8. Write Fast Code

• Whenever possible, use registers rather than constant values, and constant values rather than memory.

• Minimize changes in program flow.

• Smaller is often better. For example, the instructions

     dec  bx
     sub  bx, 1
  

  accomplish the same thing and have the same timings on 80386/486 processors, but DEC BX is 3 bytes smaller than the second, and so may reach the processor faster.