The CSC-1 architecture has a number of control points, which are wires that cause things to happen, like registers to load or the ALU to add or subtract or the memory to read or write. Another part of the computer, the control unit, sets these wires according to the instruction being executed.

Go back and carefully examine Fig. 7.1.1, the block diagram for the CSC-1. Notice that each register has a load wire, which is not explicitly labeled. PC also has an increment and clear wire. We will name these wires as PC-LD or S-LD or A-LD. PC also has PC-CLR and PC-INCR. MBR-LD is the old familiar MBRCK of Chapter 5.