This lecture covers input functions in C++ using the standard input (cin) from the <iostream> header file. It explains how to use cin for different types of inputs, including integers, multiple integers, characters with cin.get(), and strings while noting that cin extraction stops at whitespace. The document provides C++ code examples to demonstrate these input methods.

1. Introduction to Computing &
Programming
Lecture 27
Engr. Beenish Adeel

2. The input Function

3. Inputting a value in C++
• Standard input (cin)
– It is defined in <iostream>
header file
– It is used to accept the input
from the standard input device
i.e. keyboard.
– The extraction operator(>>) is
used along with the object cin
for reading inputs.
– The extraction operator
extracts the data from the
object cin which is entered
using the keyboard.
#include <iostream>
using namespace std;
int main ()
{
int i;
cout << "Please enter an integer value: ";
cin >> i;
cout << "The value you entered is " << i;
return 0;
}

4. cin for multiple inputs
#include <iostream>
using namespace std;
int main()
{
int x, y;
cout << "Enter 2 numbers: “<<endl;
cin >> x>> y;
cout << "Sum = " << (x+y)<<endl;
return 0;
}

5. cin and getline function
• The cin can also be used with
some member functions which are
as follows:
cin.getline(char *buffer, int N)
• It reads a stream of characters of
length N into the string buffer, It
stops when it has read (N – 1)
characters or it finds the end of
the file or newline character(n).
• Here is the C++ program to
implement cin.getline():
#include <iostream>
using namespace std;
int main()
{
char name[5];
cin.getline(name, 3);
cout << name << endl;
return 0;
}

6. cin and get funtion
• cin.get(char& var)
• It reads an input
character and stores it
in a variable.
• Here is the C++ program
to implement cin.get():
#include <iostream>
using namespace std;
int main()
{
char ch;
cin.get(ch, 25);
cout << ch;
}

7. cin and strings
• cin and strings
• The extraction operator can be used on cin to get strings of characters in
the same way as with fundamental data types:
• However, cin extraction always considers spaces (whitespaces, tabs, new-
line...) as terminating the value being extracted, and thus extracting a string
means to always extract a single word, not a phrase or an entire sentence.
string mystring;
cin >> mystring;

8. Example
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
int main ()
{
string mystr;
float price=0;
int quantity=0;
cout << "Enter price: ";
getline (cin,mystr);
stringstream(mystr) >> price;
cout << "Enter quantity: ";
getline (cin,mystr);
stringstream(mystr) >> quantity;
cout << "Total price: " <<
price*quantity << endl;
return 0;
}

9. THANKS