AQA A level computer science notes unit 4- hardware and software

b/ ‘Unit 4 hardware and software
Logic gates and Boolean algebra:
Logic gate- electronic circuit that manipulates voltages
Valve- Electric current amplifier (can be on (1) or off (0))
Gate Symbol Truth table Gate
name
NOT A dash above
Gate- the letter as
used to shown: Ā
reverse
the
input
AND A dot in
Gate between two
letters as
shown: A.B




OR An addition
Gate symbol
between two
letters as
shown: A+B



XOR ⊕-not used
Gate- in Boolean
Either algebra
A or B
is 1 nut
not the 56 0pm.; r--q
other
NAND AND dot
Gate- followed by
AND NOT dash
and above it-not
NOT in used in
1 gate Boolean
algebra

, NOR Addition
Gate- symbol
OR and followed by
NOT in dash above
1 gate it-not used in
Boolean
algebra

Transistor- smaller
faster and more
reliable valve


Resistor- reduces size
of current flowing
through a wire

Advantages of the NAND and NOR gate is that cost of production is reduced and processing
speed is increased. This is because less gates are used in each circuit




The above is a method to convert gates into Boolean algebra and a logic circuit.




Use the above laws to practice simplifying Boolean algebra problems.