std::dec, std::hex, std::oct

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

Input/output library

I/O manipulators

Print functions(C++23)

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

basic_spanbuf (C++23)

strstreambuf (C++98/26*)

basic_syncbuf (C++20)

Streams

Abstractions

ios_base

basic_ios

basic_istream

basic_ostream

basic_iostream

File I/O

basic_ifstream

basic_ofstream

basic_fstream

String I/O

basic_istringstream

basic_ostringstream

basic_stringstream

Array I/O

basic_ispanstream (C++23)

basic_ospanstream (C++23)

basic_spanstream (C++23)

istrstream (C++98/26*)

ostrstream (C++98/26*)

strstream (C++98/26*)

Synchronized Output

basic_osyncstream (C++20)

Types

streamoff

streamsize

fpos

Error category interface

iostream_category (C++11)

io_errc (C++11)

 

Input/output manipulators

Floating-point formatting
showpointnoshowpoint setprecision	fixedscientifichexfloatdefaultfloat (C++11)(C++11)
Integer formatting
setbase showbasenoshowbase	dechexoct
Boolean formatting
boolalphanoboolalpha
Field width and fill control
setfill setw	internalleftright
Other formatting
showposnoshowpos	uppercasenouppercase
Whitespace processing
ws ends	skipwsnoskipws
Output flushing
flush endl flush_emit (C++20)	unitbufnounitbuf emit_on_flushnoemit_on_flush (C++20)(C++20)
Status flags manipulation
resetiosflags	setiosflags
Time and money I/O
get_money (C++11) get_time (C++11)	put_money (C++11) put_time (C++11)
Quoted manipulator
quoted (C++14)

 

Defined in header <ios>
std::ios_base& dec(std::ios_base& str );	(1)
std::ios_base& hex(std::ios_base& str );	(2)
std::ios_base& oct(std::ios_base& str );	(3)

Modifies the default numeric base for integer I/O.

1) Sets the basefield of the stream str to dec as if by calling str.setf(std::ios_base::dec, std::ios_base::basefield).

2) Sets the basefield of the stream str to hex as if by calling str.setf(std::ios_base::hex, std::ios_base::basefield).

3) Sets the basefield of the stream str to oct as if by calling str.setf(std::ios_base::oct, std::ios_base::basefield).

This is an I/O manipulator. It may be called with an expression such as out << std::hex for any out of type std::basic_ostream or with an expression such as in >> std::hex for any in of type std::basic_istream.

Parameters

str

-

reference to I/O stream

Return value

str (reference to the stream after manipulation).

Example

Run this code

#include <bitset>#include <iostream>#include <sstream>   int main(){std::cout<<"The number 42 in octal: "<< std::oct<<42<<'\n'<<"The number 42 in decimal: "<< std::dec<<42<<'\n'<<"The number 42 in hex: "<< std::hex<<42<<'\n';int n;std::istringstream("2A")>> std::hex>> n;std::cout<< std::dec<<"Parsing \"2A\" as hex gives "<< n <<'\n';// the output base is sticky until changedstd::cout<< std::hex<<"42 as hex gives "<<42<<" and 21 as hex gives "<<21<<'\n';   // Note: there is no I/O manipulator that sets up a stream to print out// numbers in binary format (e.g. bin). If binary output is necessary// the std::bitset trick can be used:std::cout<<"The number 42 in binary: "<<std::bitset<8>{42}<<'\n';}

Output:

The number 42 in octal: 52 The number 42 in decimal: 42 The number 42 in hex: 2a Parsing "2A" as hex gives 42 42 as hex gives 2a and 21 as hex gives 15 The number 42 in binary: 00101010

See also

setbase	changes the base used for integer I/O (function)
showbasenoshowbase	controls whether prefix is used to indicate numeric base (function)