An A-7 computer expert was a classification with regards to computer expertise, held by Commander Spock of the USS Enterprise, as of some time before 2259, until at least 2267.
When Commodore Bob Wesley asked James T. Kirk if he'd heard of the M-5 computer in 2268, Spock demonstrated his knowledge of the device, much to the Commodore's surprise. The Vulcan then cited his classification as an A-7 computer expert. According to Spock, having such a classification meant, among other things, that he was "well acquainted with Dr. Daystrom's theories and discoveries." (TOS: "The Ultimate Computer")