Editing Ladder logic (section)

==Limitations and successor languages==
Ladder notation is best suited to control problems where only [[binary data|binary variables]] are required and where interlocking and sequencing of binary is the primary control problem. Like all [[parallel programming language]]s, the sequential order of operations may be undefined or obscure; logic [[race condition]]s are possible which may produce unexpected results. Complex rungs are best broken into several simpler steps to avoid this problem. Some manufacturers avoid this problem by explicitly and completely defining the execution order of a rung, however, programmers may still have problems fully grasping the resulting complex semantics.

Analog quantities and arithmetical operations are clumsy to express in ladder logic and each manufacturer has different ways of extending the notation for these problems.  There is usually limited support for arrays and loops, often resulting in duplication of code to express cases that in other languages would call for use of indexed variables.

As [[microprocessors]] have become more powerful, notations such as [[sequential function chart]]s and [[function block diagram]]s can replace ladder logic for some limited applications.  Some newer PLCs may have all or part of the programming carried out in a dialect that resembles [[BASIC]], [[C (programming language)|C]], or other [[programming language]] with bindings appropriate for a real-time application environment.