disassembly - How do I determine the start and end of instructions in an object file?

Question

So, I've been trying to write an emulator, or at least understand how stuff works. I have a decent grasp of assembly, particularly z80 and x86, but I've never really understood how an object file (or in my case, a .gb ROM file) indicates the start and end of an instruction.

I'm trying to parse out the opcode for each instruction, but it occurred to me that it's not like there's a line break after every instruction. So how does this happen? To me, it just looks like a bunch of bytes, with no way to tell the difference between an opcode and its operands.

Answer 1

For most CPUs - and I believe Z80 falls in this category - the length of an instruction is implicit.

That is, you must decode the instruction in order to figure out how long it is.