One of the disadvantages of the existing practice of using computers for processing geological data is the lack of devices for outputting information in graphical form. Two main functions of graphic output devices can be distinguished: 1) fixing of final results of calculations (documentation); 2) display of information for the purpose of operative estimation of results of the previous stage of iteration when solving problems by the selection method. These functions determine the technical parameters of the device: in the first case the accuracy of graphical constructions is determinant, in the second case - the speed of.