DIGITAL LOGIC

  We know, if the switches A and B are closed in the above circuit, the bulb will light up.Even if one is open, the bulb is off.  Logically we can say,  if A and B are true, the output is true else the output is false.  In digital logic it can be written, "if A AND B are 1 the output is 1 else the output is 0".

     The AND logic can be wired electronically.  Instead of switches we will be using automatic switches like diode and transistor.  

    Then we have OR  logic.  That is written as; "if either A OR B is 1 then output is 1". ( If both are 0 then output is 0).

   Next NOT  logic; here the input is reversed and given as output(0 to 1: 1 to 0 ).

    NOT  and  AND  can be combined and it is called NAND logic.  NOT + OR  is called NOR  logic.

     All this logic statements can be hard wired using electronic components and they are used in many devices.  For example :  The AND  logic is used in lift.  " If A door and B door are closed, then only lift must start".  The logic circuits are used in many devices like washing machines, coffee maker, ovens, smart phones etc,.

     The important operation in computer and calculator is binary addition. 
Examples: 0 + 0 = 0, 1 + 0 = 0, 1 + 1 = 10.  These kind of additions are done using logic circuits.

In programming; statements like, " If candidate's maths score> 80 AND  English score>.50, then select" are written.  

     In search engines, if a input "English novels AND Indian authors", it will output results which satisfies both the criteria.

     We now understand decision making hardware can be constructed and decision making software can be written.  Hence logic statements an logic circuits made our life easy.  .