Incorrectly formatted data

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Incorrectly formatted data is a means of describing data that is incompatible with or unsuitable for the mechanism for processing it. This may include data that is out of range or malformed, but not data that is valid but incorrect.

Data may be incorrectly formatted in many ways. One example is that some computer architectures, such as the IBM System 360, required data to be in a particular format for correct execution by some instructions. This format known was packed decimal, where numeric data is held in computer memory in a hexadecimal format with each four bits representing a single decimal digit, so, for example, 100000 would appear as four bytes containing hexadecimal 0100000C (the last four bits containing C indicates that the value is positive). If an attempt is made to execute an instruction using data that is not in this format (such as hexadecimal 0A00000C, as A is not a valid decimal digit) a data exception occurs which may terminate the program.