MCI code

ANSI artists don't need to worry too much about MCI codes (short for Message Command Interpreter - no relation to Microwave Communications, Inc., at one point the 2nd-largest long distance phone call provider in the US with a confusingly identical acronym)), which are really more the domain of a SysOp, but if you find yourself drawing a screen intended for dynamic use on a BBS (notably a "Stats" screen) you may find it helpful to know. MCI codes are placeholders for user-account-specific details, some obvious -- "Hi, %UN! You have %TL minutes remaining in this session!" -- and others somewhat more esoteric ("You have %FP file points remaining!") A canny ANSI artist will anticipate that you can put "Username: %UN" on a stats screen and the code only occupies three characters' worth of space, but the actual output there may run quite a bit longer, so leave a longer blank to accommodate the field.

Sometimes the unexpected use of MCI codes by non-SysOps in BBS messages (if not explicitly locked down by the SysOp) could result in unanticipated outcomes with security ramifications, like a user having their password stated back to them, apparently in plain text, and then quoted in plain text in a message to everyone else. One hacker baked a recursive MCI code into their username, so the first time the BBS attempted to read their name back to them, it got caught in an output loop and hung the board ... that sort of fun stuff! A quarter-century ago, while it was still relatively fresh in my mind, I wrote up the topic at some length over at https://everything2.com/title/MCI+code