C++ : Ch1 : 3

Objectives : Input and Output Stream in C++

  • File Name : iostream_cin_cout1.cpp
  • Introducing "#include <iostream>", a preprocessor directive which support input and output operation in C++ programming
  • C++ language, uses an objects like ,"cin” or "cout", are  predefined stream-object, and to use these object you must include the "iostream" file . The name "cin" and "cout" are suffixed for "console input", and  "console output" respectively.
  • Special Notes on Namespaces.
  • Operator Overloading:
    • bitwise left shift (<<) operator, also known as insertion operator.
    • bitwise right shift (>>) operator, also known as extraction operator.
       
 

Step 1: Create a source file, or use a template and replace the codes, whatever suits you the best.  In this example I used an existing project , created with Eclipse IDE, and then edited the source code.

 The header file “iostream” of C++ language defines “cout” and “cin” objects which handle input and output operations.

In the image below, I remarked the line, “//using namespace std; “and used those two objects with scope “::” operator. You won't have to

 

Step 2:  Now edit this code, as shown below and then run. This application will process an  integer input with object  “cin” and C++ extraction/input operator “ >>” (data extraction steps, shift to right) , then display the data with  the object “cout” and “<<” insertion/output operator (insertion operations steps, shift to left).

Step: 3 Brief Discussion:  The iostream library of C++, allows streaming data input and output. The screenshot below, demonstrate that cin object with right-shift (>>) operator was expecting an integer, but encountered a non-integral data; an error expected and  "0" will displayed as an output.

Special Notes : using namespace std:

When we add a reference of this namespace, " using namespace std;" we don't have to use the object-scope resolution operator .

The label "namespace" allows to group up classes, objects and functions as a single entity under a name. C++ has some fixed namespaces like std, but it also allow the user create new namespaces.
In ANSI C++ the standard library members (like cin, cout, string, etc) are enclosed within a namespace called std. When you cite a namespace before the "int main()" it becomes a global entity, and you don't have to use "::" operator. The name of the namespace must be unique. We will look at this example, scope_namespace1.htm, later  in this chapter.