Features Of Iostream.h

Features Of Iostream.h

It is will known that C++ is a tool for Object oriented programming (OOP). In order to handle the various object oriented features of a program, it is essential to have robust input and output facilities. Most of the object oriented programs handle three items: objects, message passing and optional parameters with the massage from the outside world. C++ provides a new way to perform the input and output operations called iostream method.

   The standard header file input and output stream (iostream.h) contains a set of small and specific general purpose functions for handling input and output data. The I/O stream is a sequence of following characters written for the screen display or read from the keyboard. The standard input and output operations in C++ are normally performed by using the I/O stream as cin for input and cout for output. The Borland C++ uses iostream.h for most stream related operations. The following are the list of various stream related header files to be included for input and output processing for different versions of the C++ compiler.

C++ compilers	Header Files To Be Included
Borland C++ Turbo C++ Microsoft Visual C++ Zortech C++ UNIX C++ (AT&T)	iostream . h,    ios .h, iomanip . h iostream . h, ios .h, iomanip . h ios . h, istream . h, ostream . h and streamb . h stream . h stream . h

   In this book, discussions on stream operations are limited only to the Borland C++ and Turbo C++ compilers. The C programming language comes with an extensive library of functions for handling input and output but it cannot add new format specifier to printf/ scanf functions. C++ supports input and output of numbers, characters and character strings more conveniently then C.

(i) Ios.h   The ‘ios’ correspond to input and output streams (hence io). The definitions based on ‘istream’ correspond to input streams and those based on ‘ostream’ to output streams. C++ allows three types of stream classes, namely,

      istream

      ostream

      iostream

(ii)  Istream  The istream consists of input functions to read a streams of characters from the keyboard.

(iii) Ostream  The ostream consists of output functions to write a character onto the screen.

(iv) 1Ostream  the iostream supports both input/output stream of functions to read a stream of characters form the keyboard and to display a stream of objects onto the video screen.

   In fact, C++ dopes not have built-in input and output functions for handling input and output of data from the outside world, but it supports different kind of stream related header files for providing these facilities. The stream library is a hierarchy of classes. The streambuf  class is the basis of all streams. It defines the basic characteristics of  buffers that hold characters for input and output. The ios class is derived from streambuf. It defines the basic formatting and error control capabilities used in streambuf. The ios is a virtual base class for the classes istream (input stream) and ostream (output stream). The iostream (input/output stream) class is derived from both istream and ostream.

Keyboard and Screen I/O

(a)   Cout   The cout is used to display an object onto the standard device, normally the video screen. The insertion operator (the double less the sign <<) is used along with the cout stream.

        The general syntax of the cout stream is,

                        Cout << variable 1 << variable 2 <<.....<< variable n;

For example, the following are certain valid cout member function usage in C++

(1)

      int x  = 123;

      float y  =  - 45 . 67;

      cout << x << y ;

The output will be  123   - 45 . 67

(3) Use of different data types freely on one line is permitted.

      int x  = 123;

      float y  =  - 45 . 67;

      cout  <<  “  x  = << x << ‘\t’ << “ y = “ << y;

The output will be x =123  y = - 45 . 67

(4) The cout stream is used to display different data types.

/ / cout is used to display different data types

#includ <iostream.h>

Void main ( )

{

   int num = 3 ;

   cout  << “ number = “ << num << “\n”;

   char  ch  = ‘a’;

   cout  << “ character = “ << ch <<  ‘\n’;

   float fa = - 34 . 45;

   cout  <<  “ real number = “ <<fa << “\n”;

}

Output of the above program

    number = 3

    character = a

    real number = - 34 . 450001

(b)  Cin  The cin is used to read a number, a character or a string of characters from a standard input device, normally the keyboard. The extraction operator (the double greater then sign >>) is use along with the cin operator.

     The general syntax of the cin is

                      cin >> variable 1 >> variable 2 >> …variable n;

For example, the following are certain valid cin member function usage in C++.

     int a,b;

     float f1, f2;

     char c1,c2;

(1)

     cin >> a >> b >> f1 >> f2 >> c1 >> c2 ;

(2)

     cin >> a >> b:

     cin >> f1 >> f2 ;

     cin >> c1 >> c2 ;

(3)

     cout << “ enter two integers \n” ;

     cin >> a >> b ;

     cout << “ enter two floating point numbers \n” ;

     cin >> f1 >> f2;

     cout << “ enter any two characters \n” ;

     cin >> c1 >> c2 ;

PROGRAM

A program to read any two numbers through the keyword and to perform simple arithmetic operations (i.e.; addition, subtraction, multiplication and division) and display the result using cin and cout functions.

/ / using cout stream

#includ <iostream.h>

Void main (void)

{‘

   int a, b, sum, sub, mul, div;

   cout << “ Enter any two numbers” << endl;

   cin >> a >> b;

   sum = a+b;

   sub = a-b

   mul = a*b;

   div = a/b;

   cout << ‘ a = “ << a << “ b = “ << b << “ sum = “;

   cout << sum << endl;

   cout << ‘ a = “ << a << “ b = “ << b << “ sub = “;

   cout << sub << endl;

   cout << ‘ a = “ << a << “ b = “ << b << “ sum = “;

   cout << mul << endl;

   cout << ‘ a = “ << a << “ b = “ << b << “ sum = “;

   cout << div << endl;

}

Output of the above program

      Enter any two numbers

10       20

 a = 10 b = 20 sum = 30

 a = 10 b = 20 sub =  -10

 a = 10 b = 20 mul = 200

 a = 10 b = 20 div  = 0

(c) Cerr and clog  In addition to the function cout, C++ provides other functions of  the class ostream called cerr and clog. They are used to redirect error messages to other devices. The output of cerr is unbuffered, while the output of clog is buffered. The use of the above functions are illustrated below.

    / / using cerr and clog

    #include <iostream.h>

   void main ( )

   {

       cout << “ My name is Komputer ! using cout \n”;

       cerr  << “ many greetings to you ! using cerr \n”;

       clog << “ helloo, computer ! using clog \n”;

   }

Summary of C++ I/O streams

Stream	Meaning
cin cout cerr clog	Keyboard input (stdin) Screen output (stdout) Standard error device output (stderr) Buffered output of standard error (stderr)