Make a context switching operating system.

To do this, we switch between three $$processes$.$ These are subroutines that do different things within our system. For us$,$ they will just print $$Process $1,$Process $2,$ and $$Process $3($though$)$ you could be more creative if you want, and prints some value that is stored in a register. This register must be re$-$used in all your $$processes$$ to show that it has been restored.

The only interrupt that LC$-3$ provides us is keyboard, so any input from the keyboard will cause the program to switch which $$process$$ is running.

To do this, you need to have a $$process control block$$ for each of your processes. This holds metadata about your process, which allows us to restore it$.$

$.$fill process$1$ ; the struct for the thread is address of the code

$.$fill x$0$ ; and the current count

$.$fill x$0$ ; this PSR

$.$fill x$0$ ; their R$7$

You will need one of these for each process, then create an array of process control blocks.

When an interrupt is received, you must store the current process state, and restore the state of the next process.

This all prints out very fast! Put a sleep in your processes to stop them from printing so quickly

and R$1,$R$1,$#$1$

sleeploop

add R$1,$R$1,$#$1$

brnp sleeploop