The following table lists the NaN codes returned by the Operating System. NaN is a Standard Apple Numeric Environment (SANE) representation which means "Not a Number." NaN appears when an operation produces a result that is beyond SANE's scope.
| Code | Description |
| 1 | Invalid square root |
| 2 | Invalid addition |
| 4 | Invalid division |
| 8 | Invalid multiplication |
| 9 | Invalid remainder |
| 17 | Converting an invalid ASCII string |
| 20 | Converting a Comp type number to floating-point |
| 21 | Creating a NaN with a zero code |
| 33 | Invalid argument to a trig function |
| 34 | Invalid argument to an inverse trig function |
| 36 | Invalid argument to a log function |
| 37 | Invalid argument to an xi or xy function |
| 38 | Invalid argument to a financial function |
| 255 | Uninitialized storage |
