Macros

#define

#define MY_MACRO "Hello World!"

Just like in C/C++, but without function-like macros (at least for now)

#include

#include myfile.lo

Note the lack of quotes around the filename. In LO they are not needed. Each file is only ever included once, and header files are not required. The compiler makes two passes over the files to collect all of the declarations so declaration order does not matter.