A fuel tank has a fuel-vapor discharge structure in which the piping connecting to external equipment is not obtrusive. In response to the triggering of an interrupt status indicating signal received through an interrupt status indicating pin of a north bridge module or by the triggering of a peripheral device coupled to the south bridge chip, the PIC sends an interrupt signal to the CPU via an interrupt request signal pin when the computer system is in a PIC mode. The system also includes ranging logic. The P-type column regions 106 in the circumferential region are formed with a depth larger than or equal to that of the P-type column regions 106 in the element-forming region.