A data processing apparatus comprising a display device for displaying the data; the first recording device for recording the large volume bit map data; the second recording device recording an index data formed as a two-dimensional image obtained by rendering the large volume bit map data; the first data processing device for reading the large volume bit map data from the first recording device and applying the image processing to the large volume bit map data; the second data processing device for reading the large volume bit map data from the first recording device, forming the two-dimensional image data by rendering the large volume bit map data and transferring the image data to the display device; the third data processing device for transmitting the index data to the display device; and the input device for sending the instructions to the first, second and third data processing devices.