Chapter 23 - Logic gates

Question 1

summarise a NOT gate

Answer 1

• triangle with a circle at the end
• if input is 0, input is 1
• if input is 1, output is 0
• reverses the output

Question 2

what are all the logic gates

Answer 2

• AND
• OR
• NOT
• XOR
• NAND
• NOR

Question 3

Booleon expression for NOT gate

Answer 3

line over the letter(s)

Question 4

summarise an AND (conjunction) gate

Answer 4

• buzzer shape (two inputs one output)
• if both inputs are 1, output is 1, otherwise output is 0
• booleon expression is dot between letters

Question 5

summarise OR gate (disjunction)

Answer 5

• if either input is 1 then output is 1, otherwise output is 0
• 2 inputs and one output
• curved arrow
• booleon expression is +

Question 6

summarise XOR gate

Answer 6

• if one, but not both of the inputs is 1, output is 1, otherwise, output is 0
• curved arrow with line going through
• booleon expression is plus in a circle

Question 7

summarise NAND gate

Answer 7

• if both A and B are 1 , output 0, else output 1
• buzzer shape with circle at the end
• booleon expression is a line over with a dot separating

Question 8

benefits of NAND gate

Answer 8

• a single type of a NAND gate can perform two separate functions, reducing development costs
• cheaper than separate gates

Question 9

summarise a NOR gate

Answer 9

• gate only produces an output of 1 if both inputs are 0
• booleon expression is A + B with line over it
• curved arrow with circle at the end

Question 10

NOT is also known as

Answer 10

negation

Question 11

how can de morgan’s law be remembered

Answer 11

“change the sign break the bar”, or “change the sign build a bar”

Question 12

why is NAND known as a universal gate

Answer 12

because all the other gates are created by using this gate