Unique FTRs helps distinguish external input from other external input. An FTR must be either an Internal Logical File and/or External Interface File. Each internal logical file that an external input maintains is counted as an FTR. Any internal logical file or external interface file that is referenced by an external input as part of the elementary process of maintaining an internal logical file would be considered an FTR also. For example, an External Input may update an internal logical file, but must also reference a "security file" to make sure that the user has appropriate security levels. This would be an example of two FTRs.