Parity Counter Lines: the two digits at the ends of each line indicate the number of odd and even digits in that line, including the end digits themselves. One digit counts odd digits; the other counts even digits. BitClock: A BitClock is a group of five cells: a central arrow cell and its four orthogonally adjacent neighbours (up, right, down, left). The arrow shows where the pattern starts, and the pattern is then read clockwise around the four neighbours. The digit in the central arrow cell tells you the odd/even pattern of those four neighbours, using a simple 4-bit code. In those neighbour cells, an even digit means the “bit” is ON; while an odd digit means the “bit” is OFF. Each arrow cell digit has its own fixed 4-bit pattern (see table below). Eg If a 3 is placed in an arrow cell, its code is OOEE.Starting from the direction of the arrow and reading clockwise, the four orthogonal neighbours must be Odd, Odd, Even, Even. Digit Codes: 1 → OOOE2 → OOEO3 → OOEE4 → OEOO 5 → OEOE 6 → OEEO 7 → OEEE 8 → EOOO 9 → EOOE