ATL has 3 terminals: North, South, and International. North and South are the original two and are completely connected with entrances facing their nominal directions. These are in the easternmost building of the airport. The International terminal is newer and on the opposite side of these, past all the concourses. You might be asking about the first concourse. If you entered in the North or South terminal, the first one after security is concourse T, which doesn't require any travel as it is in the same building as the North and South terminals. If you entered in the International terminal, the first concourse after security is concourse F, which is part of the same building as the International terminal. If you want to go to concourses A through E from any terminal, you must take the underground tunnel, which provides a train for faster travel between these. Gates do have numbers, if that's what you're asking. In each and every concourse, gate 1 is the southeasternmost gate.
Doesn't exist. Terminals at ATL use letters, not numbers.
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