And there are essentially two possible opcodes.

基本上有两种可能的操作码。

And if you disassemble this, it's the opcode for jump to address 0.

如果你反汇编它，它就是跳转到地址 0 的操作码。

In this case the opcode, which is the first four bits, is: 0010.

在这种情况下，操作码（前四位）是：0010。

This opcode corresponds to the " LOAD A" instruction, which loads a value from RAM into Register A.

该操作码对应于“LOAD A”指令，该指令将一个值从 RAM 加载到寄存器 A。

That opcode 1000 is an ADD instruction.

该操作码 1000 是一条 ADD 指令。

For example, imagine a CPU that uses 8 bit opcodes.

例如，想象一个使用 8 位操作码的 CPU。

In our hypothetical example, we use the first four bits to store the “operation code”, or opcode for short.

在我们假设的例子中， 我们使用前四位来存储“操作码”，或简称操作码。

For example, there's over a dozens different opcodes just for variants of ADD!

例如，仅针对 ADD 的变体，就有数十种不同的操作码！

But there is no instruction with an opcode of 0, and so the computer would have crashed!

但是没有操作码为 0 的指令，所以计算机会崩溃！

So, our hypothetical CPU is very basic – all of its instructions are 8 bits long, with the opcode occupying only the first four bits.

所以，我们假设的 CPU 是非常基本的——它的所有指令都是 8 位长，操作码只占据前四位。

Then, when the program was all figured out on paper, they'd painstakingly expand and translate it into binary machine code by hand, using things like opcode tables.

然后，当程序全部在纸上弄清楚时，他们会使用操作码表之类的东西，煞费苦心地手动将其扩展并翻译成二进制机器代码。

So instruction sets tend to keep getting larger and larger keeping all the old opcodes around for backwards compatibility.

因此，指令集往往会变得越来越大，保留所有旧的操作码以实现向后兼容性。

For example, to recognize a LOAD A instruction, we need a circuit that checks if the opcode matches 0010 which we can do with a handful of logic gates.

例如，要识别 LOAD A 指令，我们需要一个电路来检查操作码是否与 0010 匹配，我们可以使用少量逻辑门来完成。

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。

As we already discussed, the ALU itself can perform several different operations, so the Control Unit must configure it to perform an ADD operation by passing in the ADD opcode.

正如我们已经讨论过的，ALU 本身可以执行多种不同的操作，因此控制单元必须通过传入 ADD 操作码将其配置为执行 ADD 操作。

We can assign an ID to each instruction supported by our CPU. In our hypothetical example, we use the first four bits to store the " operation code" , or opcode for short.

我们可以为我们的 CPU 支持的每条指令分配一个 ID。在我们假设的例子中，我们使用前四位来存储“操作码”，简称操作码。