Code: Learning Disassembly Assembly

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Mark, working with assembly is kind of like working with a young child. You have to spell out every instruction to get a job done. To the processor, memory locations are mainly for storage. The accumulators are used for doing math operations or a few other larger instructions. If memory is like a storage shelf, then the accumulators are the workbench. Load accumulator means "get this thing from storage and put it on the bench." The instruction by itself doesn't do much. It's the steps that follow it that really do work. In the code section above D77D loads Accumulator B with a value from memory location 00DF. The next line is where something is done... in this case one of the bits is "set" or forced to be "1". Follow the BRA (branch) to the address it specifies and you'll see that the value from Accumulator B is then moved back to location 00DF with a "STAB" (STore Accumulator B) instruction.