In terms of structure, PLCs can be divided into two types: fixed and modular (or modular).

For fixed PLCs, they comprise elements such as the CPU board, I/O board, display panel, memory block, and power supply, which are integrated into an indivisible unit.

On the other hand, modular PLCs consist of components like CPU modules, I/O modules, memory blocks, power supply modules, and baseplates or racks. These modules can be configured and combined according to specific rules.