What ndh2 said. Don't try to follow a tutorial on how to do it, just do it. If you know how to use substring and indexOf in your preferred language you can writ

What ndh2 said. Don't try to follow a tutorial on how to do it, just do it. If you know how to use substring and indexOf in your preferred language you can write a parser. If you know how to use switch case you can write a virtual machine. Boil it down to the most basic parts and just keep going. It may be daunting at first, but its not magic ;-)