. There are two general kinds of device files in Unix-like operating systems, known as ''character special files'' and ''block special files''. The difference between them lies in how data written to them and read from them is processed by the operating system and hardware. These together can be called device special files in contrast to named pipes, which are not connected to a device but are not ordinary files either. ==Unix and Unix-like systems== Device nodes correspond to resources that an operating system's kernel has already allocated. Unix identifies those resources by a ''major number'' and a ''minor number'', both stored as part of the structure of a node. The assignment of these numbers occurs uniquely in different operating systems and on different computer platforms. Generally, the major number identifies the device driver and the minor number identifies a particular device (possibly out of many) that the driver controls: in this case, the system may pass the minor number to a driver. However, in the presence of dynamic number allocation, this may not be the case (e.g. on FreeBSD 5 and up). As with other special file types, the computer system accesses device nodes using standard system calls and treats them like regular computer files. Two standard types of device files exist; unfortunately their names are, for historical reasons, rather counter-intuitive, and explanations of the difference between the two are often incorrect as a result. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Device file」の詳細全文を読む スポンサード リンク
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