15.1. Introduction

The C++ standard libraries provide an extensive set of input/output capabilities. This chapter discusses a range of capabilities sufficient for performing most common I/O operations and overviews the remaining capabilities. We discussed some of these features earlier in the text; now we provide a more complete treatment. Many of the I/O features that we'll discuss are object oriented. This style of I/O makes use of other C++ features, such as references, function overloading and operator overloading.

C++ uses type-safe I/O. Each I/O operation is executed in a manner sensitive to the data type. If an I/O member function has been defined to handle a particular data type, then that member function is called to handle that data type. If there is no match between the type of the actual data and a function for handling that data type, the compiler generates an error. Thus, improper data cannot "sneak" through the system (as can occur in C, allowing for some subtle and bizarre errors).

Users can specify how to perform I/O for objects of user-defined types by overloading the stream insertion operator (<<) and the stream extraction operator (>>). This extensibility is one of C++'s most valuable features.