 The machine is an automatic machine (a-machine) which means that at any given moment, the behavior of the machine is completely determined by the current state and symbol (called the configuration) being scanned. This is the so-called determinacy condition  (Section 3).  These a-machines are contrasted with the so-called choice machines for which the next state depends on the decision of an external device or operator (Turing 1936–7: 232). A Turing machine is capable of three types of action: