## Wednesday, 20 March 2013

### Need of Boolean Expression

To know Need of Boolean Expression we have to know about What is a Boolean Expression ?
Boolean Expression is a expression which results has only two value true or false i,e 1 or 0.

let take a example to make clear   10 < 100 is a logical expression and answer of it is true so we can say it is a Boolean Expression. So we can say all relational / logical expression like less than, greater than, equal are the Boolean expression. And Boolean operator are OR,AND,XOR,NOR,NAND etc.

Now need of Boolean expression

At this point in our study of digital circuits, we have two methods for representing combinational logic: schematics and truth tables.

These two methods are inadequate for a number of reasons:

• Both schematics and truth tables take too much space to describe the operation of complex circuits with numerous inputs.
• The truth table "hides" circuit information.
• The schematic diagram is difficult to use when trying to determine output values for each input combination.

To make easier and more understandeble, an algebraic process much like normal algebra is practiced by helped of this describe digital circuitry. These spacial algebraic expressions, which are called boolean expressions. For use of the input variable we named it A, B, C, etc., and combine them using symbols representing the AND, OR, and NOT gates. These boolean expressions can be used to describe or evaluate the output of a circuit.
There is an additional benefit. Just like algebra, a set of rules exist that when applied to boolean expressions can dramatically simplify them. A simpler expression that produces the same output can be realized with fewer logic gates. A lower gate count results in cheaper circuitry, smaller circuit boards, and lower power consumption.