#define
In this section:
The #define options define absolute symbols at link time.

Defined symbols
Define absolute symbols to be used at link time. This is especially useful for configuration purposes. Type the symbols that you want to define for the project, one per line, and specify their value. For example:
TESTVER=1
Note that there should be no space around the equals (=) sign.
Any number of symbols can be defined in a linker configuration file. The symbol(s) defined in this manner will be located in a special module called ?ABS_ENTRY_MOD, which is generated by the linker.
The linker will display an error message if you attempt to redefine an existing symbol.