C4ISR stands for Command, Control, Communications, Computing, Intelligence, Security and Reconnaissance. It was formulated by the US Department of Defence (DoD) in response to the need to evolve a mechanism for integrating and acting on combat information coming from various sources, geographies, and using different types of media.
A C4ISR System can be thought of as a framework for organising multi-media information emanating from a situation (typically a crisis), in a manner that enables non-local users to analyse such information (from multiple sources); act on that information or advise local players on actions to be taken; receive feedback from local players on actions taken; based on which a follow-up set of actions or advice can be initiated, towards the objective of resolving the situation to the advantage of the users.