Which components make up the two fundamental memory divisions mentioned for PLC memory?

• A. Instruction memory and data memory
• B. Program memory and data memory
• C. RAM and ROM
• D. Cache memory and main memory

Answer: (B)

In PLC memory, the key idea is separating where the program lives from where the program runs with its data. The correct split is program memory and data memory. Program memory stores the user’s ladder logic or PLC program—the set of instructions the PLC will fetch, interpret, and execute. Data memory holds the runtime information the program works with: variables, flags, timers, counters, and I/O status values that change as the process runs. Keeping these two areas distinct lets you load or modify the control program without disturbing the data you’re actively using, and it clarifies what part of memory is responsible for code versus operation.

The other terms aren’t the standard way PLC memory is described. While RAM and ROM describe memory types, PLC documentation typically emphasizes program memory versus data memory rather than a RAM/ROM dichotomy. Cache memory and main memory is a computer-architecture concept and doesn’t map to how PLCs are described or organized.