Files and Streams

C++ views each file as a sequence of bytes (Fig. 17.2). Each file ends either with an end-of-file marker or at a specific byte number recorded in a system-maintained, administrative data structure. When a file is opened, an object is created, and a stream is associated with the object. In Chapter 15, we saw that objects cin, cout, cerr and clog are created when is included. The streams associated with these objects provide communication channels between a program and a particular file or device. For example, the cin object (standard input stream object) enables a program to input data from the keyboard or from other devices, the cout object (standard output stream object) enables a program to output data to the screen or other devices, and the cerr and clog objects (standard error stream objects) enable a program to output error messages to the screen or other devices.

Figure 17.2. C++'s view of a file of n bytes.

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To perform file processing in C++, header files and must be included. Header includes the definitions for the stream class templates basic_ifstream (for file input), basic_ofstream (for file output) and basic_fstream (for file input and output). Each class template has a predefined template specialization that enables char I/O. In addition, the fstream library provides a set of typedefs that provide aliases for these template specializations. For example, the typedef ifstream represents a specialization of basic_ifstream that enables char input from a file. Similarly, typedef ofstream represents a specialization of basic_ofstream that enables char output to files. Also, typedef fstream represents a specialization of basic_fstream that enables char input from, and output to, files.

Files are opened by creating objects of these stream template specializations. These templates "derive" from class templates basic_istream, basic_ostream and basic_iostream, respectively. Thus, all member functions, operators and manipulators that belong to these templates (which we described in Chapter 15) also can be applied to file streams. Figure 17.3 summarizes the inheritance relationships of the I/O classes that we have discussed to this point.

Figure 17.3. Portion of stream I/O template hierarchy.

Introduction to Computers, the Internet and World Wide Web

Introduction to C++ Programming

Introduction to Classes and Objects

Control Statements: Part 1

Control Statements: Part 2

Functions and an Introduction to Recursion

Arrays and Vectors

Pointers and Pointer-Based Strings

Classes: A Deeper Look, Part 1

Classes: A Deeper Look, Part 2

Operator Overloading; String and Array Objects

Object-Oriented Programming: Inheritance

Object-Oriented Programming: Polymorphism


Stream Input/Output

Exception Handling

File Processing

Class string and String Stream Processing

Web Programming

Searching and Sorting

Data Structures

Bits, Characters, C-Strings and structs

Standard Template Library (STL)

Other Topics

Appendix A. Operator Precedence and Associativity Chart

Appendix B. ASCII Character Set

Appendix C. Fundamental Types

Appendix D. Number Systems

Appendix E. C Legacy Code Topics

Appendix F. Preprocessor

Appendix G. ATM Case Study Code

Appendix H. UML 2: Additional Diagram Types

Appendix I. C++ Internet and Web Resources

Appendix J. Introduction to XHTML

Appendix K. XHTML Special Characters

Appendix L. Using the Visual Studio .NET Debugger

Appendix M. Using the GNU C++ Debugger


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C++ How to Program
C++ How to Program (5th Edition)
ISBN: 0131857576
EAN: 2147483647
Year: 2004
Pages: 627
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