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")
In the novel Black Fire, the temporary science officer assigned to the USS Enterprise, Lieutenant Commander Thorin Martin, claims a computer rating of six, one below a seven, stating that Spock has the only seven in Starfleet.
In Strangers from the Sky, Spock mentions that he took a period of shore leave in the 2250s at the Massachusetts Institute of Technology, to participate in a botany project that required the skills of a class A-7 computer expert.