An intermediate code instruction set

Intermediate code is like machine-independent assembler code for an abstract CPU. The instruction set defines a set of opcodes. Each opcode specifies its semantics, including how many operands it uses and what state changes occur from executing it. Because this is intermediate code, we do not have to worry about registers or addressing modes – we can just define state changes in terms of what modifications must occur in the main memory. The intermediate code instruction set includes both regular instructions and pseudo instructions, as is the case for other assembler languages. Let’s look at a set of opcodes for the Jzero language. There are two categories of opcodes: instructions and declarations.

Instructions

Except for immediate mode, the operands of instructions are addresses. Based on their operand position, most instructions implicitly dereference (read) and assign (write) values in memory located at those addresses...