A method of storing a bit at a memory device is disclosed. The daughter card includes a mating edge inserted into the slot of the card edge connector, and a rear edge opposite to the mating edge and defining an engaging hole. In a plan view, the fixing hole is opened at a predetermined central angle interval relative to the central position. The ejector includes a slider moving along the card insertionejection direction with the card insertedejected, an ejecting arm protruding into the card receiving space to eject the card, holding means to securely hold the slider in a final position, and a resilient member disposed in the slider to urge the slider to move along the card ejection direction.