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

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

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

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

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 A. B = Q

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

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

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 A + B = Q

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 A + B = Q