// show how to write interrupt code

// dummy header for compiler use
asm(x)

// ISR, assembly
// x is r1, y is r2, color is r3

interrupt()
  asm("st r1 1010")
  asm("st r2 1011")
  asm("trap r3 #15")  
  asm("add r1 r1 #1")
  asm("add r2 r2 #1")

// or write in Rz, should not mix 
//interrupt()
//  a = 10
//  b = b + a

main()
//  setup interrupt
  asm("mov r1 #interrupt")
  asm("st r1 1000")

  x = 10
  y = 10
  color = 1
  while(x < 50)
    // empty loop
    // use ISR to plot and step x,y