What is the purpose of external storage in PLC applications?

In PLC applications, the purpose of external storage is primarily to save data that exceeds the limitations of onboard memory. PLCs typically have a fixed amount of internal memory for data storage and processing tasks, which may not be sufficient for applications requiring the handling of large datasets or extensive logging of operational history. External storage devices, such as SD cards, USB drives, or other forms of removable media, allow for the expansion of storage capabilities. By utilizing external storage, PLCs can retain larger volumes of data, enabling them to manage complex processes, maintain historical records, and support data retrieval as necessary.

While other options discuss attributes like processing speed or power management, these do not directly relate to the core functionality of external storage. The additional space provided by external storage ensures that critical data is preserved and readily accessible for analysis or for program execution needs, which directly supports more robust PLC applications.