The object-oriented paradigm shows great potential as a means for revolutionizing software development. In the last decade, much research has been directed towards the development of design methods, languages, environments, reusable libraries of software components and database systems to support this paradigm. The first part of the paper presents the terminology of the object-oriented paradigm, reviews the state-of-the-art in object-oriented programming and discusses class libraries and object-oriented design. The second part of the paper discusses its application in the area of computer-aided control system design. It is argued that the adoption of these ideas will increase greatly the productivity of software developers in this field and improve the facilities that will be offered to users.