¹⁷If this were a legacy Allen-Bradley PLC system using absolute addressing, we would be forced to address the three sensor inputs as I:1/0, I:1/1, and I:1/2 (slot 1, channels 0 through 2), and the indicator lamp output as O:2/0 (slot 2, channel 0). If this were a newer Logix5000 Allen-Bradley PLC, the default tag names would be Local:1:I.Data.0, Local:1:I.Data.1, and Local:1:I.Data.2 for the three inputs, and Local:2:O.Data.0 for the output. However, in either system we have the ability to assign symbolic addresses so we have a way to reference the I/O channels without having to rely on these cumbersome labels. The programs showing in this book exclusively use tag names rather than absolute addresses, since this is the more modern programming convention.