The QIODevice class is the base class of I/O devices. ... virtual  ~QIODevice  ()  . int  flags  () const . ... virtual int  at  () const . ... virtual int  writeBlock  ( const char * data, uint len )  . ... virtual int  putch  ( int )  . ... The QIODevice class itself is not capable of reading or writing any data; it has virtual functions for doing so. These functions are implemented by the subclasses QFile and QBuffer . ... Virtual function that returns the current I/O device index. ...