**26. What is full adder ?**

Full Adder is the adder which adds three inputs and produces two outputs. The first two inputs are A and B and the third input is an input carry as C-IN.A full adder is a digital circuit that performs addition. Full adders are implemented with logic gates in hardware. A full adder adds three one-bit binary numbers, two operands and a carry bit. The adder outputs two numbers, a sum and a carry bit. The term is contrasted with a half adder, which adds two binary digits.

**27. What is a universal gate ?**

Universal gate is a gate which can implement any Boolean function without need to use any other gate type. The NAND and NOR gates are universal gates. They are called universal gates because all the other gates like and,or,not,xor and xnor can be derived from it.

**28. What is K-maps or Karnaugh Maps ?**

A Karnaugh map provides a pictorial method of grouping together expressions with common factors and therefore eliminating unwanted variables. The Karnaugh map can also be described as a special arrangement of a truth table.

**29. What is Adder in digital electronics ?**

DescriptionAn adder is a digital circuit that performs addition of numbers. In many computers and other kinds of processors adders are used in the arithmetic logic units or ALU.