digital electronic is the branch in which most of the devices used work on direct current. this current is very less as compared to the current used in electrics. The direct current is more dangerous as compared to the altenating current, but it is harmful after a certain range like above 18 volts. But all the electronics appliances work below this range . The main things in digital electonics are 0 and 1.The whole of the digital electronics depends on 0 & 1. where o stands for 'off' and 1 for 'on'. It consists of logical gates and almost all the devices work on these gates .The basic gates are 'AND','OR','NOT' gates in this the AND gate performs multiplication, OR performs addition and the NOT gate acts as an inverter i.e if the input id 0 it converts it into 1 and vicersa. the gated derives from it are 'NAND' and 'NOR'. 'NAND' and 'NOR' are knows as universal gates, and with the help of these two gates all other gates can be derived it is called the realisation of gates. the other gates used in digital electronics. These two gates are derives from 'AND' gate and 'OR' gates. when a 'NOT' gate is added to 'AND' gate we get 'NAND' gate, and when a 'NOT' gate is added tp 'OR' gate we ger 'NOR' gate. The truth table of these gates are opposite to that of the gates from which it is derived. the other two gates are 'XOR' gate and 'XNOR' gate.