The plasma addressed electro-optical display includes a panel having a plasma cell and a liquid crystal cell joined to each other with a dielectric sheet interposed in between. While the plasma cell has display channels arranged thereon in rows, the liquid crystal panel has signal electrodes arranged thereon in columns, which define pixels at the intersections with the display channels to thereby form an image. A scanning circuit is connected to the display channels and sequentially drives the display channels to discharge over the image and select pixels in each row through the dielectric sheet. A signal circuit is connected to the signal electrodes and drives the signal electrodes in synchronism with the driving for discharge and in accordance with one image of picture data, and, thereby, it writes signal voltages into the selected pixels. A calculating circuit, in accordance with externally input picture data, calculates effective potential differences occurring between adjoining signal electrodes in each row and accumulates the results over the image. A compensating circuit, in accordance with the results of accumulation, compensates for the signal voltages to be applied to the respective signal electrodes to thereby reduce the crosstalk caused by potential differences between adjoining signal electrodes.

A trajectory and a footprint of a hypothetical pen are each divided into sequences of segments, each segment having a slope associated therewith. The segments of the footprint form a closed sequence and those of the trajectory form a sequence with a beginning and an end. Each of the two approximate envolvents of the thick line are calculated in the same way, from the trajectory segments and the footprint segments. An envolvent is initialized to include the first segment of the trajectory starting at an appropriate offset from the trajectory start point, followed by zero or more footprint segments and then followed by the next trajectory segment until each of the trajectory segments are concatenated. In determining how many footprint segments to concatenate before concatenating the next trajectory segment, the slopes of the last concatenated trajectory segment and the next trajectory segment are compared to the slopes of the footprint segments. If any footprint segments have slopes between the slopes of the last and next trajectory segments, those footprint segments are concatenated before the next trajectory segment is concatenated. The selection of one of the two sets of footprint slope vectors, either the clockwise set or the counterclockwise set, determines which envolvent of the two envolvents are generated.

Input position is accurately detected. In an x-detection period of a non-display period, a source drive circuit simultaneously applies to all signal wiring lines a pulse of a peak value proportional to a distance from a gate drive circuit. A coordinate detection circuit obtains an x-coordinate on the basis of a voltage induced at a pen corresponding to the peak value (x-coordinate) of the applied pulse. In a y-detection period, a pulse generation circuit applies one pulse to a common line. The pen detects a potential variation in amplitude proportional to a distance (y-coordinate) from the source drive circuit, generated approximately simultaneously on all the signal wiring lines via a capacitance. The coordinate detection circuit obtains the y-coordinate similarly to the case of x-coordinate detection.

Handwriting recognition is performed by sensing a trace signal, where the trace represents a handwritten intended symbol. A digital representation of the trace signal is then stored and compared with a plurality of candidate symbols. Depending on the outcome of the comparison, a best candidate symbol among the candidate symbols is recognized and displayed, or the digital representation of the trace signal is displayed.

A dummy electrode 217 having an L-shape as a whole in plan view is formed on a surface of an element substrate 210 so that a dummy electrode unit 217a which is disposed on the side opposite to the side on which a scanning line 221 of a liquid crystal drive area S is formed outside the liquid crystal drive area S extending along and substantially parallel to a data line 211 is continuous to a dummy electrode 217c passing between a connection unit 211a of the data line 211 and an input terminal 213. The dummy electrode 217 is not formed on the scanning line 221 side of the liquid crystal drive area S.