Interfaces are often designed to provide decoupling between component parts or subsystems. Types of Systems Four basic types of systems Closed system totally isolated from its environment Relatively closed system reacts with its environment in a known and controlled way. Open system system s interaction with the environment is not controlled. Accounting Information Systems Accounting as a System A well-designed accounting system is an example of a relatively closed system. Inputs to an AIS are the economic events and become accounting transactions.
Internal controls help to prevent or detect disturbances from the environment.
The accounting system is composed of application systems. An application system is a set of procedures and computer programs that perform a specific accounting objective. Auditors look at an accounting system as a set of transaction cycles . Transaction cycles are a set of economic events that normally follow each other in a cyclical manner. Expenditure cycle transactions that acquire material and supplies.