## AQA Computer Science GCSE

### 4.2 Computer Systems – Boolean Logic Gates

Boolean Logic Gates are electronic components which can take Boolean inputs and provide an output – again as a Boolean value. Remember, Boolean values are either True or False.

Logic Gates – intro slides from class

There are four logic gates you need to know: AND, OR, XOR (the evil one) and NOT (the "easy" one which you'll get wrong more times than you think).

Each logic gate has a truth table that you need to know.

Truth tables – an intro on how they work

How logic symbols work – a short intro

Four Logic Gates – a slide on each to make notes from

There's also a textbook double page on these, which will help if you get confused or stuck.

Logic Gates Textbook – a double page spread with questions

A table – can you fill it in correctly?

#### Truth Table Questions

#### Logic Gates and Circuits

You might have to draw a simple logic circuit diagram in an exam.

Logic Expressions – types of question

Logic Diagrams – types of question

Example logic gates – with images

An alternate way asking this sort of question:

Blank gates – another way of asking similar questions

A revision exercise:

Logic Quickfire – slides from class

#### More complex Truth Tables

Truth tables get more complex when you start to do more things to the inputs. And especially when you start to add a third input.

Slightly more complex Truth Tables – a set of exercises to work through