Folder Structure 
All development components (DCs) are stored in a shared folder named DCs. Under DCs, you create folders for the different vendors of components. The folder names are created from the vendor ID of the DC (for example, sap.com, example.organd so on). This separates the DCs of different vendors also physically in the file system.
Below the vendor folder, the DC tree starts. Every segment of a DC name is mapped to a folder. Under the folder hierarchy of a DC, you find the reserved folder _comp. This is used to label those folders in the DC tree that actually represent a DC.
You must store all development objects and files that belong to a particular DC in folders underneath of _comp.
Example
The following figure shows an exemplary file structure below the _comp folder. The src folder contains all development objects of the DC. The DC defines two packages com.sap.X and com.sap.Y with several files. There are also two package-free files a and b. The file with the reserved name .dcdef contains the DC description.
Example of a file structure
Component Definition
Every component (DC) is defined by a set of files, stored and versioned together with the DC.
A file with the reserved name .dcdefstores the basic attributes such as name, description and component type, the parent DC (if there is one), a list of child DC (if there are any), a list of dependencies, links to the DC sources, and the access control list (ACL). The .dcdeffile must be stored directly in the _comp folder.
The folder _comp/def contains one file for each public part of the DC, which carries the name of the public part with the extension .pp. This file contains a list of the development objects belonging to the public part and an ACL for this public part.
Both .dcdef and .pp files are stored in an XML-based format.
Caution
Direct manipulations of these files can make a DC unusable.