A device node is a special file type used on many Unix-like operating systems. Device nodes facilitate transparent communication between user space applications and computer hardware. A Unix-like operating system is one that behaves in a manner similar to a UNIX system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. ... An operating system usually segregates the available system memory into kernel space and user space. ... Hardware comprises all of the physical parts of a computer, as distinguished from the data it contains or operates on, and the software that provides instructions for the hardware to accomplish tasks. ...

By definition, device nodes correspond to resources that have already been allocated by the operating system kernel. In order to represent these resources, nodes are composed of a major number and a minor number. The assignment of these numbers is specific to different operating systems and computer platforms. The word kernel has a a variety of meanings in a several fields. ... In computing, an operating system (OS) is the system software responsible for the direct control and management of hardware and basic system operations. ... In computing, a platform describes some sort of framework, either in hardware or software, which allows software to run. ...

Like other special file types, device nodes are accessed using standard system calls and treated like regular files. There are two types of device nodes: In computing, a system call is the mechanism used by an application program to request service from the operating system. ...

1. Character special files, through which data is transmitted one character at a time. These device nodes are often used for serial communications devices such as teletype machines, virtual terminals, and serial modems.
2. 'Block special files, through which data is transmitted in the form of blocks. These device nodes are often used for parallel communications devices such as hard disks, optical media, and line printers.

In telecommunications and computer science, serial communications refers to any data transmission scheme in which data is sent one symbol at one time, sequentially over a communications channel. ... For blocks on Wikipedia, please see Wikipedia:Blocking policy. ... In computing, a parallel port is an interface from a computer system where data is transferred in or out in parallel, that is, on more than one wire. ... Typical hard drives of the mid-1990s. ... The CD-ROM (an abbreviation for Compact Disc Read-Only Memory (ROM)) is a non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive. ...

See Also

• File system
• Hardware abstraction
• User space
• Special file types