Proposed extensions to PL/I for real-time applications

The paper is a revision of an earlier paper [4l, and contains numerous suggestions made by both committees. The paper is expected to serve as the basis for the development of a set of standard extensions to the PL/I language defined by ANSI standard X, 3-53-1976 [21. However, these extensions are not part of any existing or proposed standard and are subject to further revision. The Paper assumes that the reader is familiar with PL/I as specified by ANSI standard X3 .53-1976. The language extensions defined in this paper are designed to provide : 1. The ability for multiple PL/I programs to share variables and files in a manner which ensures that all shared objects always have a consistent state. The sharing mechanism is designed so that by following a very simple discipline, a real-time applications programmer can ensure that his or her system will not contain potential deadlocks. 2. The ability for a program to schedule the execution of another program, hereinafter called a task. Each task can be given a set of arguments and a priority. Futhermore, tasks can be created and scheduled to respond to the occurrence of specific events. Each task has a lifetime that is' independent of the lifetime of any other task. 3. The ability for a task to delay its own execution until a specific event has occurred .