Definition - What does Ladder Logic mean?
Ladder logic is a programming language that creates and represents a program through ladder diagrams that are based on circuit diagrams. It is mainly used in developing programs or software for programmable logic controllers (PLCs), which are used in industrial applications.
The language evolved from originally being a method for documenting the design and construction of relay racks used in manufacturing and process control, with each relay rack represented by a symbol on the ladder diagram that has connections to devices below them that look like vertical rails. The relay symbols themselves look like rungs in a ladder.
Techopedia explains Ladder Logic
Ladder logic is widely used in industrial settings for programming PLCs where sequential control of manufacturing processes and operations is required. The programming language is quite useful for programming simple yet critical systems or for reworking old hard-wired systems into newer programmable ones. This programming language is also used heavily in highly sophisticated automation systems such as electronics and car factories.
The idea behind ladder logic is that even personnel without programming backgrounds can quickly program since it makes use of conventional and familiar engineering symbols for programming. But this advantage is quickly negated since manufacturers of PLCs often also provide ladder logic programming systems with their products, which sometimes do not use the same symbols and conventions as those made for other models of PLCs from other manufacturers; in fact, the programming system is usually meant only for specific models, so the programs cannot be ported easily to other PLC models or must be outright rewritten.