The handling logic should be common to SBCS and DBCS as much as possible.
If the handling logic can be applied for both SBCS and DBCS, but with different resource, then application program should just prepare the different resources and keep the logic in common.
It is recommended that those functions, which require different handling methods for SBCS and DBCS be separated from the main routine. An application program can check the DBCS environment vector to decide which method, SBCS or DBCS, to be applied. See the Single Module.