Ultimate Digital Logic & Computer Architecture Study Guide – Clear, Concise & Exam-Ready!

Digital Logic Design and
Computer Architecture


Dr. Rahma Bouaziz, maître-assistant, FSG


A.U. 2023_2024




Chapter 3

Boolean algebra and logic
gates




Describing Circuit Functionality: Inverter
● Basic logic functions have symbols
● The same functionality can be
represented with a truth table
● Truth table completely specifies outputs for all input
combinations
● This is an inverter (NOT) Truth Table

● An input of 0 is inverted to a 1 A Y
● An input of 1 is inverted to a 0 0 1

1 0
A Y
Input Output
Symbol

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, The AND Gate
● This is an AND gate Truth Table

● If the two input signals A B Y
are asserted (i.e. high) the 0 0 0
output will also be asserted. 0 1 0
Otherwise, the output will 1 0 0
be deasserted (i.e. low) 1 1 1



A A B
Y
B
Y=A.B
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The OR Gate
● This is an OR gate A B Y
● If either of the two 0 0 0
input signals is
0 1 1
asserted, or both of
1 0 1
them are, the output
1 1 1
will be asserted.
A


A B
Y
B
Y=A+B
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The NAND Gate
● The NAND gate is a combination of an AND gate
followed by an inverter
● NAND(A, B) → (A AND B)’


A B Y
A 0 0 1
Y
B 0 1 1
1 0 1
Y=A.B 1 1 0




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