cout

Library:  Input/output

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Predefined stream that controls output to a stream buffer associated with the object stdout declared in <cstdio>

#include <iostream>

namespace std {
  extern 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.

The formatting is done through member functions or manipulators.

Table 16: Formatting functions and manipulators for cout

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	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 notation
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 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)	Sets the precision (number of digits after the decimal point) to generate on certain output conversions
setw(int n)	Sets the field width (number of characters) to generate on certain output conversions
endl	Inserts a newline character into the output sequence and flushes the output buffer
ends	Inserts a null character into the output sequence
flush	Flushes the output buffer

precision()            6
width()                0
fill()                 the space character
flags()                skipws | dec
getloc()               locale::locale()

Keep in mind that while the manipulator endl flushes the stream buffer, outputting the character '\n' is not guaranteed to flush the stream buffer. You should output the '\n' character without endl only if you do not need the buffer flushed. Note that outputting the '\n' character in such cases, and hence not forcing a buffer flush, may result in a performance improvement. It greatly improves performance when C and C++ streams are not synchronized.

basic_ostream, basic_iostream, basic_filebuf, cin, cerr, clog, wcin, wcout, wcerr, wclog

ISO/IEC 14882:1998 -- International Standard for Information Systems --Programming Language C++, Section 27.3.1