You must specify an address of the place where you will spend most of your time.

你必须填一个你待的时间最久的那个地方。

For our hypothetical CPU, the first four bits specified the operation code, or opcode, and the second set of four bits specified an address or registers.

对于我们假设的 CPU，前四位指定操作码或操作码，第二组四位指定地址或寄存器。