Topic 10 - boolean logic

Question 1

Why are logic gates needed

Answer 1

Data in computer is stored in the form of BINARY
Computer process/run/stores in the form of electrical impulses or charges that are either absent or present
In order to process these binary bits, a system is needed - LOGIC GATES

Question 2

Logic gate

Answer 2

an electronic circuit that relies on ‘on/off’ logic; the most common gates are
NOT, AND, OR, NAND, NOR and XOR (binary input/output)

Question 3

Logic circuit

Answer 3

these are formed from a combination of logic gates and designed to carry out
a particular function; the output from a logic circuit will be 0 or 1

Question 4

Truth table

Answer 4

method of checking the output from a logic circuit
lists every binary output for every possible combination of binary inputs.

Starting from the right side with one 1’s and one 0’s then double each time they move to the left. (2nd one = two 1’s, 2 0’s)

Question 5

Number of outputs in a truth table

Answer 5

number of outputs depends on the number of inputs (2^x)
Ex) 2 input = 2^2(4) outputs, 3 input = 2^3 (8) outputs

Question 6

Boolean algebra

Answer 6

a form of algebra linked to logic circuits and based on TRUE or FALSE
(represents logic gates)

Question 7

Some basic Boolean algebras

Answer 7

A.B = A AND B
A+B = A OR B
NOT A = Ā
A XOR B = A ⊕ B

Question 8

NOT

Answer 8

One with singular input
Gives the opposite value
X= 1 if A=0

Question 9

AND

Answer 9

When both inputs are on/1 it turns on/1
X= 1 if both A & B = 1

Question 10

NAND

Answer 10

Opposite of AND - when both inputs are on/1 it turns off/0

Question 11

OR

Answer 11

If either gates are on/1 it turns on/1
X = 1 if either A/B =1

Question 12

XOR

Answer 12

OR gate but turns off/0 when they are both on/1

Question 13

NOR

Answer 13

Opposite of OR - If either gates are on/1 it turns off/0

Question 14

XNOR

Answer 14

NOR gate but turns on/1 if both A & B are turned on/1 OR both A & B is turned off/0