The theory and structure of programming real-time computer applications has not yet advanced to such a point that a particular choice of language facilities is inevitable. Further, the design of real-time language is handicapped by the lack of agreed standard software interfaces for applications programmers or compiler writers. This does not imply that real-time programs cannot yet be written in a high-level language. The use of Coral 66 in real-time applications implies the presence of a supervisory system for the control of communications, which may have been designed independently of the compiler. The programmer's control over external events, and the computer's reaction to them, is expressed by the use of procedures or macros which communicate with the outside world indirectly through the agency of the supervisory software. No fixed conventions are laid down for the names or action of such calls on the supervisor.