how gates useful in electronics?

logic gates are in fact the building block of digital electronics , they are formed by the combination of transistors (either BJT or MOSFET) to realize some digital operations
(like logical OR, AND, INVERT ). every digital product like computers, mobile, calculators even digital watches contains logic gates. the use of logic gates in digital world can be understood better by the following example : the single bit full adder in digital electronics is an logic circuit which perform the logical addition of two single bit binary numbers (a,b,cin) a and b are the the two binary number of single digit (either 1 or 0) and cin is the carry input . say for example a,b,cin= 1,1,1 gave an logical sum output of 1 and a carry of 1 , a,b,cin= 110 gave sum= 0 and carry of 1. now this adder can be formed by the combination of many gate like by using NAND gates only. or by using XOR , AND ,OR gates and so on. so in a nutshell the adder which is of great importance in your computer processor (and also in many more applications ) is basically build from the logic gates .

they build the world........

Some times logic gates r used to store data such as in buffers & many AND, OR , NAND , NOR gates r used in construction of multiplexers, adders, multipliers etc,. These gates make the computer logic or functionality.

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regards

Ramesh