- The Information Header which describes details about the plugin (author and description). This is contained in a large PHP /* comment */.
- User-defined functions, such as the hello_dolly() function.
- The add_action() and/or add_filter() functions, which hook a WordPress event to a user-defined function.
That’s all you need for a plugin.
update I table according physical input(s) from outside PLC
1st rang: read I bit(s), execute instruction(s), write O bit(S); 2nd rang …
Energize the device(s) according to O table
Latch example: Keep a AC run or not run after a power shut down.