A quadrangular or rectangular area on a medium surface of a printed material and the like is defined as a block. A straight line in a vertical direction and a horizontal direction nuclear along an edge of the block is defined as a reference grid line. A virtual grid point is placed at a predetermined interval on the reference grid line. A reference grid point dot is placed each on a virtual grid point on the horizontal reference grid lines. A straight line connecting the reference grid point dots and virtual grid points on a vertical line is defined as a grid line. An intersection point of grid lines is defined as a virtual grid point. A dot pattern is generated by arranging one or more information dots having a distance and a direction on the base of the virtual grid point. An optical reading means is used to scan the dot pattern into image information. Then, the dot pattern is converted into a numerical value, and the information corresponding to the numerical information is read from a storage means and output.