This paper presents a medium‐sized operating system written in Concurrent Pascal, thereby describing further experience with this language and giving further indications of its scope. The operating system was developed to support an application in the area that is usually termed ‘commercial’ or ‘administrative’. Both the functional capabilities and the structure of the operating system are described, with emphasis on its facilities for data file management, and its size and performance are given. A secondary theme of the paper is the relationship of the operating system's qualities to the properties and facilities of the programming language Concurrent Pascal used for its development.