在类Unix操作系统中，设备文档系统允许软件通过标准输入输出系统调用与驱动进程交互，从而简化了许多任务。

设备文档系统包括设备文档、设备节点及设备特定文档，它们是驱动进程的接口，而在文档系统中，它们就像是普通文档。在微软的MS-DOS和Windows等操作系统中，也有专门的设备文档。

设备文档通常为周边设备提供简单的接口，如打印机。它也可访问这些设备的特定资源，如硬盘。它还可以访问没有连接到任何真实设备的系统资源，如数据接受器和随机数生成器。

MS-DOS的设备文档借鉴了Unix的特殊文档的概念。MS-DOS的早期版本并不支持文档目录层次，设备文档的文档名被设定为保留字以区分普通文档，新文档或新目录不能够使用这些设备文档的文档名。

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.