This International Standard as a whole specifies a serial data network for control and communications on forestry or agricultural tractors and mounted, semi-mounted, towed, or self-propelled implements. Its purpose is to standardize the method and format of transfer of data between sensors, actuators, control elements, and information storage and display units, whether mounted on, or part of, the tractor or implement. This part of ISO 11783 describes the task controller applications layer, which defines the requirements and services needed for communicating between the task controller (TC) and electronic control units. The data format to communicate with the farm-management computer, the calculations required for control, and the message format sent to the control function are defined in this part of ISO 11783.