This section discusses routines and methods used to check and handle errors that occur in IDL programs. The routines covered here are rarely used interactively.
IDL divides possible execution errors into three categories: input/output, math, and all others. There are three main error-handling routines: CATCH, ON_ERROR, and ON_IOERROR. CATCH is a generalized mechanism for handling exceptions and errors. The ON_ERROR routine handles regular errors when an error handler established by the CATCH procedure is not present. The ON_IOERROR routine allows you to change the default way in which input/output errors are handled. The FINITE and CHECK_MATH routines provide control over math errors.