All independent acoustical physical constants of a material are predetermined as a function of its chemical composition, and the calibration line between the acoustic velocity for each of the substrate crystal plane, the propagation direction and the propagation mode, and other chemical and physical properties is numerically calculated with ease without making any experiments. The visual sensor senses whether a user is looking at the display screen. A substrate to be polished is held on a lower side of the support member surrounded by the retainer ring, and the substrate is pressed against a polishing surface of a polishing table. In response to receiving a command from the user, the plurality of packet headers for at least one packet flow in the first subset is communicated to the user. Displaying the line contents includes visually differentiating the synchronization points from remaining portions of the program source code segment. The recognization is based upon successive transitions in the node tree stored in memory in which each node corresponds to a recognized sequence of a character string.