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1 definition found From The Jargon File (version 4.4.7, 29 Dec 2003) [jargon]: fall through v. (n. fallthrough, var.: fall-through) 1. To exit a loop by exhaustion, i.e., by having fulfilled its exit condition rather than via a break or exception condition that exits from the middle of it. This usage appears to be really old, dating from the 1940s and 1950s. 2. To fail a test that would have passed control to a subroutine or some other distant portion of code. 3. In C, ?fall-through? occurs when the flow of execution in a switch statement reaches a case label other than by jumping there from the switch header, passing a point where one would normally expect to find a break. A trivial example: switch (color) { case GREEN: do_green(); break; case PINK: do_pink(); /* FALL THROUGH */ case RED: do_red(); break; default: do_blue(); break; } The variant spelling /* FALL THRU */ is also common. The effect of the above code is to do_green() when color is GREEN, do_red() when color is RED, do_blue() on any other color other than PINK, and (and this is the important part) do_pink() and then do_red() when color is PINK. Fall-through is considered harmful by some, though there are contexts (such as the coding of state machines) in which it is natural; it is generally considered good practice to include a comment highlighting the fall-through where one would normally expect a break. See also {Duff's device}.