cout (3C++std) - Tru64 UNIX
Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.
NAME
cout
SYNOPSIS
#include <iostream>
extern ostream cout;
DESCRIPTION
ostream cout;
The object cout controls output to a stream buffer associated with the
object stdout declared in <cstdio>. By default the standard C and C++
streams are synchronized, but performance 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 manipulators.
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 unconditionally in
generated floating-point output.
boolalpha Insert and extract 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, or identical to right if no such point is
designated.
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 notation.
scientific Generates floating-point output in scientific notation.
resetiosflagss
(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 parameter 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) Set 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()
EXAMPLES
//
// cout example one
//
#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 two
//
#include <iostream>
void main ( )
{
using namespace std;
char p[50];
cin.getline(p,50);
cout << p;
}
//
// cout example three
//
#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 '0 if your only intent is to go at the line. It
will greatly improve performance when C and C++ streams are not
synchronized.
SEE ALSO
basic_ostream(3C++std), iostream(3C++std), basic_filebuf(3C++std),
cin(3C++std), cerr(3C++std), clog(3C++std), wcin(3C++std), wcout(3C++std),
wcerr(3C++std), wclog(3C++std), iomanip(3C++std)
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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