PURPOSE: To obtain a high density bar code system suitable for discriminating a wafer and a chip in a semiconductor manufacturing process by using bars of a single width and using a bar code having a self clocking characteristic. CONSTITUTION: The bar code is encoded so as to be provided with the bar with a uniform single width size and special synchronism and to contain sub-sequence of a timing mark for enhancing readability. Preferably, like the figure, the code of the bar code with the single width of a presence/absence system capable of expressing Arabic numerals 0-9 and the alphabet characters A-Z (except a character 'O') is used. The bar code encoded in such a manner is attached to an object for displaying target information to be read and discriminated by an optical reader. Thus, the high density bar code system suitable for discriminating the wafer and the chip in the semiconductor manufacturing process is obtained. COPYRIGHT: (C)1991,JPO