A survey of the theoretical problems connected with the organization and design of systems for processing and transmitting information is presented in this article. It gives a definition of Information Systems (IS) and classifies them from various points of view. It discusses briefly the most important aspects of the organization of IS, such as physical structure, functional structure, software, and operating principles. It presents certain problems connected with estimating the value of information supplied to its users by an IS. In a supplement it gives an example of the solution of the problem of optimum distribution of information in mass memory units of an IS, based on methods of Integer Programming. (Author)