Operating System: An operating system is software which is used for managing hard drives, memory, printer, keyboard, mouse, monitors, network interfaces, and other input and output devices. A user accesses the hardware by the use of the operating system. Operating system acts as a bridge between the hardware and the user interface program. It is also used for managing the resources in a computer so that users can access different resources simultaneously. Here is a simple architecture of operating system:
Files and directory: A file in an operating system is kept in a tree directory structure. A directory is a group of files. A file can be accessed by using a path name from the root directory. This is known as the absolute path name. For Example: /More.Process/Operating.Systems/Windows/file1
A file can also be retrieved from the current directory. For example, if the current directory is /More.Process/Operating.Systems then the above given file can be retrieved by using path name Windows/file1. This is knows as a relative path name.
To access a file for reading or writing, an indicator is used known as file descriptor.