1. An apparatus for the development and execution of an application program having at least one sequential program for controlling at least one sequential machine function and having at least one continuous program for controlling at least one continuous machine function, said apparatus comprising: means for producing the application program in the form of a diagram, said means for producing including: means for producing at least one step box having therein a sequential program including one or more sequential program statements, each sequential program statement including a sequential program statement label, and means for producing at least one action box having therein at least one continuous program identifier for identifying a continuous program, each continuous program identifier associated with at least one sequential program statement label, each said action box associated with one of said at least one step boxes; execution means for executing said application program; and means for linking said at least one step box and said at least one action box for producing said application program.