can't happen
INPUT WHERE A FUNCTION OUTPUT DOESN'T MATTER.
Don't care condition; Don't Care Condition; Dont care term; Don't care term; Don't care; Don't cares; Don't-care (logic); Don´t care; Can't-happen term; Can't happen (logic); Don't-care condition; Do-not-care condition; Do not care condition; Do not care term; Do-not-care term; Don't care (logic); X value; W value; Forced unknown; Weak unknown; Forced unknown value; Weak unknown value; Power-up don't care logic; Power-up don't care minimization; Power-up don't care; Can't happen state; Can't-happen state; Satisfiability don't care; Satisfiability DC; Controllability don't care; Controllability DC; Observability don't care; Observability DC; Don't care alarm; Don't-care alarm; Forbidden input; Don't-care situation; Don't care situation; Optional entry (logic); Invalid combination (logic); Vacuous combination (logic); Vacuous combinations (logic); Optional entries (logic); Invalid combinations (logic); Can't happen condition; Can't-happen condition; "Can't happen" condition; "Don't care" condition; Vacuous variable; Vacuous variables; Don't-care point; Don't care point; "don't care" point; Vacuous variable (logic); Vacuous variables (logic); Forbidden combination (logic); Forbidden combinations (logic); Redundancies (logic); Irrelevancies (logic); Redundancy (logic); Irrelevancy (logic); Unused state (logic); Unused states (logic); Unutilized state (logic); Useless state (logic); Unutilized states (logic); Useless states (logic); Don't-care set; Don't care set; Don't know (logic); Don't care network; Don't care region; Don't care response; Don't care minimization; Don't care minimisation; Don't-care network; Don't-care region; Don't-care response; Don't-care minimization; Don't-care minimisation; Care output; Care output response; External global CDC; Internal local CDC; External global controllability don't care; Internal local controllability don't care; External global controllability DC; Internal local controllability DC; Multi-level don't care; Multi-level DC; Two-level don't care; Two-level DC; Don't know condition; Forbidden digit; Forbidden digit check; Forbidden-digit check; Logical remainder; Logical remainders; Don't happen condition; Don't-care state; Don't care state; Conditional don't-care state; Conditional don't care state; Conditional don't-care; Conditional don't care; Don't care status; Don't-care status; Conditional don't care status; Conditional don't-care status; Absolute don't care status; Absolute don't-care status; Absolute don't care state; Absolute don't-care state; Absolute don't care; Absolute don't-care; Don't care bit; Don't-care bit; Don't care variable; Don't-care variable; Unconditional don't care status; Unconditional don't-care status; Unconditional don't care state; Unconditional don't-care state; Unconditional don't care; Unconditional don't-care; Can't happen
<
programming> The traditional program comment for code
executed under a condition that should never be true, for
example a file size computed as negative. Often, such a
condition being true indicates data corruption or a faulty
algorithm; it is almost always handled by emitting a fatal
error message and terminating or crashing, since there is
little else that can be done.
Some case variant of "can't happen" is also often the text
emitted if the "impossible" error actually happens. Although
"can't happen" events are genuinely infrequent in production
code, programmers wise enough to check for them habitually are
often surprised at how frequently they are triggered during
development and how many headaches checking for them turns out
to head off.
See also
firewall code,
professional programming.
[
Jargon File]
(1996-05-10)