GCSE Computing: A451 Computer Systems & Programming
Activity 1
Grab a whiteboard and pen, come to the
front and work out the Truth Table for the
following circuit:
A
B
C
R
Q
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
How do the gates work
together to process data?
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Learning
Objectives:
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
A
B
Remembering Last Lesson
Binary Logic Circuits
In your exam you will be expected to be able to
look at a circuit and produce a truth table for
the inputs and outputs.
Q
A
B
Q
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Worked Example
Learning
Objectives:
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
INPUTS:
A, B, C etc
OUTPUTS:
P, Q, R etc
Q
A
P
B
A
B
1
1
0
0
1
0
0
0
0
1
1
1
0
0
1
0
Q = Not A
= Q AND
B B
P =P(NOT
A) AND
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Tips:
Learning
Objectives:
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
1.
2.
3.
4.
5.
6.
Label the inputs on the circuit diagram
Label the outputs on the circuit diagram
Create a table with a column for each input and output
Label the columns (outputs labelled in the form of an
expression)
Place the combinations of different zeros and ones in the input
columns
Workout the outputs for each output column in turn
A
Q
B
INPUTS:
A, B, C etc
OUTPUTS:
P, Q, R etc
P
A
B
Q = A AND B
P = NOT (A AND B)
1
1
1
0
1
0
0
1
0
1
0
1
0
0
0
1
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Tips:
Learning
Objectives:
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
1.
When you place the combinations of
different zeros and ones in the input
columns…there are patterns that you
can remember to help you…
A
B
C
1
1
1
1
1
0
0
0
1
0
A
B
1
1
1
0
1
1
0
1
0
1
1
0
0
0
0
1
0
0
1
0
0
0
2 inputs
3 inputs
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Learning
Objectives:
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
This Lesson…
Binary Logic Circuit Expressions
In your exam you will also be expected to be
able to draw a diagram from an expression.
A
?
How to we
draw a
diagram from
an expression
P
B
A
B
Q = A AND B
P = NOT (A AND B)
1
1
1
0
1
0
0
1
0
1
0
1
0
0
0
1
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Learning
Objectives:
Binary Logic Circuit Expressions
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
P = A AND (NOT B)
----BRACKETS FIRST!----
A
1st
2nd
A
P
B
B
P
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Learning
Objectives:
Binary Logic Circuit Expressions
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
P = NOT (A AND B)
----BRACKETS FIRST!----
A
1st
A
B
B
2nd
P
P
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Learning
Objectives:
Binary Logic Circuit Expressions
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
P = (A OR B) AND C
----BRACKETS FIRST!---1st
A
B
A
B
C
C
2nd
P
P
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Binary Logic Circuit Expressions
Learning
Objectives:
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
P = (NOT A) AND B
----BRACKETS FIRST!---1st
A
A
B
B
2nd
P
P
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GCSE Computing: A451 Computer Systems & Programming
Binary Logic Circuits
Learning
Objectives:
Binary Logic Circuit Expressions
(a) Explain why data is represented
in computer systems in binary
form
(b) Understand and produce
simple logic diagrams using the
operations NOT, AND and OR
(c) Produce a truth table from a
given logic diagram
P = ((NOT B) AND C) OR A
----BRACKETS inside BRACKETS FIRST!---1st
A
A
B
C
B
C
2nd
3rd
P
P
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