In this tutorial you will learn about the C++ Basic Input/Output and its application with practical example.
C++ Basic Input/Output
Input/Output operation is the way general purpose computer can communicate or interact to the outside world. In C++, I/O occurs in form of a data streams, which basically nothing other than a sequences of bytes. When bytes flow from a input device such as a keyboard, mouse, disk drive, or from a network to main memory, then this sequence of bytes is called as input stream and operation is called as input operation and if bytes flow from main memory to a output device like such as computer screen, a printer, a disk drive, or to a network , then this sequence of bytes is called as output stream and this operation is called as output operation. The C++, comes with an rich set of standard libraries for input/output operations. To perform any of the standard input and output operation we must have to include respective header files in our program.
In C++, we have following header files important for basic I/O operation –
Header File | Function and Description |
---|---|
<iostream> | It is used to define the cout, cin and cerr objects, which correspond to standard output stream, standard input stream and standard error stream, respectively. |
<iomanip> | It is used to declare services useful for performing formatted I/O, such as setprecision and setw. |
<fstream> | It is used to declare services for user-controlled file processing. |
There are following standard streams are available to all c++ programs –
- cin (standard input)
- cout (standard output)
- cerr (standard error)
- clog (standard log)
C++ Standard Output Stream (cout)
The cout is basically a predefined object of ostream class. The cout object in conjunction with stream insertion operator (<<) allows us to send data to standard output device(screen).
Example:-
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#include <iostream> using namespace std; int main( ) { char str[] = "W3Adda - C++ Tutorial"; cout << "Welcome to " << str << endl; } |
Output:-
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Welcome to W3Adda - C++ Tutorial |
C++ Standard Input Stream (cin)
The cin is basically a predefined object of istream class. The cin object in conjunction with stream extraction operator (>>) allows us to accept/extract data from standard input device(keyboard).
Example:-
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#include <iostream> using namespace std; int main( ) { int age; cout << "Enter your age: "; cin >> age; cout << "Your age is: " << age << endl; } |
Output:-
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Enter your age: 35 Your age is: 35 |
C++ Standard Error Stream (cerr)
The cerr is also a predefined object of ostream class. The cerr object in conjunction with stream insertion operator (<<) allows us to send un-buffered error messages to standard error device(screen).
Example:-
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#include <iostream> using namespace std; int main() { char str[] = "Unable to read..."; cerr << "Error message : " << str << endl; } |
Output:-
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Error message : Unable to read... |
C++ Standard Log Stream (clog)
The clog is also a predefined object of ostream class. The clog object in conjunction with stream insertion operator (<<) allows us to send buffered error messages to standard error device(screen) until the buffer is filled or until the buffer is flushed.
Example:-
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#include <iostream> using namespace std; int main() { char str[] = "Unable to read..."; cerr << "Error message : " << str << endl; } |
Output:-
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Error message : Unable to read... |