# Technical studies – study 15
Boolean algebra is an algebraic system that expresses the digital circuits. It has two elements 0 and 1, two binary operators AND and OR and one unary operator NOT. We can express any complex logic statement by Boolean algebra. It has some rules and laws to write expressions.
Boolean algebra is different from both binary number system and ordinary algebra. In Boolean algebra A.A =A and A+A=A, while in ordinary algebra and A+A=2A. In Boolean algebra 1+1=1, while in binary number system 1+1=10 and in ordinary algebra 1+1=2. In Boolean algebra there is no negative and fractional numbers and no subtraction and division. It has only logical operators AND, OR, NOT, NAND, NOR, X-OR, X-NOR.
AND operation in Boolean algebra is the ordinary multiplication. It is the logical multiplication as performed by AND gate. The operator for AND operation is (.).
OR operation in Boolean algebra is the ordinary addition. It is the logical addition as performed by OR gate. The operator for OR operation is (+).
NOT operation in Boolean algebra is complement of the operand. It is same as the operation performed by NOT gate. The operator for NOT operation is bar (_).
NAND operation is the complement of AND operation and same as the operation of NAND gate.
NOR operation is the complement of OR gate and same as the operation of NOR gate.
X-OR operation using two variables A and B in Boolean algebra can be-
X-NOR operation using two variables A and B in Boolean algebra can be-
Please write on the comment box if you have any questions.