Primary control of the IUA is exercised by the process running in the ACU CP under a real-time operating system. The CP process has many concurrent tasks each with their own thread of control. These tasks share all the resources of the CP and generally are cooperating. Some tasks are supplied by the user and some are supplied as part of the IUA system software. The ACU User's Guide provides more information on these tasks.
The primary task, supplied by the user and written in C++, uses the IUA Class Library to generate instructions for the Micro Controller which controls the CAAPP. No other task or process on the IUA may generate these instructions. The primary task is also responsible for coordinating the CAAPP with the other elements of the IUA.
Other tasks exist to control the IDTS image-data subsystem, communicate with other processors on the IUA VMEbus, and respond to requests made by the IPEs. User's CP tasks may also respond to interrupts generated by the IPEs or the other devices.