SAP SOURCE CODE ORGA - Guide

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Source Code Organization
ABAP source code is saved in the ABAP Repository in the central database of an AS ABAP, and not in source code files like in most other programming environments. Source codes can be split into individual units by using include programs. There are also macros that are handled for callable modularization units in the context of these guidelines.

Source code modularization

ABAP Code Snippet