Front-end protocol errors

When the front-end receives an invalid instruction from the runtime system, it stops the application connection.

The runtime system then stops and displays error -6313 with an additional message, for example:

Program stopped at 'myprog.4gl', line number 675.
 FORMS statement error number -6313.
 The User Interface has been destroyed: Unexpected interface version sent 
 by the runtime system.

When the runtime system receives an invalid AUI event from a front-end, it will raise a C assertion and produce a core file on UNIX® systems.