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In C++, the formatted console input/output functions are used for performing input/output operations at the console by formatting the data in a particular format.

Some of the most important formatted console input/output functions in C++ are -

Functions	Description
width(int width)	Using this function, we can specify the width of a value to be displayed in the output at the console.
fill(char ch)	Using this function, we can fill the unused white spaces in a value(to be printed at the console), with a character of our choice.
setf(arg1, arg2)	Using this function, we can set the flags, which allow us to display a value in a particular format.
peek()	The function returns the next character from the input stream, without removing it from the stream.
ignore(int num)	The function skips over a number of characters, when taking an input from a user at the console.
putback(char ch)	This function appends a character(which was last read by the get() function), back to the input stream.
precision(int num_of_digts)	Using this function, we can specify the number of digits to the right of a decimal in a floating-point value to be printed in the output.

In C++, we can read the input entered by a user at the console by using the cin object of the istream class, and we can write the output at the console by using the cout object of the ostream class.

Note: Through the cin and cout objects, we can access the formatted I/O functions.

• Using the width() formatted output function


Using this function, we can specify the width of a value to be displayed in the output at the console. Let's see the syntax of width() function-



width(int width);

Where, width is the width of a value to be displayed in the output at the console.


Example of width(int width) function -

//C++ The width() formatted output function defines the width of a next value to be displayed in the output at the console.


#include<iostream>

using namespace std;

int main()
{
	//First value
	char ch = 'a';

	//Adjusting the width of the next value to displayed to 5 columns.
	cout.width(5);

	//Adjusted width of the first value
	cout<<ch <<"\n";

	//Second value
	int i = 1;

	//Width of the second value to be displayed in the output will not be adjusted to 5 columns.
	cout<<i;
}




Output




    a
1




• As you can see in the example, first we have displayed the value of a char variable after calling the width() function. Next, we have directly displayed a char value i.e. without calling the width() function.





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• Using the fill() formatted output function


Using this function, we can fill the unused white spaces in a value(to be printed at the console), with a character of our choice Let's see the syntax of fill() function-



fill(char ch);

Where, ch is a char value which fills the unused white spaces in a value.


Example of fill(char ch) function-

//C++ The fill() formatted output function fills the unused white spaces in a value(to be printed at the console), with a character of our choice.


#include<iostream>

using namespace std;

int main()
{
	//First value
	char ch = 'a';

	//Calling the fill function to fill the white spaces in a value with a character our of choice.
	cout.fill('(');

	//Setting the width of this value to 10
	cout.width(10);
	
	//Printing the first value
	cout<<ch <<"\n";

	//Second value
	int i = 1;

	//Once you call the fill() function, you don't have to call it again to fill the white space in a value with the same character.
	//Setting the width of this value to 5
	cout.width(5);
	
	//Printing the second value
	cout<<i;
}




Output




(((((((((a
((((1




• As you can see in the example, first we have displayed the value of a char variable after calling the fill() function. Next, we have directly displayed an int value i.e. without calling the fill() function but the fill() function is stil at work.








• Using the peek() formatted input function


The function returns the next character from the input stream, without removing it from the stream. Let's see the syntax of peek() function-



peek(void);



Example of peek() function -

//C++ The peek() function is used to return the next character from the input stream, without removing it from the stream.


#include<iostream>

using namespace std;

int main()
{
	//First char value
	char d;
	
	cout<<"Please enter a character to be read by the peek() function : ";

	//Calling the peek() function to return the next character from input stream, without removing it from the stream
	d = cin.peek();

	//Printing the first char value
	cout<<"The value in d is : " << d <<"\n";

	//Second char value
	char e;
	
	//Calling the get() function to return the next character from input stream, and also removing it from the stream
	e = cin.get();
	
	//Printing the second char value
	cout<<"The value in e is : " << e;
 
	return 0;
}




Output




Please enter a character to be read by peek() function : a
The value in d is : a
The value in e is : a








• Using the ignore() formatted input function


The function skips over a number of characters while taking an input from a user at the console. Let's see the syntax of ignore() function-



ignore(int num);

Where, num is the number of characters that will be skipped while taking an input from a user at the console.


Example of ignore(int num) function -

//C++ ignore() functionto skip over a number of characters, when taking an input from the user at console.


#include<iostream>

using namespace std;

int main()
{
	//A char array
	char season[10];
	
	//Prompting a user to enter the favorite season
	cout<<"Enter the favorite season : ";
	
	//Calling the ignore() function to skip over first 4 characters in the input from the user
	cin.ignore(4);
	
	//Taking the input from the user to fill the char array, season
	cin>>season;
	
	//Printing the value of char array, season
	cout<<"Your favorite season : " << season <<"\n";


	//A String
	string city;
	
	//Prompting a user to enter the favorite city name
	cout<<"Enter your favorite city : ";
	
	//Calling the ignore() function to skip over first 2 characters in the input from the user
	cin.ignore(2);
	
	//Taking the input from the user to fill the string, city
	cin>>city;
	
	//Printing the value of string, city
	cout<<"The city you have entered : " << city;

	return 0;
}




Output




Enter the favorite season : Autumn
Your favorite season : mn
Enter the city : California
The city you have entered : alifornia








• Using the putback() formatted output function


This function appends a character(which was last read by the get() function), back to the input stream. Let's see the syntax of the putback() function-



putback(char ch);

Where, ch is a char value appended back to the input stream.


Example of the putback() function-

//C++ putback() function is used to putback a character(which was last read by get() function) back to the input stream.


#include<iostream>

using namespace std;

int main()
{
	//First char value
	char c;
	
	//Promting a user to enter a character value
	cout<<"Please enter a character : ";
	
	//Calling the get() function to take an input from the user and assign it to our first char value
	c = cin.get();
	
	//Printing the value of our first char value
	cout<<"The value in c is : " << c << "\n";


	//Calling the function putback(char c) to put back the last character read back to the input stream
	cin.putback(c);

	//Second char value
	char d;
	
	//Calling the get() function to take an input from the user and assign it to our second char value
	d = cin.get();
	
	//Printing the value of our second char value
	cout<<"The value in d is : " << d;
 
	return 0;
}




Output




Please enter a character : a
The value in c is : a
The value in d is : a








• Using the setf() formatted output function


The setf() function allows us to set the flags to display a value in a particular format. Let's see the syntax of setf() function-



setf(arg1, arg2);

Where, arg1 and arg2 are formatting flags which are defined in the ios class.


Example of setf() function-

//C++ The setf() function is used to set the flags, which allow us to display a value in a particular format. 


#include<iostream>

using namespace std;

int main()
{
	//The first int
	int a = 10;

	//Calling the setf() function to set the flags to display a number, which is right-justified.
	cout.setf(ios::right,ios::adjustfield);

	//Calling the width() function to set the number of columns used to display a value at the console.
	cout.width(10);

	//Displaying the value of our first int value after calling the setf() and width() function
	cout<< a << "\n";


	//The second int 
	int b = 20;

	//Calling setf() function to set the flags to display a number, which is left-justified.
	cout.setf(ios::left,ios::adjustfield);

	//Calling the width() function to set the number of columns used to display a value at the console.
	cout.width(10);

	//Displaying the value of our second int after calling the setf() and width() function
	cout<< b;
 	
	return 0;
}




Output




        10
20








• Using the precision() formatted output function


By using the precision function, we can specify the number of digits to the right of the decimal in a floating-point value, which is to be printed in the output at the console. Let's see the syntax of precision() function -



precision(int num_of_digits);

Where, num_of_digits is number of digits to the right of the decimal, to be printed in the output at the console.


Note : Before calling the precision() function, we should call the setf() function to set the flag to display a fixed number of digits after the decimal in a floating-point number by using the flag values, ios::fixed and ios::floatfield, otherwise, directly calling the precision() function would only fix the total number of digits to display in the output.


Example of precision() function -

//C++ The precision() function defines the number of digits to be diplayed after the decimal, after rounding off a floating number, at the console.


#include<iostream>

using namespace std;

int main()
{
	//A floating-point value
	float d = 12.3458998f;
	
	//Printing the floating-point value
	cout<< "The floating value in variable d : " << d <<"\n";

	//Calling setf() function to set the flags to display a fixed number of digits after decimal in a floating-point value.
	cout.setf(ios::fixed, ios::floatfield);

	//Defining the number of digits to be displayed after the decimal in a floating number.
	cout.precision(3);

	//Printing the floating-point value after calling the setf() and precision() function
	cout<< "The floating value in variable d, after calling the precision() function : " << d;
}




Output




The floating value in variable d : 12.3459
The floating value in variable d, after calling the precision() function : 12.346








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