A printer includes a housing; an openable top cover disposed at the top of the housing; a printing unit disposed in the housing and comprising a printing portion fixedly mounted within the housing and a roll portion fixed to the openable top cover; and a paper channel between the printing portion and the roll portion; and a paper outlet between a top portion of the housing and the openable top cover, the paper channel leading to the paper outlet the printer further including a movable paper-tearing mechanism disposed in the paper outlet, the movable paper-tearing mechanism moving away from the paper outlet when the openable top cover is opened and into the paper outlet and overlapping partly the openable top cover when the openable top cover is closed, where an extension of the paper channel is between the movable paper-tearing mechanism and an upper surface of the openable top cover.