The I/O numbering system is decimal to make it easier to comprehend, assign and count the I/O points and data registers. Many older PLCs use octal numbering schemes which can be confusing, and also lead to common mistakes. 

CLICK Physical I/O points are also numbered starting with 1, instead of 0 to make addressing more straightforward.

CLICK automatically assigns MODBUS addresses to all I/O points and memory registers, to make communications faster and easier.