C++ Basic I/O
In this tutorial, we will learn about basic input/output in C++ to use the cin object to take input from the user, and the cout object to display output to the user with the help of examples.
Basic Input/Output
C++ comes with libraries that provide us with many ways for performing input and output functions. In C++ Input and Output are performed in the form of a sequence of bytes or more commonly known as “streams”.
1) “Input Stream” :- If the direction of flow of bytes is from the device (like- keyboard, a disk drive, etc) to the main memory then this process is called input.
2) “Output Stream” :- If the direction of flow of bytes is opposite, i.e. from main memory to device (display screen, a printer, etc) then this process is called output.
C++ Output
The C++Â cout
 statement is the instance of the ostream class. In C++, cout
 sends formatted output to standard output devices, such as the screen. We use the cout
 object along with the <<
 operator for displaying output.
Example 1: String Output
#include <iostream>
using namespace std;
int main() {
// prints the string enclosed in double quotes
cout << "This is C++ Programming Example1: String Output";
return 0;
}
Output
This is C++ Programming Example1: String Output
How does this program work?
- We first include theÂ
iostream
 header file that allows us to display output. - TheÂ
cout
 object is defined inside theÂstd
 namespace. To use theÂstd
 namespace, we used theÂusing namespace std;
 statement. - Every C++ program starts with theÂ
main()
 function. The codeexecution begins from theÂmain()
 function. cout
 is an object that prints the string inside quotation marksÂ" "
. It is followed by theÂ<<
 operator.return 0;
 is the “exit status” of theÂmain()
 function. The program ends with this statement, however, this statement is not mandatory, but it is good practice for better programming.
Note: 1) If we don’t include the using namespace std;
 statement, we need to use std::cout
 instead of cout
.
2) This is the preferred method as using the std
 namespace can create potential problems.
However, we have used the std
 namespace in our tutorials in order to make the codes more readable.
#include <iostream>
int main() {
// prints the string enclosed in double quotes
std::cout << "This is C++ Programming Example1: String Output with
std namespace.";
return 0;
}
Output
This is C++ Programming Example1: String Output with std namespace.
Example 2: Numbers and Characters Output
To print the numbers and character variables, we use the same cout
 object but without using quotation marks.
#include <iostream>
using namespace std;
int main() {
int num1 = 20;
double num2 = 126.181;
char ch = 'A';
cout << num1 << endl; // print integer
cout << num2 << endl; // print double
cout << "character: " << ch << endl; // print char
return 0;
}
Output
20 126.181 character: A
Notes:
1) The endl
 manipulator is used to insert a new line. That’s why each output is displayed in a new line.
2) The <<
 operator can be used more than once if we want to print different variables, strings and so on in a single statement.
For example:
cout << "character: " << ch << endl;
C++ Input
1) C++Â cin
 statement is the instance of the class istream and is used to read input device.
2) In C++, cin
 takes formatted input from standard input devices such as the keyboard.
3) We use the cin
 object along with the >>
 operator for taking input.
Example 3: Integer Input/Output
Example To take input from the user
#include <iostream>
using namespace std
int main() {
int age;
cout << "Enter an age: ";
cin >> age; // Taking input from the user.
cout << "The age is: " << age;
return 0;
}
Output
Enter an age: 20 The age is: 20
In the program, we used
cin >> age
to take input from the user. The input is stored in the variable age. We use the >>
 operator with cin
 to take input.
Note: If we don’t include the using namespace std;
 statement, we need to use std::cin
 instead of cin
.
Example 4: C++ Taking Multiple Inputs
Take multiple input from the user
#include <iostream>
using namespace std;
int main() {
char a;
int age;
cout << "Enter a character and an integer: ";
cin >> a >> age;
cout << "Character: " << a << endl;
cout << "Age: " << age;
return 0;
}
Output
Enter a character and an integer: A 20 Character: A Number: 20