If you're teaching yourself (what I assume you mean from bootstrapping), you ought to take a Coursera or EdX class on computer architecture or at least get a go

If you're teaching yourself (what I assume you mean from bootstrapping), you ought to take a Coursera or EdX class on computer architecture or at least get a good textbook on the subject. The class should cover microprocessor architecture, assembly language and how the assembler works. My EE course on the subject at UT Austin used the 6800 micro family, and my CS friends at UT took a similar class that used MIPS.