What is application systems?

An application system normally consists of a user interface, business logic and a database of some sort.

The user interface is something that you can see and something that is used to interact with the computer.  It could consist of set of screens, web pages or reports.  Sometimes the user interface is an input device such as a bar code reader or a voice recognition device.

Some application systems have non-visual interfaces.  These application systems exchange data electronically with other applications via a network.

Programming logic consists of one or more computer programs, scripts or other type of computer instructions that are used to validate data, perform calculations or navigate the user through the application system. Most large computer systems use multiple computer languages.

A database is a repository of data that is used to store information of interest to the organization in a structured format.  The database could be a set of flat files and/or database tables.  The structure of the database is designed to facilitate data access and/or updates. 

A computer system is simply a set of computer components that are assembled into an integrated package.  The components can be large or small and can be designed for a single purpose or for multiple purposes.