SAP NetWeaver AS ABAP Release 740, ©Copyright 2014 SAP AG. All rights reserved.
ABAP Keyword Documentation → ABAP − Reference → Calling and leaving program units →Calling Processing Blocks
In every processing block of an ABAP program, you can call processing blocks of the same program (internal call) or processing blocks of other ABAP programs (external call).
The statement MODULE does not call dialog modules in the processing blocks of an ABAP program, however, but in the processing blocks of the dynpro flow logic.