Which type of data structure would be essential when managing the continuous speed of a motor in an automated system?

The selection of the data structure is critical when managing the continuous speed of a motor in an automated system. The type designated as 'REAL' would be the most effective choice in this scenario.

When dealing with motor speed, the requirement often includes representing decimal values, as speed can be measured in fractional terms to provide finer control and accuracy. The 'REAL' data type in most control systems allows for floating-point numbers, which means it can handle both whole numbers and decimals. This capability is essential for applications where precision is necessary, such as adjusting motor speeds to achieve specific operational conditions.

Other data types like ARRAY, DINT, and STRING may not be suitable for this particular application. For instance, while arrays can be useful for holding collections of values, they do not inherently provide the precision required for continuous measurements of speed. DINT is limited to whole numbers and would not suffice for cases where fractional speeds are necessary. Strings are designed for text and don’t apply effectively to numerical calculations related to speed management. Therefore, using the REAL data structure ensures the ability to work with the necessary precision for controlling the motor's speed effectively.