RET(93) is used to mark the end of a subroutine program; SBN(92) is used to mark the beginning. Each subroutine is identified with a subroutine number, N, that is programmed as a definer for SBN(92). This same subroutine number is used in any SBS(91) that calls the subroutine. No subroutine number is required with RET(93).
All subroutines must be programmed at the end of the main program. When one or more subroutines have been programmed, the main program will be executed up to the first SBN(92) before returning to address 00000 for the next scan. Subroutines will not be executed unless called by SBS(91) or activated by an interrupt.
END(01) must be placed at the end of the last subroutine program, that is, after the last RET(93). It is not required at any other point in the program