Abstract
A system is an assemblage of things that are combined to form a complex whole. When we study systems we study the interactions and behavior of such an assemblage when subjected to certain conditions. These conditions are called inputs. In its simplest case a system can have one input and one output. This chapter describes a linear continuous system with a voltage divider circuit as an example. If we can determine the input by measuring the output, then the system under consideration is said to be invertible. If the coefficients of the characteristic equation have the same sign, then the system is stable. If there are sign changes in the coefficients of the characteristic equation, we can test stability by finding the roots of the characteristic equation analytically, or we can use the MATLAB function "roots" to find the roots of the characteristic equation.