An undefined value represents the absence of a value.

Related concepts:  ValueNull

Closest Wikipedia entry:  Undefined value — In computing (particularly, in programming), undefined value is a condition where an expression does not have a correct value, although it is syntactically correct. An undefined value must not be confused with empty string, Boolean "false" or other "empty" (but defined) values. Depending on circumstances, evaluation to an undefined value may lead to exception or undefined behaviour, but in some programming languages undefined values can occur during a normal, predictable course of program execution.

Misconceptions about Undefined
3 documented Misconceptions

Check Yourself

Stay up-to-date

Follow us on  twitter to hear about new misconceptions.