Generating sequences for control

The way in which switching and sequences are generated for practical control in industry are introduced and described. Methods have changed with the introduction of PLCs though programming and methodology are still related to the earlier methods used. The extra facilities built into PLCs are also reviewed. Such facilities make them a new tool in their own right with the ability to compute and control online. Large systems require much checking and testing. Software tools and methodologies to facilitate this are an important way of reducing project costs and demonstrating that the system will do what it should (and nothing that it shouldn't).