An image pickup apparatus in which a display surface of a display device can be looked at favorably when imaging a subject and in which it never happens that the display device becomes obstructive during imaging and it is possible to carry out an imaging operation with good stability. A special purpose server computer\u2014a Device Registry Server \u2014is switched between a large variety of different mobile device types and a plurality of backend systems for improving the communication between a mobile device and a backend system. It is determined whether the memory usage of the memory is greater than a first threshold or a second threshold, wherein the second threshold is greater than the first threshold. A FIFO threshold defines the minimum number of data points in FIFO memory before it issues an interrupt to inform the host that data is ready to be fetched. In the case of a printed circuit precursor the surface may be then etched in conventional manner to yield the required printed circuit. An eccentricity phase of each of the photosensitive drums is calculated based on the positional deviation detected, and a rotational phase of the photosensitive drums is controlled based on the eccentricity phase calculated.