All wires in the diagram are assumed to be single wires unless there is a slash through the wire with a number next to it, which indicates how many wires there are in the group. Thus, the line coming out of the PC register is slashed with 16, meaning there are 16 different wires coming from the PC register.

Each wire is labeled, although the full names are often implied. The several wires labeled "LD" are really different wires; their full names are prepended by the register into which these wires go. For example, the LD wire going into PC is really called "PC-LD", and the two multiplexor control wires going into the MBR's mux are MBR-MUX1 and MBR-MUX0.