flash lights impressively

from The Free On-line Dictionary of Computing (8 July 2008)

Flash Lights Impressively

   <programming, command, humour> (FLI) /FLY/ A joke {assembly
   language} instruction first documented in the late 1970s in
   "The Hackers Dictionary".

   The FLI instruction was frequently referred to by engineers
   when {minicomputers} such as the DEC {PDP-8}, {PDP-11} and
   some early {microcomputers} such as the {IMSAI} and {Altair}
   had dozens of front panel lights.

   "When the computer is about to do some long I/O operation,
   stick in a FLI so the accountants won't think the machine has
   hung again."

   (2004-08-23)