P/CL: A flexible input processor

An interactive program inevitably has a need for a user interface which exceeds the simple combination of a write and a read statement. This is necessary to prevent a program abort due to an input error from the side of the user. Also it is desirable to allow for more advanced types of input than single characters or numbers. For these reasons a general-purpose input package has been developed which allows for sophisticated command-driven programs while offering the programmer as well as the user an easy-to-use interface. The structure of the package is described and examples of its use are given.