NSException

NSException is used to implement exception handling and contains information about an exception. An exception is a special condition that interrupts the normal flow of program execution. Each application can interrupt the program for different reasons. For example, one application might interpret saving a file in a directory that is write-protected as an exception. In this sense, the exception is equivalent to an error. Another application might interpret the user’s key-press (for example, Control-C) as an exception: an indication that a long-running process should be aborted.

Note: The exception handling mechanism uses longjmp to control the flow of execution. Any code written for an application that uses exception handling is therefore subject to the restrictions associated with this functionality. See your compiler documentation for more information on the longjmp function.