A conversion routine CONV (also known as conversion exit) is represented by two function modules, which follow the naming convention CONVERSION_EXIT_CONV_INPUT|OUTPUTwhere CONV is the name of the conversion routine. Statements leading to an interruption of the program flow or terminating an SAP-LUW cannot be executed in the function modules. A conversion routine can be assigned to a domain in the ABAP Dictionary. If a screen field refers to a domain with a conversion routine, the function module ..._INPUT is automatically executed with each entry in the corresponding screen. The function module ..._OUTPUT is automatically executed when values are displayed in this screen and the corresponding converted content is used. If a data object refers to a domain of this type, the function module ..._OUTPUT is executed when the data object is output using WRITE or WRITE TO and the converted content is output. Before release 6.40, it was not possible to debug conversion routines.