Boolean

Logic gates 1

There are different types of logic gate, depending upon what the gate is needed to do.

OR gates

An OR gate will give a high output if any of the inputs is high. For example, in a simple lighting circuit with two switches in parallel the lamp will light if either switch is pressed.

The relationship between the inputs and the output can be captured in a truth table. A and B represent the inputs and Q is the output.

Truth table for an OR gate

A	B	Q
0	0	0
0	1	1
1	0	1
1	1	1

OR gate symbol

AND gates

An AND gate will give a high output only if all of the inputs are high. For example, in a simple lighting circuit with two switches in series the lamp will light only if both switches are pressed.

Truth table for an AND gate

A	B	Q
0	0	0
0	1	0
1	0	0
1	1	1

AND gate symbol


http://wiki.schoolcoders.com/gcse/computational-logic/logic-gates/