How does an interpreter interpret the code?

Question

For simplicity imagine this scenario, we have a 2-bit computer, which has a pair of 2 bit registers called r1 and r2 and only works with immediate addressing.

Lets

Answer 1

Not all computers have the same instruction set. Java bytecode is a kind of Esperanto - an artificial language to improve communication. The Java VM translates the universal Java bytecode to the instruction set of the computer it runs on.

So how does JIT figure in here? The main purpose of the JIT compiler is optimization. There are often different ways to translate a certain piece of bytecode into the target machine code. The most performance-ideal translation is often non-obvious because it might depend on the data. There are also limits to how far a program can analyze an algorithm without executing it - the halting problem is a well-known such limitation but not the only one. So what the JIT compiler does is try different possible translations and measure how fast they are executed with the real-world data the program processes. So it takes a number of executions until the JIT compiler found the perfect translation.