a. M+A+N

4.

A logic diagram which contains both an AND and an OR operation

b. THIS

is a second-order-logic diagram.

c. I+S

d. FUN

The diagram above is an example of second-order logic, an AND

circuit supplying an OR circuit. The output of each logic symbol

must be determined in order to develop an output Boolean

expression correctly. Start with the inputs to the first symbol and

proceed to the final output. Use the output of each logic symbol as

an input to the next succeeding symbol as follows:

Step 1. The first symbol is recognized as an AND gate with two

inputs, A and B. The output, AB, in turn, is one of the

inputs to the OR gate.

Step 2. The final output from this logic diagram is from the OR

gate. An examination of the output expression reveals

that it is correctly indicating the output from an OR gate

which had three separate inputs, AB, C, and D.