汇编代码转成机器码——对输入有几点要求：指令是小写；一行只能有一条指令；每行开头不能有空格，必须一上来就是操作符，后面可以有空格；立即数只处理十进制数；输入-1代表程序结束-Turn assembly code into machine code- there are several points of entry requirements: command is lowercase　line can only have one instruction　beginning of each line can not have spaces, the operator must be up against the back can have spaces　immediate treatment only decimal number -1 means the end of the input program