Answer from cs61c-ap (Nicole Rungsitiyakorn 13543412) for Question 4
Memory-mapped io refers to keyboard and display.

              lui  $t0, 0xFFFF
waitloop:     lw   $t1, 0($t0)
              andi $t1, $t1, 0x1
              beq  $t1, $0
              lw   $v0, 4($t0)