# 04 - Logic circuit diagrams #1

1. Recap: What does Boolean Logic mean?
```Definitions
===========
#1
Boolean logic describes the states of the inputs and outputs to the
logic gates.

#2
Boolean logic represents all values as TRUE (1) or FALSE (0).

#3
Boolean logic represents the way that George Boole depicted the CPU and
modelled it with boole variables.```

All of the above

Only #1

None of the above

#1 and #2

2. What is a truth table?

A truth table is a table that shows the combinations of all binary addition outcomes

A table that will tell the truth no matter what, with regard to Binary addition

A table showing the output from all possible combinations of input.

A table that shows the truth about any given boole variable

3. What logic gate does this truth table describe?
```-----Inputs----Output--
A    |   B   |    Q
=======================
0    |   0   |    0
=======================
0    |   1   |    1
=======================
1    |   0   |    1
=======================
1    |   1   |    1```

None of the above

And Gate

Not Gate

Or Gate

4. Logic gates are used to build complex logic systems, such as burglar alarms and combination locks. What are D and E in this complex logic gate?

D and E are inputs

D and E are logic gates

D and E are outputs but also inputs required to find Z

D and E are outputs

5. Looking at the logic gate and the truth table below, can you fill in the blank (for the question mark in the truth table)
```A	B	C	D	E	Z
0	0	0	1	0	1
0	0	1	1	0	1
0	1	0	1	0	1
0	1	1	1	1	1
1	0	0	0	0	0
1	0	1	0	0	0
1	1	0	0	0	0
1	1	1	0	?	1```

2

3

0

1

6. How is this XOR gate different from an OR gate?

In an OR gate an input of a 1 and 1 would give a 0

In an OR gate an input of a 1 and 1 would give a 1 not a 0

In an OR gate an input of a 0 and 1 would give a 0

It isn't different

7. What output will go in the '?' in the truth table shown?

0

3

2

1

8. If A =0 and B = 0, what is the output C?

1,1

0

0,0

1

9. If the inputs are both 1, analyse the outputs as shown on the diagram and point out, if any, the error.

The output after the NOT gate at the top should be a 1 because it inverts the 0 to a 1

There are no errors. The outputs are all shown correctly

The last output C should be a 1 and 0 (e.g. 1,0) because it has more than one input coming in

The last output C should be 0, because a 0 and 1 give a 0.

10. Which colour/color box is showing an incorrect output?

The white 0 at the end should be a 1

The yellow box should be a 1

The red box should be a 1

The green box should be a 0