Beginning with this chapter, and in the two chapters following, we will take a comprehensive look
at various building blocks used to design more complex combinational circuits. A combinational
logic circuit is one where the output or outputs depend upon the present state of combination of
the logic inputs. The logic gates discussed in Chapter 4 constitute the most fundamental building
block of a combinational circuit. More complex combinational circuits such as adders and subtractors, multiplexers and demultiplexers, magnitude comparators, etc., can be implemented using a combination of logic gates. However, the aforesaid combinational logic functions and many more, including more complex ones, are available in monolithic IC form. A still more complex combinational circuit may be implemented using a combination of these functions available in IC form. In this chapter, we will cover devices used to perform arithmetic and other related operations. These include adders, subtractors, magnitude comparators and look-ahead carry generators. Particular emphasis is placed upon the functioning and design of these combinational circuits. The text has been adequately illustrated with the help of a large number of solved problems, the majority of which are design oriented.
