Types of Software Systems : Diagnostic Software Systems, Sensor and Signal Processing Systems, Simulation Systems

The type of software system refers to the processing that will be performed by that system.
Diagnostic Software Systems:
These systems helps in diagnosing the computer hardware components. When a new device is plugged into your computer, a diagnostic software system does some work. The "New Hardware Found" dialog can be seen as a result of this system.

Sensor and Signal Processing Systems:
The message processing system helps in sending and receiving messages. These systems are more complex because they make use of mathematics for signal processing. In a signal processing system, the computer receives input in the form of signals and then transforms the signals to a user understandable output.

Simulation Systems:
Simulation is the process of designing a model of a real system and conducting experiments with this model for the purpose of understanding the behavior of the system or evaluating various strategies for the operation of the system. A simulation is a software package that re-creates or simulates, albeit in a simplified manner, a complex phenomenon, environment, experience providing the user an opportunity for some new level of understanding.
Simulation systems are easier, cheaper and safer to use as compared to real systems and often the only way to build the real systems. For example, learning to fly a fighter plane using a simulator is much safer and less expensive than learning on a real fighter plane. System simulation mimics the operation of a real system such as the operation in a bank or the running of an assembly line in a factory.
Simulation in the early stage of design cycle is important because the cost of mistakes increases dramatically later in the product life cycle. Also, simulation software can analyze the operation of a real system without the improvement of an expert i.e. it can also be analyzed with a non-expert like a manager.

Overview to System Simulation Tools

System simulation tools provide the software engineer with the ability to predict the behavior of a real-time system prior to the time that it is built. In addition, these tools enable the software engineer to develop mock-ups of the real-time system, allowing the customer to gain insight into the function, operation, and response prior to actual implementation.
Tools in this category allow a team to define the elements of a computer-based system and then execute a variety of simulations to better understand the operating characteristics and overall performance of the system. Two broad categories of system simulation tools exist :
- General purpose tools that can model virtually any computer-based system.
- Special purpose tools that are designed to address a specific application domain.

REPRESENTATIVE TOOLS :
- CSIM : Developed by Lockheed Martin Advanced Technology labs, is a general purpose discrete-event simulator for block diagram-oriented systems.
- Simics : Developed by Virtutech, is a system simulation platform that can model and analyze both hardware and software-based systems.
- SIX : Developed by Wolverine Software, provides general purpose building blocks for modeling the performance of a wide variety of systems.

Introduction to System Simulation

Systems simulation is a set of techniques for using computers to imitate, or simulate, the operations of various kinds of real-world facilities or processes.The computer is used to generate a numerical model of reality for the purposes of describing complex interaction among components of a system. The complexity of the system surges from the stochastic (probabilistic) nature of the events, from the rules for the interactions of the elements, and the difficulty to perceive the behavior of the systems as a whole with the passing of time.

When to use simulations?
Systems that change with time, such as a gas station where cars come and go (called dynamic systems) and involve randomness.Modeling complex dynamic systems theoretically need too many simplifications and the emerging models may not be therefore valid. Simulation does not require that many simplifying assumptions, making it the only tool even in absence of randomness.

System terminology:
- State: A variable characterizing an attribute in the system.
- Event: An occurrence at a point in time which may change the state of the system.
- Entity: An object that passes through the system.
- Queue: It is a task list.
- Creating: Creating is causing an arrival of a new entity to the system at some point in time.
- Scheduling: Scheduling is the act of assigning a new future event to an existing entity.
- Random variable: A random variable is a quantity that is uncertain.
- Random variate: A random variate is an artificially generated random variable.
- Distribution: A distribution is the mathematical law which governs the probabilistic features of a random variable.