Партнёры:
Хостинг:
Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.
NAME
cout
- Controls output to a stream buffer associated with the
object stdout declared in <cstdio>.
SYNOPSIS
#include <iostream>
extern ostream cout;
ostream cout;
DESCRIPTION
The object cout controls output to a stream buffer associ-
ated with the object stdout declared in <cstdio>. By default
the standard C and C++ streams are synchronized, but perfor-
mance improvement can be achieved by using the ios_base
member function synch_with_stdio to desynchronize them.
After the object cin is initialized, cin.tie() returns
&cout, which implies that cin and cout are synchronized.
FORMATTING
The formatting is done through member functions or manipula-
tors.
MANIPULATORS MEMBER FUNCTIONS
showpos setf(ios_base::showpos)
noshowpos unsetf(ios_base::showpos)
showbase setf(ios_base::showbase)
noshowbase unsetf(ios_base::showbase)
uppercase setf(ios_base::uppercase)
nouppercase unsetf(ios_base::uppercase)
showpoint setf(ios_base::showpoint)
noshowpoint unsetf(ios_base::showpoint)
boolalpha setf(ios_base::boolalpha)
noboolalpha unsetf(ios_base::boolalpha)
unitbuf setf(ios_base::unitbuf)
nounitbuf unsetf(ios_base::unitbuf)
internal setf(ios_base::internal,
ios_base::adjustfield)
left setf(ios_base::left,
ios_base::adjustfield)
right setf(ios_base::right,
ios_base::adjustfield)
dec setf(ios_base::dec,
ios_base::basefield)
hex setf(ios_base::hex,
ios_base::basefield)
oct setf(ios_base::oct,
ios_base::basefield)
fixed setf(ios_base::fixed,
ios_base::floatfield)
scientific setf(ios_base::scientific,
ios_base::floatfield)
resetiosflags
(ios_base::fmtflags flag) setf(0,flag)
setiosflags
(ios_base::fmtflags flag) setf(flag)
setbase(int base) see above
setfill(char_type c) fill(c)
setprecision(int n) precision(n)
setw(int n) width(n)
endl
ends
flush flush( )
DESCRIPTION
showpos Generates a + sign in non-negative generated
numeric output.
showbase Generates a prefix indicating the numeric base of
generated integer output
uppercase Replaces certain lowercase letters with their
uppercase equivalents in generated output
showpoint Generates a decimal-point character uncondition-
ally in generated floating-point output
boolalpha Inserts and extracts bool type in alphabetic
format
unitbuf Flushes output after each output operation
internal Adds fill characters at a designated internal
point in certain generated output. If no such
point is designated, it's identical to right.
left Adds fill characters on the right (final positions)
of certain generated output
right Adds fill characters on the left (initial positions)
of certain generated output
dec Converts integer input or generates integer output in
decimal base
hex Converts integer input or generates integer output in
hexadecimal base
oct Converts integer input or generates integer output in
octal base
fixed Generates floating-point output in fixed-point nota-
tion
scientific Generates floating-point output in scientific
notation
resetiosflags
(ios_base::fmtflags flag) Resets the fmtflags field flag
setiosflags
(ios_base::fmtflags flag) Sets up the flag flag
setbase(int base) Converts integer input or generates
integer output in base base. The parame-
ter base can be 8, 10 or 16.
setfill(char_type c) Sets the character used to pad (fill)
an output conversion to the specified
field width
setprecision(int n) Sets the precision (number of digits
after the decimal point) to generate
on certain output conversions
setw(int n) Sets the field with (number of characters) to
generate on certain output conversions
showpos Generates a + sign in non-negative generated
numeric output.
showbase Generates a prefix indicating the numeric base of
generated integer output
uppercase Replaces certain lowercase letters with their
uppercase equivalents in generated output
showpoint Generates a decimal-point character uncondition-
ally in generated floating-point output
boolalpha Inserts and extracts bool type in alphabetic
format
unitbuf Flushes output after each output operation
internal Adds fill characters at a designated internal
point in certain generated output. If no such
point is designated, it's identical to right.
left Adds fill characters on the right (final positions)
of certain generated output
right Adds fill characters on the left (initial positions)
of certain generated output
dec Converts integer input or generates integer output in
decimal base
hex Converts integer input or generates integer output in
hexadecimal base
oct Converts integer input or generates integer output in
octal base
fixed Generates floating-point output in fixed-point nota-
tion
scientific Generates floating-point output in scientific
notation
resetiosflags
(ios_base::fmtflags flag) Resets the fmtflags field flag
setiosflags
(ios_base::fmtflags flag) Sets up the flag flag
setbase(int base) Converts integer input or generates
integer output in base base. The param-
eter base can be 8, 10 or 16.
setfill(char_type c) Sets the character used to pad (fill)
an output conversion to the specified
field width
setprecision(int n) Sets the precision (number of digits
after the decimal point) to generate
on certain output conversions
setw(int n) Sets the field with (number of characters) to
generate on certain output conversions
endl Inserts a newline character into the output sequence
and flush the output buffer.
ends Inserts a null character into the output sequence.
flush Flush the output buffer.
DEFAULT VALUES
precision() 6
width() 0
fill() the space character
flags() skipws | dec
getloc() locale::locale()
EXAMPLE
//
// cout example #1
//
#include<iostream>
#include<iomanip>
void main ( )
{
using namespace std;
int i;
float f;
// read an integer and a float from stdin
cin >> i >> f;
// output the integer and goes at the line
cout << i << endl;
// output the float and goes at the line
cout << f << endl;
// output i in hexa
cout << hex << i << endl;
// output i in octal and then in decimal
cout << oct << i << dec << i << endl;
// output i preceded by its sign
cout << showpos << i << endl;
// output i in hexa
cout << setbase(16) << i << endl;
// output i in dec and pad to the left with character
// @ until a width of 20
// if you input 45 it outputs 45@@@@@@@@@@@@@@@@@@
cout << setfill('@') << setw(20) << left << dec << i;
cout << endl;
// output the same result as the code just above
// but uses member functions rather than manipulators
cout.fill('@');
cout.width(20);
cout.setf(ios_base::left, ios_base::adjustfield);
cout.setf(ios_base::dec, ios_base::basefield);
cout << i << endl;
// outputs f in scientific notation with
// a precision of 10 digits
cout << scientific << setprecision(10) << f << endl;
// change the precision to 6 digits
// equivalents to cout << setprecision(6);
cout.precision(6);
// output f and goes back to fixed notation
cout << f << fixed << endl;
}
//
// cout example #2
//
#include <iostream>
void main ( )
{
using namespace std;
char p[50];
cin.getline(p,50);
cout << p;
}
//
// cout example #3
//
#include <iostream>
#include <fstream>
void main ( )
{
using namespace std;
// open the file "file_name.txt"
// for reading
ifstream in("file_name.txt");
// output the all file to stdout
if ( in )
cout << in.rdbuf();
else
{
cout << "Error while opening the file";
cout << endl;
}
}
WARNINGS
Keep in mind that the manipulator endl flushes the stream
buffer. Therefore it is recommended to use `\n' if your only
intent is to go at the line. It greatly improves performance
when C and C++ streams are not synchronized.
If your compiler does not support namespaces, then you do
not need the using declaration for std.
SEE ALSO
basic_ostream(3C++), basic_iostream(3C++),
basic_filebuf(3C++), cin(3C++), cerr(3C++), clog(3C++),
wcin(3C++), wcout(3C++), wcerr(3C++), wclog(3C++),
iomanip(3C++)
Working Paper for Draft Proposed International Standard for
Information Systems--Programming Language C++, Section
27.3.1
STANDARDS CONFORMANCE
ANSI X3J16/ISO WG21 Joint C++ Committee
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