The Progression
In its early days, the PLC was relatively unsophisticated, with only a fraction of the features it boasts today. Notably, it was exceptionally expensive at the time. Over the decades, the PLC expanded considerably but adhered to the fundamental definition of being an electronic device with programmable memory, I/Os, and a power supply, executing user-entered instructions. It resembled a computer but required a programming device to correctly code addresses. 
The Transition
Initially employed for discrete and process-control applications, as sophistication increased, the PLC transitioned into a comprehensive automation controller. The price/performance ratios underwent a drastic change, with today’s PLCs being 30 times more efficient than their counterparts from a decade ago. Technological advancements made electronics more affordable on a broader scale.
A New Era
Simultaneously, software also underwent significant evolution. The introduction of Windows 95 ushered in a new era of computer-based programming, significantly reducing development time. Over time, a clear pattern emerges: PLCs are evolving into appliances, requiring internet connectivity for optimal performance. This evolution has given rise to another device—the Programmable Logical Controller or PAC.
The Evolution
By definition, a PAC is a PLC, encompassing all the elements of a traditional PLC. PACs have the capacity to manage discrete, drive, motion, and safety control applications from a common platform, tasks that PLCs handled a decade or two ago. The development of PACs is deeply influenced by evolution, integrating components and functionalities into a dedicated box to simplify on-site challenges for engineers, such as adding axes of motion. PACs have emerged as a parallel automation technology, in some ways overshadowing PLCs due to their enhanced ease-of-use and simplification of complex processes found in the latter.
