An operator can select image processing for a half tone image area among a plurality of processing methods, and image processing appropriate for the image can be carried out thereby. An interrupt controller stores CPU context information set in a CPU in a memory before resetting the CPU. If the answer is negative, a heater is energized to heat the ramp for raising the temperature of the ramp. The luminescent layer in each organic electroluminescent device contains an organic material having substantially the same HOMO level as that of a hole-transporting material constituting the hole-transport layer, the content of the organic material being set according to the thickness of the luminescent layer. A nitride semiconductor includes a P-type nitride layer formed on a active layer, wherein the P-type nitride layer is a P-type nitride layer with the group 4 element doped.