# 02 - Truth tables and logic circuits

1. The concept may be confusing at first but all digital circuits are created using a combination of logic _______________
```Learning note: Electronic gates require a power supply.
Gate INPUTS are driven by voltages having two nominal values, e.g. 0V and 5V representing logic 0 and logic 1 respectively.
The OUTPUT of a gate provides two nominal values of voltage only, e.g. 0V and 5V representing logic 0 and logic 1 respectively. In general, there is only one output to a logic gate except in some special cases.
There is always a time delay between an input being applied and the output responding.```

mates

bulbs

CPUs

gates

2. Digital systems are said to be constructed by using logic gates. These gates are the AND, OR, NOT, NAND, NOR, EXOR and EXNOR gates.

TRUE

FALSE

3. The functionality of each gate can be described using a ________________

logic gate correlation

mathematical formula that uses brackets

alegebraic expression

truth table

4. The following gate is an '_______' gate.

NOT

OR

AND

NAND

5. The following gate is an '_______' gate.

NOT

OR

NAND

AND

6. The following gate is an '_______' gate.

NAND

NOT

AND

OR

7. The AND gate is an electrical circuit that gives an output of ____ only if all of its inputs are also _____.

0

1

3

2

8. The OR gate is an electrical circuit that gives an output of a 1 if_______________ of its inputs are a 1.

at least two

none

at least one

all

9. The NOT gate is an electrical circuit that produces an _______ version of the input as the output. (e.g. a 1 will be a 0)

positive

negative

converted

inverted

10. If the input into a NOT gate is a 0 the output will also be a 0.

FALSE

TRUE

11. A truth table can show the operations (with inputs and outputs) of any given gates. The following shows the truth table for the ________
```2 Input truth table for an ____gate
======================
A      B      Output
------------------------
0       0            0
0       1            0                                   1       0            0
1       1            1```

Or Gate because when either A or B inputs are 1 the output is 1

And Gate because both inputs (A and B) need to be 1 in order for the output to be 1

NOT Gate - because the output is always the inversion (opposite) of what is in A or B

This truth table is incorrect and doesn't describe any gate

12. Logic gates are electronic circuits that manipulate _______ or in effect manipulate the binary 1s and 0s that are inside your computer.

binary sequences

ASCII values

voltages

waves

13. The ENIAC is widely thought to be the first ever electronic general purpose computer. These sort of computers had hundreds of ___________________________________
`______ can also be thought of as special types of switch. _____ can be in one of two states: on or off. `

valves - that are electric current amplifiers

microscopic atomic cells - that allow for storage

binary bits - that are the building blocks of computers

small CPU chips - brains of any machine

14. One of the problems with valves is that they were bulky, burned out easily and weren't terribly efficient. (as compared to transistors)

FALSE

TRUE

15. Transistors were much much larger than valves and were therefore much more efficient and powerful.

FALSE

TRUE