Difference of opinion on DCS and PLC

PLC

PLC or Programmable Logic Controller designed to control or to make automated work in industries. A programmable controller is an industrial digital computer that has been used for control of manufacturing processes.
Processes such as assembly lines, robotic devices, or any activity that requires high reliability, easy programming, to process fault diagnosis.
I/O: the CPU retains and processes data while the input and output modules connect the PLC to the machinery. I/O modules provide the CPU with information and trigger specified results. This module can be analog or digital.
Communication: Apart from the input and output device, PLCs must connect with the other system types. We may need to export application data recorded by the PLC to a SCADA (supervisory control and data acquisition) system designed to monitor several connected devices. A PLC provides communication protocols and ports to facilitate communication between the PLC and the other system.
So based on the input and output, a PLC can easily monitor and record runtime data like temperature, machine productivity, mostly generation of alarms
This means that PLCs are robust and flexible manufacturing process control solutions that are adapted to the most application.

DCS or A distributed control system is a computerized control system designed especially automated control system that consists of control loops, distributed control elements over the plants or control area.
These controllers can communicate among themselves and also with other controllers like supervisory terminals, operator terminals, historians, etc.
DCS has an in build distributed controller for each different control operation. And even when we want to expand I/Os, it’s very easy to configure and modify the controller in DCS. This makes it suitable for complex structures.
System redundancy: DCS facilitates system redundancy at the entry level. Redundancy raises system reliability by maintaining system operation endlessly during the time of some faults or abnormalities even when the system is in operation.
Scalable platform: the structure of DCS can be easily scalable just by adding some more control units or process units.
System security: Distributed control system design offers a perfect secured system to handle system function better factory automation control. Security is also provided at different levels, entrepreneur level, operator level, etc.