5.24. 5.24 UNITs and the EXTERNAL Directive
Technically, the #include directive provides you with all the facilities you need to create modular programs. You can create several modules, each containing some specific routine, and include those modules, as necessary, in your assembly language programs using #include. However, HLA provides a better way: external and public symbols.
One major problem with the #include mechanism is that once you've debugged a routine, including it into a compilation still wastes time because HLA must recompile bug-free code every time you assemble the main program. A much better solution would be to preassemble the debugged modules and link the object code modules together. This is what the @external directive allows ...
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