The file system and simple terminal I/O are often the first OS features that the developer encounters. Early PC OSs such as MS-DOS did little more than manage files and terminal (or console) I/O, and these resources are also central features of nearly every OS.
Files are essential for the long-term storage of data and programs. Files are also the simplest form of program-to-program communication. Furthermore, many aspects of the file system model apply to interprocess and network communication.
The file copy programs in Chapter 1 introduced the four essential file processing functions:
This chapter explains these and related functions and also ...