Chapter 8. The IO Library

Section 8.1 The IO Classes

Section 8.2 File Input and Output

Section 8.3 string Streams

Chapter Summary

Defined Terms

The C++ language does not deal directly with input and output. Instead, IO is handled by a family of types defined in the standard library. These types support IO to and from devices such as files and console windows. Additional types allow in-memory IO to and from strings.

The IO library defines operations to read and write values of the built-in types. In addition, classes, such as string, typically define similar IO operations to work on objects of their class type as well.

This chapter introduces the fundamentals of the IO library. Later chapters will cover additional capabilities: Chapter 14 will look at how we can write our own input and output operators, and Chapter 17 will cover how to control formatting and how to perform random access on files.

Our programs have already used many IO library facilities. Indeed, we introduced most of these facilities in § 1.2 (p. 5):

• istream (input stream) type, which provides input operations

• ostream (output stream) type, which provides output operations

• cin, an istream object that reads the standard input

• cout, an ostream object that writes to the standard output

• cerr, an ostream object, typically used for program error messages, that writes to the standard error

• The >> operator, which is used to read input from an istream object

• The << operator, which is used to write output to an ostream object

• The getline function (§ 3.2.2, p. 87), which reads a line of input from a given istream into a given string