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In our last article, we have introduced you to the formatted input/output functions in C++. In this article, we are only going to focus on the unformatted input functions. Unformatted console input functions are used to perform input operations at console i.e. to read an input entered by a user at the console.


Some of the most important unformatted console input functions comes from the istream class and these functions are-

Functions	Description
get()	Reads a single character from a user at the console and returns it.
get(char& s)	Reads a single character entered by a user at the console and assigns it to a char variable s.
get(char* array, streamsize n))	Reads a character or a multi-word string value entered by a user at the console and assigns it to a char array.
getline(char* array, int length)	Reads a character or a multi-word string value entered by a user at the console and assigns it to a char array.
getline(istream& is, string& str)	Reads a character or a multi-word string value entered by a user at the console by using the istream object, and assigns it to a string.

How to access these unformatted I/O functions?

• In C++, we can read the input entered by a user at the console by using the cin object of the istream class, and through this object we can access the first four of the above mentioned unformatted input functions, such as-
  • get(void)
  • get(char& s)
  • get(char* array, streamsize n)
  • getline(char* array, int length)
  
  
• To call the fourth variant of the getline() function. i.e. getline(istream& is, string& str), we don't need to use the cin object of the istream class as we can directly call this version.







• Using the cin object to read a string from the console


We can read characters/single-word string entered by a user by using the in-built cin object of the istream class. Let's see how it done.



//C++ Using the cin object to read a string


#include<iostream>

using namespace std;

int main()
{
	//A char array
	char season[20];
	
	//Enter a string
	cout<<"Enter your favorite season : ";
	
	//Using the cin object to read a single-word string, which is assigned to a char array
	cin>> season;
	
	//Printing the value of char array
	cout<<"Your favorite season is : " << season;

	return 0;
}






Output




Enter your favorite season : Spring
Your favorite season is :  Spring




In this example, a user is asked to type in his/her favorite season. As soon as the user enters the asked information and presses the enter button on the keyboard, all the characters entered by the user get stored in a char array named season, by using the in-built cin object of the istream class.




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• The cin object cannot read a multi-word string


By using the cin object of the istream class, we cannot read a multi-word string entered by a user. Let's see an example.



//C++ By using a cin object we cannot read multi-word strings


#include<iostream>

using namespace std;

int main()
{
	//A char array
	char country[20];
	
	//Enter a string
	cout<<"Enter a country you want to visit : ";
	
	//Using the cin object to read a single-word string, which is assigned to a char array
	cin>>country; // cin object can't read a multi-word string
	
	////Printing the value of char array
	cout<<"The country you want to visit is : " << country;

	return 0;
}






Output




Enter a country you want to visit : United Kingdom
The country you want to visit is :  United




In this example, a user is asked to type in his/her favorite country. As soon as the user enters the asked information i.e. United Kingdom and presses the enter button on the keyboard, only the characters in the first word i.e. United get stored in a char array named country.

The second word i.e. Kingdom entered after the space does not get stored in our char array. This proves that by using the cin object of the istream class, we cannot read multi-word string typed at the console.

In this situation, a variant of the built-in get() function comes to the rescue, which is explained just below.






• Using get(char* array, streamsize n) function to read char/multi-word string


We can read a character or a multi-word string value entered by a user at the console, by calling a variant of get() function. Let's see its syntax.



get(char* array, streamsize n);



• The get(char* array, streamsize n) function pulls the character/multi-word string value entered at the console by using the cin object of the istream class, and set it as the value of its function argument i.e. a character array.


• The reading ends when the user presses the Enter(a newline character) key.


• The streamsize argument specifies the total number of character to be extracted from the console and assigned to the character array. This number should be less than the size of the character array to be which extracted characters will be assigned.




//C++ Using the cin object to read a string

#include<iostream>

using namespace std;

int main()
{
	//A char array
	char country[30];
	
	//Enter a string
	cout<<"Enter a country you want to visit: ";
	
	//Using the cin object with a variant of get function to read a multi-word string, which is assigned to a char array
	cin.get(country,30);
	
	//Printing the value of char array
	cout<<"The country you want to visit is : " << country;

	return 0;
}






Output




Enter a country you want to visit: : New Zealand
The country you want to visit is :  New Zealand








• Using get(char& s) function to read a char


By calling another variant of the get() function, we can read a character value entered by a user at the console. Let's see the syntax of this get() function -



get(char& s);


The get(char& s) function pulls the character value entered at the console by using the cin object of the istream class, and set it as the value of its function argument, s i.e. a char variable. The reading ends when the user presses the Enter(a newline character) key.



//C++ Calling the get(char& s) function to read a character

#include<iostream>

using namespace std;

int main()
{
	//First char
	char c;
	
	//Enter a char value
	cout<<"Please enter a character : ";
	
	//Calling the get() function to read a character
	cin.get(c);
	
	//Printing the char value
	cout<< "The value of char is : " << c << "\n";



	//Second char
	char d;
	
	//Enter a char value
	cout<<"\n Please enter a character : ";
	
	//Calling the get() function to read a character
	cin.get(d);
	
	//Printing the char value
	cout<< "The value in char is : " << d;



	//Third char
	char e;
	
	//Enter a char value
	cout<<"Please enter a character : ";
	
	//Calling the get() function to read a character
	cin.get(e);
	
	//Printing the char value
	cout<< "The value in char is : " << e;
}






Output




Please enter a character : x
The value of char is : x
Please enter a character : The value in char is :
Please enter a character : y
The value in char is : y




• As you can see in the example, the first character x entered by the user at the console gets stored in char variable c. The reading ends when pressing an Enter key i.e. a newline character.
• The user was not asked to enter the second character because the newline character entered by user at the end of entering the first character still exists in the input queue, which is assigned to the second char variable d.
• The user was asked to enter the third character at the console, which gets stored in char variable e.


Up next, let us see another variant of the get function i.e.get(void).






• Using get(void) function to read a char


By calling another variant of the get() function, we can read a character value entered by a user at the console. Let's see the syntax of this get() function-



 get(void);


The get(void) function pulls the character entered at the console by using the cin object of the istream class and assigns it to a char variable. The reading ends when the user presses the Enter(a newline character) key.



//C++ Calling the get(void) function to read a character


#include<iostream>

using namespace std;

int main()
{
	//Fist char
	char c;
	
	//Enter a char value
	cout<<"Please enter a character : ";
	
	//Calling the get() function to read a character
	c = cin.get();
	
	//Printing the char value
	cout<< "The value in char is : " << c <<"\n";



	//Second char
	char d;
	
	//Enter a char value
	cout<<"Please enter a character : ";
	
	//Calling the get() function to read a character
	d = cin.get();
	
	//Printing the char value
	cout << "The value in char is : "<< d;



	//Third char
	char e;
	
	//Enter a char value
	cout<<"Please enter a character : ";
	
	//Calling the get() function to read a character
	e = cin.get();
	
	//Printing the char value
	cout<< "The value in char is : " << e;
}






Output




Please enter a character : h
The value of char is : h
Please enter a character : The value in char is :
Please enter a character : p
The value in char is : p




• As you can see in the example, the first character h entered by the user at the console gets stored in char variable c. The reading ends when pressing an Enter key i.e. a newline character.
• The user was not asked to enter the second character because the newline character entered by user at the end of entering the first character still exists in the input queue, which is assigned to the second char variable d.
• The user was asked to enter the third character at the console, which gets stored in char variable e.







• Using getline(char* array, int length) function


We can call an in-built variant of the getline() function to read a character or a string(single or multi-word) entered by a user at the console. Let's see the syntax of this variant of the getline() function-



getline (char* arr, int length);


The getline(char* arr, int length) function pulls the string entered at the console by using the cin object of the istream class and stores this string into a c-style char array, with a specified maximum length.



//C++ Callig the getline(char* arr, int length) function to read a char/string

#include<iostream>

using namespace std;

int main()
{
	//A char array
	char country[20];
	
	//Enter a character/string value
	cout<<"Enter a country you want to visit : ";
	
	//Calling the getline() function to read a character/string value entered at the console
	cin.getline(country,20);
	
	//Printing the char/string value
	cout<<"The country you want to visit is : " << country;

	return 0;
}






Output




Enter a country you want to visit : New Zealand
The country you want to visit is :  New Zealand



As you can in the example, the whole multi-word string i.e. name of the country entered by the user gets stored in the char array by using a variant of getline() function, which is accessed by the cin object of the istream class, something which we couldn't achieve using the cin object alone.






• Using getline(istream& is, string& str) function.


We can call another in-built variant of the getline() function to read a character or a string entered by the user at the console. But this variant of the getline() function assigns the read character/string value to a string, and not char array(like the previous variant of the getline() function). Let's see the syntax of this variant of getline() function -



getline (istream& is, string& str);


Looking at the syntax, this version of getline() function pulls a string entered at the console by using an object of the istream class and stores it into a string, str.



//C++ Calling the getline(istream& is, string& str) function to read a char/string

#include<iostream>

using namespace std;

int main()
{
	//A string
	string country;
	
	//Enter a char/string value
	cout<<"Enter a country you want to visit : ";
	
	//Calling the getline() function to read a character/string value entered at the console
	//which is assigned to a string
	getline(cin, country);
	
	//Priting the char/string value
	cout<<"The country you want to visit is : " << country;

	return 0;
}






Output




Enter a country you want to visit : South Africa
The country you want to visit is :  South Africa



As you can see in the example, the whole multi-word string i.e. South Africa entered by a user gets stored in a string, by using a variant of getline() function, which is passed the cin(an object of istream class) and also a string object, to which the user entered char/string value is assigned.

In the next article, we will discuss some important unformatted output functions in C++.





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