Input and Output
The I/O functions read and write data to and from files and devices. File I/O operations take place in text mode or binary mode. The Microsoft run-time library has three types of I/O functions:
Stream I/O functions treat data as a stream of individual characters.
Low-level I/O functions invoke the operating system directly for lower-level operation than that provided by stream I/O.
Console and port I/O functions read or write directly to a console (keyboard and screen) or an I/O port (such as a printer port).
Notes
Because stream functions are buffered and low-level functions are not, these two types of functions are generally incompatible. For processing a particular file, use either stream or low-level functions exclusively.