C++ Input and Output

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The standard libraries provide a set of input and output capabilities. It is based on the stream concept. The C++ language take place in streams are sequences of bytes.

Bytes flows from main memory to device like a printer, display screen and etc is called Output operation.

Bytes flow from the device like a printer, display screen and etc to main memory is called Input operation.

C++ input and output

Input/output Library Header Files:

Header File Description
  It defines the cin, cout, cerr and clog objects which belongs to the standard output stream, standard input stream, and the buffered/un-buffered standard error stream.
  This header file declare services useful for performing format input/output, such as setw and setprecision.
  This header file help to declare services for user-controlled file processing.

cout(Standard Output stream):

  • COUT is an instance of the ostream class. It says that “connected to” the output standard device.
  • It is used in conjunction with the stream insertion operator. It is written as cout <<. It determines the appropriate stream insertion operator to display the value.
  • It is overloaded to output data items of built-in like float, integer, double, pointer and string values. It can be used more than once in a single statement.

Example for cout:

#include <iostream>       
using namespace std;
int main() 
{  
   cout << "Welcome to Onlinetpoint"; 
   return 0;
}
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cin(Standard Input stream):

  • The predefined object Standard Input stream(cin) is an instance of the istream class.
  • The object is said to be the standard input device.
  • Used in conjunction with the stream extraction operator.
  • It is written as cin >> and may be used more than once in a single statement.

Example for cin:

#include <iostream>     
using namespace std;
int main()
{
	int a,b,c;    
	cout << "Enter the numbers:";
    cin >> a >> b;    
	c=a+b;
    cout << "Addition Of Two Number is:" << c << endl; 
	return 0;  
}
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cerr(Standard Error stream):

  • The predefined object Standard Error stream(cerr) is an instance of the ostream class.
  • The object is said to be the standard error device.
  • Used in conjunction with the stream insertion operator.
  • It is written as cerr <<.

Example for cerr:

#include <iostream>  
using namespace std;
int main() {
	char ch[] = "Unable to read....";
	cerr << "Error message : " << ch << endl;
    return 0;
}
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endl(Standard End Line):

  • The predefined object Standard End Line(endl) is an instance of the ostream class.
  • ENDL helps to insert a new line character.

Example for endl:

#include <iostream>  
using namespace std;
int main()
{
	int a,b,c;    
	cout << "Enter the numbers:";
    cin >> a >> b;    
	c=a+b;
    cout << "Addition Of Two Number is:" << c << endl; 
	return 0;  
}
Run ›
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