C++ cin

Cin : Extracting Input from User Using Keyboard

In C++ Extraction operator is used to accept value from the user.User can able to accept value from user and that value gets stored inside value container i.e. Variable.

Syntax : Get Value from User

cin >> variable;

Explanation : Extraction Operator

• Include <iostream.h> header file to use cin.

#include<iostream.h>//traditional C++
OR
#include<iostream>// ANSI Standard
using namespace std;

• cin is used for accepting data from the keyboard.
• The operator >> called as extraction operator or get from operator.
• The extraction operator can be overloaded.
• Extraction operator is similar to the scanf() operation in C.
• cin is the object of istream class.
• Data flow direction is from input device to variable.
• Due to the use of input statement, the program will wait till the user type some input and that input is stored in variable.
• Multiple inputs can be accepted using cin.

Live Example : Accepting Input From User

#include<iostream.h>
using namespace std;
int main()
{
    int number1;
    int number2;
    cout<<"Enter First Number: ";
    cin>>number1;                 //accept first number
    cout<<"Enter Second Number: ";
    cin>>number2;                 //accept first number
    cout<<"Addition : ";
    cout<<number1+number2;        //Display Addition
    return 0;
}

Output :

Enter First Number: 8
Enter Second Number: 8
Addition : 16

Different ways of using cin in c++

Way 1. Simple Use of cin and Extraction Operator:

int tempNumber;
cin >> tempNumber;

• In above example, tempNumber is declared as integer variable.
• when control comes over cin , Program waits for the input from user.
• We have written integer variable after extraction operator so it will wait and expect integer as input from user .
• If you request an integer you will get an integer, character for character, string for string etc

Way 2 : Cascading Multiple Variables in Cin

int a,b;
cin >> a >> b;

is similar to -

int a,b;
cin >> a;
cin >> b;

While Accepting Two values cin consider next value when it found -

1. Space
2. Tab
3. Newline.

*Note : In this case, User is forced to input two variables (a and b).

Way 3 : cin to get string

cin >> string ; //for getting string input

• The extraction operator is also used for getting string.
• When blank space is detected, extraction operator stops reading input.
• cin allow us to enter only one word.
• For reading entire line, we use getline() function.