Register
Register: an n-bit D flip-flop that stores the whole D bus on each rising CLK edge.
Pins
D (n bits) and CLK on the left; Q (n bits) on the right.
How to use it
Hold a result; feed an adder's output back into D for an accumulator. Use + / − to set the width.
Usage example
A number input feeds D (a thick multi-bit wire), the clock drives CLK and Q goes to a number display. On a rising edge it stores D (5 here).
Common mistakes
D and Q are buses: single-bit signals need a Joiner first, and the widths must match.