1. LOGIC GATES “ Logic, like whiskey, loses its beneficial effect when taken in too large quantities “

2. LOGIC GATES  They are the true fundamentals of a computer  They control the way in which electricity can move around the computer, by using switches  You have to know the following types of gates  NOT  OR  XOR  NOR  AND  NAND

3. REPRESENTATIONS In order to represent a gate there are a couple of ways to describe them Symbol format Text ShorthandReal life A + B = Y It’s really important that you remember all of the different symbols and shorthand, as the exam paper will use either

4. NOT GATE Input (A) Output (B) 01 10 A This is the simplest of all gates and will only have one input. Its function is just to reverse the input

5. AND GATE  Things get a little more challenging now  Firstly there will always be 2 or more inputs for the remaining gates  The purpose of an AND gate is to give an output only if all the inputs are on Input AInput BOutput Q 000 010 100 111 A. B = Q

6. NAND GATE  NAND gate can be though of as just an AND gate followed by a NOT gate A.B = Q Input AInput BOutput Q 001 011 101 110

7. OR GATE  An OR gate will produce an output if one or more of the two inputs are on. Input AInput BOutput Q 000 011 101 111 A + B = Q

8. NOR GATE  This is the opposite of an OR gate and it means that there will only be an output if the inputs aren’t on Input AInput BOutput Q 001 010 100 110 A + B = Q

9. XOR GATE  This gate will only have an output if A or B are on, it wont have an output if both A and B are on Input AInput BOutput Q 000 011 101 110 A + B = Q