The fluorescence, including the intensity and emission peaks, and enhanced photochromism of a simple photochromic compound, bis(5-pyridyl-2-methylthien-3-yl)cyclopentene (Py-BTE) can be reversibly regulated by alternating ultraviolet/visible light irradiation and addition of Zn2+ and protons. A new combinational molecular logic switch with four optical outputs responding to four inputs (see Figure) is proposed.