Welcome to the Situation Room, YOUR NAME. Thank you for coming in at such short notice. Eleven hours and sixteen minutes ago, our scientists lost contact with the Trailblazer 1 probe, en route to Proxima Centauri. Since then we've been trying without success to re-establish contact with the spacecraft's onboard computer. Unless the fault can be rectified, and soon, we are facing a total loss of the vehicle and mission.
The problem appears to be localised to a subsystem known as the RTFM (Remote Telemetry and Flight Management) computer, responsible for the communications link between the spacecraft and Earth. Engineers are speculating that its memory may have been corrupted by a cosmic ray impact, causing the software to malfunction.
That's where you come in. We urgently need your help to investigate the RTFM software issue. Specifically, the first thing we need is a Go program that can execute code written for the spacecraft's onboard computer. A program like this is called an emulator: it acts like a model of the computer's central processing unit (CPU), and will enable us to write and test code before uploading it to the RTFM for real.
You might also have heard the term virtual machine, meaning not “nearly a machine”, but something more like “not physically a machine, but behaving in the same way”. Emulator, virtual machine, same thing.
It may sound complicated, but emulators are actually fairly easy to write, once you understand how the emulated machine (the guest) works. The RTFM computer uses a relatively small and simple CPU, compared to the one in your computer (the host machine).
This CPU is called the R8, and to emulate it, you'll be writing the necessary Go code to implement the R8's instruction set: the commands it understands.
The first thing the emulator needs is a properly-initialised CPU, ready to work. So there's a r8.New() function that returns a CPU in its default initial state, which is specified by a test.
The test is in the file r8_test.go, and the New function is already implemented in the r8.go file, so your first challenge is a straightforward one:
GOAL: Run the test and make sure it passes.
That's a great start! For the next challenge, read the tutorial: