Commands, printers, terminals, and application programs are all stored in files. This allows users to access diverse elements of the system in a uniform way and gives the operating system great flexibility. No format is implied when a file is created. This standardizes access to both software and hardware. Input occurs when the content of a file is modified or written to.
Output occurs when the content of one file is read or transferred to another file.
For example, to create a hardcopy printout of a text file, the system reads the information from the text file and writes the data to the file representing the printer. Collections of files are stored in directories. These collections of files are often related to each other, and storing them in a structure of directories keeps them organized. There are many ways to create, use, and manipulate files. All file types recognized by the system fall into one of these categories.