Or gate and And gate.

 Or gate working

A=0,B=0 Both D1 and D2 don't conduct. Hence output y=0

A=0,B=0, D1 conducts D2 does not conduct.hence output y=1.

A=1,B=0  D1 conducts,D2 does not conduct. Hence output y=1 .

A=1,B=1, Both  D1 and D2 conduct.

Hence output y=1.

AND gate

It is realised by using two junction diode.

It has two or more inputs but one output.

It is expressed as y=A AND B=A.B (reads as y equals A AND B).

Conclusion

It all input are 1 them output is 1.

Working

If A=0,B=0, Both D1 and D2 are Forward biased and conduct.since both diodes are short circuited, output y=0.

If A=0,B=1,D1 is Forward blased but short circuited. 

Hence output y=0.

If A=1,B=0,D1 does not conduct. D2 is Forward biased but short circuited . Hence output y=0.

Logic gate

 Ordinary algebra

Addition,substraction, multiplication, are basic operator in ordinary algebra.

0,1,2,3,4,5,6,7,8,9 ten digits are used known as decimal system.

Boolean algebra

OR,AND,NOT,  basic operator in Boolean algebra.

Binary digits are used (0,1) known as binary system.

Analong circuit

A current or voltage which varies continuously with time is called analog signal.

The electronic circuit which process analong circuit.

 Exp- Ammeter, voltmeter, Galvanometer.

Digital circuit

A current or voltage which does not vary continuously with time.only gives two discreate values high or low is called digital signal. The high value is denoted as 0.

The electronic circuit which process digital signal is called digital circuit.

Exp- digital multimeter, digital clock, morden computer,pocket calculator.

OR gate

It is realised by using two junction diodes.

It has two or more inputs but one output.

It is expressed as y=A+B=A OR B(reads as Y equuals A OR B.