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LOGIC GATES

THE 'OR' GATE  

Logic Gates        Main

 The symbol used when showing an OR gate in a logic circuit is shown as follows:

X and Y are True and false (Boolean) variables capable at any time of having the value 1 or 0. This type of logic gate haves 4 types of combinations, x could have the value of 0 and y the value 1, also x could have a value of 1 and y being 0. The function of an OR gate is when there is at least one 1 in one of the inputs 'X' or 'Y' then the output is 1. 

The table below is known as a 'Truth Table' and defines the operation of an OR gate for every combination of inputs and outputs. Truth table are a useful way for describing logic Circuits
   

 Truth Table

X       Y       X OR Y

0       0          0

0       1          1

1       0          1

1       1          1

The combination of the X and Y using an OR gate is written as :-  X  OR  Y  or X  +  Y  ( read as X or Y)

Both formulas mean X and Y are inputs to an OR gate. The second formula is the same as the first but the + is known as the OR operator and meaning X 'OR' Y.