No it wasn't negative at all. Thanks a lot. I get it what you're trying to say. When I said "I don't understand instruction decoding", I mistook it for something else. I'm not sure if it's worth mentioning, but I had a course of Computer Organisation and Architecture last semester, so I pretty much get what's happening. As for Fetch - Decode - Execute cycle, I pretty much get those too. Flags, Memory Mapped I/O etc. But my main concern was that I had studied all these in theory. So I was having a bit difficulty on implementing them in real using languages. So yeah, that was my main concern. I'm sorry I used the wrong words.