"operating statements 30 are transferred to comparator 408 which requests the authority table from memory 406. If there is no match, the operating statement is acceptable without authority and the secondary computer moves to the next statement. If there is a match, then the statement is either forbidden or requires authority. The secondary computer then scans for an accompanying authority card 412 which is brought to comparator 410 for comparison against authority code table 402. If a corresponding authority passcode is found, the operating statement is accepted. If not found at 415, an impulse is sent to the alarm console 46 for counteraction, as at 416 (FIG. 7). This will normally result in suppression of the statement and prevent its taking effect in the host 10. " "To perform the checksum technique, a questionable copy taken from the library device during initial program load (IPL), as will be subsequently more fully described, is resubjected to the same statistical analysis by the secondary computer as was applied to the base copy. If differences are found, an illegitimate copy is assumed and a predetermined counteraction may be initiated. "