1.4. Standard Input and Output

1.4. Standard Input and Output
	Chapter 1. C++ Introduction

[ fromfile: cppintro.xml id: stdinout ]

In Example 1.1, the directive
```
  #include <iostream>
```
enabled you to make use of predefined global input (istream) and output (ostream) objects.

cin, console input, the keyboard by default.
cout, console output, the console screen by default.
cerr, console error, another output stream to the console screen that flushes more often and is normally used for error messages.

We also made use of the output operator<<(). (from the <iostream> class)
This is an overloaded operator symbol.
Instead of using the rather bulky function notation,
```
  cout.operator<<("Factorial of: ");
  
```
we invoked the same function using the more elegant and readable infix syntax:
```
cout << "Factorial of: "; 
```
This operator can be chained, and is predefined for use with many built-in types.

  cout << "The cost is $" << 23.45 << " for " << 6 << " items." << '\n';

In Example 1.2, we use the operator>>() for input with the istream object cin.

Example 1.2. src/iostream/io.cpp

#include <string>
#include <iostream>

int main() {
    using namespace std;
    const int THISYEAR = 2011;  
    string yourName;
    int birthYear;

    cout << "What is your name? "  << flush;
    cin >> yourName;

    cout << "What year were you born? " ;
    cin >> birthYear;

    cout << "Your name is " << yourName
            << " and you are approximately " 
            << (THISYEAR - birthYear)
            << " years old. " << endl;
}

The symbols, flush and endl are manipulators, ^[2] from the std namespace.

In Example 1.2, we make use of the string class, also from the C++ Standard Library.^[3]

	For Windows/MSVC Users
	By default, MSVC generates applications with no console support. This means that you cannot use the standard i/o/error streams unless you tell MSVC to build a console application. See the note [ `CONFIG += console` (for MSVC users) ] in Section 1.6.

^[2]Manipulators are function references that can be inserted into an input or output stream to modify its state. We discuss these further in Section 1.9.

^[3]We discuss classes in detail in Chapter 2. For now, you can think of a class as a data type with built-in functions.


1.3. C++ First Example		1.4.1. Exercises: Standard Input and Output