# 09 - Boolean Expressions and Diagrams

1. Read the definition of a LOGIC CIRCUIT and decide whether it is true or false
```A logic circuit is a combination of logic gates.
```

TRUE

FALSE

2. In a statement like this: (A+B) . (C + D) - what do the brackets mean?

That the brackets are done first (just like BODMAS rules in maths)

The brackets are there for aesthetic and artistic effect

It doesn't mean anything

The brackets mean that the expression inside them is processed LAST

3. What is the boolean expression for this circuit? ….
`Note: that the '.' is an AND gate and a + refers to an OR gate`

NOT Y = AB

A AND B

(A+B) . (C + D)

(A+B)+(C.D)

4. What is the boolean expression for this circuit? …..

(A+B) . NOT C

None of the above

NOT C (A+B+C)

(A + B) AND (NOT C)

5. The boolean expression for this circuit is: (AB + C)D

True

False

6. What is the boolean expression for this circuit? …….

None of the above

(AB + C)D

(A + B) AND (NOT C)

(A.B).C.D

7. Look at the image below and the output shown for this circuit. Is it correct? (Yes: True or No: False)

FALSE

TRUE

8. Which output of the two shown outputs is INCORRECT?

They are both incorrect

The first one (the one at the top) is incorrect

The second one (near the bottom)

Actually, they are both correct

9. What would the boolean expression be for the output C?

C = A AND C

A = A AND B

C = A AND B

C = S AND B

10. Write the boolean expression for this particular logic diagram (note that you can use brackets to denote an 'AND')
`Don't forget that a + is an OR gate and a . (or brackets) is an AND gate. `

C(D) + A

A + C (D)

(AB + C)D

A(BD) + C