An introduction to Boolean Login and Logic Gates


Boolean is one of the main data types in a computer. Boolean logic reflects the binary logic of logic gates and transistors in a computer’s CPU.

A Boolean’s expression is a value that is either TRUE or FALSE – these values control the flow of the execution of programs.

A Boolean’s operator consists of AND, OR, NOT.

Logic Gates

Electronic circuits have to make decisions, they look at two or more inputs and use these to determined outputs from the circuit.

Each input and output of the gates must be either:

  • True – 1 – “on”
  • False – 0 – “off”

AND gate

  • An AND gate takes two inputs but only a single output
  • Both inputs have to be 1 for the output to be 1

AND gateAND logic gate truth table


NOT gate

  • Not gates takes a single Boolean value (1 or 0) and negatives (flips) it


OR gate

  • OR gates have two inputs
  • One or both needs to be 1, otherwise it will output 0


Truth Tables

Next to each gate diagram is a Truth Table. This table represents the outputs from all possible combinations of input.

If you are still struggling with the concept of Boolean and Logic Gates, watch Getting the Logic Expression and Truth Table from a Circuit by Mandy Orzechowski.

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