std::dec,std::hex,std::oct(3)

NAME
std::dec,std::hex,std::oct - std::dec,std::hex,std::oct

Synopsis
   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 changed
     std::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)
   showbase controls whether prefix is used to indicate numeric base
   noshowbase (function)