Put character at current put position.
  The character whose value is parameter c is stored at current put position and the put pointer is increased by one.
  This virtual protected function is called by sputc and sputn in case there is no room in the internal output sequence to successfully perform the output operation.
  As a virtual function it can be overriden in derived classes in order to provide additional output positions where to write out characters and to set appropriate values for pptr and pbase pointers if, for example, the external source of characters used by the streambuf-derived object can physically grow.

Parameters.

c

Character to be put.

Return Value.
  EOF if the function failed to put the character or any other value in case of success.

Basic template member declaration ( basic_streambuf<charT,traits> ):

typedef traits::int_type int_type; int_type underflow ( int_type c = traits::eof() );

See also.
  sputc
  streambuf class