Inherited by QBuffer and QFile. These functions are implemented by the subclasses QFile and QBuffer. Files can normally be accessed directly, except stdin etc., which must be processed sequentially.
Buffers are always direct access devices.
QFile objects can be created using one of these. Raw access mode is more low level, while buffered access use smart buffering techniques. Buffered access works better when reading small portions of data at a time. The QDataStream and QTextStream provide binary and text operations on QIODevice objects. QIODevice provides numerous pure virtual functions you need to implement when subclassing it.