For the last decade a passionate debate has raged about the advantages and disadvantages of PLCs (programmable logic controllers) compared to PC-based control. As the technological differences between PC and PLC wane, with PLCs using commercial off the shelf (COTS) hardware and PC systems incorporating real-time operating systems, a new class of controllers, the PAC is emerging. PAC, a new acronym created by Automation Research Corporation (ARC), stands for Programmable Automation Controller and is used to describe a new generation of industrial controllers that combine the functionality of a PLC and a PC. The PAC acronym is being used both by traditional PLC vendors to describe their high end systems and by PC control companies to describe their industrial control platforms. 
During the three decades after their introduction, PLCs have evolved in order to integrate the analog I / O, communication over networks, and new standards such as IEC 61131-3 programming. However, 80% of engineers to create industrial applications with digital I / O, analog few I / O points, and simple programming techniques. Experts from the CRA, Venture Development Corporation (VDC), and online training PLC PLCS.net source maintained that:
- 77% of PLCs are used in applications for small (less than 128 I / O)
- 72% of PLC I / O Digital
- 80% of PLC application challenges are resolved with a series of 20 scale logic instructions Read the rest of this entry »