Boolean expressions can be computed by implementing them in hardware using logic gates. This is most easily seen with an example. Consider the Boolean expression AB+CD. The corresponding digital logic circuit is:
Sometimes circuits get so complex that the same variable is input into multiple gates, or the only way to draw wires on the diagram is to have them cross, even though they do not connect. When two wires cross and are supposed to be connected, we draw a small, dark dot at the intersection. This is called a junction. If two wires cross on the drawing but are not connected, then no junction appears. The following example illustrates this point.
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