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Manipulators in C++ with Examples

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  • Difficulty Level : Medium
  • Last Updated : 12 Jun, 2022

Manipulators are helping functions that can modify the input/output stream. It does not mean that we change the value of a variable, it only modifies the I/O stream using insertion (<<) and extraction (>>) operators. 

  • Manipulators are special functions that can be included in the I/O statement to alter the format parameters of a stream. 
  • Manipulators are operators that are used to format the data display.
  • To access manipulators, the file iomanip.h should be included in the program.
     

For example, if we want to print the hexadecimal value of 100 then we can print it as:

cout<<setbase(16)<<100

Types of Manipulators There are various types of manipulators:

  1. Manipulators without arguments: The most important manipulators defined by the IOStream library are provided below.
    • endl: It is defined in ostream. It is used to enter a new line and after entering a new line it flushes (i.e. it forces all the output written on the screen or in the file) the output stream.
    • ws: It is defined in istream and is used to ignore the whitespaces in the string sequence.
    • ends: It is also defined in ostream and it inserts a null character into the output stream. It typically works with std::ostrstream, when the associated output buffer needs to be null-terminated to be processed as a C string.
    • flush: It is also defined in ostream and it flushes the output stream, i.e. it forces all the output written on the screen or in the file. Without flush, the output would be the same, but may not appear in real-time. Examples: 

CPP




#include <iostream>
#include <istream>
#include <sstream>
#include <string>
 
using namespace std;
 
int main()
{
    istringstream str("           Programmer");
    string line;
    // Ignore all the whitespace in string
    // str before the first word.
    getline(str >> std::ws, line);
 
    // you can also write str>>ws
    // After printing the output it will automatically
    // write a new line in the output stream.
    cout << line << endl;
 
    // without flush, the output will be the same.
    cout << "only a test" << flush;
 
    // Use of ends Manipulator
    cout << "\na";
 
    // NULL character will be added in the Output
    cout << "b" << ends;
    cout << "c" << endl;
 
    return 0;
}

Output:

Programmer
only a test
abc
  1. Manipulators with Arguments: Some of the manipulators are used with the argument like setw (20), setfill (‘*’), and many more. These all are defined in the header file. If we want to use these manipulators then we must include this header file in our program. For Example, you can use following manipulators to set minimum width and fill the empty space with any character you want: std::cout << std::setw (6) << std::setfill (’*’);
    • Some important manipulators in <iomanip> are:
      1. setw (val): It is used to set the field width in output operations.
      2. setfill (c): It is used to fill the character ‘c’ on output stream.
      3. setprecision (val): It sets val as the new value for the precision of floating-point values.
      4. setbase(val): It is used to set the numeric base value for numeric values.
      5. setiosflags(flag): It is used to set the format flags specified by parameter mask.
      6. resetiosflags(m): It is used to reset the format flags specified by parameter mask.
    • Some important manipulators in <ios> are:
      1. showpos: It forces to show a positive sign on positive numbers.
      2. noshowpos: It forces not to write a positive sign on positive numbers.
      3. showbase: It indicates the numeric base of numeric values.
      4. uppercase: It forces uppercase letters for numeric values.
      5. nouppercase: It forces lowercase letters for numeric values.
      6. fixed: It uses decimal notation for floating-point values.
      7. scientific: It uses scientific floating-point notation.
      8. hex: Read and write hexadecimal values for integers and it works same as the setbase(16).
      9. dec: Read and write decimal values for integers i.e. setbase(10).
      10. oct: Read and write octal values for integers i.e. setbase(10).
      11. left: It adjusts output to the left.
      12. right: It adjusts output to the right.

There are two types of manipulators used generally:
1] Parameterized and 
2] Non-parameterized
 

1] Parameterized Manipulators:-

Manipulator               ->          Meaning
setw (int n)                 ->          To set field width to n
setprecision (int p)     ->          The precision is fixed to p
setfill (Char f)              ->          To set the character to be filled
setiosflags (long l)      ->          Format flag is set to l
resetiosflags (long l)   ->          Removes the flags indicated by l
Setbase(int b)             ->          To set the base of the number to b

  • setw () is a function in Manipulators in C++:

         The setw() function is an output manipulator that inserts whitespace between two variables. You must enter an integer value equal to the                  needed space. 
         Syntax:
              setw ( int n) 
              As an example, 
              int a=15;  int b=20;
              cout << setw(10) << a << setw(10) << b << endl; 

  • setfill() is a function in Manipulators in C++:
    It replaces setw(whitespaces )’s with a different character. It’s similar to setw() in that it manipulates output, but the only parameter required is a single character. 
    Syntax:
         setfill(char ch) 
    Example:
         int a,b;
         a=15;   b=20;
         cout<< setfill(‘*’) << endl;

                cout << setw(5) << a << setw(5) << a << endl;

  • setprecision() is a function in Manipulators in C++:
    It is an output manipulator that controls the number of digits to display after the decimal for a floating point integer. 
    Syntax:
         setprecision (int p)
    Example:

              float A = 1.34255;

              cout <<fixed<< setprecision(3) << A << endl;

  • setbase() is a function in Manipulators in C++:
    The setbase() manipulator is used to change the base of a number to a different value. The following base values are supported by the C++ language: 
    • hex (Hexadecimal = 16) 
    •  oct (Octal = 8) 
    •  dec (Decimal = 10)  

           The manipulators hex, oct, and dec can change the basis of input and output numbers.
 

C++




// Example:
 
#include <iostream>   
#include <iomanip>
 
using namespace std;
main()
{
 
int number = 100;
 
cout << "Hex Value =" << " " << hex << number << endl;
 
cout << "Octal Value=" << " " << oct << number << endl;
 
cout << "Setbase Value=" << " " << setbase(8) << number << endl;
 
cout << "Setbase Value=" << " " << setbase(16) << number << endl;
 
 
return 0;
 
}

Output

Hex Value = 64
Octal Value= 144
Setbase Value= 144
Setbase Value= 64

2] Non-parameterized
Examples are endl, fixed, showpoint and flush.
• endl – Gives a new line
• ends – Adds null character to close an output string
• flush – Flushes the buffer stream
• ws – Omits the leading white spaces present before the first field
• hex, oct, dec – Displays the number in hexadecimal or octal or in decimal format
 

C++




// Example: ws – Omits the leading white spaces present before the first field
 
#include<iostream>
using namespace std;
 
int main()
 
{
      char name[125];
      cout << "Enter your name" << endl;
 
      cin >> ws;
 
      cin.getline(name,125);
 
      cout << name << endl;
       
      return 0;
}

Output

Enter your name
ram
ram

References:


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