汇编语言的基本知识

1）instruction和directive

中文翻译都叫“指令”，但是instruction才是最终被翻译成机器码的，directive是用来告诉汇编器怎么去处理汇编程序的（就像C语言的define、include等一样）。

2）

•Statement format:

–[label:] mnemonic [operands][;comments]

•Label:

–Cannot exceed 31 characters.

–Consists:

•Alphabetic characters both upper and lowercase.

•Digits 0 through 9.

•Special characters ( ? ), ( . ), ( @ ), ( _ ),and ( $ ).

–The first character cannot be a digit.

–The period can only be used as the firstcharacter, but its use is not recommended. Several reserved words begin with itin later versions of MASM.

3）注释

用；

4）

•Label:

–Must end with a colon when it refers to anopcode generating instruction.

–Do not need to end with a colon when it refers to adirective.

•Mnemonicand operands:

–Instructions are translated into machine code.

–Directives do not generate machine code. They are used by theassembler to organize the program and direct the assembly process.