1. Definitions The OR gate is an electronic device which receives two inputs each in the form of a binary digit, that is 0 or 1, and produces a binary digit as output, depending upon the values of the two inputs. It is represented by the symbol shown in Figure 5.5. A and B are the two inputs, and F is the single output. As high (1) or low (0) voltages are applied to A and B various possible outputs are achieved, these being de ned by means of a truth table as shown in Table 5.3. So, for example, if a low (0) voltage is applied to A and a high (1) voltage is applied to B, the output is a high (1) voltage at F. We note that a ‘1’ appears in the right-hand column of the truth table whenever A or B takes the value 1, hence the name OR gate. We use the symbol + to represent OR. Because it connects the variables A and B, OR is known as a logical connective.We shall meet other logical connectives shortly. This connective is also known as a disjunction, so that A + B is said to b...