Real‐Time Languages
Stephen H. Kaisler · Encyclopedia of Software Engineering · 2002
Abstract A real‐time language (RTL) is a programming language used to implement an information processing system that can respond to externally generated stimuli within a finite and specifiable delay. Real‐time languages are typically used to program embedded computer systems that interface directly to physical equipment and are dedicated to monitoring and operating that equipment in a larger information processing system. The type of stimuli, the length of the delay, and the type of response depend on the application context. A delay of 15 seconds may be acceptable in an ATM transaction, but intolerable when flying an advanced fighter such as the F‐18. Because the definition of “real time” varies so widely, the features of real time languages also vary widely. Real‐time software is usually comprised of multiple processes that are executed concurrently and interact, where necessary, to synchronize on events and exchange information. Real‐time software must be extremely reliable, must be capable of responding to a wide variety of events with differing, but guaranteed, response times, and must be able to interface with a variety of nonstandard I/O devices as well as conventional peripherals. It is not sufficient to verify that real‐time software performs its function correctly, but that it does so in a predictable, timely manner. To meet the requirements of real‐time systems, an RTL requires both conventional programming constructs such as abstract data types, structured and dynamic data types, and classical program control structures, as well as specific features to support real‐time programming (Young, 1982). To produce real‐time software with predictable timing properties, a real‐time language must provide, among other things, features for: specifying time constraints, estimating resource requirements, and providing predictable synchronization mechanisms. These features are discussed availability and the future of real‐time language systems are detailed