<ios> functions
The latest version of this topic can be found at <ios> functions.
| defaultfloat | boolalpha | dec |
| fixed | hex | internal |
| left | noboolalpha | noshowbase |
| noshowpoint | noshowpos | noskipws |
| nounitbuf | nouppercase | oct |
| right | scientific | showbase |
| showpoint | showpos | skipws |
| unitbuf | uppercase |
boolalpha
Specifies that variables of type bool appear as true or false in the stream.
ios_base& boolalpha(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
By default, variables of type bool are displayed as 1 or 0.
boolalpha effectively calls str.setf( ios_base::boolalpha), and then returns str.
noboolalpha reverses the effect of boolalpha.
Example
// ios_boolalpha.cpp
// compile with: /EHsc
#include <iostream>
int main( )
{
using namespace std;
bool b = true;
cout << b << endl;
boolalpha( cout );
cout << b << endl;
noboolalpha( cout );
cout << b << endl;
cout << boolalpha << b << endl;
}
1
true
1
true
dec
Specifies that integer variables appear in base 10 notation.
ios_base& dec(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
By default, integer variables are displayed in base 10.
dec effectively calls str``.setf( ios_base::dec, ios_base::basefield), and then returns str.
Example
// ios_dec.cpp
// compile with: /EHsc
#include <iostream>
int main( )
{
using namespace std;
int i = 100;
cout << i << endl; // Default is base 10
cout << hex << i << endl;
dec( cout );
cout << i << endl;
oct( cout );
cout << i << endl;
cout << dec << i << endl;
}
100
64
100
144
100
defaultfloat
Configures the flags of an ios_base object to use a default display format for float values.
ios_base& defaultfloat(ios_base& _Iosbase);
Parameters
_Iosbase
An ios_base object.
Remarks
The manipulator effectively calls _I osbase.ios_base::unsetf(ios_base::floatfield), then returns _I osbase.
fixed
Specifies that a floating-point number is displayed in fixed-decimal notation.
ios_base& fixed(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
fixed is the default display notation for floating-point numbers. scientific causes floating-point numbers to be displayed using scientific notation.
The manipulator effectively calls * str.*setf( ios_base::fixed, ios_base::floatfield), and then returns str.
Example
// ios_fixed.cpp
// compile with: /EHsc
#include <iostream>
int main( )
{
using namespace std;
float i = 1.1F;
cout << i << endl; // fixed is the default
cout << scientific << i << endl;
cout.precision( 1 );
cout << fixed << i << endl;
}
1.1
1.100000e+000
1.1
hex
Specifies that integer variables shall appear in base 16 notation.
ios_base& hex(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
By default, integer variables are displayed in base 10 notation. dec and oct also change the way integer variables appear.
The manipulator effectively calls str.setf( ios_base::hex, ios_base::basefield), and then returns str.
Example
See dec for an example of how to use hex.
internal
Causes a number's sign to be left justified and the number to be right justified.
ios_base& internal(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which str is derived.
Remarks
showpos causes the sign to display for positive numbers.
The manipulator effectively calls str. setf( ios_base::internal, ios_base::adjustfield), and then returns str.
Example
// ios_internal.cpp
// compile with: /EHsc
#include <iostream>
#include <iomanip>
int main( void )
{
using namespace std;
float i = -123.456F;
cout.fill( '.' );
cout << setw( 10 ) << i << endl;
cout << setw( 10 ) << internal << i << endl;
}
..-123.456
-..123.456
left
Causes text that is not as wide as the output width to appear in the stream flush with the left margin.
ios_base& left(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
The manipulator effectively calls str.setf( ios_base::left, ios_base::adjustfield), and then returns str.
Example
// ios_left.cpp
// compile with: /EHsc
#include <iostream>
int main( )
{
using namespace std;
double f1= 5.00;
cout.width( 20 );
cout << f1 << endl;
cout << left << f1 << endl;
}
5
5
noboolalpha
Specifies that variables of type bool appear as 1 or 0 in the stream.
ios_base& noboolalpha(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
By default, noboolalpha is in effect.
noboolalpha effectively calls str.unsetf( ios_base::boolalpha), and then returns str.
boolalpha reverses the effect of noboolalpha.
Example
See boolalpha for an example of using noboolalpha.
noshowbase
Turns off indicating the notational base in which a number is displayed.
ios_base& noshowbase(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
noshowbase is on by default. Use showbase to indicate the notational base of numbers.
The manipulator effectively calls str.unsetf( ios_base::showbase), and then returns str.
Example
See showbase for an example of how to use noshowbase.
noshowpoint
Displays only the whole-number part of floating-point numbers whose fractional part is zero.
ios_base& noshowpoint(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
noshowpoint is on by default; use showpoint and precision to display zeros after the decimal point.
The manipulator effectively calls str.unsetf( ios_base::showpoint), and then returns str.
Example
// ios_noshowpoint.cpp
// compile with: /EHsc
#include <iostream>
int main( )
{
using namespace std;
double f1= 5.000;
cout << f1 << endl; // noshowpoint is default
cout.precision( 4 );
cout << showpoint << f1 << endl;
cout << noshowpoint << f1 << endl;
}
5
5.000
5
noshowpos
Causes positive numbers to not be explicitly signed.
ios_base& noshowpos(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
noshowpos is on by default.
The manipulator effectively calls str.unsetf( ios_base::showps), then returns str.
Example
See showpos for an example of using noshowpos.
noskipws
Cause spaces to be read by the input stream.
ios_base& noskipws(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
By default, skipws is in effect. When a space is read in the input stream, it signals the end of the buffer.
The manipulator effectively calls str.unsetf( ios_base::skipws), and then returns str.
Example
// ios_noskipws.cpp
// compile with: /EHsc
#include <iostream>
#include <string>
int main() {
using namespace std;
string s1, s2, s3;
cout << "Enter three strings: ";
cin >> noskipws >> s1 >> s2 >> s3;
cout << "." << s1 << "." << endl;
cout << "." << s2 << "." << endl;
cout << "." << s3 << "." << endl;
}
nounitbuf
Causes output to be buffered and processed on when the buffer is full.
ios_base& nounitbuf(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
unitbuf causes the buffer to be processed when it is not empty.
The manipulator effectively calls str.unsetf( ios_base::unitbuf), and then returns str.
nouppercase
Specifies that hexadecimal digits and the exponent in scientific notation appear in lowercase.
ios_base& nouppercase(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
The manipulator effectively calls str.unsetf( ios_base::uppercase), and then returns str.
Example
See uppercase for an example of using nouppercase.
oct
Specifies that integer variables appear in base 8 notation.
ios_base& oct(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
By default, integer variables are displayed in base 10 notation. dec and hex also change the way integer variables appear.
The manipulator effectively calls str.setf( ios_base::oct, ios_base::basefield), and then returns str.
Example
See dec for an example of how to use oct.
right
Causes text that is not as wide as the output width to appear in the stream flush with the right margin.
ios_base& right(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
left also modifies the justification of text.
The manipulator effectively calls str.setf( ios_base::right, ios_base::adjustfield), and then returns str.
Example
// ios_right.cpp
// compile with: /EHsc
#include <iostream>
int main( )
{
using namespace std;
double f1= 5.00;
cout << f1 << endl;
cout.width( 20 );
cout << f1 << endl;
cout.width( 20 );
cout << left << f1 << endl;
cout.width( 20 );
cout << f1 << endl;
cout.width( 20 );
cout << right << f1 << endl;
cout.width( 20 );
cout << f1 << endl;
}
5
5
5
5
5
5
scientific
Causes floating-point numbers to be displayed using scientific notation.
ios_base& scientific(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
By default, fixed notation is in effect for floating-point numbers.
The manipulator effectively calls str.setf( ios_base::scientific, ios_base::floatfield), and then returns str.
Example
// ios_scientific.cpp
// compile with: /EHsc
#include <iostream>
int main( )
{
using namespace std;
float i = 100.23F;
cout << i << endl;
cout << scientific << i << endl;
}
100.23
1.002300e+002
showbase
Indicates the notational base in which a number is displayed.
ios_base& showbase(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
The notational base of a number can be changed with dec, oct, or hex.
The manipulator effectively calls str.setf( ios_base::showbase), and then returns str.
Example
// ios_showbase.cpp
// compile with: /EHsc
#include <iostream>
int main( )
{
using namespace std;
int j = 100;
cout << showbase << j << endl; // dec is default
cout << hex << j << showbase << endl;
cout << oct << j << showbase << endl;
cout << dec << j << noshowbase << endl;
cout << hex << j << noshowbase << endl;
cout << oct << j << noshowbase << endl;
}
100
0x64
0144
100
64
144
showpoint
Displays the whole-number part of a floating-point number and digits to the right of the decimal point even when the fractional part is zero.
ios_base& showpoint(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
By default, noshowpoint is in effect.
The manipulator effectively calls str.setf( ios_base::showpoint), and then returns str.
Example
See noshowpoint for an example of using showpoint.
showpos
Causes positive numbers to be explicitly signed.
ios_base& showpos(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
noshowpos is the default.
The manipulator effectively calls str.setf( ios_base::showpos), and then returns str.
Example
// ios_showpos.cpp
// compile with: /EHsc
#include <iostream>
int main( )
{
using namespace std;
int i = 1;
cout << noshowpos << i << endl; // noshowpos is default
cout << showpos << i << endl;
}
1
+1
skipws
Cause spaces to not be read by the input stream.
ios_base& skipws(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which _ Str is derived.
Remarks
By default, skipws is in effect. noskipws will cause spaces to be read from the input stream.
The manipulator effectively calls str.setf( ios_base::skipws), and then returns str.
Example
#include <iostream>
#include <string>
int main( )
{
using namespace std;
char s1, s2, s3;
cout << "Enter three characters: ";
cin >> skipws >> s1 >> s2 >> s3;
cout << "." << s1 << "." << endl;
cout << "." << s2 << "." << endl;
cout << "." << s3 << "." << endl;
}
1 2 3
1 2 3.1.
.2.
.3.
unitbuf
Causes output to be processed when the buffer is not empty.
ios_base& unitbuf(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which str is derived.
Remarks
Note that endl also flushes the buffer.
nounitbuf is in effect by default.
The manipulator effectively calls str.setf( ios_base::unitbuf), and then returns str.
uppercase
Specifies that hexadecimal digits and the exponent in scientific notation appear in uppercase.
ios_base& uppercase(ios_base& str);
Parameters
str
A reference to an object of type ios_base, or to a type that inherits from ios_base.
Return Value
A reference to the object from which str is derived.
Remarks
By default, nouppercase is in effect.
The manipulator effectively calls str.setf( ios_base::uppercase), and then returns str.
Example
// ios_uppercase.cpp
// compile with: /EHsc
#include <iostream>
int main( void )
{
using namespace std;
double i = 1.23e100;
cout << i << endl;
cout << uppercase << i << endl;
int j = 10;
cout << hex << nouppercase << j << endl;
cout << hex << uppercase << j << endl;
}
1.23e+100
1.23E+100
a
A