Boolean Logic (Cambridge (CIE) IGCSE Computer Science)
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What is Boolean logic?
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What is Boolean logic?
Boolean logic is a system used in computer science and electronics to make logical decisions, where operators are either TRUE or FALSE (often represented as 1 or 0).
Define the term logic gate.
A logic gate is a visual way of representing a Boolean expression.
True or False?
AND gates return TRUE only if both inputs are TRUE.
True.
AND gates return TRUE only if both inputs are TRUE.
Describe the OR gate in Boolean logic?
OR returns TRUE if either input is TRUE.
State the meaning of NOT in Boolean logic.
NOT reverses the input value.
What is the function of XOR in Boolean logic?
XOR (exclusive OR) returns TRUE if either input is TRUE but NOT both.
What gate is this?
NAND
returns TRUE if both inputs are NOT true.
What gate is this?
NOR
returns TRUE if both inputs are FALSE.
True or False?
OR gates return TRUE if both inputs are FALSE.
False.
OR gates return FALSE if both inputs are FALSE.
What is the symbol used for AND gates?
What is a logic circuit?
A logic circuit performs logical operations on binary information.
True or False?
In the exam, logic circuits can have unlimited inputs and outputs.
False.
In the exam, logic circuits are limited to a maximum of three inputs and one output.
Define Boolean expression.
A statement that can be evaluated to either true or false.
What are brackets used for in Boolean expressions?
Brackets are used to clarify the order of operations in Boolean expressions.
True or False?
In a logic diagram, inputs are typically represented by letters.
True.
In a logic diagram, inputs are typically represented by letters.
Define logic diagram.
A logic diagram is a visual representation of combinations of Boolean operators within a logic circuit.
Draw the logic diagram for the Boolean expression P = (A AND B) OR C
Draw the logic diagram for the Boolean expression P = (A XOR B) AND (NOT C)
Draw the logic diagram for the Boolean expression P = NOT(C AND (A OR B))
Draw the logic diagram for the Boolean expression P = (A AND B) OR (NOT C)
What is a truth table?
A truth table is a tool used in logic and computer science to visualise the results of Boolean expressions.
True or False?
Truth tables show only the inputs of a Boolean expression.
False.
Truth tables represent all possible inputs and the associated outputs for a given Boolean expression.
How many rows are needed in a truth table with 3 inputs?
A truth table with 3 inputs needs 8 rows (2^3).
What is the output of an AND gate when both inputs are 1?
The output of an AND gate when both inputs are 1 is 1.
True or False?
In a NOR gate, the output is 1 when both inputs are 0.
True.
In a NOR gate, the output is 1 when both inputs are 0.
What is the output of an XOR gate when both inputs are 1?
The output of an XOR gate when both inputs are 1 is 0.
How do you determine the number of rows in a truth table?
The number of rows in a truth table is determined by 2^(number of inputs).
What are the missing inputs in the truth table?
A
B
C
0
0
0
0
0
0
1
1
0
1
0
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
What is the output of a NOT gate when the input is 0?
The output of a NOT gate when the input is 0 is 1.
Draw a truth table for the Boolean expression P = (A AND B) AND NOT C
A
B
C
P
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
1
1
1
1
0
What is a logic expression?
A logic expression is a way of expressing a logic gate or logic circuit as an equation.
True or False?
In a logic expression, the output appears on the right of the equals sign.
False.
In a logic expression, the output appears on the left of the equals sign.
State the logic expression for a NOT gate where A is the input and Z is the output.
Z = NOT A.
True or False.
((NOT A) OR B) NAND C = P is a valid logic expression.
False.
The correct logic expression is P = ((NOT A) OR B) NAND C
True or False?
The logic expression for an OR gate is Z = A NOR B.
False.
The logic expression for an OR gate is Z = A OR B.
State the logic expression for this logic diagram.
P = (A XOR B) AND (NOT C)
State the logic expression for this logic diagram.
P = NOT((A OR B) AND C)
OR
P = NOT(C AND (A OR B))
True or False?
Logic expressions can represent circuits with multiple gates.
True.
Logic expressions can represent circuits with multiple gates.
State the logic expression for this logic diagram.
P = (A AND B) OR (NOT C)
How are complex logic circuits expressed as logic expressions?
Complex logic circuits are expressed as logic expressions by combining multiple operations using brackets to show the order of operations.