Now, im working on a virtual machine project, where I am tasked to write a simple virtual machine that will be stack based. At the initial viewing of the instruction set, stack machines appear simple, as almost all operands are implicit. This allows us to create an instruction format which is relatively simple and small. The problem arises when an immediate value is required. My dillemma is such: my instructions are byte-sized, but immediate values may need to be up to 4 bytes long. Should i create a variable-length instruction format (1-5 bytes) to handle immediates? This solution initially appeared unviable to me, because it introduces complexity within a simple system. Variable width instruction formats are a pain in the butt. So the other option that jumped out at me would be to use a 32 bit instruction format, where the first byte is the opcode, and the next 3 bytes are the immediate value (I think i can get away with 24 bit immediates). This also has a major drawback: Since the majority of instructions do not require immediate operands, most instructions are wasting 3 bytes. sigh. Anyone have experience with stack machines they wish to share with me?