The invention relates to a programmable controller, comprising an arithmetic unit, a screen (6), an operator unit (4, 5), signal inputs (2) and signal outputs (3). Said arithmetic unit, screen (6), operator unit (4, 5), signal inputs (2) and signal outputs (3) are accommodated in a common housing (1). Switching functions can be programmed by the user using a menue-assisted user interface on the screen (6) and on the basis of pre-set functions. A button of the operator unit (4, 5) can be switched to an active button by a programmable function. The operation of a switching function then depends on the activation of this button.