1. Introduction Digital systems operate on digital signals. The digital signals are a set of finite discrete levels as contrast to analog signals which are continuous in time domain. All signals in nature are analog, and thus can be interpreted by analog systems directly. For these signals to be interpreted by the digital system, require them to be converted from analog to digital form. Some of the examples of digital systems are: Laptop / Desktop, calculator, Digital weighing machine, digital watches and timers, camera, video games, digital music recording, digital video game etc. A digital system can be broadly classified as either a combinational or a sequential system. In combinational systems the output at any instant depends only on the inputs supplied at