The five parts of an information system is people procedures software hardware and data of which people are surely the most important.
(1)People: Every system needs people if it is to be useful. Often the most over-looked element of the system are the people probably the component that most influence the success or failure of information systems. This includes "not only the users but those who operate and service the computers those who maintain the data and those who support the network of computers."
(2)Procedures: Procedures are the policies that govern the operation of a computer system. "Procedures are to people what software is to hardware" is a common analogy that is used to illustrate the role of procedures in a system.
(3)Software: The term software refers to computer programs and the manuals (if any) that support them. Computer programs are machine-readable instructions that direct the circuitry within the hardware parts of the system to function in ways that produce useful information from data. Programs are generally stored on some input / output medium often a disk or tape.
(4)Hardware: The term hardware refers to machinery. This category includes the computer itself which is often referred to as the central processing unit (CPU) and all of its support equipments. Among the support equipments are input and output devices storage devices and communications devices.
(5)Data: Data are facts that are used by programs to produce useful information. Like programs data are generally stored in machine-readable form on disk or tape until the computer needs them.

Differentiating IS from related disciplines

Information Systems relationship to Information Technology Computer Science Information Science and Business.
Similar to computer science other disciplines can be seen as both related and foundation disciplines of IS. The domain of study of IS involves the study of theories and practices related to the social and technological phenomena which determine the development use and effects of information systems in organization and society. But while there may be considerable overlap of the disciplines at the boundaries the disciplines are still differentiated by the focus purpose and orientation of their activities.

In a broad scope the term Information Systems is a scientific field of study that addresses the range of strategic managerial and operational activities involved in the gathering processing storing distributing and use of information and its associated technologies in society and organizations. The term information systems is also used to describe an organizational function that applies IS knowledge in industry government agencies and not-for-profit organizations. Information Systems often refers to the interaction between algorithmic processes and technology. This interaction can occur within or across organizational boundaries. An information system is the technology an organization uses and also the way in which the organizations interact with the technology and the way in which the technology works with the organization’s business processes. Information systems are distinct from information technology (IT) in that an information system has an information technology component that interacts with the processes' components.

One problem with that approach is that it prevents the IS field from being interested in non-organizational use of ICT such as in social networking computer gaming mobile personal usage etc. A different way of differentiating the IS field from its neighbours is to ask "Which aspects of reality are most meaningful in the IS field and other fields?" This approach based on philosophy helps to define not just the focus purpose and orientation but also the dignity destiny and responsibility of the field among other fields.