in figurative sense of "first-rate," 1837, in Dickens; from Lloyd's of London designation for ships in first-class condition (with the letter referring to the condition of the ship and the number to that of the stores).
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
a1 in Technology
language Address 1 code. An a1 code interpreter, by Matthew Newhook firstname.lastname@example.org was used to test compiler output. It requires gcc 2.4.2 or higher and is portable to computers with memory segment protection. (ftp://ftp.cs.mun.ca/pub/a1). (1994-07-19)