Intel 4004 Disassembler

I would like to make a Intel 4004 Disassembler as a hobby project but it seems I'm stuck on some things.I assume the instruction size is same as 8080 and that is 8 bits.I found some instruction set online,but I'm not sure how to implement it,except the NOP operation.
http://ift.tt/29UgNCh
It all seems so confusing. I can't find what registers Intel 4004 uses.I only know it has 1 Carry Flag. For example the operation: JCN 0 a8. I have no idea what 0 represents neither do I know what a8 means.
Here is my code so far:
http://ift.tt/2aES7eg