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."