Pass1 parses the file, pass2 uses the parsed file to build the object file.
Text location counter and data location counter both start at zero. As we move through the code, we increment the counters to determine where things go.
When we encounter .data, we know we’re working with the DLC (data location counter)
deftab - table of all external definitions and their addresses. There are also flags, but we aren’t going to learn about those right now.
.byte 0 writes a zero byte, aka a null-terminator.
REFTAB - table of external references and lines of code that use them. This is so the linker can fill in some labels later on.
RELTAB - tells everywhere in the code that an absolute address was used. Linker adds load point offset to each of these.
The Linker:
Linker takes multiple Obj modules and squishes them together. This is quite litteraly appending t2 to t1 and d3 to d2 to d1 and so on.
To be executable, all references must be resolved, and there must be an entry point.
We don’t need a main if we’re building a library, but we still need an external def so that something can run.