Errors that the compiler can detect fall into five categories of severity.
| Level of message | Return code | Purpose |
|---|---|---|
| Informational (I) | 0 | To inform you. No action is required and the program runs correctly. |
| Warning (W) | 4 | To indicate a possible error. The program probably runs correctly as written. |
| Error (E) | 8 | To indicate a condition that is definitely an error. The compiler attempted to correct the error, but the results of program execution might not be what you expect. You should correct the error. |
| Severe (S) | 12 | To indicate a condition that is a serious error. The compiler was unable to correct the error. The program does not run correctly, and execution should not be attempted. Object code might not be created. |
| Unrecoverable (U) | 16 | To indicate an error condition of such magnitude that the compilation was terminated. |