An A-7 Computer expert was a classification with regards to computer expertise, held by Commander Spock of the USS Enterprise in 2267. According to Spock, having such a classification meant, among other things, that he was "well acquainted with Dr. Daystrom's theories and discoveries."
When Commodore Robert Wesley mentioned the M-5 computer, Spock demonstrated much knowledge on the subject, much to the Commodore's surprise. The Vulcan then cited his qualifications as justification for his familiarity with the computer. (TOS: "The Ultimate Computer")