Abstract: The invention relates to a device for simultaneously effecting on the one hand, the plotting or erasing of graphical data on a material medium and, on the other hand, the recording or erasing of corresponding data in a computer memory. Write and/or erase means in the form of one or more pens comprise: write and/or erase members for selectively producing visible plottings or effective erasings on a drawing table; means for generating a magnetic field having a frequency corresponding to the selected write or erase function; and electrical supply means permitting the or each pen to be self-operating. The table comprises detection and computing circuits for working out from signals received on the conductors of the grid, data which is representative of the position of the pen with respect to the table, and data representative of the selected write or erase function.