In UNIX, path names can’t be prefixed by a drive name. To access a CD ROM in UNIX, it has to be mounted on a particular directory. A CD ROM can be mounted to the root or to a particular directory as per the requirements.
For Example: Below given is a file structure before mounting the CD ROM:
and here is the file structure in the CD ROM:
Now, say the CD ROM is mounted to the directory A. Here, the CD ROM becomes the part of the file structure. To access a file in C, the path can be followed is: /A/C
Special file: By using the concept of a special file an input and output device can be treated as a file. Special files are put in /dev directory.
There are two types of special files:
Block special files: A block special file is used for a disk where the disk can be divided in to addressable blocks.
Character special files: It is used for devices which input or output a character stream like printers and modems.
Pipe: Pipe is a pseudo file which is used for connecting two processes. It is used for communication between two processes. When a process wants to communicate with another process then it writes data to the pipe. The other process can read the data from the pipe.