A simple stack base virtual machine

Cpu + Register + Program counter (PC) has 3 steps in it's circle:

• fetch instruction from memory to register
• pc++
• decode register current instruction pieces
• check if decoded instruction pieces is a complete instruction
  • if complete, Cpu execute instruction
  • if not move to step1

An add instruction looks like:

3 4 ADD

It has 3 pieces, data 3, data 4, primitive operation ADD, SUB, MUL, DIV

The action of read string from source file, and break it up into tokens.