ILCS differentiates between implicit language-specific event handling and event handling that can be explicitly enabled and disabled. The ILCS interface SEH (Standard Event Handler) is available for implicit event handling, and SSH (Standard STXIT Handler) is available for explicit event handling.
Standard event handler (SEH)
Event handling using the SEH interface is possible only for the STXIT events ERROR and PROCHK. This interface is used internally by the runtime system either to implement the language resources to be used for exception handling in the various programming languages (e.g. Pascal, Pl/1, Ada) or to take certain measures - such as the output of error messages - in response to an ERROR or PROCHK event before the program aborts
(e.g. COBOL85).
Standard STXIT handler (SSH)
The SSH interface can be used to explicitly enable and disable user-defined routines for all BS2000-STXIT events. This interface is currently used by the C/C++ and ASSEMBH runtime systems: C/C++ programs can use the C library functions signal and cstxit to enable user-defined routines for event handling; Assembler programs do this with the ASSEMBH structure macros @STXEN and @STXDI.
The explicit enabling of user-defined routines for the STXIT event classes ERROR and PROCHK (SSH) disables the implicit handling of these events by other languages (SEH). If implicit event handling of other languages (COBOL85, Pascal-XT, etc.) is to be reactivated, the event handling routines for ERROR and PROCHK must be explicitly disabled when leaving the C or ASSEMBH language environment. In C/C++ the routines are disabled by allocating SIG_DFL in the C library function signal, in Assembler it is done with the aid of the ASSEMBH structure macro @STXDI.
STXIT routines directly enabled for BS2000
In Assembler programs, use of the BS2000 macro STXIT makes it possible to enable STXIT routines directly for BS2000. However, these routines cannot be coordinated by ILCS. For example, if STXIT routines are enabled directly for PROCHK and ERROR events, the implicit handling of these events via the SEH interface remains active.