📄 c51运算符和表达式(指针和地址运算符).htm
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<P>char a;</P>
<P>int Aa = 0xFB1C;</P>
<P>long Ba = 0x893B7832;</P>
<P>float Ca = 3.4534;</P>
<P>SCON = 0x50; //串行口方式 1,允许接收 TMOD =
0x20; //定时器 1 定时方式 2</P>
<P>TH1 = 0xE8; //11.0592MHz 1200 波特率
TL1 = 0xE8;</P>
<P>TI = 1;</P>
<P>TR1 = 1; //启动定时器</P>
<P>XROM=(char xdata *) 0xB012;
//给指针变量赋 XROM 初值</P>
<P>*XROM = ‘R’; //给 XROM 指向的绝对地址赋值</P>
<P>a = *((char xdata *) 0xB012);
//等同于 a = *XROM</P>
<P>printf (“%bx %x %d %c
\n”,(char) Aa, (int) Ba,(int)Ca,
a);//转换类型并输出</P>
<P>while(1);</P>
<P>}</P>
<P>程序运行结果：1c 7832 3 R
在上面这段程序中，能很清楚到到各种类型进行强制类型转换的基本使用方法，程序中先</P>
<P>在外部数据存储器 XDATA 中定义了一个字符型指针变量 XROM，当用 XROM=(char xdata
*)</P>
<P>0xB012 这一语句时，便把 0xB012 这个地址指针赋于了 XROM，如你用 XROM 则会是非法的，
这种方法特别适合于用标识符来存取绝对地址，如在程序前用#define ROM 0xB012
这样的 语句，在程序中就能用上面的方法用 ROM 对绝对地址 0xB012
进行存取操作了。运算符的优先级说明表格能在笔者的 <A
href="http://www.51hei.com/mcuteach/131.html"
target=_blank><U><FONT color=#800080>本教程附录</FONT></U></A>
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