An information bearing medium comprising: a media substrate; and a plurality of unit data zones, wherein a mark is provided on each of some of the unit data zones so as to form a digital code, wherein the mark is a convex portion having a predetermined height formed on a surface of the media substrate and the presence or absence of the convex portion provides binary data for the unit data zones; characterised in that: the unit data zones are formed on the media substrate in an array having a first direction and a second direction that crosses the first direction, the array is formed from unit data zone strings (14a, 14b, 14c, 14d) each extending in the first direction, and mark patterns of any second-directional adjacent two of the unit data zone strings (14a, 14b, 14c, 14d) based on an arrangement of marks in the first direction differ from each other, and/or a mark pattern based on the arrangement of marks in the first direction of a beginning unit data zone string at one end of the array of unit data zones in the second direction differs from each of the mark patterns based on the arrangement of marks in the first direction and a direction opposite to the first direction of a terminal unit data zone string at the other end of the array of unit data zones in the second direction. a media substrate; and a plurality of unit data zones, wherein a mark is provided on each of some of the unit data zones so as to form a digital code, wherein the mark is a convex portion having a predetermined height formed on a surface of the media substrate and the presence or absence of the convex portion provides binary data for the unit data zones; characterised in that: the unit data zones are formed on the media substrate in an array having a first direction and a second direction that crosses the first direction, the array is formed from unit data zone strings (14a, 14b, 14c, 14d) each extending in the first direction, and mark patterns of any second-directional adjacent two of the unit data zone strings (14a, 14b, 14c, 14d) based on an arrangement of marks in the first direction differ from each other, and/or a mark pattern based on the arrangement of marks in the first direction of a beginning unit data zone string at one end of the array of unit data zones in the second direction differs from each of the mark patterns based on the arrangement of marks in the first direction and a direction opposite to the first direction of a terminal unit data zone string at the other end of the array of unit data zones in the second direction. the unit data zones are formed on the media substrate in an array having a first direction and a second direction that crosses the first direction, the array is formed from unit data zone strings (14a, 14b, 14c, 14d) each extending in the first direction, and mark patterns of any second-directional adjacent two of the unit data zone strings (14a, 14b, 14c, 14d) based on an arrangement of marks in the first direction differ from each other, and/or a mark pattern based on the arrangement of marks in the first direction of a beginning unit data zone string at one end of the array of unit data zones in the second direction differs from each of the mark patterns based on the arrangement of marks in the first direction and a direction opposite to the first direction of a terminal unit data zone string at the other end of the array of unit data zones in the second direction.