Introduction There are so many different signals and systems that it is impossible to describe them one by one The best approach is to represent the signal as a combination of some kind of the simplest signals which will pass through the system and produce a response.Combine the responses of all simplest signals,which is the system response for the original input signal. This is the basic approach to study the signal analyses and processing.Introduction There are so many different signals and systems that it is impossible to describe them one by one The best approach is to represent the signal as a combination of some kind of the simplest signals which will pass through the system and produce a response. Combine the responses of all simplest signals, which is the system response for the original input signal. This is the basic approach to study the signal analyses and processing