What type of a circuit do flashlights use?

A flashlight is a series circuit. The batteries positive end connects to the flashlights switch. The switch connects to the center pin of the light bulb. The bulb filament is connected to the center pin of the bulb and the outer metal shell of the bulb socket. The shell of the bulb socket is connected to the metal flashlight's body which returns to the negative end of the battery. Turn on the switch and you have light.