Virtual device
Encyclopedia
A virtual device in Unix
is a file such as :/dev/null or :/dev/urandom, that is treated as a device, as far as user level software is concerned, but is generated by the kernel without reference to hardware
.
For instance when /dev/null is written to, the kernel tells the program it wrote everything to it (without actually writing it anywhere), and when read from, the reading program is told that it has reached the end of the file. It is a device file (it can be made with mknod for instance), but does not reference any hardware.
DOS
-, Windows
- and OS/2
-like operating system
s define the NUL device that performs a similar function (but is implemented as part of the file name processing – no actual file exists by that name).
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
is a file such as :/dev/null or :/dev/urandom, that is treated as a device, as far as user level software is concerned, but is generated by the kernel without reference to hardware
Hardware
Hardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....
.
For instance when /dev/null is written to, the kernel tells the program it wrote everything to it (without actually writing it anywhere), and when read from, the reading program is told that it has reached the end of the file. It is a device file (it can be made with mknod for instance), but does not reference any hardware.
DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
-, Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
- and OS/2
OS/2
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...
-like operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s define the NUL device that performs a similar function (but is implemented as part of the file name processing – no actual file exists by that name).