我有关于bt汇编指令的问题。我提供了一部分书籍来提供背景信息。请看最后一个例子，bt Testme, bx。为什么要复制TestMe + 8？难道不应该复制TestMe + 65吗？
非常感谢您的帮助！
6.6.4.2 The Bit Test Instructions: BT, BTS, BTR, and BTC
On an 80386 or later processor, you can use the bt instruction (bit test) to test a single bit. Its second operand specifies the bit index into the first operand. Bt copies the addressed bit into the carry flag. For example, the instruction
bt ax, 12copies bit twelve of ax into the carry flag.
The bt/bts/btr/btc instructions only deal with 16 or 32 bit operands. This is not a limitation of the instruction. After all, if you want to test bit three of the al register, you can just as easily test bit three of the ax register. On the other hand, if the index is larger than the size of a register operand, the result is undefined.
If the first operand is a memory location, the bt instruction tests the bit at the given offset in memory, regardless the value of the index. For example, if bx contains 65 then
bt TestMe, bxwill copy bit one of location TestMe+8 into the carry flag. Once again, the size of the operand does not matter. For all intents and purposes, the memory operand is a byte and you can test any bit after that byte with an appropriate index. The actual bit bt tests is at bit position index mod 8 and at memory offset effective address + index/8.