Assembler instruction       Effect of the assembler instruction
  ------------------------    --------------------------------------
    add  r0, r1, r2              r0 = r1 + r2
    add  r0, r0, r0              r0 = r0 + r0 = 2×r0
    add  r0, r0, #1              r0 = r0 + 1

    sub  r0, r1, r2         r0 = r1 - r2
    rsb  r0, r1, r2              r0 = r2 - r1
    rsb  r0, r0, #0              r0 =  0 - r1 = -r0  (negation !!)

    mul  r0, r1, r2              r0 = r1 * r2
    mul  r1, r0, r0              r1 = r0 * r0 = r02