An Information System (IS) is the system of persons, data records and activities that process the data and information in a given organization, including manual processes or automated processes. Usually the term is used erroneously as a synonym for computer-based information systems, which is only the Information technologies component of an Information System. The computer-based information systems are the field of study for Information technologies (IT); however these should hardly be treated apart from the bigger Information System that they are always involved in.

The term information system has different meanings:
In computer security, an information system is described by three objects (Aceituno, 2004):
Structure:
Repositories, which hold data permanent or temporarily, such as buffers, RAM, hard disks, cache, etc.
Interfaces, which exchange information with the non-digital world, such as keyboards, speakers, scanners, printers, etc.
Channels, which connect repositories, such as buses, cables, wireless links, etc. A Network is a set of logical or physical channels.
Behavior:
Services, which provide value to users or to other services via messages interchange.
Messages, which carries a meaning to users or services.
In geography and cartography, a geographic information system (GIS) is used to integrate, store, edit, analyze, share, and display georeferenced information. There are many applications of GIS, ranging from ecology and geology, to the social sciences.
In knowledge representation, an information system consists of three components: human, technology, organization. In this view, information is defined in terms of the three levels of semiotics. Data which can be automatically processed by the application system corresponds to the syntax-level. In the context of an individual who interprets the data they become information, which correspond to the semantic-level. Information becomes knowledge when an individual knows (understands) and evaluates the information (e.g., for a specific task). This corresponds to the pragmatic-level.
In mathematics in the area of domain theory, a Scott information system (after its inventor Dana Scott) is a mathematical structure that provides an alternative representation of Scott domains and, as a special case, algebraic lattices.
In mathematics rough set theory, an information system is an attribute-value system.
In sociology information systems are also social systems whose behavior is heavily influenced by the goals, values and beliefs of individuals and groups, as well as the performance of the technology.[1]
In systems theory, an information system is a system, automated or manual, that comprises people, machines, and/or methods organized to collect, process, transmit, and disseminate data that represent user information.
In telecommunications, an information system is any telecommunications and/or computer related equipment or interconnected system or subsystems of equipment that is used in the acquisition, storage, manipulation, management, movement, control, display, switching, interchange, transmission, or reception of voice and/or data, and includes software, firmware, and hardware.[2]

History of information systems
The study of information systems, originated as a sub-discipline of computer science, in an attempt to understand and rationalize the management of technology within organizations. It has matured into a major field of management, that is increasingly being emphasized as an important area of research in management studies, and is taught at all major universities and business schools in the world.
Today, Information and Information technology have become the fifth major resource available to executives for shaping an organization, alongside people, money, material and machines.[3] Many companies have created a position of Chief Information Officer (CIO) that sits on the executive board with the Chief Executive Officer (CEO), Chief Financial Officer (CFO), Chief Operating Officer (COO) and Chief Technical Officer (CTO).The CTO may also serve as CIO, and vice versa

Study of information systems
Ciborra (2002) defined the study of information systems as the study, that deals with the deployment of information technology in organizations, institutions, and society at large.[4]
Many colleges and universities, such as the Carnegie Mellon University, the University of California - Berkeley, the University of Michigan, University of Colorado, Syracuse University, George Mason University, University of Washington, George Washington University, New York University, Claremont Graduate University, the University of Toronto, Multimedia University, University of Idaho, and the University of Limerick currently offer undergraduate and graduate degrees in information systems and closely related fields.

Applications of information systems
Information systems deal with the development, use and management of an organization's IT infrastructure.
In the post-industrial, information age, the focus of companies has shifted from being product oriented to knowledge oriented, in a sense that market operators today compete on process and innovation rather than product : the emphasis has shifted from the quality and quantity of production, to the production process itself, and the services that accompany the production process.
The biggest asset of companies today, is their information, represented in people, experience, know-how, innovations (patents, copyrights, trade secrets), and for a market operator to be able to compete, he/she must have a strong information infrastructure, at the heart of which, lies the information technology infrastructure. Thus, the study of information systems, focuses on why and how technology can be put into best use to serve the information flow within an organization.

Areas of work
Information Systems has a number of different areas of work:
Information Systems Strategy
Information Systems Management
Information Systems Development
Each of which branches out into a number of sub disciplines, that overlap with other science and managerial disciplines such as computer science, pure and engineering sciences, social and behavioral sciences, and business management.

Information technology development
The IT Department partly governs the information technology development, use, application and influence on a business or corporation. A computer based information system, following a definition of Langefors[5], is:
a technologically implemented medium for recording, storing, and disseminating linguistic expressions,
as well as for drawing conclusions from such expressions.
which can be formulated as a generalized information systems design mathematical program