.NODE

Stream Output

Formatted and unformatted output capabilities are provided by ostream. Capabilities for output include output of standard data types with the stream insertion operator (<<); output of characters via the put member function; unformatted output via the write member function (Section 15.5); output of integers in decimal, octal and hexadecimal formats (Section 15.6.1); output of floating-point values with various precision (Section 15.6.2), with forced decimal points (Section 15.7.1), in scientific notation and in fixed notation (Section 15.7.5); output of data justified in fields of designated widths (Section 15.7.2); output of data in fields padded with specified characters (Section 15.7.3); and output of uppercase letters in scientific notation and hexadecimal notation (Section 15.7.6).

15.3.1. Output of char * Variables

C++ determines data types automatically, an improvement over C. Unfortunately, this feature sometimes "gets in the way." For example, suppose we want to print the value of a char * to a character string (i.e., the memory address of the first character of that string). However, the << operator has been overloaded to print data of type char * as a null-terminated string. The solution is to cast the char * to a void * (in fact, this should be done to any pointer variable the programmer wishes to output as an address). Figure 15.3 demonstrates printing a char * variable in both string and address formats. Note that the address prints as a hexadecimal (base-16) number. [Note: The reader who wants to learn more about hexadecimal numbers should read Appendix D, Number Systems.] We say more about controlling the bases of numbers in Section 15.6.1, Section 15.7.4, Section 15.7.5 and Section 15.7.7. [Note: The memory address shown in the output of the program in Fig. 15.3 may differ among compilers.]

Figure 15.3. Printing the address stored in a char * variable.

(This item is displayed on page 776 in the print version)

 1 // Fig. 15.3: Fig15_03.cpp
 2 // Printing the address stored in a char * variable.
 3 #include 
 4 using std::cout;
 5 using std::endl;
 6 
 7 int main()
 8 {
 9 char *word = "again";
10 
11 // display value of char *, then display value of char *
12 // static_cast to void *
13 cout << "Value of word is: " << word << endl
14 << "Value of static_cast< void * >( word ) is: "
15 << static_cast< void * >( word ) << endl;
16 return 0;
17 } // end main
 
 Value of word is: again
 Value of static_cast< void * >( word ) is: 00428300
 

15.3.2. Character Output using Member Function put

We can use the put member function to output characters. For example, the statement

cout.put( 'A' );

displays a single character A. Calls to put may be cascaded, as in the statement

cout.put( 'A' ).put( '
' );

which outputs the letter A followed by a newline character. As with <<, the preceding statement executes in this manner, because the dot operator (.) evaluates from left to right, and the put member function returns a reference to the ostream object (cout) that received the put call. The put function also may be called with a numeric expression that represents an ASCII value, as in the following statement

cout.put( 65 );

which also outputs A.

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

Templates

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

Bibliography

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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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