Advanced ladder logic functions allow controllers to perform calculations, make decisions and do other complex tasks.
Timers and counters are examples of ladder logic functions. They are more complex than basic inputs contacts and output coils and relay heavily upon data stored in the memory of the PLC.
The user program will account for most of the memory of a PLC system. Program files contain the logic controlling machine operation. This logic consists of instructions that are programmed in a ladder logic format.
The data file portion of memory stores input and output status, processor status, the status of various bits and numerical data.