Components of a System
In order to understand and analyse a system, we need to define a number of terms. i) entity: This is an object of interest in the system. An attribute is a property of an entity. ii) activity: Represents a time period of specified length. If a bank is being studied, customers might be one of the entities, the balance in their checking accounts might be an attribute, and making deposits might be an activity.iii) state of a system: A collection of variables necessary to describe a system at a particular time, relative to the objectives of a study. In a study of a bank, examples of possible state variables are the number of busy tellers, the number of customers in the bank, and the time of arrival of each customer in the bank.We categorise systems to be one of two types, discrete and continuous.