Complex logic operations

The term complex, when used to describe the logic operation, does not mean complicated necessarily. A more apt adjective might be composite. But there are several cases when logic operations are quite complicated.No matter how messy a particular logic operation may appear, it can always be broken down into elementary operations which are defined above.

                                  Figure-- Four-input AND gate (A) and four-input NOR gate (B).

Assume that you want to find an arrangement of logic gates for complex logic operation. This can be done in 2 ways. You can use truth tables or Boolean algebra.  For any complex logic operation, there might be several solutions, some requiring more gates than others. A digital design can has the job not only of finding out an arrangement of gates for the given complex operation, but of finding the scheme which will yield the desired result with least number of gates.