Information is written into a matrix-addressed electroscopic display by means of a writing stylus having a magnetic tip, utilized to attract a moveable plate electrode in a selected one of the display matrix cells. A capacitance detector, connected to sequential ones of the column electrodes of the display via a first multiplexer and to sequential ones of the row electrodes of the matrix display via a second multiplexer, detects the change in cell interelectrode capacitance caused by movement of the moveable plate electrode. The capacitance of each display cell is compared with the data for the output state commanded for that cell, to recognize input data sites programmed by the magnetic writing stylus.