  A typewriter automaton is a special variant of a two-dimensional automaton
that receives two-dimensional words as input and is only capable of moving its
input head through its input word in three directions: downward, leftward, and
rightward. In addition, downward and leftward moves may only be made via a
special "reset" move that simulates the action of a typewriter's carriage
return.
  In this paper, we initiate the study of the typewriter automaton model and
relate it to similar models, including three-way two-dimensional automata,
boustrophedon automata, and returning automata. We study the recognition powers
of the typewriter automaton model, establish closure properties of the class of
languages recognized by the model, and consider operational state complexity
bounds for the specific operation of row concatenation. We also provide a
variety of potential future research directions pertaining to the model.
