Two basic types of I/O manipulators: parameterless and parameterized.

Introduction

The parameterless manipulators that operate on output streams are shown here:

Manipulator	Purpose
boolalpha	Turns on boolalpha flag.
endl	Outputs a newline.
ends	Outputs a null.
dec	Turns on dec flag. Turns off the hex and oct flags.
fixed	Turns on fixed flag. Turns off the scientific flag.
flush	Flushes the stream.
hex	Turns on hex flag. Turns off the dec and oct flags.
internal	Turns on internal flag. Turns off the left and right flags.
left	Turns on left flag. Turns off the right and internal flags.
noboolalpha	Turns off boolalpha flag.
noshowbase	Turns off showbase flag.
noshowpoint	Turns off showpoint flag.
noshowpos	Turns off showpos flag.
nounitbuf	Turns off unitbuf flag.
nouppercase	Turns off uppercase flag.
oct	Turns on oct flag. Turns off the dec and hex flags.
right	Turns on right flag. Turns off the left and internal flags.
scientific	Turns on scientific flag. Turns off the fixed flag.
showbase	Turns on showbase flag.
showpoint	Turns on showpoint flag.
showpos	Turns on showpos flag.
unitbuf	Turns on unitbuf flag.
uppercase	Turns on uppercase flag.

To use a parameterized manipulator, you must include <iomanip>.

It defines the following manipulators:

Item	Value
resetiosflags (ios_base::fmtflags f)	Turn off the flags specified in f.
setbase(int base)	Set the number base to base.
setfill(int ch)	Set the fill character to ch.
setiosflags(ios_base::fmtflags f)	Turn on the flags specified in f.
setprecision (int p)	Set the number of digits of precision.
setw(int w)	Set the field width to w.

cout << setprecision(8) << left << 123.23;
cout << setw(12) << fixed << showpos << 98.6 << setw(10) << avg;

The same result can be obtained by use of stream member functions, but in a less compact form:

cout.width(12);
cout.setf(ios::fixed, ios::floatfield);
cout.setf(showpos);
cout << 98.6;
cout.width(10);
cout << avg;

Example,

Demo Code

#include <iostream>
#include <iomanip>
using namespace std;
int main()//from   w  w w.j  av a 2s .  co  m
{
   cout << "Default format: " << 123.123456789 << endl;
   cout << "Fixed format with precision of 7: ";
   cout << setprecision(7) << fixed << 123.123456789 << endl;
   cout << "Scientific format with precision of 7: ";
   cout << scientific << 123.123456789 << endl;
   cout << "Return to default format: ";
   cout << resetiosflags(ios::floatfield) << setprecision(6)
   << 123.123456789 << "\n\n";
   cout << "Use a field width of 20:\n";
   cout << "|" << setw(20) << "Testing" << "|\n\n";
   cout << "Use a field width of 20 with left justification:\n";
   cout << "|" << setw(20) << left << "Testing" << "|\n\n";
   cout << "Returning to right justification.\n\n" << right;
   cout << "Booleans in both formats: ";
   cout << true << " " << false << " " << boolalpha
   << true << " " << false << "\n\n";
   cout << "Default: " << 10.0 << endl;
   cout << "After setting the showpos and showpoint flags: ";
   cout << showpos << showpoint  <<  10.0 << "\n\n";
   cout << "The setw manipulator is very useful when repeated field\n"
   << "widths must be specified. For example:\n";
   cout << setw(8) << "this" << endl <<  setw(8) << "is" << endl
   << setw(8) << "a" << endl << setw(8) << "column" << endl
   << setw(8) << "of" << endl << setw(8) << "words";
   return 0;
}

Two basic types of I/O manipulators: parameterless and parameterized. - C++ File Stream

Introduction

Demo Code

Result

Related Tutorials