Test Units should be numbered according to some logical sequence, which is determined by the TU Developer. Zero should not be used as a TU number. The allowable range for TU numbers is 1 through 61439 (1 through EFFF hex). This numbering requirement must be respected even though the TU member of the tucb header structure is defined as a 32 bit integer. It is desirable that a numbering scheme be developed by the TU Developer allowing TUs to be executed in sequential numerical order when executing them as designated. This might include spacing the TUs so that future TUs can be inserted into the number sequence, where appropriate.