All definitions (#define) and macro’s have to be placed under the DEFINITIONS AND MACROS section. This can be done in both the header and source file. In which file the definition or macro appears will depend on it’s scope. Definitions or macro’s which have to be known outside the modules (thus exported) will have to be put in the header file. A definition is everything that is defined using a #define. A macro is a definition that uses arguments. To allow for a good recognition of defines and macro’s it is recommended to use capitals completely. To increase readability in this case it is allowed to use underscores. Logical groups of defines and macro's have to be ordered together. All defines use the same indentation columns starting at the left margin. The different groups can be separated by using proper comment blocks and empty lines.