This document defines information systems and their components. It discusses how information systems have developed over time from the introduction of punch cards to today's cloud computing systems. It identifies the key components of information systems as people, hardware, software, data, input, processing, output, storage and feedback. It also describes different types of information systems like transaction processing systems, decision support systems, executive information systems and management information systems. Finally, it outlines the five eras in the evolution of management information systems from mainframes to personal computers to today's cloud computing models.